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Polydimethylsiloxane (PDMS) is the most studied organosilicon polymer, finding broad applications in soft lithography of microfluidic devices, wearable electronics insulation, medical tubing, shielding coatings, and sealant elements. However, their cross‐linked forms swell severely in nonpolar oils due to the comparable solubility parameters. Here, an oil‐stable cross‐linked PDMS discovered by grafting flexible PDMS chains onto its polymeric networks is reported, which enables surface‐exposed chains with high dynamics. It is found that the synergetic effect of mobile nanopore filling and quasi‐liquid lubrication of PDMS brushes endows the cross‐linked matrix with a reduced oil absorption ratio of up to 91.7% without altering its surface composition. Moreover, stretching polymeric networks can be re‐arranged with an adequate grafting of PDMS chains, further enhancing the antipenetration performance. This discovery of the oil‐stable surface configuration of cross‐linked PDMS breaks the constraint of siloxane elastomers not being applicable in nonpolar soluble liquid, opening a new era of research in organosilicon chemistry. [ABSTRACT FROM AUTHOR]

The self-consistent field theory (SCFT) was employed to numerically study the interaction and interpenetration between two opposing weak polyelectrolyte (PE) brushes formed by grafting weak PE chains onto the surfaces of two long and parallel columns with rectangular-shaped cross-section immersed in a salty aqueous solution. The dependences of the brush heights and the average degree of ionization on various system parameters were also investigated. When the brush separation is relatively large compared with the unperturbed brush height, the degree of interpenetration between the two opposing PE brushes was found to increase with increasing grafting density and bulk degree of ionization. The degree of interpenetration also increases with the bulk salt concentration in the osmotic brush regime. Numerical results further revealed that, at a brush separation comparable to the unperturbed brush height, the degree of interpenetration does not increase further with increasing bulk degree of ionization, bulk salt concentration in the osmotic regime and grafting density. The saturation of the degree of interpenetration with these system parameters indicates that the grafted PE chains in the gap between the two columns retract and tilt in order to reduce the unfavorable electrostatic and steric repulsions between the two opposing PE brushes. Based on salt ion concentrations at the midpoint between the two opposing brushes, a quantitative criterion in terms of the unperturbed brush height and Debye screening length was established to determine the threshold value of the brush separation beyond which they are truly independent from each other. [ABSTRACT FROM AUTHOR]

We present the study of millisecond-resolved polymer brush swelling dynamics using infrared spectroscopy with a home-built quantum cascade laser-based infrared spectrometer at a 1 kHz sampling rate after averaging. By cycling the humidity of the environment of the polymer brush, we are able to measure the swelling dynamics sequentially at different wavenumbers. The high sampling rate provides us with information on the reconformation of the brush at a higher temporal resolution than previously reported. Using spectroscopic ellipsometry, we study the brush swelling dynamics as a reference experiment and to correct artefacts of the infrared measurement approach. This technique informs on the changes in the brush thickness and refractive index. Our results indicate that the swelling dynamics of the polymer brush are poorly described by Fickian diffusion, pointing toward more complicated underlying transport. [ABSTRACT FROM AUTHOR]

The polymer grafted materials are frequently used in antifouling and oil–water separation, while the microscopic mechanism of liquid slippage on this surface remains unclear. This study uses molecular dynamics (MD) simulations to explore the structure and transport of oil (n‐hexadecane) on polydimethylsiloxane (PDMS) grafted surface as a function of grafting density. Simulation results indicate that PDMS chain structure undergoes a transition from liquid‐like to solid‐like structure when the grafting density increases. As a result, the entanglement between the PDMS and n‐hexadecane is also weakened. The direct consequence of this structural change is that the slip length of n‐hexadecane shows a non‐monotonic dependence on the grafting density, and a maximum slip length appears at intermediate grafting density. Further analysis indicate that the slip length also increases as the applied shear rate increases, which facilitates the transport of fluid at the grafted surface. These simulation results illustrate the subtle interplay between polymer–alkane interface structure and the transport property of the fluids, which are consistent with recent experimental studies, and will be helpful for rational design of polymer grafted materials in separation technologies. [ABSTRACT FROM AUTHOR]

Coating of magnetic nanoparticles with functional polymers increases the applicability of these nanomaterials. A modular approach to functionalizing these polymer coatings can be achieved using click chemistry. This work reports the synthesis of magnetic nanoparticles coated with a dopamine anchoring group containing polymer with furan groups as side chain residues. Using the 'graft-to' approach, polymers are coated onto magnetic nanoparticles using a simple place exchange reaction. Various analytical techniques were used to characterize the polymer-coated nanoparticles for their size and surface composition. Utilization of poly(ethylene glycol) (PEG)-based polymer renders the magnetic nanoparticles water dispersible. The presence of the furan ring on the polymer brushes enables their facile functionalization using a maleimide group-bearing molecule under catalyst-free conditions. A hydrophobic fluorescent dye, used as a model drug, is conjugated onto the nanoparticles using the Diels-Alder reaction. One can anticipate that the facile fabrication and functionalization of these clickable polymer-coated magnetic nanoparticles will be attractive for various biomedical applications. [ABSTRACT FROM AUTHOR]

We present the results of molecular dynamics simulations of steady shear between a pair of neutral polymer brushes, as well as a pair of charged polymer brushes in the strongly compressed regime. The results of the molecular dynamic simulations of neutral and polyelectrolyte brushes in implicit solvent including normal forces, shear forces, viscosities and friction coefficients as a function of separation between brushes, are presented in the study. The comparison of the simulation results of neutral and charged brushes shows that the charged brushes is in the quasi-neutral regime, and the dependence of viscosity on the separation distance show the similar power law of neutral brushes. Our simulation results confirm that the implicit solvent simulations of polyelectrolyte brushes that ignore hydrodynamics interaction are in agreement with the scaling predictions qualitatively because of screening of hydrodynamic interaction and long-range electrostatic interactions on the correlation length scale. Both of neutral and charged brushes show the lubrication properties that the friction coefficient decreases with the separation decreases at enough large loads. However, a maximum of friction coefficients is observed for polyelectrolyte brushes, which is in contrast to the neutral brushes with monotonical dependence. [ABSTRACT FROM AUTHOR]

Stimuli-responsive catalysts with exceptional kinetics and complete recoverability for efficient recyclability are essential in, for example, converting pollutants and hazardous organic compounds into less harmful chemicals. Here, we used a novel approach to stabilize silver nanoparticles (NPs) through magneto/hydro-responsive anionic polymer brushes that consist of poly (acrylic acid) (PAA) moieties at the amine functional groups of chitosan. Two types of responsive catalyst systems with variable silver loading (wt.%) of high and low (PAAgCHI/Fe3O4/Ag (H, L)) were prepared. The catalytic activity was evaluated by monitoring the reduction of organic dye compounds, 4-nitrophenol and methyl orange in the presence of NaBH4. The high dispersity and hydrophilic nature of the catalyst provided exceptional kinetics for dye reduction that surpassed previously reported nanocatalysts for organic dye reduction. Dynamic light scattering (DLS) measurements were carried out to study the colloidal stability of the nanocatalysts. The hybrid materials not only showed enhanced colloidal stability due to electrostatic repulsion among adjacent polymer brushes but also offered more rapid kinetics when compared with as-prepared Ag nanoparticles (AgNPs), which results from super-hydrophilicity and easy accumulation/diffusion of dye species within polymer brushes. Such remarkable kinetics, biodegradability, biocompatibility, low cost and facile magnetic recoverability of the Ag nanocatalysts reported here contribute to their ranking among the top catalyst systems reported in the literature. It was observed that the apparent catalytic rate constant for the reduction of methyl orange dye was enhanced, PAAgCHI/Fe3O4/Ag (H) ca. 35-fold and PAAgCHI/Fe3O4/Ag (L) ca. 23-fold, when compared against the as prepared AgNPs. Finally, the regeneration and recyclability of the nanocatalyst systems were studied over 15 consecutive cycles. It was demonstrated that the nanomaterials display excellent recyclability without a notable loss in catalytic activity. [ABSTRACT FROM AUTHOR]

Fluorinated hydrocarbons are excellent building blocks for hydrophobic coatings but also yield undesirable toxicity and environmental persistence. In precision industries such as high-resolution printing, polymer brushes are a valuable tool, as they can be tuned on the nanometer scale and can impart the underlying surface with desired properties and/or functionalities. Here, we report that the beneficial properties typically associated with (partially) fluorinated polymer brush coatings can to a large degree also be achieved with their nonfluorinated counterparts. To this end, we have successfully grafted 13 poly-(alkyl methacrylate) homopolymer brushes from a flat silicon surface using surface-initiated atom transfer radical polymerization (SI-ATRP). These polymer brushes were characterized by XPS, ellipsometry, and static water contact angle measurements. They were then shown to be repeatedly self-repairing by thermal treatment at 120 °C after damage by pH 3, with longer side chains being more resistant to damage from the acid. Branching of the side chains did not significantly influence this resistance, but it lowered the static water contact angle. Some polymer brushes with intermediate side chain length displayed an increase in the contact angle over the first four cycles. This was not caused by impurities but was the result of an annealing effect that improved the packing of the side chains of the brushes. In all, these coatings are suitable, self-healing, environmentally friendly, and fully nonfluorinated alternatives for current fluorine-based hydrophobic coatings. [ABSTRACT FROM AUTHOR]

The aim of this study was to develop self-healable and robust electroconductive film based on polyaniline copolymer for application as electrode in flexible supercapacitor. For this purpose, the electroconductive polymer brushes (EPB) was elaborated. The synthesis of EPB is based on graft polymerizations of acrylamide (AAm) on poly(vinyl alcohol) (PVA) with formation of PVA-PAAm polymer brush and subsequent graft copolymerization of aniline and p-phenylenediamine on PVA-PAAm resulting in formation of EPB with electroconducting copoly(aniline-co-p-phenylenediamine) (PAPhDA). It was found that the ratio between PVA and PAAm at the first stage greatly influence the electrochemical performance of the EPBs. Electroconducting films were prepared by casting of EPB solution with subsequent drying. Investigation of electrical current distribution through the film with AFM reveal more uniform distribution of PAPhDA in EPB in comparison with reference PVA-PAPhDA and PAAm-PAPhDA samples. It was demonstrated that mechanical characteristics and electrical conductivity values of films restore at large extent after curring and self-healing under optimal relative humidity level (58%). The flexile supercapacitor cell with EPB film electrodes demonstrate specific capacitance 602 mF·cm−2 at the current density of 1 mA·cm−2 and retention 94% of initial capacitance after 5000 charge/discharge cycles. [ABSTRACT FROM AUTHOR]

In this work, new nanoadsorbents consisting of polymer‐modified multi‐walled carbon nanotubes (MWCNTs) were used to remove toxic ionic dyes, of methylene blue (MB) and methyl orange (MO), effectively from aqueous solutions. The MWCNTs were coated with polymer brushes of poly(potassium 3‐sulfopropyl methacrylate) (PKSPMA) and poly(2‐methacryloyloxyethyltrimethylammonium chloride) (PMETAC) via surface‐initiated atom transfer‐radical polymerization. The PKSPMA@MWCNTs and PMETAC@MWCNTs delivered removal efficiencies of ~80% at pH 7. Maximum adsorption capacity (qmax) reached 411.62 mg/g for MB using PKSPMA@MWCNTs and 224.60 mg/g for MO using PMETAC@MWCNTs, showcasing the effectiveness of these novel nanoadsorbents. The experimental results were analyzed using adsorption isotherm models (Langmuir, Freundlich, and Temkin) and kinetic models (pseudo‐first‐order, pseudo‐second‐order, and intraparticle diffusion). The Freundlich model provided an excellent fit for MB adsorption on both adsorbents, whereas the Temkin model best described MO adsorption on PKSPMA@MWCNTs and the Langmuir model on PMETAC@MWCNTs. The fitting results showed that the pseudo‐second‐order kinetic model was the most accurate fit for MB and MO adsorption on both nanoadsorbents, suggesting that the removal mechanism was chemisorption. In conclusion, PKSPMA@MWCNTs and PMETAC@MWCNTs demonstrate significant potential as effective adsorbents for dye removal from water, providing a promising approach for water treatment and environmental remediation. [ABSTRACT FROM AUTHOR]

We propose a simulation approach to explore surface-initiated atom transfer radical polymerization (SI-ATRP), in which how the chain growth is affected by activation/deactivation process could be considered explicitly. Our findings indicate that these activation and deactivation mechanisms provide all polymer chains with equal growth opportunities. This process leads to a significant increase of grafting density while concurrently reducing the dispersity of the grafted chains. The ratio of activated and dormant chains is theoretically proved to eventually reach equilibrated within the activation/deactivation process. The shorter lifetime of activation/deactivation cycle leads to an even equal opportunity and a faster “stop-continue” pace for the growth of all chains. Our study is helpful for better understanding the role of activation/deactivation process in SI-ATRP from a microscopic perspective.

The development of highly effective bio‐lubricant coatings for arthritis treatment is extremely demanded. Herein, inspired by the efficient lubrication of articular cartilage, acrylic acid (AA) with (3‐(methacryloylamino) propyl) dimethyl (3‐sulfopropyl) ammonium hydroxide (MPDSAH) hydrogel coatings containing nanoparticles on Ti6Al4V substrate were designed and fabricated via UV grafting technology. SiO2 and SiO2 grafted with PAA polymer brushes (SiO2‐g‐PAA) were separately doped into the PAA‐PMPDSAH hydrogel. The PAA‐PMPDSAH/SiO2‐g‐PAA exhibits good tensile and compressive properties compared with PAA‐PMPDSAH/SiO2 hydrogel, with an enhancement of 183.4% in tensile modulus and 60.8% in compressive modulus. The PAA‐PMPDSAH/SiO2‐g‐PAA hydrogel coatings exhibit a low wear volume, 2.9 ± 0.16 × 106 μm3, representing a decline of 32.1% and 61.3% compared with the PAA‐PMPDSAH and PAA‐PMPDSAH/SiO2 hydrogel coatings, respectively. The antiwear performance has obviously improved. The hydrophilic PAA polymer brushes prevent the agglomeration of nanoparticles and promote homogeneously dispersion within the hydrogel. The three‐dimensional crosslinked network structure of hydrogel effectively protects the structural integrity of the polymer brushes, thereby facilitating enduring lubrication properties. This work provides a strategy for promising artificial joint lubrication in biomedical fields. [ABSTRACT FROM AUTHOR]

Among the methods for onsite detection of specific biomolecules, the use of retroreflective Janus particles (RJPs) is a simple and efficient method for biophotonic probes to detect biotarget molecules with spatioselectivity, which can make the RJPs align toward light sources after capturing the target biomolecules, enhancing retroreflection. Because RJP has two distinct regions with different properties, specific reagents can be easily functionalized through chemical reactions between the functional groups and biotarget molecules. The number of functional groups on RJP will be the critical parameter for efficiency of sensing ability. Here, clickable (azide) polymer brush is introduced on surface of RJP via different surface polymerization methods (grafting to and grafting from method). Azide groups allow for the easy modification of dibenzocyclooctyne‐linked biomolecules onto silica particles through click chemistry. RJPs are prepared with different quantities of azide functional groups on their surfaces via solvent volatilization method and metal deposition. Using a retroreflective immunosensing system, sensitive detection of target biomolecules is performed. [ABSTRACT FROM AUTHOR]

To better characterize the properties of surface-initiated polymers, simultaneous bulk- and surface-initiated polymerizations are usually carried out by assuming that the properties of the surface-initiated polymers resemble those of the bulk-initiated polymers. Through a Monte Carlo simulation using a heterogeneous stochastic reaction model, it was discovered that the bulk-initiated polymers exhibit a higher molecular weight and a lower dispersity than the corresponding surface-initiated polymers, which indicates that the equivalent assumption is invalid. Furthermore, the molecular weight distributions of the two types of polymers are also different, suggesting different polymerization mechanisms. The results can be simply explained by the heterogeneous distributions of reactants in the system. This study is helpful to better understand surface-initiated polymerization. [ABSTRACT FROM AUTHOR]

The effects of a cross-linking layer on the wear resistance of polymer brush were investigated by using molecular dynamics-based sliding simulations. We found that a cross-linking layer improved wear resistance. The cross-linking layer suppressed the interpenetration of polymer chains on the counter surface and thus lowered the frictional force and wear. The degrees of interpenetration decreased as the cross-linking layer closed to the tip of the chain. A cross-linking layer in the tip of the polymer chains was thus found to improve wear resistance most effectively. [ABSTRACT FROM AUTHOR]

Thermoresponsive polymer brushes have attracted considerable research attention owing to their unique properties. Herein, we developed silica beads grafted with poly(N-isopropylacrylamide (NIPAAm)-co-3-acrylamidopropyl trimethylammonium chloride (APTAC)-co-tert-butyl acrylamide (tBAAm) and P(NIPAAm-co-APTAC-co-n-butyl methacrylate(nBMA)) brushes. The carbon, hydrogen, and nitrogen elemental analysis of the copolymer-grated silica beads revealed the presence of a large amount of the grafted copolymer on the silica beads. The electrostatic and hydrophobic interactions between biomolecules and prepared copolymer brushes were analyzed by observing their elution behaviors via high-performance liquid chromatography using the copolymer-brush-modified beads as the stationary phase. Adenosine nucleotides were retained in the bead-packed columns, which was attributed to the electrostatic interaction between the copolymers and adenosine nucleotides. Insulin was adsorbed on the copolymer brushes at high temperatures, which was attributed to its electrostatic and hydrophobic interactions with the copolymer. Similar adsorption behavior was observed in case of albumin. Further, at a low concentration of the phosphate buffer solution, albumin was adsorbed onto the copolymer brushes even at relatively low temperatures owing to its enhanced electrostatic interaction with the copolymer. These results indicated that the developed thermoresponsive strong cationic copolymer brushes can interact with peptides and proteins through a combination of electrostatic and temperature-modulated hydrophobic interactions. Thus, the developed copolymer brushes exhibits substantial potential for application in chromatographic matrices for the analysis and purification of peptides and proteins.

Stimuli-responsive catalysts with exceptional kinetics and complete recoverability for efficient recyclability are essential in, for example, converting pollutants and hazardous organic compounds into less harmful chemicals. Here, we used a novel approach to stabilize silver nanoparticles (NPs) through magneto/hydro-responsive anionic polymer brushes that consist of poly (acrylic acid) (PAA) moieties at the amine functional groups of chitosan. Two types of responsive catalyst systems with variable silver loading (wt.%) of high and low (PAAgCHI/Fe3O4/Ag (H, L)) were prepared. The catalytic activity was evaluated by monitoring the reduction of organic dye compounds, 4-nitrophenol and methyl orange in the presence of NaBH4. The high dispersity and hydrophilic nature of the catalyst provided exceptional kinetics for dye reduction that surpassed previously reported nanocatalysts for organic dye reduction. Dynamic light scattering (DLS) measurements were carried out to study the colloidal stability of the nanocatalysts. The hybrid materials not only showed enhanced colloidal stability due to electrostatic repulsion among adjacent polymer brushes but also offered more rapid kinetics when compared with as-prepared Ag nanoparticles (AgNPs), which results from super-hydrophilicity and easy accumulation/diffusion of dye species within polymer brushes. Such remarkable kinetics, biodegradability, biocompatibility, low cost and facile magnetic recoverability of the Ag nanocatalysts reported here contribute to their ranking among the top catalyst systems reported in the literature. It was observed that the apparent catalytic rate constant for the reduction of methyl orange dye was enhanced, PAAgCHI/Fe3O4/Ag (H) ca. 35-fold and PAAgCHI/Fe3O4/Ag (L) ca. 23-fold, when compared against the as prepared AgNPs. Finally, the regeneration and recyclability of the nanocatalyst systems were studied over 15 consecutive cycles. It was demonstrated that the nanomaterials display excellent recyclability without a notable loss in catalytic activity.

Hepatic tissue engineering has been investigated for the treatment of liver disease. One promising tissue is the hepatocyte sheet, cultured in temperature-responsive cell culture dishes. However, the preparation of hepatocyte sheets requires precoating of the dish with fetal bovine serum (FBS), which is not desirable for clinical applications. To overcome this issue, we developed a thermoresponsive polymer-modified glass with an affinity for hepatocytes. Poly(N-p-vinylbenzyl-O-β-d-galactopyranosyl-(1→4)-d-guliconamide)-b-poly(N-isopropylacrylamide) (PVLA-b-PNIPAAm) was prepared through two steps of atom transfer radical polymerization (ATRP). The prepared copolymer brushes were characterized using X-ray photoelectron spectroscopy, atomic force microscopy, gel permeation chromatography, contact angle measurements, and fluorescence labeled-fibronectin and -lectin adsorption assays. These characterizations showed that the smooth block copolymer layer was successfully modified by ATRP. The feasibility of using the prepared polymer brush-grafted glass as a hepatocyte sheet fabrication dish was investigated using primary rat hepatocytes. The PVLA-b-PNIPAAm brushes exhibited hepatocyte adhesion and proliferation without FBS precoating. By reducing the temperature from 37 °C to 20 °C, the hepatocyte sheet was recovered from the copolymer brush. These results indicated that the prepared PVLA-b-PNIPAAm brushes can be utilized for effective hepatocyte sheet fabrication without the need for FBS precoating.

Preservation of growth factor sensitivity and bioactivity (e.g., bone morphogenetic protein-2 (BMP-2)) post-immobilization to tissue engineering scaffolds remains a great challenge. Here, we develop a stable and soft surface modification strategy to address this issue. BMP-2 (a model growth factor) is covalently immobilized onto homogeneous poly (glycidyl methacrylate) (PGMA) polymer brushes which are grafted onto substrate surfaces (Au, quartz glass, silica wafer, or common biomaterials) via surface-initiated atom transfer radical polymerization. This surface modification method multiplies the functionalized interfacial area; it is simple, fast, gentle, and has little effect on the loaded protein owing to the cilia motility. The immobilized BMP-2 (i-BMP-2) on the surface of homogeneous PGMA polymer brushes exhibits excellent bioactivity (⁓87% bioactivity of free BMP-2 in vitro and 20%–50% higher than scaffolds with free BMP-2 in vivo), with conformation and secondary structure well-preserved after covalent immobilization and ethanol sterilization. Moreover, the osteogenic activity of i-BMP-2 on the nanoline pattern (PGMA-poly (N-isopropylacrylamide)) shows ⁓110% bioactivity of free BMP-2. This is superior compared to conventional protein covalent immobilization strategies in terms of both bioactivity preservation and therapeutic efficacy. PGMA polymer brushes can be used to modify surfaces of different tissue-engineered scaffolds, which facilitates in situ immobilization of growth factors, and accelerates repair of a wide range of tissue types.

The modification of surfaces with various polymer chains through interactions involving strong covalent bonds is a current focal point. The relevance of this subject lies in the diversification of polymeric structures, particularly applicable in biomedical engineering and medicine. Presently, designs for drug carrier systems have reached an advanced stage, and novel polymer-based materials have been successfully synthesized. Polymeric brushes find applications in crucial medical areas such as artificial tissue engineering, implants, and biosensors. The advantages of polymeric brushes include their sensitivity to stimuli, a variety of polymer types and synthesis methods, tunability, and high biocompatibility. This study comparatively examines grafting approaches and polymerization techniques frequently encountered in the literature, highlighting their primary medical applications.

Polymer‐grafted hybrid materials have been ubiquitously employed in various engineering applications. The design of these hybrid materials with superior performances requires a molecularly detailed understanding of the structure and dynamics of the polymer brushes and their interactions with the grafting substrate. Molecular dynamics (MD) simulations are very well suited for the study of these materials which can provide molecular insights into the effects of polymer composition and length, grafting density, substrate composition and curvatures, and nanoconfinement. However, few existing tools are available to generate such systems, which would otherwise reduce the barrier of preparation for such systems to enable high throughput simulations. Here polyGraft, a general, flexible, and easy to use Python program, is introduced for automated generation of molecular structure and topology of polymer grafted hybrid materials for MD simulations purposes, ranging from polymer brushes grafted to hard substrates, to densely grafted bottlebrush polymers. polyGraft is openly accessible on GitHub (https://github.com/nanogchen/polyGraft). [ABSTRACT FROM AUTHOR]

Slippery covalently‐attached liquid surfaces (SCALS) with low contact angle hysteresis (CAH, <5°) and nanoscale thickness display impressive anti‐adhesive properties, similar to lubricant‐infused surfaces. Their efficacy is generally attributed to the liquid‐like mobility of the constituent tethered chains. However, the precise physico‐chemical properties that facilitate this mobility are unknown, hindering rational design. This work quantifies the chain length, grafting density, and microviscosity of a range of polydimethylsiloxane (PDMS) SCALS, elucidating the nanostructure responsible for their properties. Three prominent methods are used to produce SCALS, with characterization carried out via single‐molecule force measurements, neutron reflectometry, and fluorescence correlation spectroscopy. CO2 snow‐jet cleaning was also shown to reduce the CAH of SCALS via a modification of their grafting density. SCALS behavior can be predicted by reduced grafting density, Σ, with the lowest water CAH achieved at Σ≈2. This study provides the first direct examination of SCALS grafting density, chain length, and microviscosity and supports the hypothesis that SCALS properties stem from a balance of layer uniformity and mobility. [ABSTRACT FROM AUTHOR]

Hydrogel-like structures are responsible for the low friction experienced by our joints when we walk or by our eyelids when we blink. At low loads, hydrogel contacts show extremely low friction that rises with velocity beyond a threshold speed. Here we combine mesoscopic simulations and experiments to test the polymer-relaxation hypothesis for this velocity dependence, where a velocity-dependent regime emerges when the perturbation of interfacial polymer chains occurs faster than their relaxation at high velocity. Our simulations quantitatively match the experimental findings, with a friction coefficient that rises with velocity to some power of order unity in the velocity-dependent regime. We show that the velocity-dependent regime is characterized by reorientation and stretching of polymer chains in the direction of shear, leading to an entropic stress that can be quantitatively related to the shear response. The detailed exponent of the power law in the velocity-dependent regime depends on how chains interact: We observe a power close to 1/2 for chains that can stretch, while pure reorientation leads to a power of unity. These results show that the friction of hydrogel interfaces can be engineered by tuning the morphology of near-surface chains. [ABSTRACT FROM AUTHOR]

Concentrated polymer brushes (CPBs) synthesized by advanced surface-initiated controlled radical polymerization have received increasing attention in the tribological field because CPBs in good solvents exhibit superlow friction phenomena under macroscopic severe sliding conditions. To realize tribological applications of CPBs, an understanding of the wear mechanisms of CPBs is required to develop a method to enhance their durability. In this study, an operando tribo-Raman spectroscopic experiment, which is an effective approach for revealing the wear mechanisms of tribo-materials, was conducted on the frictional interface between a polymethyl methacrylate (PMMA)-CPB and a bearing steel ball immersed in an ionic liquid (IL), which is a good solvent for PMMA-CPBs. From the operando tribo-Raman results, the concentrations and molecular structures of the PMMA-CPBs and IL at the frictional interface were found to be constantly changing with the sliding cycles during operation. Moreover, their time-dependent changes strongly affected the wear process and superlow friction phenomena of the PMMA-CPB lubricated with the IL. Consequently, our results suggest that controlling the degree of swelling of CPBs at frictional interface is an effective approach for realizing a durable-superlow frictional tribo-system of CPBs.

A simple and compact intensity-interrogated terahertz (THz) relative humidity (RH) sensing platform is successfully demonstrated in experiments on the basis of combining a porous polymer sensing membrane and a continuous THz electronic system. The RH-sensing membrane is fabricated by surface modification of a porous polymer substrate with hydrophilic and photosensitive copolymer brushes via a UV-induced graft-polymerization process. The intensity interrogation sensing scheme indicated that the power reduction of the 0.4 THz wave is dependent on the grafting density of the copolymer brushes and proportional to the RH percent levels in the humidity-controlled air-sealed chamber. This finding was verified by the water contact angle measurement. Based on the slope of the proportional relation, the best sensitivity of the hydrophilic surface-modified sensing membrane was demonstrated at 0.0423 mV/% RH at the copolymer brush density of 1.57 mg/mm3 grafted on the single side of the sensing membrane. The sensitivity corresponds to a detection limit of approximately 1% RH. The THz RH sensing membrane was proven to exhibit the advantages of low loss, low cost, flexibility, high sensitivity, high RH resolution, and a wide RH working range of 25–99%. Thus, it is a good candidate for novel applications of wearable electronics, water- or moisture-related industrial and bio-sensing. [ABSTRACT FROM AUTHOR]

The great success of controlled radical polymerizations has encouraged researchers to develop more facile and robust approaches for surface‐initiated polymerizations (SIPs) to fabricate polymer brushes, even for non‐experts. In recent years, external‐stimuli‐mediated radical polymerization methods have come to the fore as SIPs because of their less rigorous synthetic procedures and high controllability, which expand the opportunities for synthesizing macromolecules with desired chemical compositions and structures, as well as tailor‐made polymers and bioconjugates that show broad applicability and physiological compatibility. This review discusses the latest developments in surface‐initiated polymerization methods, in particular, external‐stimuli mediated atom transfer radical polymerization (ATRP), photo‐induced polymerizations, and reversible addition‐fragmentation chain transfer (RAFT) polymerization, as well as other methods and their combination for the application in surface grafting. The implementation of these methods is of great interest due to their unique possibilities to temporally control a polymerization process, fast and straightforward polymerization, and environmentally benign features, which lead to established and emerging applications in biolubrication, antifouling, and biosensing. [ABSTRACT FROM AUTHOR]

During oil and gas drilling in deep complex formations, the technical requirements of high temperature and salt-resistance of drilling fluid should be met. In this paper, a polymer brush lubricant (HLM) for water-based drilling fluids was prepared using methyl methacrylate, lauryl acrylate and 2-hydroxyethyl acrylate as the main raw materials and 2-methylpropionitrile as the initiator. The HLM was characterized by means of Fourier infrared spectroscopy, nuclear magnetic resonance spectroscopy, thermogravimetric analysis and gel chromatography. The compatibility of HLM with drilling fluids and the lubricity performance of HLM under high temperature, high salt and high density conditions were evaluated. The lubricity was further analyzed using a multifunctional material surface performance tester and a four-ball friction tester. The experimental results showed that HLM had a good thermal stability with a weight average molecular mass of 3494. HLM had good compatibility with the bentonite-based mud at room temperature and had essentially no effect on rheology. The temperature resistance can reach 260 ℃.When concentration of HLM was 2%, the lubrication coefficient reduction rates were 91.16% under room temperature, 88.24% after ageing at 260 ℃, 75.69% for the saturated salt-based mud, and larger than 40% in the high-density drilling mud. The multifunctional material surface performance experiment further demonstrated that HLM could substantially reduce metal-to-metal friction. The four-ball friction experiment demonstrated that HLM could form a stable lubricating film on metal surfaces. Since HLM had multiple adsorption sites and strong adsorption capacity, the adsorption film still had high strength under high temperature and high salt conditions, giving HLM good lubricating properties. This paper can provide technical reference for the construction of drilling fluids for deep/ultradeep formations. [ABSTRACT FROM AUTHOR]

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Phthalocyanine pigments have many problems in waterborne coating applications because of their low polarity, poor dispersion in water, and easy agglomeration properties. In order to solve these problems, the phthalocyanine pigments were encapsulated with a copolymer of methyl methacrylate (MMA) and butyl acrylate (BA) by a mini-emulsion polymerization method. The pigments are effectively dispersed in water and have good compatibility with the resin. Concerning the bacterial reproduction and growth problem for the waterborne system, the resin-encapsulated phthalocyanine pigments were further grafted with antibacterial polymer poly(N-(2-hydroxyethyl) acrylamide) (PHEAA) on its surface using the photoemulsion polymerization technique. Comprehensive properties, including centrifugal stability and chromaticity change, were studied. The polymer encapsulation improved the centrifugal stability of the pigment. The thermogravimetric results showed that the residual mass of C.I. Pigment Green 7 (52.30%) was higher than that of C.I. Pigment Blue 15:3 (30.06%), and the sublimation fastness of PG7 was higher. The TEM results revealed that the shape of the PG7 after encapsulation and grafting was more regular than that of PB15:3. The L* of the pigment decreased after encapsulation but then increased after further grafting. The phthalocyanine pigment composite latex had good antibacterial properties after the grafting of PHEAA. [ABSTRACT FROM AUTHOR]

[Display omitted] • Polymer brush grafted films with different architectures were synthesized. • Combined method of electrodeposition and SI-PET-RAFT polymerization was employed. • Thickness, morphology, absorptivity, and electrochemistry of the films were studied. • Hyperbranched polymers exhibit compactness and ability to passivate brush gaps. • Hyperbranched polymer brushes are promising as protective thin coatings. Hyperbranched polymers, not only possess higher functionality, but are also easier to prepare compared to dendrimers and dendric polymers. Combining electrodeposition and surface-initiated photoinduced electron transfer-reversible addition-fragmentation chain transfer (SI-PET-RAFT) polymerization is hypothesized to be a novel strategy for preparing hyperbranched polymer films on conductive surfaces without degassing. Polymer brush grafted films with four different architectures (i.e. linear, branched, linear- block -branched, and branched- block -linear) were prepared on gold-coated glass substrates using electrodeposition, followed by SI-PET-RAFT polymerization. The resulting film structure and thickness, surface topology, absorption property, and electrochemical behavior were confirmed by spectroscopy, microscopy, microbalance technique, and impedance measurement. These hyperbranched polymer brushes were capable of forming a thicker but more uniformly covered films compared to linear polymer brush films, demonstrating that hyperbranched polymer films can be potentially useful for fabricating protective polymer coatings on various conductive surfaces. [ABSTRACT FROM AUTHOR]

Grafting of polymer brush (assembly of polymer chains tethered to the substrate by one end) is emerging as one of the most viable approach to alter the surface of inorganic nanomaterials. Inorganic nanomaterials despite their intrinsic functional superiority, their applications remain restricted due to their incompatibility with organic or biological moieties vis‐à‐vis agglomeration issues. To overcome such a shortcoming, polymer brush modified surfaces of inorganic nanomaterials have lately proved to be of immense potential. For example, polymer brush‐modified inorganic nanomaterials can act as efficient substrates/platforms in biomedical applications, ranging from drug‐delivery to protein‐array due to their integrated advantages such as amphiphilicity, stimuli responsiveness, enhanced biocompatibility, and so on. In this review, the current state of the art related to polymer brush‐modified inorganic nanomaterials focusing, not only, on their synthetic strategies and applications in biomedical field but also the architectural influence of polymer brushes on the responsiveness properties of modified nanomaterials have comprehensively been discussed and its associated future perspective is also presented. This article is categorized under:Diagnostic Tools > In Vivo Nanodiagnostics and ImagingTherapeutic Approaches and Drug Discovery > Emerging TechnologiesNanotechnology Approaches to Biology > Nanoscale Systems in Biology [ABSTRACT FROM AUTHOR]

With the intensification of the aging population and the development of transcatheter heart valve replacement technology (THVR), clinical demand for bioprosthetic valves is increasing rapidly. However, commercial bioprosthetic heart valves (BHVs), mainly manufactured from glutaraldehyde cross-linked porcine or bovine pericardium, generally undergo degeneration within 10-15 years due to calcification, thrombosis and poor biocompatibility, which are closely related to glutaraldehyde cross-linking. In addition, endocarditis caused by post-implantation bacterial infection also accelerates the failure of BHVs. Herein, a functional cross-linking agent bromo bicyclic-oxazolidine (OX-Br) has been designed and synthesized to crosslink BHVs and construct a bio-functionalization scaffold for subsequent in-situ atom transfer radical polymerization (ATRP). The porcine pericardium cross-linked by OX-Br (OX-PP) exhibits better biocompatibility and anti-calcification property than the glutaraldehyde-treated porcine pericardium (Glut-PP) as well as comparable physical and structural stability to Glut-PP. Furthermore, the resistance to biological contamination especially bacterial infection of OX-PP along with anti-thrombus and endothelialization need to be enhanced to reduce the risk of implantation failure due to infection. Therefore, amphiphilic polymer brush is grafted to OX-PP through in-situ ATRP polymerization to prepare polymer brush hybrid BHV material SA@OX-PP. SA@OX-PP has been demonstrated to significantly resist biological contamination including plasma proteins, bacteria, platelets, thrombus and calcium, and facilitate the proliferation of endothelial cells, resulting in reduced risk of thrombosis, calcification and endocarditis. Altogether, the proposed crosslinking and functionalization strategy synergistically achieves the improvement of stability, endothelialization potential, anti-calcification and anti-biofouling performances for BHVs, which would resist the degeneration and prolong the lifespan of BHVs. The facile and practical strategy has great potential for clinical application in fabricating functional polymer hybrid BHVs or other tissue-based cardiac biomaterials. Bioprosthetic heart valves (BHVs) are widely used in valve replacements for severe heart valve disease, and clinical demand is increasing year over year. Unfortunately, the commercial BHVs, mainly cross-linked by glutaraldehyde, can serve for only 10–15 years because of calcification, thrombus, biological contamination, and difficulties in endothelialization. Many studies have been conducted to explore non-glutaraldehyde crosslinkers, but few can meet high requirements in all aspects. A new crosslinker, OX-Br, has been developed for BHVs. It can not only crosslink BHVs but also serve as a reactive site for in-situ ATRP polymerization and construct a bio-functionalization platform for subsequent modification. The proposed crosslinking and functionalization strategy synergistically achieves the high requirements for stability, biocompability, endothelialization, anti-calcification, and anti-biofouling propeties of BHVs. [Display omitted] [ABSTRACT FROM AUTHOR]

Formation of plasmonic structure in closely packed assemblies of metallic nanoparticles (NPs) is essential for various applications in sensing, renewable energy, authentication, catalysis, and metamaterials. Herein, a surface-enhanced Raman scattering (SERS) substrate is fabricated for trace detection with ultrahigh sensitivity and stability. The SERS substrate is constructed from a simple yet robust strategy through in situ growth patterned assemblies of Au NPs based on a polymer brush templated synthesis strategy. Benefiting from the dense and uniform distribution of Au NPs, the resulting Au plasmonic nanostructure demonstrates a very strong SERS effect, while the outer polymer brush could restrict the excessive growth of Au NPs and the patterned design could achieve uniform distribution of Au NPs. As results, an ultra-low limit of detection (LOD) of 10−15 M, which has never been successfully detected in other work, is determined for 4-acetamidothiophenol (4-AMTP) molecules and the Raman signals in the random region show good signal homogeneity with a low relative standard deviation (RSD) of 7.2%, indicating great sensitivity and reliability as a SERS substrate. The LOD values of such Au plasmonic nanostructures for methylene blue, thiram, and R6G molecules can also reach as low as 10−10 M, further indicating that the substrate has a wide range of applicability for SERS detection. With the help of finite difference time domain simulations (FDTD) calculation, the electric field distribution of the Au plasmonic nanostructures is simulated, which quantitatively matches the experimental observations. Moreover, the Au plasmonic nanostructures show good shelf stability for at least 10 months of storage in an ambient environment, indicating potentials for practical applications. [ABSTRACT FROM AUTHOR]

[Display omitted] Specific ion effects govern myriad biological phenomena, including protein–ligand interactions and enzyme activity. Despite recent advances, detailed understanding of the role of ion hydrophobicity in specific ion effects, and the intersection with hydrotropic effects, remains elusive. Short chain fatty acid sodium salts are simple amphiphiles which play an integral role in our gastrointestinal health. We hypothesise that increasing a fatty acid's hydrophobicity will manifest stronger salting-out behaviour. Here we study the effect of these amphiphiles on an exemplar thermoresponsive polymer brush system, conserving the carboxylate anion identity while varying anion hydrophobicity via the carbon chain length. Ellipsometry and quartz crystal microbalance with dissipation monitoring were used to characterise the thermoresponse and viscoelasticity of the brush, respectively, whilst neutron reflectometry was used to reveal the internal structure of the brush. Diffusion-ordered nuclear magnetic resonance spectroscopy and computational investigations provide insight into polymer-ion interactions. Surface sensitive techniques unveiled a non-monotonic trend in salting-out ability with increasing anion hydrophobicity, revealing the bundle-like morphology of the ion-collapsed system. An intersection between ion-specific and hydrotropic effects was observed both experimentally and computationally; trending from good anti-hydrotrope towards hydrotropic behaviour with increasing anion hydrophobicity, accompanying a change in hydrophobic hydration. [ABSTRACT FROM AUTHOR]

[Display omitted] Modifying surfaces with concentrated polymer brushes (CPBs) is an effective way to reduce friction of tribo-pairs lubricated with liquids. We investigate the hypothesis that colloids grafted with CPBs (hybrid colloids) can deposit onto tribo-substrates by varying the solvent quality with respect to the polymer, in order to obtain ultra-low coefficients of friction (CoFs), so-called superlubricity. Hybrid colloids are synthesized and characterized, and a dynamic light scattering compares their swellings in aqueous solutions of glycerol or polyethylene glycol. A mini-traction machine with viscoelastic tribo-pairs is used for lubrication experiments. Adsorption of colloids and film structures are tested using a quartz crystal microbalance and an atomic force microscope. The solvent controls whether hybrid colloids spontaneously adsorb to the substrate under quiescent conditions or require contact forces to enable (tribo-)deposition. In both cases, the friction in the boundary-mixed lubrication regimes is lower upon increasing the degree of swelling of CPBs and upon increasing coverage of deposited colloids. The greatest lubrication enhancement and surface coverage occur for the spontaneously adsorbed colloids, with ultra-low CoFs of order 10-3 over a large range of speeds. The results demonstrate the potential for hybrid colloids to be used as solvent dispersible "friction modifier additives". [ABSTRACT FROM AUTHOR]

Development of point-of-care (POC) diagnostic tools is an emerging area with significant potential for disease surveillance, monitoring, and diagnosis, especially for underdeveloped or developing countries. Our current research focuses on rapid, POC technologies for DNA or RNA detection that can be deployed to significantly decrease the turnaround time when encountering demands for massive quantities of tests, e.g. during a pandemic. Hairpin-like DNA or molecular beacon (MB) probes can be used as bioreceptors to specifically bind to a pathogen DNA or RNA. In the presence of complementary DNA, the immobilized MBs undergo a conformational change, and the fluorescent signal of 5’-FAM is restored from the internally quenched fluorophore. Here we studyinvestigating 3D polymer brush (PB) structures with antifouling surface properties, functionalized with a particular MB-DNA probe. Patterns of polymer brushes were created on foils of poly(ethylene-co-tetrafluoroethylene) (ETFE) activated through a metal mask using extreme ultraviolet (EUV) radiation, yielding patterns of initiators for the subsequent graft-copolymerization of vinylpyrrolidone (VP) and glycidyl methacrylate (GMA). The successful copolymerization of VP and GMA on the EUV-exposed areas was proved based on characteristic peaks of VP and GMA in ATR-IR spectra. Structure heights in the range of micrometers were achieved, which enables binding of considerably higher densities of probe molecules compared to monolayer systems. The grown polymer brush structures provide both hydrophilicity, beneficial to minimize bio-fouling, and epoxide functional groups for further functionalization. These were biotinylated and functionalized with streptavidin and 3′-biotinylated MBs, resulting in a promising platform for fluorescence-based DNA detection as demonstrated by significant fluorescence increase upon addition of target DNA down to nM concentrations. Finally, embedding of optimized MB/PB structures into a microfluidic channel and coupling to a mobile-phone-based fluorescence microscope for signal detection was demonstrated.

During the last few decades, thermoresponsive materials for modulating cell adhesion have been investigated for the application of tissue engineering. In this study, we developed thermoresponsive mixed polymer brushes consisting of poly(N-isopropylacrylamide) (PNIPAAm) and poly(N,N-dimethylaminopropylacrylamide) (PDMAPAAm). The mixed polymer brushes were prepared on a glass substrate via the reversible addition-fragmentation chain transfer polymerization of DMAPAAm and subsequent atom transfer radical polymerization of NIPAAm. The mixed polymer brushes grafted to glass exhibited increased cationic properties by increasing the grafted PDMAPAAm length. The shrinking and extension of PNIPAAm exposed and concealed PDMAPAAm, respectively, indicating that the surface cationic properties can be controlled by changing the temperature. At 37 ​°C, the prepared mixed polymer brushes enhanced cell adhesion through their electrostatic interactions with cells. They also exhibited various thermoresponsive adhesion and detachment properties using various types of cells, such as mesenchymal stem cells. Temperature-controlled cell adhesion and detachment behavior differed between cell types. Using the prepared mixed polymer brush, we separated MSCs from adipocytes and HeLa cells by simply changing the temperature. Thus, the thermoresponsive mixed polymer brushes may be used to separate mesenchymal stem cells from their differentiated or contaminant cells by altering the temperature.

Polyethersulfone (PES) polymers are useful for a variety of membranes' bio-related applications. However, due to its failure to satisfy certain performance and biocompatibility standards, PES requires further surface modification. Herein, we report a facile and flexible method of PES membrane modification by combining the synthesis of silicon oxide nanoparticles grafted with polyvinylpyrrolidone (PVP) as hydrophilic macromolecules via reversible addition fragmentation chain-transfer polymerization (RAFT) and aminated polyethersulfone. The blending of polyethersulfone-modified membranes with SiO2@PVP and aminated polyethersulfone results in a robust, hydrophilic, and biocompatible surface. This research work uniquely uses this strategy to stabilize the existence of the hydrophilic modifiers (SiO2@PVP and aminated polyethersulfone) within the membrane matrix. Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) are used to analyze the prepared polymer brush and the modified membranes. The modified membranes demonstrate high pure water flux at 345 ​L ​m−2 ​h−1 and bovine serum albumin (BSA) rejection at 98 ​%. The prepared membranes also show favorable hydrophilicity with a contact angle of 46.8° compared with pristine polyethersulfone at 79°. Furthermore, the modified membranes demonstrate an acceptable degree of blood biocompatibility according to partial thromboplastin time (APTT), prothrombin time (PT), thrombin time (TT), and fibrinogen (FIB) concentration analysis. Based on inductively coupled plasma optical emission spectroscopy (ICP-OES), the silicon nanoparticle leaching in permeate is in a safe range. Accordingly, the modified polyethersulfone membrane is safe and suitable for hemodialysis and bio-related applications. [ABSTRACT FROM AUTHOR]

We study the role of temperature on the structure of pure polymer brushes and their mixture with attractive nanoparticles in flat and cylindrical geometries. It has previously been established that the addition of such nanoparticles causes the polymer brush to collapse and the intensity of the collapse depends on the attraction strength, the nanoparticle diameter, and the grafting density. In this work, we carry out molecular dynamics simulation under good solvent conditions to show how the collapse transition is affected by the temperature, for both plane grafted and inside-cylinder grafted brushes. We first examine the pure brush morphology and verify that the brush height is insensitive to temperature changes in both planar and cylindrical geometries, as expected for a polymer brush in a good solvent. On the other hand, for both system geometries, the brush structure in the presence of attractive nanoparticles is quite responsive to temperature changes. Generally speaking, for a given nanoparticle concentration, increasing the temperature causes the brush height to increase. A brush which contracts when nanoparticles are added eventually swells beyond its pure brush height as the system temperature is increased. The combination of two easily controlled external parameters, namely, concentration of nanoparticles in solution and temperature, allows for sensitive and reversible adjustment of the polymer brush height, a feature which could be exploited in designing smart polymer devices. [ABSTRACT FROM AUTHOR]

[Display omitted] We demonstrate an approach to examine the local segmental dynamics of a polymer near the interface of an inorganic filler by observing the rotational dynamics of the fluorescent probe at the chain ends of polymer brushes grafted onto the surface of the filler particles. Localization of the fluorescent probe was realized by designing and synthesizing fluorophore-tethered polystyrene (PS) brushes anchored on the surface of silica particles of controlled sizes. Fluorophore-functionalized telechelic PS with an azide functionality at the other chain end was achieved via a combination of atom transfer radical polymerization and post-polymerization modification. The azide-bearing PS chains were tethered to alkyne-functionalized particles via copper-catalyzed cycloaddition reaction. The molecular weight of the grafted polymer chains was controlled to be less than the critical entanglement molecular weight, and the chain density was controlled to be low enough so that the observed dynamics was not perturbed by the polymer brush conformation and brush-matrix polymer entanglement. The polymer dynamics near the surface of the particles at low concentrations was closely examined in the bulk film geometry by employing imaging rotational fluorescence correlation microscopy (irFCM). The observed polymer dynamics near the interface were not altered in the inorganic/polymer composite geometry when the surface did not have favorable interaction with the matrix polymer. The presented rational design of the chemical route and examination of local dynamics highlight a feasible approach to construct material systems with high complexities towards a deeper understanding of composite materials. [ABSTRACT FROM AUTHOR]

We performed molecular dynamics simulations to characterize the role of enthalpic interaction in impacting the static and dynamic properties of solvent-free polymer brushes. The intrinsic enthalpic interaction in the simulation was introduced using different attraction strengths between distinct species. Two model systems were considered: one consisting of binary brushes of two different polymer types and the other containing a mixture of homopolymer brushes and free molecules. In the first system, we observed that, when two originally incompatible polymers were grafted to opposing surfaces, the miscibility between them was significantly enhanced. A less favorable intrinsic enthalpic interaction in the brushes resulted in a more stretched chain configuration, a lower degree of inter-brush penetration, and faster segmental relaxation. In the second system, we characterized the solvent capacity of the homopolymer brushes from variations in the energy components of the system as a function of the number of free molecules. We determined that molecular absorption was driven by the release of the entropic frustration for the grafted chains in conjunction with the chemical affinity between the solutes and polymers. The solute distribution function within the inter-wall space showed that solute–polymer mixing in the middle of the gap occurred preferentially when the enthalpic interaction was more favorable. When this was not the case, absorption was predominantly localized near the grafting surface. From the mean square displacement of the solute, we found that the brush profiles restrained the molecular diffusion perpendicular to the grafting wall; the weaker the attraction from the brush, the higher the solute mobility. [ABSTRACT FROM AUTHOR]

[Display omitted] • A dual-functionalizable furan-containing polymer brush-coated magnetic nanoparticle is synthesized. • Orthogonal functionalization using Diels-Alder and Azide-Alkyne cycloaddition is demonstrated. • Drug-conjugated targeted nanoparticle platforms are obtained using the dual-functionalizable polymer brush-coated nanoparticle. Effective methods of multi-functionalization of nanomaterials are essential for fabricating effective targeted drug delivery systems. Herein, we disclose the fabrication of polymer brush-coated magnetic nanoparticles that could be functionalized with drugs and targeting ligands through orthogonal click reactions. In particular, polymers containing electron-rich furan groups as functionalization handles are grown from the surface of magnetic nanoparticles using the 'graft-from' approach. Furthermore, azide groups are installed at the chain end of polymer brushes to furnish an orthogonally functionalizable system. The attachment of maleimide-containing fluorescent dyes and cytotoxic drugs using the Diels-Alder reaction is demonstrated. Drug-conjugated nanoparticles functionalized with integrin-targeting peptide using the azide-alkyne cycloaddition reaction undergo preferential uptake in cancer cells and show dose-dependent cytotoxicity. We envision that the modularly functionalizable system disclosed here could target various cancer cells using an appropriate combination of drugs and targeting groups. [ABSTRACT FROM AUTHOR]

[Display omitted] • A dual-functionalizable thiolactone-based polymer brush-coated magnetic nanoparticle is synthesized. • Functionalization in a reversible and non-reversible manner is obtained on the nanoparticle. • Redox-responsive cargo containing targeted nanoparticle platforms are obtained. Polymer brush-coated magnetic nanoparticles have been used in many applications, from localized drug delivery to imaging. In this study, polymer brush-coated iron oxide magnetic nanoparticles were synthesized using reversible addition-fragmentation chain transfer polymerization, and the dual-reactive feature was added to the polymeric coating by employing thiolactone units as side chains. In particular, first, thiolactone-containing N , N -dimethylacrylamide-based copolymers bearing a catechol end group were synthesized. A 'graft-to' approach was investigated to anchor these polymers onto the surface of magnetic iron oxide nanoparticles. Alternatively, to increase the amount of polymer coating, a 'graft-from' approach was followed, where a trithiocarbonate-based chain transfer agent group anchored to the nanoparticle using a catechol group was employed to grow polymer brushes. After obtaining the dual-functionalizable polymer brush-coated nanoparticles, the thiolactone group was reacted with an azide group containing amine to obtain a clickable group, and the newly formed thiol group was capped with pyridyl disulfide to obtain a thiol-exchangeable unit. A fluorescent thiol-bearing hydrophobic dye was conjugated onto the polymer-coated nanoparticles using a thiol-disulfide exchange reaction. The clickable azide groups were reacted with a cell adhesive cyclic peptide using the metal-free strain-promoted azide-alkyne cycloaddition (SPAAC) reaction. It was demonstrated that the fluorescent nanoparticles with the targeting group were internalized preferentially by breast cancer cells. One can envision that such dual-functionalizable polymer brush-coated magnetic nanoparticles would be attractive nanomaterials for a variety of biomedical applications. [ABSTRACT FROM AUTHOR]

Autonomous and heteronomous switchable selectivity for electrochemical reactions was examined in an electrolyte solution containing pyrocatechol (PC) and dopamine (DA) using a fabricated thermo- and photo-responsive poly(N-isopropylacrylamide) (PNIPA)-modified cup-stacked carbon nanofiber (CSCNF) electrode. PNIPA can be autonomously and reversibly switched by environmental temperature changes between hydrophilic expanded coil structure and hydrophobic collapsed globule structure. CSCNFs as the electrode materials can effectively convert absorbed external near-infrared (NIR) light into heat. Although the molecular size of DA is larger and the octanol-water partition coefficient of DA is smaller than those of PC, both PC and DA could permeate to the CSCNF electrode surface through the expanded coil structure of the PNIPA layer at 25 ˚C, which temperature is below the lower critical solution temperature (LCST), causing their electrochemical signal readout. In contrast, transport of DA to the electrode surface was selectively suppressed by exposing the polymer to temperature at 45 ˚C, which value is above the LCST, or NIR light irradiation (> 940 nm, ca. 77 mW cm–2) to the CSCNF electrode surface even at 25 ˚C due to the steric hindrance and hydrophobicity of collapsed globule structure of the polymer layer. This resulted in the preferential electrochemical signal of PC. The switchable sensitivity of the electrode also allowed it to be successfully demonstrated for the simultaneous determination of PC and DA even at a single transducer, though electrode arrays with different sensitivity and selectivity are widely used for the determination of multiple chemicals simultaneously. • Selectivity control of electrochemical responses by external stimuli. • Thermo- and photo-switchable electrodes modified with phase transition polymers. • Chemical separation and determination of catechol derivatives. [ABSTRACT FROM AUTHOR]

Extracted from Platycodon grandiflorum , platycodon grandiflorum polysaccharides (PGPs) with diverse biological functions have been extensively employed for modification and fabrication of hydrogels for biomedical applications, such as wound dressings. However, since the lack of effective structural design, the reported polysaccharide-based hydrogel dressings are still suffered from structural failures and limited bio-functionality. Herein, we demonstrate a facile and general strategy to fabricate a supramolecular hydrogel composed of PGP-based polymer brush as building blocks combined with a Ca2+-mediated self-assembly process. The specific polymer brush with high branch functionality was achieved with polyacrylamide arms evenly grown on the PGP (grafting efficiency as high as 80 %) with series of chemical modifications. With above structural merits, the resulting hydrogel with densely crosslinked polymer brush featured enhanced mechanical strength as well as self-healing, and shear-thinning behaviors. Further biocompatible investigation indicated the as-prepared hydrogels with admirable performances in self-adhesion (adhesive strength of 16.7–79.5 kPa), a pH-responsive swelling ratio as high as 44 at pH 5.4, and pH-responsive degradation. They also showed antioxidant capacity by scavenging DPPH activity of nearly 80 % in 20 min, hemocompatibility, cell viability and cell migration. Impressively, the PGP-based polymer brush hydrogel served as a wound dressing revealed significant acceleration on wound closure. [ABSTRACT FROM AUTHOR]

• SMA copolymer brush-based HPLC stationary phases were exploited and developed. • Sil-SMA-DGME and Sil-SMA-EHOE chromatographic columns were successfully fabricated. • They were successfully used for identification of lipids from human lung cancer cells. Styrene-maleic acid (SMA) copolymer has received much attention for its excellent solubilization characteristics. In this work, SMA copolymer brush-based chromatographic stationary phases were exploited and developed for the first time. First, SMA copolymer brush was in situ grown on the surface of spherical silica via living/controlled reversible addition-fragmentation chain transfer (RAFT) polymerization method. Subsequently, as a proof-of-concept demonstration, the copolymer was esterified by diethylene glycol mono-2-ethylhexyl ether (DGME) and 2-(2-ethylhexyloxy) ethanol (EHOE), respectively. The obtained Sil-SMA-DGME and Sil-SMA-EHOE copolymer-brush chromatographic stationary phases were characterized by transmission electron microscopy, Fourier transform infrared spectrometer, X-ray photoelectron spectroscopy, and thermogravimetric analysis, respectively. The chromatographic retention mechanism indicated that both the two packed columns exhibited hydrophilic/reverse mixed-mode retention modes. The maximum column efficiency was up to 71,000 N/m. The chromatographic separation performance evaluation indicated that the novel kind of stationary phases had excellent separation capabilities for hydrophilic, hydrophobic compounds and phospholipid standards. In addition, by combination with mass spectrometry identification, the Sil-SMA-DGME column was further exploited for separation and identification of phospholipids in human lung cancer cells. Totally, 9 classes including 186 phospholipid species were successfully identified. The results demonstrated the promising application prospects of the novel kind of SMA copolymer-brush chromatographic stationary phases. [ABSTRACT FROM AUTHOR]

The existing methods for exosome isolation, such as ultracentrifugation, size exclusion, and affinity separation, suffer from some limitations. Herein, we aimed to develop temperature-modulated exosome-capturing materials using thermoresponsive polymers and peptides with affinity for exosomes. Poly(2-hydroxyethyl methacrylate-co-propargyl acrylate)-b-poly(N-isopropylacrylamide) (P(HEMA-co-PgA)-b-PNIPAAm) was grafted on silica beads via a two-step process of activator regenerated by electron transfer atom transfer radical polymerization. Peptides with affinity for exosomes were conjugated to the propargyl group of the bottom P(HEMA-co-PgA) segment of the copolymer via a click reaction. The prepared copolymer-grafted beads were characterized by elemental analysis, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, gel permeation chromatography, and the turbidity of the polymer solution. Results indicated that the copolymer and peptide were successfully modified on the silica beads. Exosomes from SK-BR-3 ​cells, a human breast cancer cell line, were selectively captured on the prepared beads at 37 ​°C, as the upper PNIPAAm segment shrank and the affinity between the peptide and exosome was enhanced. Upon lowering the temperature to 4 ​°C, the captured exosomes were released from the copolymer brush because of the extension of the PNIPAAm segment that reduced the affinity between peptides and exosomes. These findings demonstrated that the prepared copolymer brush-grafted silica beads can capture and release targeted exosomes via temperature modulation. Taken together, the developed copolymer brush-grafted silica beads would be useful for the separation of exosomes using simple procedures such as temperature modulation.

Polyethersulfone (PES) polymers are useful for a variety of membranes' bio-related applications. However, due to its failure to satisfy certain performance and biocompatibility standards, PES requires further surface modification. Herein, we report a facile and flexible method of PES membrane modification by combining the synthesis of silicon oxide nanoparticles grafted with polyvinylpyrrolidone (PVP) as hydrophilic macromolecules via reversible addition fragmentation chain-transfer polymerization (RAFT) and aminated polyethersulfone. The blending of polyethersulfone-modified membranes with SiO2@PVP and aminated polyethersulfone results in a robust, hydrophilic, and biocompatible surface. This research work uniquely uses this strategy to stabilize the existence of the hydrophilic modifiers (SiO2@PVP and aminated polyethersulfone) within the membrane matrix. Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) are used to analyze the prepared polymer brush and the modified membranes. The modified membranes demonstrate high pure water flux at 345 ​L ​m−2 ​h−1 and bovine serum albumin (BSA) rejection at 98 ​%. The prepared membranes also show favorable hydrophilicity with a contact angle of 46.8° compared with pristine polyethersulfone at 79°. Furthermore, the modified membranes demonstrate an acceptable degree of blood biocompatibility according to partial thromboplastin time (APTT), prothrombin time (PT), thrombin time (TT), and fibrinogen (FIB) concentration analysis. Based on inductively coupled plasma optical emission spectroscopy (ICP-OES), the silicon nanoparticle leaching in permeate is in a safe range. Accordingly, the modified polyethersulfone membrane is safe and suitable for hemodialysis and bio-related applications.