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Understanding the adsorption features of polymer microgels with different chemical compositions and structures is crucial in studying the mechanisms of respective emulsion stabilization. Specifically, the use of stimuli-responsive particles can introduce new properties and broaden the application range of such complex systems. Recently, we demonstrated that emulsions stabilized by microgels composed of interpenetrating networks (IPNs) of poly-N-isopropylacrylamide (PNIPAM) and polyacrylic acid (PAA) exhibit higher colloidal stability upon heating compared to PNIPAM homopolymer and other relevant PNIPAM-based copolymer counterparts. In the present work, using pendant drop tensiometry, we studied the evolution of water–tetradecane interfacial tension during the adsorption of PNIPAM-PAA IPN particles, comparing them with single-network P-(NIPAM-co-AA) and PNIPAM microgels. The results showed that, despite having the same chemical composition, copolymer particles exhibit completely different adsorption behavior in comparison to other microgel architectures. The observed disparity can be attributed to the nonuniform distribution of charged acrylic acid groups within the P-(NIPAM-co-AA) network obtained through precipitation polymerization. Oppositely, the presence of IPN architecture provides a uniform distribution of different monomers inside respective microgels. Additionally, hydrogen bonding between PNIPAM and PAA subchains appears to reduce the electrostatic energy barrier, enhancing the ability of IPN particles to successfully cover the liquid interface. Overall, our findings confirm the efficiency of using PNIPAM-PAA IPN microgels for the preparation of oil-in-water emulsions and their stability, even when the temperature rises above the lower critical solution temperature of PNIPAM. [ABSTRACT FROM AUTHOR]

Sorption‐based atmospheric water harvesting (SAWH) has great potential for clean water acquisition and renewable energy use. Adsorption and desorption properties of sorbents play a crucial role in SAWH systems. However, most sorbents with high adsorption capacities are hindered by either slow sorption/desorption kinetics or poor regeneration performance. Here, a highly efficient block copolymer composite sorbent with dual functions of thermo‐responsive and photothermal properties is designed based on rape pollens. This sorbent has a hierarchical porous structure, in which the outermost layer of poly‐pyrrole enables it to convert light energy into heat and the second layer of poly(N‐isopropylacrylamide) imparts thermo‐responsive properties to improve the desorption ability. Meanwhile, confined LiCl improves its sorption capacity and cavities of the pollen can store captured moisture to avoid liquid leakage. This sorbent can sorb moisture to more than 144% of its own weight within 3 h under 20 °C&80% relative humidity (RH) and 82% of captured water can be released within 0.5 h under 1 sun. The water harvester using this sorbent can realize an exceptional water productivity of up to 2.21gwater gsorbent−1 day−1 only by three continuous water adsorption‐desorption cycles in a day. The high‐performance sorbent smooths the path for efficiently extracting water from the atmosphere to tackle water scarcity. [ABSTRACT FROM AUTHOR]

Smart microgels can be used as sorbents, possessing high surface area and rapid stimuli‐responsiveness. A series of poly(N‐isopropylacrylamide) (pNIPAM) and pNIPAM‐co‐starch nanoparticles (pNIPAM‐co‐SNPs) thermo‐responsive microgels were synthesized, presenting different hydrophilic/hydrophobic behavior according to the composition. The adsorption studies were carried out for methylparaben (MPB), ethylparaben (EPB), propylparaben (PPB), butylparaben (BPB), and bisphenol A (BPA), and the extraction and desorption efficiency were determined by high‐performance liquid chromatography and spectrophotometric detection (HPLC‐UV). The effect of microgel phase transition according to the temperature and the copolymerization with SNPs in each sorptive step was investigated. The extraction of less polar compounds (BPA, PPB, and BPB) above the volume phase transition temperature (VPTT) was favored, driven by a predominant hydrophobic interaction. According to microgel composition, the desorption capacity as a function of temperature can be influenced by hydrophilic interactions and water competition. Molecular dynamics (MD) simulations and binding free energy calculations were performed to provide theoretical evidence about binding energies between pNIPAM and BPA, which experimentally showed the best extraction efficiency results. These findings may provide a strategy for designing high‐performance sorptive phases that could remove hydrophilic and hydrophobic compounds from water and a hypothesis about the driving forces of such processes. [ABSTRACT FROM AUTHOR]

Materials with ultra‐fast responsive properties are essential for various applications. Among the responsive materials, poly(N‐isopropylacrylamide) (PNIPAM) stands out due to its well‐studied temperature‐responsive properties. Improving the kinetics of the responsive properties of PNIPAM is, however, still essential for advancing its practical use. Here, the responsive rate of PNIPAM hydrogels is enhanced by first incorporating sub‐micrometer porosity into the material through polymerization‐induced phase separation (PIPS), followed by introducing millimeter scale pores via 3D printing, thereby rendering the material with hierarchical porosity. The 3D‐printed porous PNIPAM structures show accelerated swelling and deswelling, when compared to non‐porous PNIPAM structures, due to enhanced water permeability associated with the continuous network of micrometer to millimeter‐sized pores. Additionally, thinner polymer structures result in faster temperature response rates. At the same time, the mechanical strength of PNIPAM hydrogels with high porosity and thinner polymer walls is not compromised, overcoming the common trade‐off between swelling and mechanical properties. [ABSTRACT FROM AUTHOR]

Smart materials for drug delivery are designed to offer a precise and controlled release of therapeutic agents. By responding to specific physiological stimuli, such as changes in temperature and pH, these materials improve treatment efficacy and minimize side effects, paving the way for personalized therapeutic solutions. In this study, we present the fabrication of dual-responsive alginate/poly(N-isopropylacrylamide) (PNIPAM) microspheres, having the ability to respond to both pH and temperature variations and embedding the lipophilic bioactive compound Ozoile. Ozoile® Stable Ozonides is obtained from extra virgin olive oil and acts as an inducer, interacting with major biological pathways by means of modulating the systemic redox balance. The dual-responsive microspheres are prepared by electrospray technique without the use of organic solvents. PNIPAM is synthesized by radical polymerization using the APS/TEMED redox initiators. The microspheres are further optimized with a chitosan coating to enhance their stability and modulate the degradation kinetics of the gel matrix. A comprehensive morphological analysis, Fourier transform infrared (FTIR) spectroscopy, and degradation assays are conducted to confirm the structural stability and pH-responsive behavior of the hydrogel microspheres. A study of the volume phase transition temperature (VPTT) by differential scanning calorimetry (DSC) is used to assess the microsphere thermal response. This research introduces a promising methodology for the development of targeted drug delivery systems, which are particularly useful in the context of oxidative stress modulation and inflammation management. [ABSTRACT FROM AUTHOR]

In this study, poly(n-isopropylacrylamide) (PNIPA) has been synthesized by the free-radical polymerization method using azobisisobutyronitrile the initiator. Then, nanoparticle-PNIPA composite is prepared with magnetic iron oxide (Fe3O4) nanoparticles synthesized by co-precipitation. The thermal decomposition kinetics of synthesized PNIPA and nanocoated PNIPA have been investigated. It has been observed that nanocoated PNIPA has a more stable structure at high temperatures than synthesized PNIPA. In the newly improved model equations relate to thermal decomposition kinetics, a special solution has been made with the new approach. Moreover, the calculated activation energies of the samples have been evaluated with response surface methodology (RSM). The ratios required to synthesize nanocoated-PNIPA under the optimum conditions have been determined by RSM. The activation energy of the nanocomposite obtains when 0.3170 g PNIPA is coated with 0.048 g Fe3O4 nanoparticle is determined as 127.757 kJ/mol. In other words, nanocoating has been increased the thermal stability of the synthesized composite. Poly (n-isopropylacrylamide) has been synthesized by free radical polymerization The Fe-O stretching vibration proves the existence of nanoparticle in FTIR spectra The thermal decomposition kinetics of synthesized PNIPA and Fe3O4-PNIPA nanocomposite have been evaluated by RSM. Magnetic nanoparticle reinforcement enhances the thermal stability of PNIPA [ABSTRACT FROM AUTHOR]

The development of temperature-sensitive sensors upgraded by poly(N-isopropylacrylamide) (PNIPAM) represents a significant stride in enhancing performance and tailoring thermoresponsiveness. In this study, an array of temperature-responsive electrochemical sensors modified with different PNIPAM-based copolymer films were fabricated via a "coating and grafting" two-step film-forming technique on screen-printed platinum electrodes (SPPEs). Chemical composition, grafting density, equilibrium swelling, surface wettability, surface morphology, amperometric response, cyclic voltammograms, and other properties were evaluated for the modified SPPEs, successively. The modified SPPEs exhibited significant changes in their properties depending on the preparation concentrations, but all the resulting sensors showed excellent stability and repeatability. The modified sensors demonstrated favorable sensitivity to hydrogen peroxide and L-ascorbic acid. Furthermore, notable temperature-induced variations in electrical signals were observed as the electrodes were subjected to temperature fluctuations above and below the lower critical solution temperature (LCST). The ability to reversibly respond to temperature variations, coupled with the tunability of PNIPAM's thermoresponsive properties, opens up new possibilities for the design of sensors that can adapt to changing environments and optimize their performance accordingly. [ABSTRACT FROM AUTHOR]

Förster resonance energy transfer (FRET) is ubiquitous in optical processes in the natural world. A methodology is proposed that uses an optical force to control its efficiency without contact in an aqueous solution of a thermo‐responsive polymer, polyvinyl methyl ether (PVME). Focusing irradiation of a near infrared laser beam into the solution results in the formation and trapping of a single polymer droplet. The polymer concentration in the droplet is controllable by changing the optical force from the laser light is shown. The polarity inside the droplet decreases with increasing the optical force. When small amounts of dye molecules, D (energy donor) and A (energy accepter), are dissolved in the polymer solution, D and A are absorbed (extracted) into the droplet. The concentrations of D and A are controllable by the optical force. Based on this mechanism, FRET between D and A is induced successfully, and can control the FRET efficiency. Finally, the modulation of fluorescence color of the droplet from blue, green, yellow, to an orange color is demosntrated simply by changing the optical force. The concept and technique are unique and will open a new channel to develop droplet chemistry and photochemistry. [ABSTRACT FROM AUTHOR]

A temperature‐responsive surface‐enhanced Raman scattering (SERS) substrate with "ON–OFF" switching based on poly(ionic liquid)s (PILs) block copolymer microgels have been designed and synthesized. The PIL units act as a joint component to anchor the gold nanoparticles (AuNPs) and analytes onto poly(N‐isopropylacrylamide) (PNIPAm). This anchor allows the analytes to be fixed at the formed hot spots under temperature stimulus. Owing to the regulation of the PNIPAm segment, the SERS substrates exhibit excellent thermally responsive SERS activity with a reversible "ON–OFF" effect. Additionally, because of the anion exchange of PILs, microgels can introduce new analytes, which offers more flexibility for the system. The substrate shows excellent reversibility, controllability, and flexibility of SERS activity, which is expected to have a broad application in the field of practical SERS sensors. [ABSTRACT FROM AUTHOR]

In the present work, we describe the fabrication of a thermosensitive hydrogel. To fabricate the hydrogel (Sq1@PNIPAAm), we opted to use biocompatible poly(N-isopropylacrylamide) (PNIPAM) and squaraine dye (Sq1) as the polymer and the crosslinker, respectively. It is noteworthy that Sq1@PNIPAAm can be loaded with fluorescein, and we evaluated the fluorescein release behavior of Sq1@PNIPAAm hydrogel. We noted that on demand sustainable release of fluorescein was feasible upon gradual heating of Sq1@PNIPAAm hydrogel. Furthermore, Sq1@PNIPAAm hydrogels can be used as photosensitizers pertinent to photodynamic therapy (PDT). Our results show that hydrogel possesses favorable biological safety for use in in vitro anticancer studies. In vitro experiments confirmed that Sq1@PNIPAAm hydrogels could kill over 40% of cancer cells. Overall, we have successfully shown that Sq1@PNIPAAm enabled photodynamic therapy. Moreover, fluorescein loading into Sq1@PNIPAAm was possible, and it could be used to successfully accomplish temperaturecontrolled on-demand release. Given the abundance of low-cost, commercially accessible monomers available for use in hydrogel synthesis, this method offers access to a wide range of functional hydrogels for use in biomedical applications. [ABSTRACT FROM AUTHOR]

Understanding the adsorption features of polymer microgels with different chemical compositions and structures is crucial in studying the mechanisms of respective emulsion stabilization. Specifically, the use of stimuli-responsive particles can introduce new properties and broaden the application range of such complex systems. Recently, we demonstrated that emulsions stabilized by microgels composed of interpenetrating networks (IPNs) of poly-N-isopropylacrylamide (PNIPAM) and polyacrylic acid (PAA) exhibit higher colloidal stability upon heating compared to PNIPAM homopolymer and other relevant PNIPAM-based copolymer counterparts. In the present work, using pendant drop tensiometry, we studied the evolution of water–tetradecane interfacial tension during the adsorption of PNIPAM-PAA IPN particles, comparing them with single-network P-(NIPAM-co-AA) and PNIPAM microgels. The results showed that, despite having the same chemical composition, copolymer particles exhibit completely different adsorption behavior in comparison to other microgel architectures. The observed disparity can be attributed to the nonuniform distribution of charged acrylic acid groups within the P-(NIPAM-co-AA) network obtained through precipitation polymerization. Oppositely, the presence of IPN architecture provides a uniform distribution of different monomers inside respective microgels. Additionally, hydrogen bonding between PNIPAM and PAA subchains appears to reduce the electrostatic energy barrier, enhancing the ability of IPN particles to successfully cover the liquid interface. Overall, our findings confirm the efficiency of using PNIPAM-PAA IPN microgels for the preparation of oil-in-water emulsions and their stability, even when the temperature rises above the lower critical solution temperature of PNIPAM.

Epoxidized natural rubber (ENR) grafted Poly(N-isopropylacrylamide) (ENR-g-PNIPAM) hydrogel was exploited by classic free radical polymerization, which exhibited practical potential for temperature-sensitive material. Free ENR was introduced in the ENR-g-PNIPAM hydrogel to construct a secondary network that will form chain entanglement and further improve the chemical and physical properties of the hydrogel. The renewable ENR and a facile fabrication process make large-scale production of the ENR-g-PNIPAM hydrogel possible and prompt its commercial value. The content of ENR was systematically varied and studied to ensure optimal ratio. Among various compositions examined, the 7:3 weight ratio of ENR/NIPAM in the hydrogel(70ENR) exhibited excellent properties. Additionally, a simple scheme was also designed for fabricating multifunctional ENR-g-PNIPAM/polypyrrole/cotton (EPPC) composites with simultaneous adsorption of Cr (VI) and electrothermal conversion. The EPPC composites demonstrated good adsorption capacity with 127 mg/g at pH = 2 in an aqueous solution containing 100 mg/L Cr (VI), while also functioning as a thermistor with enhanced sensitivity. The adsorption data can be better described by the pseudo-second-order kinetic model and the Freundlich isotherm model, indicating that the adsorption was a chemical and multilayer. Benefiting from these research results, enabling the synthesized hydrogel a crucial role in terms of Cr (VI) treatment and thermal sensor. [ABSTRACT FROM AUTHOR]

Objectives: This study aimed to present an innovative method for synthesizing pH-thermo-glucose responsive poly(NIPA-co-DMAEMA)-PBA hydrogel nanoparticles via single-step aqueous free radical polymerization. Methods: The synthesis process involved free radical polymerization in an aqueous solution, and the resulting nanoparticles were characterized for their physical and chemical properties by 1H NMR, Dynamic Light Scattering (DLS) and Scanning Electron Microscopy (SEM). Insulin-loaded poly(NIPA-co-DMAEMA)-PBA hydrogel nanoparticles were prepared and evaluated for their insulin capture and release properties at different pH and temperature, in addition to different glucose concentrations, with the release profile of insulin quantitatively evaluated using the Bradford method. Results: 1H NMR results confirmed successful PBA incorporation, and DLS outcomes consistently indicated a transition to a more hydrophobic state above the Lower Critical Solution Temperature (LCST) of NIPA and DMAEMA. While pH responsiveness exhibited variation, insulin release generally increased with rising pH from acidic to neutral conditions, aligning with the anticipated augmentation of anionic PBA moieties and increased hydrogel hydrophilicity. Increased insulin release in the presence of glucose, particularly for formulations with the lowest mol % PBA, along with a slight increase for the highest mol % PBA formulation when increasing glucose from 1 to 4 mg/mL, supported the potential of this approach for nanoparticle synthesis tailored for glucose-responsive insulin release. Conclusions: This work successfully demonstrates a novel method for synthesizing responsive hydrogel nanoparticles and underscores their potential for controlled insulin release in response to glucose concentrations. The observed pH-dependent insulin release patterns and the influence of PBA content on responsiveness highlight the versatility and promise of this nanoparticle synthesis approach for applications in glucose-responsive drug delivery systems. Poly(NIPA) nanoparticles containing PBA moieties are normally synthesized in two or more steps in the presence of organic solvents. Here we propose a new method for the synthesis of multiresponsive hydrogel poly(NIPA-co-DMAEMA)-PBA nanoparticles in aqueous medium in a single reaction to provide a fast and effective strategy for the production of glucose-responsive multi-systems in aqueous media from free radical polymerization [ABSTRACT FROM AUTHOR]

Smart hydrogels responsive to external stimuli are promising for various applications such as soft robotics and smart devices. High mechanical strength and fast response rate are particularly important for the construction of hydrogel actuators. Herein, tough hydrogels with rapid response rates are synthesized using vinyl‐functionalized poly(N‐isopropylacrylamide) (PNIPAM) microgels as macro‐crosslinkers and N‐isopropylacrylamide as monomers. The compression strength of the obtained PNIPAM hydrogels is up to 7.13 MPa. The response rate of the microgel‐crosslinked hydrogels is significantly enhanced compared with conventional chemically crosslinked PNIPAM hydrogels. The mechanical strength and response rate of hydrogels can be adjusted by varying the proportion of monomers and crosslinkers. The lower critical solution temperature (LCST) of the PNIPAM hydrogels could be tuned by copolymerizing with ionic monomer sodium methacrylate. Thermo‐responsive bilayer hydrogels are fabricated using PINPAM hydrogels with different LCSTs via a layer‐by‐layer method. The thermo‐responsive fast swelling and shrinking properties of the two layers endow the bilayer hydrogel with anisotropic structures and asymmetric response characteristics, allowing the hydrogel to respond rapidly. The bilayer hydrogels are fabricated into clamps to grab small objects and flowers that mimicked the closure of petals, and it shows great application prospects in the field of actuators. [ABSTRACT FROM AUTHOR]

The potential of photoactive Prussian blue nanoparticles dispersed in thermo‐responsive PNIPAM hydrogels in 4D printing using a stereolithography is investigated with digital light processing. The proportion of Prussian blue nanoparticles used in the resin is chosen to deliver a significant photothermal effect providing a heating above the volume phase transition temperature of the final nanocomposite hydrogels; while, giving only a limited effect on light scattering during the 3D printing process. Four formulations with various amounts of Prussian blue nanoparticles are used to print 3D structures with different shapes, such as Aztec pyramids, cylinders, gyroid porous cubes, and porous films. The shrinkage effect triggered by light irradiation at 808 nm on the as‐obtained nanocomposite hydrogels is demonstrated through the delivery of a representative molecule fluorescein and a triggered 4D shape‐morphing effect. [ABSTRACT FROM AUTHOR]

Cyclic polymers have many interesting properties compared to their linear analogs, but there are very few examples of their synthesis. This is because most cyclic polymers have been synthesized by stepwise processes, including synthesizing homo- or hetero-telechelic end-functionalized precursor polymers and consecutive intramolecularly coupling of both ends of the polymers. This requires a complicated synthesis, and the product yields are very low because the target cyclic polymers are usually synthesized under highly dilute conditions, consequently, making it difficult to systematically analyze the properties of cyclic polymers. In the present research, we have synthesized cyclic polymers using a ring expansion polymerization method. Particularly, the ring expansion RAFT polymerization (RE-RAFT polymerization) that we have developed using a cyclic chain transfer agent is a smart method that can synthesize cyclic polymers very efficiently. In this paper, we successfully synthesized cyclic-poly(N-isopropylacrylamide), which is widely known as a thermo-responsive polymer, by RE-RAFT polymerization. Furthermore, we have compared the thermo-responsive properties of the cyclic-poly(N-isopropylacrylamide)s with those of their linear analogs.

Bacterial adhesion and biofilm formation on the surface of titanium implants are the main causes of implant-associated infection. An antibacterial coating on the implant surface can reduce the risk of biofilm formation. The aim of this study was to investigate the bactericidal effects of a van-comycin-loaded polymer coated on an implant surface. For this purpose, poly(N-isopropylacrylamide) (PNIPAAm) was first synthesized as a homopolymer or by co-polymerization with acrylamide (PNIPAAm-AAm) at a 5% weight ratio. Then, thin and uniform polymer coatings were prepared using the spin coating technique. The degree of surface hydro-philicity of the polymer coatings was evaluated by measuring the water contact angle (CA). For the antibacterial tests, the polymer-coated surfaces were loaded with vancomycin. The tests were performed in three conditions: on a glass surface (control), on a PNIPAAm-AAm-coated surface, and on a PNIPAAm-AAm-coated surface loaded with vancomycin. The death rates of the bacteria in contact with the coated surfaces were evaluated at different temperatures with fluorescence microscopy. A scanning electron microscopy (SEM) analysis of cross sections of the polymer coatings revealed a uniform thin film of approximately 200 nm in thickness. The water contact angle analysis performed at different temperatures revealed that the polymer-coated surfaces were more hydrophobic (CAs ranging between 53° and 63°) than the uncoated glass surface (CA ranging between 15° and 35°). The bacterial death rate, measured at 40 °C or while continuously switching the temperature between 37 °C and 40 °C, was higher in the presence of the surface coated with vancomycin-loaded PNIPAAm-AAm than when using the other surfaces (p-value ≤ 0.001). The vancomycin-loaded polymer coating evaluated in this study exhibited effective antibacterial properties when the polymer reached the phase transition temperature.

Understanding the complex interactions between polymers and surfactants is required to optimise commercially relevant systems such as paint, toothpaste and detergent. Neutral polymers complex with surfactants, forming 'pearl necklace' structures that are often conceptualised as pseudo-polyelectrolytes. Here we pose two questions to test the limits of this analogy: Firstly, in the presence of salt, do these polymer-surfactant systems behave like polyelectrolytes? Secondly, do polymer-surfactant complexes resist geometric confinement like polyelectrolytes? We test the limits of the pseudo-polyelectrolyte analogy through studying a poly(N -isopropylacrylamide) (PNIPAM) brush in the presence of sodium dodecylsulfate (SDS). Brushes are ideal for interrogating pseudo-polyelectrolytes, as neutral and polyelectrolyte brushes exhibit distinct and well understood behaviours. Spectroscopic ellipsometry, quartz crystal microbalance with dissipation monitoring (QCM-D), and neutron reflectometry (NR) were used to monitor the behaviour and structure of the PNIPAM-SDS system as a function of NaCl concentration. The ability of the PNIPAM-SDS complex to resist geometric confinement was probed with NR. At a fixed SDS concentration below the zero-salt CMC, increasing NaCl concentration <100 mM promoted brush swelling due to an increase in osmotic pressure, not dissimilar to a weak polyelectrolyte. At these salt concentrations, the swelling of the brush could be described by a single parameter: the effective CMC. However, at high NaCl concentrations (e.g., 500 mM) no brush collapse was observed at all (non-zero) concentrations of SDS studied, contrary to what is seen for many polyelectrolytes. Study of the polymer-surfactant system under confinement revealed that the physical volume of surfactant dominates the structure of the strongly confined system, which further differentiates it from the polyelectrolyte case. [ABSTRACT FROM AUTHOR]

In this work, we investigate a synthesis method for novel systems that involve the use of gold nanotriangles arrays (AuNTs) coated with poly(N-isopropylacrylamide) (pNIPAM) brushes, designed as smart platforms for the reversible confinement of bio-particles. Initially, we employed cost-effective nanosphere lithography to fabricate gold nanotriangles arrays. Next, polymer initiator groups were attached to the AuNTs surface through a spontaneous reduction approach, enabling exclusive functionalization of pNIPAM on the gold surface. Finally, we utilized surface-initiated atom transfer radical polymerization to graft pNIPAM brushes onto the gold surface. We systematically investigated the polymer initiator groups' grafting time and the polymerization time to control the thickness of the grafted pNIPAM brushes. Subsequently, we characterized the thermoresponsive properties of these hybrid structures using Atomic Force Microscopy (AFM) measurements, evaluating their ability to undergo on/off adsorption and desorption of polystyrene (PS) beads on their surface. Indeed, the combination of the thermosensitive pNIPAM polymer with AuNTs arrays results in the development of a precisely regulated two-dimensional active device which exhibits tunable properties with external temperature changes, making it a versatile platform suitable for a wide range of applications. [ABSTRACT FROM AUTHOR]

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In this study, artificial neural networks (ANNs) and genetic algorithms (GAs) are employed together to design optimized polymeric structures with superior cloud points. The database from a previous study of polymer synthesis with thermoresponsive polymers was used to create ANN-based models, which enabled the formulation and solution of the inverse problem using the GA. The regressors, with an average RMSE of less than 0.7 °C, were used in the polymer evolution process over 20 generations. Mutation and selection operations led to the creation of 10 novel hybrid macromolecules with an average cloud point of 80 °C. Furthermore, the special roles of some chemical groups are recognized and favor the structural mapping of PNIPAM-based materials. The computational approach presented here demonstrates that it is a promising tool in the development of new materials. [ABSTRACT FROM AUTHOR]

[Display omitted] The stability of purely aqueous emulsions (W/W) formed by mixing incompatible polymers, can be achieved through the Pickering effect of particles adsorption at the interface. However, there is, as yet, no guideline regarding the chemical nature of the particles to predict whether they will stabilize a particular W/W emulsion. Bis-hydrophilic soft microgels, made of copolymerized poly(N -isopropylacrylamide) (pNIPAM) and dextran (Dex), act as very efficient stabilizers for PEO/Dextran emulsions, because the two polymers have an affinity for each polymer phase. The ratio between both components of the microgels is varied in order to modulate the bis-hydrophilic balance, the content of Dex compared to pNIPAM varying from 0 to 60 wt%. The partition between the two aqueous phases and the adsorption of microgels at the W/W interface is measured by confocal microscopy. The stability of emulsions is assessed via turbidity measurements and microstructural investigations under sedimentation or compression. The adsorption of particles and their partitioning is found to evolve progressively as a function of bis-hydrophilic balance. At room temperature, the stability of the resulting W/W emulsions also depends on the bis-hydrophilic balance with a maximum of stability for the particles containing 50%wt of Dex, for the Dex-in-PEO emulsions, while the PEO-in-Dex become stable above this value. The thermo-responsiveness of the microgels translates into stability inversion of the emulsions below 50 wt% of Dex in the microgels, whereas above 50 wt%, no emulsion is stable. This work paves the way of a guideline to design efficient and responsive W/W stabilizers. [ABSTRACT FROM AUTHOR]

A freeze-resistant PNIPAM-based smart window with simultaneous regulation of solar and thermal radiation, which further improves the energy efficiency of the window and broadens its application range, showing good potential for reducing building energy consumption. [Display omitted] Adaptive regulation of solar and thermal radiation by windows in diverse (hot and cold) climates is essential to reduce building energy consumption. However, conventional hydrogel-based thermochromic smart windows lack thermal radiation regulation, and have difficulty to combine high solar regulation with excellent freezing resistance. It is challenging to integrate the above performance into one hydrogel-based thermochromic window. Here, we firstly prepared poly(N-isopropylacrylamide- co -N, N-dimethylacrylamide)/ethylene glycol (PNDE) hydrogels with tunable and excellent freezing resistance (below −100 °C) by adding the anti-freezing agent ethylene glycol, and assembled PNDE hydrogels, polyvinylidene fluoride and polymethyl methacrylate-silver nanowires panels into a freezing-resistant smart window with solar and thermal radiation regulation (STR). PNDE hydrogels had an excellent thermochromic performance with luminous transmittance (T lum) of 89.3 %, solar regulation performance (Δ T sol) of 80.7 % and tunable phase change temperature (τ c , 22–44 °C). The assembled STR window showed high T lum of 68.2 %, high Δ T sol of 62.6 %, suitable τ c of ∼30 °C and freezing resistance to low temperature of −27 °C. Moreover, the different thermal emissivity (0.94 and 0.68) of the two sides of the STR window gave it the ability of radiative cooling in hot climates and warm-keeping in cold climates. Compared to the conventional thermochromic windows, the STR window promotes heat dissipation in hot conditions while reduces heat loss in cold conditions and is applicable to diverse climates, which is a promising energy-saving device for reducing building energy consumption. [ABSTRACT FROM AUTHOR]

The hard-healing chronic wounds of diabetics are still one of the most intractable problems in clinical skin injury repair. Wound microenvironments directly affect wound healing speed, but conventional dressings exhibit limited efficacy in regulating the wound microenvironment and facilitating healing. To address this serious issue, we designed a thermo-sensitive drug-controlled hydrogel with wound self-adjusting effects, consisting of a sodium alginate (SA), Antheraeapernyi silk gland protein (ASGP) and poly(N-isopropylacrylamide) (PNIPAM) for a self-adjusting microenvironment, resulting in an intelligent releasing drug which promotes skin regeneration. PNIPAM has a benign temperature-sensitive effect. The contraction, drugs and water molecules expulsion of hydrogel were generated upon surpassing lower critical solution temperatures, which made the hydrogel system have smart drug release properties. The addition of ASGP further improves the biocompatibility and endows the thermo-sensitive drug-controlled hydrogel with adhesion. Additionally, in vitro assays demonstrate that the thermo-sensitive drug-controlled hydrogels have good biocompatibility, including the ability to promote the adhesion and proliferation of human skin fibroblast cells. This work proposes an approach for smart drug-controlled hydrogels with a thermo response to promote wound healing by self-adjusting the wound microenvironment. [ABSTRACT FROM AUTHOR]

The continuous and irresponsible addition of environmental pollutants into aqueous reservoirs due to excessive industrialization is a significant contemporary challenge. Nanomaterial-based catalytic reduction provides an effective way to convert these materials into environmentally useful products. Responsive polymeric assemblies, complemented with nanomaterials, represent advanced nanocatalysts that are gaining interest within the scientific community. These assemblies exhibit reversible morphological transitions in response to variations induced by external factors such as temperature, pH, or electromagnetic irradiation treatment. The term hybrid microgels has been coined for assemblies that contain both nanomaterial and smart polymeric components. This review presents recent advancements in the field of hybrid microgels as nanocatalysts for conducting reduction reactions on pollutants present in aqueous media. Apart from placing detailed emphasis on the advancements documented for these assemblies, the fundamentals associated with hybrid microgels, as well as the typical catalytic reduction, are also emphasized to develop an understanding for new academicians looking to explore this field. The author hopes that this critical review of the most recent academic literature, including the years spanning 2020 to 2023, will serve as a tutorial for the identification of research gaps in this field, along with its prospective solutions. [ABSTRACT FROM AUTHOR]

Hydrogels, composed of hydrophilic homopolymer or copolymer networks, have structures similar to natural living tissues, making them ideal for applications in drug delivery, tissue engineering, and biosensors. Since Wichterle and Lim first synthesized hydrogels in 1960, extensive research has led to various types with unique features. Responsive hydrogels, which undergo reversible structural changes when exposed to stimuli like temperature, pH, or specific molecules, are particularly promising. Temperature-sensitive hydrogels, which mimic biological processes, are the most studied, with poly(N-isopropylacrylamide) (PNIPAm) being prominent due to its lower critical solution temperature of around 32 °C. Additionally, pH-responsive hydrogels, composed of polyelectrolytes, change their structure in response to pH variations. Despite their potential, conventional hydrogels often lack mechanical strength. The double-network (DN) hydrogel approach, introduced by Gong in 2003, significantly enhanced mechanical properties, leading to innovations like shape-deformable DN hydrogels, organic/inorganic composites, and flexible display devices. These advancements highlight the potential of hydrogels in diverse fields requiring precise and adaptable material performance. In this review, we focus on advancements in the field of responsive acrylamide-based hydrogels with IPN structures, emphasizing the recent research on DN hydrogels.

This report describes the influence of polymer particle purification on the in situ generation of gold nanoparticles (AuNPs) and their catalytic properties. The use of purified polymer particles after radical polymerization solely yields the generation of smaller and more uniform AuNPs (average diameter from ~ 5 nm to ~ 14 nm), despite controlling the gold ions and reducing agent ratios. However, unpurified polymer particles allow for the formation of relatively larger and slightly polydisperse AuNPs (average diameter from ~ 14 to ~ 29 nm) with an elongated shape. Although the interactions between the AuNPs and polymer matrices are known to be very weak, the presence of additional hydrophilic small molecular species, including oligomers and unreacted monomers, readily disturbs the growth of AuNPs. Regardless of the purification, highly stable AuNPs are successfully incorporated across the polymer particles where the representative composite particles are tested as catalysts in the aerobic homocoupling of arylboronic acid. Although the experimental activation energy was examined to be very similar (56–57 kJ/mol), the turnover frequency was detectably different (~ 46/h and ~ 69/h for the composite particles possessing elongated AuNPs and ~ 58/h and ~ 81/h for the composite particles possessing uniform AuNPs). However, the composite particles possessing the uniform AuNPs have shown a greater catalytic reactivity (e.g., 30% higher yields) toward base-free homocoupling reactions. The influence of polymer particle purification is evident in the generation of AuNPs in situ, as well as their catalytic properties in the chemical reaction, which offers an interesting insight for designing various metal-polymer composite particles. [ABSTRACT FROM AUTHOR]

Temperature is a widely incorporated stimulus in pharmaceutical applications because of its efficiency as a therapeutic medium; thus, substantial evidence on temperature‐responsive polymer applications is reported. Poly(N‐isopropylacrylamide) (PNIPAAm) is a well‐established, temperature‐responsive polymer that exhibits a low critical solution temperature (LCST) at ≈ 32°C, which is close to physiological temperature. Hence, they are widely used in various pharmaceutical applications, such as drug delivery with nanocarriers and thermogels. Varying the LCST for different applications can be achieved by copolymerization with other hydrophobic or hydrophilic molecules, making it a favorable smart polymer. PNIPAAm is reported to enhance drug delivery by incorporation with nanocarriers and to facilitate prolonged drug delivery, thereby avoiding the burst release of drugs in temperature‐responsive hydrogels. The application of PNIPAAm is not limited to drug delivery, and it is also applied in biomedical applications such as chromatography systems and cell culture applications, where its incorporation in cell culture media enhances cell production. The unique and versatile properties of PNIPAAm render it a promising smart polymer for various functional applications. Hence, this review focuses on the diverse applications of PNIPAAm. [ABSTRACT FROM AUTHOR]

Bacterial adhesion and biofilm formation on the surface of titanium implants are the main causes of implant-associated infection. An antibacterial coating on the implant surface can reduce the risk of biofilm formation. The aim of this study was to investigate the bactericidal effects of a van-comycin-loaded polymer coated on an implant surface. For this purpose, poly(N-isopropylacrylamide) (PNIPAAm) was first synthesized as a homopolymer or by co-polymerization with acrylamide (PNIPAAm-AAm) at a 5% weight ratio. Then, thin and uniform polymer coatings were prepared using the spin coating technique. The degree of surface hydro-philicity of the polymer coatings was evaluated by measuring the water contact angle (CA). For the antibacterial tests, the polymer-coated surfaces were loaded with vancomycin. The tests were performed in three conditions: on a glass surface (control), on a PNIPAAm-AAm-coated surface, and on a PNIPAAm-AAm-coated surface loaded with vancomycin. The death rates of the bacteria in contact with the coated surfaces were evaluated at different temperatures with fluorescence microscopy. A scanning electron microscopy (SEM) analysis of cross sections of the polymer coatings revealed a uniform thin film of approximately 200 nm in thickness. The water contact angle analysis performed at different temperatures revealed that the polymer-coated surfaces were more hydrophobic (CAs ranging between 53° and 63°) than the uncoated glass surface (CA ranging between 15° and 35°). The bacterial death rate, measured at 40 °C or while continuously switching the temperature between 37 °C and 40 °C, was higher in the presence of the surface coated with vancomycin-loaded PNIPAAm-AAm than when using the other surfaces (p-value ≤ 0.001). The vancomycin-loaded polymer coating evaluated in this study exhibited effective antibacterial properties when the polymer reached the phase transition temperature. [ABSTRACT FROM AUTHOR]

Temperature is a characteristic often correlated with environmental and health issues. This paper presents an organic thin film transistor (OTFT) based temperature sensor having a detection range of 30–45 °C, which, therefore, encompasses the human body temperature. The OTFT sensor featured thermosensitive poly(N-isopropylacrylamide) (PNIPAM) and pentacene as the gate dielectric and semiconductor, respectively. The PNIPAM film possessed a dielectric constant of 4.2 with very low leakage current density. The OTFT exhibited high electrical performance, with a hole mobility (μ) of 0.90 ± 0.04 cm2 V−1 s−1, a threshold voltage (Vth) of −15.4 ± 1.16 V, and an on/off ratio of 104. Significant changes in the drain current and the values of Vth and μ occurred when the temperature of the device was varied within the range 30–45 °C at an interval of 0.5 °C. The operating principle for this temperature sensor was based on the structural transformation of the PNIPAM dielectric and the enhanced charge transport of the pentacene semiconductor upon varying the temperature. Flexible OTFTs fabricated on polyethylene terephthalate substrate displayed hole mobilities as high as 0.39 ± 0.01 cm2 V−1 s−1, values of Vth of −18.6 ± 0.45, and on/off ratios of 102, and were workable for over 100 bending cycles.

Temperature is a characteristic often correlated with environmental and health issues. This paper presents an organic thin film transistor (OTFT) based temperature sensor having a detection range of 30–45 °C, which, therefore, encompasses the human body temperature. The OTFT sensor featured thermosensitive poly(N-isopropylacrylamide) (PNIPAM) and pentacene as the gate dielectric and semiconductor, respectively. The PNIPAM film possessed a dielectric constant of 4.2 with very low leakage current density. The OTFT exhibited high electrical performance, with a hole mobility (μ) of 0.90 ± 0.04 cm2 V−1 s−1, a threshold voltage (Vth) of −15.4 ± 1.16 V, and an on/off ratio of 104. Significant changes in the drain current and the values of Vth and μ occurred when the temperature of the device was varied within the range 30–45 °C at an interval of 0.5 °C. The operating principle for this temperature sensor was based on the structural transformation of the PNIPAM dielectric and the enhanced charge transport of the pentacene semiconductor upon varying the temperature. Flexible OTFTs fabricated on polyethylene terephthalate substrate displayed hole mobilities as high as 0.39 ± 0.01 cm2 V−1 s−1, values of Vth of −18.6 ± 0.45, and on/off ratios of 102, and were workable for over 100 bending cycles.

The thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) is widely applied in the biomedical field particularly as thermoresponsive substrate for culture of cells. To be used as a stimuli-responsive coating for cell culture, combining PNIPAM with glycosaminoglycans might be an effective approach to improve its bioactivity. In this study, chitosan is grafted with PNIPAM moieties (PCHI) possessing a cloud point at 31 ​°C and used as a polycation to fabricate thermoresponsive polyelectrolyte multilayers (PEM) with the bioactive polyanion chondroitin sulfate (CS) at pH 4 by layer-by-layer technique. The in-situ investigation by surface plasmon resonance and quartz crystal microbalance with dissipation monitoring confirms that the formation of PEMs with CS can be achieved despite the bulky structure of PCHI at 25 ​°C. The stability of the PEMs is further improved at physiological pH 7.4 by chemical crosslinking using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide. Moreover, these PEMs exhibit de-swelling and swelling ability with different surface wettability in response to temperature, which triggers the adsorption and desorption of adhesive protein vitronectin on the PEMs. At 37 ​°C, the PEMs containing PNIPAM particularly associated with CS terminal layer supports protein adsorption and consequently enhances cell adhesion using multipotent murine stem cells. Overall, due to improved stability, crosslinked PNIPAM-modified biogenic multilayers are cytocompatible and hold great potential as culture substrate for different tissue cells and application in tissue engineering.

Carbon-based nanomaterials, such as carbon nanotubes, fullerenes, nanodiamonds, and graphene, have been investigated for various biomedical applications, including biological imaging, photothermal therapy, drug/gene delivery, cancer therapy, biosensors, and electrochemical sensors. Graphene oxide (GO) has unique physicochemical properties and can be used to restore conductivity through oxidation. In this study, we developed poly(N-isopropylacrylamide) (PNIPAM)-based nanogel systems containing GO for controlled in vitro drug delivery. The photothermal effects of the PNIPAM/GO- and PNIPAMAAM/GO-based nanogel systems were enhanced. The release of DOX from the PNIPAM/GO-based nanogel was achieved using the photothermal effect of near-infrared irradiation. Using a Cell Counting Kit-8 assay, the cytotoxicity of all conditions demonstrated that the PNIPAM composite-based nanogels were biocompatible with no significance.

Over the past few decades, stimuli‐responsive materials have been widely applied to porous surfaces. Permeability and conductivity control of ions confined in nanochannels modified with stimuli‐responsive materials, however, have been less investigated. In this work, the permeability and conductivity control of ions confined in nanochannels of anodic aluminum oxide (AAO) templates modified with thermo‐responsive poly(N‐isopropylacrylamide) (PNIPAM) brushes are demonstrated. By surface‐initiated atom transfer radical polymerization (SI‐ATRP), PNIPAM brushes are successfully grafted onto the hexagonally packed cylindrical nanopores of AAO templates. The surface hydrophilicities of the membranes can be reversibly altered because of the lower critical solution temperature (LCST) behavior of the PNIPAM polymer brushes. From electrochemical impedance spectroscopy (EIS) analysis, the temperature‐gating behaviors of the AAO‐g‐PNIPAM membranes exhibit larger impedance changes than those of the pure AAO membranes at higher temperatures because of the aggregation of the grafted PNIPAM chains. The reversible surface properties caused by the extended and collapsed states of the polymer chains are also demonstrated by dye release tests. The smart thermo‐gated and ion‐controlled nanoporous membranes are suitable for future smart membrane applications. [ABSTRACT FROM AUTHOR]

A thermo-sensitive film composed of polycaprolactone and poly(N-isopropylacrylamide) was fabricated via electrospinning, with ketoconazole as the model drug. The morphology, elemental composition, and surface hydrophilicity of the nanofibres were characterized, and the results showed that nanofibres switched from a hydrophilic to a hydrophobic state as the temperature increased from 25 °C to 37 °C. The drug release profiles of the films suggested that sustained drug release behavior was achieved, and a lower temperature induced a faster delivery. Therefore, the prepared nanofibres could be highly applicable as wound dressings for on-demand and sustained drug release systems based on their temperature-responsive properties. [ABSTRACT FROM AUTHOR]

Most marketed HA-based dermal fillers use chemical cross-linking to improve mechanical properties and extend their lifetime in vivo; however, stiffer products with higher elasticity require an increased extrusion force for injection in clinical practice. To balance longevity and injectability, we propose a thermosensitive dermal filler, injectable as a low viscosity fluid that undergoes gelation in situ upon injection. To this end, HA was conjugated via a linker to poly(N-isopropylacrylamide) (pNIPAM), a thermosensitive polymer using "green chemistry", with water as the solvent. HA-L-pNIPAM hydrogels showed a comparatively low viscosity (G′ was 105.1 and 233 for Candidate1 and Belotero Volume®, respectively) at room temperature and spontaneously formed a stiffer gel with submicron structure at body temperature. Hydrogel formulations exhibited superior resistance against enzymatic and oxidative degradation and could be administered using a comparatively lower injection force (49 N and >100 N for Candidate 1 and Belotero Volume®, respectively) with a 32G needle. Formulations were biocompatible (viability of L929 mouse fibroblasts was >100% and ~85% for HA-L-pNIPAM hydrogel aqueous extract and their degradation product, respectively), and offered an extended residence time (up to 72 h) at the injection site. This property could potentially be exploited to develop sustained release drug delivery systems for the management of dermatologic and systemic disorders. [ABSTRACT FROM AUTHOR]

To meet the increasing global demand for energy, better recovery of crude oil from reservoirs must be achieved using methods that are economical and environmentally benign. Here, we have developed a nanofluid of amphiphilic clay-based Janus nanosheets via a facile and scalable method that provides potential to enhance oil recovery. With the aid of dimethyl sulfoxide (DMSO) intercalation and ultrasonication, kaolinite was exfoliated into nanosheets (KaolNS) before being grafted with 3-methacryloxypropyl-triemethoxysilane (KH570) on the Alumina Octahedral Sheet at 40 and 70 °C to form amphiphilic Janus nanosheets (i.e., KaolKH@40 and KaolKH@70). The amphiphilicity and Janus nature of the KaolKH nanosheets have been well demonstrated, with distinct wettability obtained on two sides of the nanosheets, and the KaolKH@70 was more amphiphilic than the KaolKH@40. Upon preparing Pickering emulsion in a hydrophilic glass tube, the KaolKH@40 preferentially stabilized emulsions, while the KaolNS and KaolKH@70 tended to form an observable and high-strength elastic planar interfacial film at the oil–water interface as well as films climbing along the tube's surface, which were supposed to be the result of emulsion instability and the strong adherence of Janus nanosheets towards tube's surface. Subsequently, the KaolKH was grafted with poly(N-Isopropylacrylamide) (PNIPAAm), and the prepared thermo-responsive Janus nanosheets demonstrated a reversible transformation between stable emulsion and the observable interfacial films. Finally, when the samples were subjected to core flooding tests, the nanofluid containing 0.01 wt% KaolKH@40 that formed stable emulsions showed an enhanced oil recovery (EOR) rate of 22.37%, outperforming the other nanofluids that formed observable films (an EOR rate ~13%), showcasing the superiority of Pickering emulsions from interfacial films. This work demonstrates that KH-570-modified amphiphilic clay-based Janus nanosheets have the potential to be used to improve oil recovery, especially when it is able to form stable Pickering emulsions. [ABSTRACT FROM AUTHOR]

[Display omitted] PNIPAM as a stimuli-responsive polymer has generated extreme interests due to its versatile applications. However, there is no research report on whether PNIPAM micro/nano-particles can be extracted from its suspension after phase separation. In the present work, LCST-type phase separation in self-synthesized PNIPAM/water system was investigated in depth by dividing the DLS testing process into four stages. In addition to quenching duration, temperature rise process, quenching temperature and PNIPAM concentration all have a great influence on particle size of the suspension. Meanwhile, the steady-state rheology and dynamic viscoelasticity results show that PNIPAM micro/nano-particles in the suspension are "soft" that can deform. Finally, FE-SEM was used to observe the morphology of dehydrated PNIPAM extracted by sessile droplet evaporation under different conditions. The results indicate that these "soft" particles are easier to fuse together, do not have sufficient mechanical strength to maintain their spherical morphology after dehydration. But the above fusion can be suppressed by adjusting evaporation conditions to acquire smaller PNIPAM particles which have sufficient mechanical properties to keep their basic particle morphology. Further, by changing evaporation pressure to positive or negative pressure, dehydrated PNIPAM micro/nano-particles with excellent uniformity and separation can be obtained. This work will provide guidance for extracting micro/nano-particles from polymer/diluent systems with LCST. [ABSTRACT FROM AUTHOR]

Several clinical studies have reported the benefit of the administration of Mesenchymal Stem Cells (MSCs) in cell therapies. However, their routine applications need new substrates to amplify MSCs in vitro according to Good Manufacturing Practices (GMP) conditions and microcarriers are particularly suited for these purposes. In order to optimize the surface properties of Cytodex I microcarriers (Cyt), poly N-isopropylacrylamide (pNIPAM) has been grafted on their surface to promote MSCs adhesion, proliferation, but also to control their detachment by a decrease in temperature. The polymer coating generated on the microcarriers was analyzed using Time-of-Flight, Nanoscale Secondary Ion Mass Spectrometry, and Atomic Force Microscopy. We have confirmed the success of the pNIPAM grafting on Cyt with a two-steps reaction and correlated the influence on matrix functionalization in the function of the organic solvent used to disperse the microcarriers. The effects of pNIPAM functionalization have been explored on Wharton's jelly-MSCs (WJ-MSCs) culture and cell thermal detachment was monitored with fluorescent microscopy. The in vitro results have indicated that WJ-MSCs have a better growth on Cyt-pNIPAM. However, pNIPAM thermal cell detachment was lower than trypsinization, implying that the minimum effective molecular weight and surface density of polymer chains have still to be future optimized. [ABSTRACT FROM AUTHOR]