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Renewable nanocellulose materials received increased attention owing to their small dimensions, high specific surface area, high mechanical characteristics, biocompatibility, and compostability. Nanocellulose coatings are among many interesting applications of these materials to functionalize different by composition and structure surfaces, including plastics, polymer coatings, and textiles with broader applications from food packaging to smart textiles. Variations in porosity and thickness of nanocellulose coatings are used to adjust a load of functional molecules and particles into the coatings, their permeability, and filtration properties. Mechanical stability of nanocellulose coatings in a wet and dry state are critical characteristics for many applications. In this work, nanofibrillated and nanocrystalline cellulose coatings deposited on the surface of polymer films and textiles made of cellulose, polyester, and nylon are studied using atomic force microscopy, ellipsometry, and T-peel adhesion tests. Methods to improve coatings' adhesion and stability using physical and chemical cross-linking with added polymers and polycarboxylic acids are analyzed in this study. The paper reports on the effect of the substrate structure and ability of nanocellulose particles to intercalate into the substrate on the coating adhesion.

Designing biomaterials capable of functioning in harsh environments is vital for a range of applications. Using molecular dynamics simulations, we show that conjugating lysozymes with a copolymer [poly(GMA- stat-OEGMA)] comprising glycidyl methacrylate (GMA) and oligo(ethylene glycol) methyl ether methacrylate (OEGMA) results in a dramatic increase of stability of these enzymes at high temperatures provided that the concentration of the copolymer in the close vicinity of the enzyme exceeds a critical value. In our simulations, we use triads containing the same ratio of GMA to OEGMA units as in our recent experiments (N. S. Yadavalli et al., ACS Catalysis, 2017, 7, 8675). We focus on the dynamics of the conjugate at high temperatures and on its structural stability as a function of the copolymer/water content in the vicinity of the enzyme. We show that the dynamics of phase separation in the water-copolymer mixture surrounding the enzyme is critical for the structural stability of the enzyme. Specifically, restricting water access promotes the structural stability of the lysozyme at high temperatures. We identified critical water concentration below which we observe a robust stabilization; the phase separation is no longer observed at this low fraction of water so that the water domains promoting unfolding are no longer formed in the vicinity of the enzyme. This understanding provides a basis for future studies on designing a range of enzyme-copolymer conjugates with improved stability.

The self-assembly of nanoparticles is an efficient and precise method to fabricate nanoscale devices. By manipulating iron oxide nanoparticles in suspension with an external field to form magnetically directed linear assemblies, we demonstrate the feasibility of using this structure to template the synthesis of PEDOT:PSS conducting polymer nanowires in suspension. Furthermore these conducting wires can be assembled on interdigitated electrodes to form an array of conducting nanowires.

The use of nanoparticles for targeted delivery of therapeutic agents to sites of injury or disease in the central nervous system (CNS) holds great promise. However, the biodistribution of nanoparticles following in vivo administration is often unknown, and concerns have been raised regarding potential toxicity. Using poly(glycidyl methacrylate) (PGMA) nanoparticles coated with polyethylenimine (PEI) and containing superparamagnetic iron oxide nanoparticles as a magnetic resonance imaging (MRI) contrast agent and rhodamine B as a fluorophore, whole animal MRI and fluorescence analyses are used to demonstrate that these nanoparticles (NP) remain close to the site of injection into a partial injury of the optic nerve, a CNS white matter tract. In addition, some of these NP enter axons and are transported to parent neuronal somata. NP also remain in the eye following intravitreal injection, a non-injury model. Considerable infiltration of activated microglia/macrophages occurs in both models. Using magnetic concentration and fluorescence visualization of tissue homogenates, no dissemination of the NP into peripheral tissues is observed. Histopathological analysis reveals no toxicity in organs other than at the injection sites. Multifunctional nanoparticles may be a useful mechanism to deliver therapeutic agents to the injury site and somata of injured CNS neurons and thus may be of therapeutic value following brain or spinal cord trauma., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

This paper focuses on the attachment of densely grafted polymer layers (polymer brushes) to various inorganic and polymeric substrates by the "grafting to" method. A brief overview of synthesis of polymer brushes by the method is first provided, with emphasis on chemical approaches to polymer attachment. The second part of the paper covers the synthesis of polymer layers via a recently developed macromolecular anchoring layer approach. Several examples of application of the grafting technique are presented for generation of hydrophobic, hydrophilic, gradient, and switchable surfaces., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Fluorescent silica nanoparticles decorated with a responsive shell, a mixed polymer brush, were synthesized. Specifically, a poly(2-vinylpyridine), P2VP, and poly(ethylene glycol), PEG, binary polymer brush was synthesized on silica nanoparticles via the "grafting to" technique. The selection of the components (PEG and P2VP) for the responsive brush shell was motivated by potential biomedical applications. Poly(glycidyl methacrylate), PGMA, labeled with Rhodamine B, RhB, was used to form a reactive and fluorescent shell on the nanoparticle surface. The interaction between the particles themselves and the particles and their environment can be precisely tuned by a change in pH. At lower pH, aqueous dispersions of the particles are stable, since PEG and P2VP are water-soluble, extended and contribute to the steric and electrostatic mechanisms of colloidal stability. An increase of pH to 6 causes a slow aggregation as a consequence of the hydrophobic attraction between the collapsed and almost nonprotonated P2VP macromolecules. The aggregation was well controlled and occurred within 90-120 min of the pH change. The aggregation was fully reversible after the decrease in pH. The pH variation did not quench the fluorescence of the colloidal suspensions. The pH-tunable aggregation of the fluorescent nanoparticles could find diverse applications for labeling and contrasting of cells and tissues when the size of the label and the intensity of the optical signals can be tuned by and related to the pH of the host environment.

Responsive polymer materials can adapt to surrounding environments, regulate transport of ions and molecules, change wettability and adhesion of different species on external stimuli, or convert chemical and biochemical signals into optical, electrical, thermal and mechanical signals, and vice versa. These materials are playing an increasingly important part in a diverse range of applications, such as drug delivery, diagnostics, tissue engineering and 'smart' optical systems, as well as biosensors, microelectromechanical systems, coatings and textiles. We review recent advances and challenges in the developments towards applications of stimuli-responsive polymeric materials that are self-assembled from nanostructured building blocks. We also provide a critical outline of emerging developments.

An effective approach is described for the synthesis of binary patterned polymer brushes using a combination of capillary force lithography and surface-initiated polymerization. First, the approach calls for an ultrathin polystyrene (PS) mask to be deposited, in a pattern, over a surface to which a layer of polymerization initiator has already been anchored. Next, surface-initiated atom transfer radical polymerization (ATRP) is performed. This can graft the initial polymer brush onto those areas of the surface unprotected by the PS mask. After grafting is complete, the PS mask is removed and a second brush is synthesized on the newly exposed areas.

In the scope of drug delivery, the transdermal route is desirable because it provides attainable therapeutic concentrations and has minimal systemic side effects. To make the skin a feasible route for the delivery of therapeutic agents, the biggest challenge is overcoming its natural coating. In this paper, we investigate the effect of the architectures (homopolymer vs. block copolymer vs. hybrid block–graft copolymer) of several amphiphilic polymeric derivatives of poly(2-oxazoline) on skin permeability. The block copolymers are composed of a hydrophobic poly(2-oxazoline) block and a hydrophilic PEG block. The hybrid block–graft copolymers are obtained by grafting hydrophobic side chains of polycaprolactone to a poly(2-oxazoline) backbone. We used the commercially available EpiDerm™ by MatTek, composed of human epidermal cells, as a model of human skin. Two parameters of skin permeation are reported: penetration rate and lag time. We hypothesize that the skin permeation characteristics correlate with the critical micelle concentration and particle size of the studied polymers, while both parameters are a function of the complex architectures of the presented macromolecular constructs. While homopolymer poly(2-oxazolines) show the least permeation, the block copolymers demonstrate partial permeation. The hybrid block–graft copolymers exhibited full penetration through the model skin samples. [ABSTRACT FROM AUTHOR]

Depolymerization of the addition polymer polystyrene to monomeric styrene is facilitated by mechanochemical processing at room temperature under ambient atmosphere. The reaction occurs in metal-based milling media in concert with scission of macromolecular chains that generates carbon-centered free-radicals detectable by EPR spectroscopy, even though the processing is performed in air. [ABSTRACT FROM AUTHOR]

We present a radio-frequency (RF) sensor and its measurement results of three volatile organic compounds (VOCs) at multiple frequency points from ~ 2 to ~ 11 GHz, which is a convenient range in our examination. The sensor is based on a simple RF interferometer and uses two coplanar waveguides (CPWs), A and B of 5 and 25 mm length, respectively, as VOC sensing electrodes. Approximately 70-nm-thick poly copolymer films are coated on CPW surfaces for VOC adsorption and concentration. It is shown that ethanol, acetone, and isopropyl (IPA) induce frequency-dependent RF responses, which are also VOC-dependent. Thus, the frequency-dependent properties provide a possible new approach for better VOC sensing selectivity. With CPW A, the limit-of-detections (LODs) are ~ 600 ppm for ethanol, ~ 270 ppm for acetone, and ~ 330 ppm for IPA at 9.29 GHz. With CPW B, the LODs are roughly four times better. These LODs are also better than most of other RF VOC sensor results. In the future work, it is promising to further improve RF sensitivity and selectivity significantly. [ABSTRACT FROM PUBLISHER]

Highlights: [•] Bioplastics from protein feedstock have advantages over traditional plastics, especially in areas such as packaging. [•] This article focuses on fabrication of binary bioplastics from whey, natural rubber latex and egg white albumin. [•] Whey based binary bioplastics can be fabricated by the thermoprocessing methods such as compression molding. [•] Natural latex and albumin containing amino acids with reactive groups make it potentially compatible with whey protein. [ABSTRACT FROM AUTHOR]

In situ characterization of minute amounts of fluidsthat rapidlychange their rheological properties is a challenge. In this paper,the rheological properties of fluids were evaluated by examining thebehavior of magnetic nanorods in a rotating magnetic field. We proposeda theory describing the rotation of a magnetic nanorod in a fluidwhen its viscosity increases with time exponentially fast. To confirmthe theory, we studied the time-dependent rheology of microdropletsof 2-hydroxyethyl-methacrylate (HEMA)/diethylene glycol dimethacylate(DEGDMA)-based hydrogel during photopolymerization synthesis. We demonstratedthat magnetic rotational spectroscopy provides rich physicochemicalinformation about the gelation process. The method allows one to completelyspecify the time-dependent viscosity by directly measuring characteristicviscosity and characteristic time. Remarkably, one can analyze notonly the polymer solution, but also the suspension enriched with thegel domains being formed. Since the probing nanorods are measuredin nanometers, this method can be used for the in vivo mapping ofthe rheological properties of biofluids and polymers on a microscopiclevel at short time intervals when other methods fall short. [ABSTRACT FROM AUTHOR]

A combination of structural and electrical characterization techniques was applied to polymer Ta capacitors with in situ and prepolymerized poly(3,4-ethylenedioxythiophene) (PEDOT) cathodes with a broad range of Ta[sub2]O[sub5] dielectric thicknesses. The in situ PEDOT was produced by polymerizing the EDOT monomer using an oxidizer/dopant. The prepolymerized material was an aqueous suspension of doped polymer which was dried to produce the PEDOT film. Experimental data show that polymer Ta capacitors with prepolymerized PEDOT have lower dc leakage and higher breakdown voltage (BDV) compared to polymer Ta capacitors with in situ PEDOT. The difference in dc leakage and BDV between these two types of capacitors becomes greater with increasing thickness and improved structure of the Ta[sub2]O[sub5] dielectric film. These experimental results are inconsistent with current theories presented in the literature. An alternative model is presented based on classical metal/insulator/semiconductor (MIS) theory, where in this case M corresponds to the Ta metal, I corresponds to the Ta[sub2]O[sub5] insulator, and S corresponds to the semiconducting PEDOT. According to this model, a potential barrier for the current carriers at the insulator/semiconductor interface controls the current flow through the Ta[sub2]O[sub5] dielectric under normal operating conditions (positive polarity on the Ta anode and a temperature range of -55°C ⩽ T ⩽ 105°C). In Situ polymerization of the PEDOT adversely affects this barrier, while the prepolymerized PEDOT suspension leaves it essentially intact. The different migratory ability of the dopants in in situ and prepolymerized PEDOT also contributes to the differences in electrical performance of polymer Ta capacitors with in situ and prepolymerized PEDOT cathodes. [ABSTRACT FROM AUTHOR]

Well-defined cleavable poly(styrene-block-ethylene oxide) polymers were prepared by living anioinc polymerization, using cumyl potassium as the initiator. These polymers contained an acid cleavable moiety, such as diphenyl methyl or anthracenyl methyl ether linkage, between polystyrene and poly ethylene oxide block. Atomic force microscopy (AFM) studies on the thin films illustrate the formation of nanoporous architecture due to acid cleavage of the polyethylene oxide fraction. [ABSTRACT FROM AUTHOR]

Atomic force microscopy (AFM) studies of interactions between slurry particles and substrates treated by chemical mechanical polishing (CMP) processes were carried out. To conduct adhesion measurements, the particles present in a CMP system were first attached to the surface of a silicon wafer covered with thin polymer film having high affinity for both particles and the silicon wafer. A silica glass sphere was attached to the AFM cantilever with an appropriate spring constant. The sphere represented the surface of the material being polished and was used as received or covered with a layer of copper. The sphere can be modified with various materials in future research. The AFM force volume mode, which uses the collection of the force-distance curves over selected surface areas, was used for the adhesion measurements. The adhesion in the systems studied was strongly dependent on the pH value of the aqueous environment, and the concentration and type of surfactants added. [ABSTRACT FROM AUTHOR]

Hydrophobic grafted polymer layers were permanently anchored from the melt onto poly(ethylene terephthalate) (PET) and nylon substrates modified with air plasma and poly(glycidyl methacrylate) (PGMA) anchoring layer. Polypentafluorostyrene (PPFS) of different molecular weights with an end carboxyl group was used for the grafting. Atomic force microscopy imaging revealed that, in general, the grafted chains evenly covered all substrates. Thickness of the grafted layer increased with temperature and time of grafting. To reach a significant level of grafting and consequently high hydrophobicity temperature above 140°C, 5 min of grafting had to be used. For longer grafting time (1 h) the hydrophobicity could be reached at 120°C. The thickness of the grafted layer should be at least 2-3 nm to attain the high water-contact angle. The polymer grafting technique developed could be readily applied to surface modification of fibers and textiles leading to generation of hydrophobic fibrous materials. [ABSTRACT FROM AUTHOR]

An immiscible polymer blend of poly(glycidyl methacrylate) and poly(vinylpyridine), PGMA/PVP, was used as an anchoring layer to attach silica nanoparticles to an oxidized silicon wafer surface. The stability of the arrays of colloidal particles was studied in pH 4 and pH 10 buffer solutions, deionized (DI) water, and nonionic surfactant solution. The array was determined to be stable. Attachment of the nanoparticles to one-component homogeneous PGMA and PVP films was also studied in order to determine the role of each polymer in the anchoring layer. Virtually no particles were adsorbed on the surface modified with PGMA. The nanoparticles could be adsorbed on PVP, but the integrity of the polymer layer was destroyed in the environment used for adsorption, i.e., a dispersion of nanoparticles at pH 10. Measurement of adhesion between the nanoparticles attached to the anchoring layer and the glass substrate were performed in aqueous media having different pH values using a colloidal probe atomic force microscopy (AFM) technique. [ABSTRACT FROM AUTHOR]

The present manuscript offers an overview of the current state of affairs within the research field of adaptive and environmentally sensitive polymer surfaces designed to respond to external stimuli in a controlled and predictable manner. Intensive study in the field of the adaptive/responsive surfaces began several decades ago in an attempt to understand relationships between bulk properties/composition of pristine polymeric materials and their surface characteristics. With time, the focus of the research has moved to the design of materials with ‘smart’ or ‘intelligent’ surface behavior. This review describes a number of approaches that has been employed to fabricate such materials, which include but not limited to (a) synthesis of functional polymers with specific composition and architecture; (b) blending of a virgin polymer material with small amounts of (macro)molecular additive; (c) surface modification by various chemical/physical treatment. [Copyright &y& Elsevier]

Abstract: Comparative study of efficiency of macromolecular anchoring layers in the grafting of end-functionalized polymers to a surface was conducted. Poly(glycidyl methacrylate) (PGMA) and epoxydized polybutadienes (EPB) were utilized as the primary anchoring films. Amount of the epoxy moieties introduced to the surface was varied via thickness of the modifying polymer layer or amount of epoxy groups in the polymer backbone. Comparison between the grafting of polystyrene and poly(ethylene glycol) to the various macromolecular anchoring layers indicated that grafting ability of a layer was mostly governed by thickness of the interpenetration zone between the two polymers (anchoring and being grafted). In case of low level of the interpenetration, only functional groups at the periphery of the primary polymer layer were available for the grafting. Then, amount of grafted polymer did not increase with total number of epoxy groups in the anchoring film. However, as the thickness of the interpenetration zone increased, higher amount of the functional groups become available for the grafting. [Copyright &y& Elsevier]

The article focuses on the combination of capillary force lithography and surface-initiated polymerization (SIP) to synthesize binary patterned polymer brushes. This integration is based on the employment of a polystyrene mask to hinder grafting on the fraction of a surface protected by the polymer pattern. Its limitation involves the conduction of SIP in an environment that does not dissolve the mask that is presenting the pattern. The method can also be applied to different substrates.

A reversible locking mechanism is established for thegenerationof anisotropic nanostructures by a magnetic field pulse in liquidmatrices by balancing the thermal energy, short-range attractive andlong-range repulsive forces, and dipole–dipole interactionsusing a specially tailored polymer shell of nanoparticles. The lockingmechanism is used to precisely regulate the dimensions of self-assembledmagnetic nanoparticle chains and to generate and disintegrate three-dimensional(3D) nanostructured materials in solvents and polymers. [ABSTRACT FROM AUTHOR]

Abstract: This contribution describes a methodology to convert commercially available, microporous membranes into ion-exchange membranes using primary anchoring polymer (mono)layers and graft polymerization from the surfaces of the membranes. Atom transfer radical polymerization (ATRP) was used to modify the membranes with pyridinium exchange groups. Polymerization time was used as the independent variable to manipulate the amount of grafted poly(2-vinylpyridine) on the membrane surface. Results indicate that by changing polymerization time, it is possible to tune the ion-exchange capacity and the average pore size in rational ways. Equally important, membranes with initially broad pore-size distributions had narrower pore-size distributions following polymerization. A polymerization time of 24h reduced the pore-diameter polydispersity (PDP) from 2.05 to 1.44. A polymerization time of 8h resulted in a static ion-exchange capacity of 7.32×10−2 mmol/g (7.32×10−2 meq/g) of dry membrane. [Copyright &y& Elsevier]