Engineering the Surface Properties of Poly(dimethylsiloxane) Utilizing Aqueous RAFT Photografting of Acrylate/Methacrylate Monomers

Development and Evaluation of Butyl Norbornene Based Cross-Linked Anion Exchange Membranes for Enhanced Nonaqueous Redox Flow Battery Efficiency

Nonaqueous redox flow batteries (NARFBs) have been plagued by the lack of appropriate separators to prevent crossover. In this article, the synthesis and characterization of poly(norbornene) (PNB) anion-exchange membranes (AEMs) were studied. PNB is a copolymer of butyl norbornene (BuNB) and bromobutyl norbornene (BrBuNB) with varying amounts of tetramethyl hexadiamine cross-linker. The performance of the AEMs was investigated in nonaqueous redox flow batteries under ideal conditions. Performance evaluation encompassed several key factors, including durability in a nonaqueous solvent, charge-carrying ions permeability, electric cell resistance, crossover of redox-active molecules, and mechanical properties. The BuNB-based AEMs outperformed the commercial Fumasep membrane in battery cycling tests, showcasing their superior performance characteristics. Long-term performance tests showed that the top performing PNB membrane exhibited an impressive 83% total capacity retention over 1000 charge/discharge cycles. The low loss was primarily due to minimal crossover. In contrast, the FAPQ-375 commercial membrane experienced significantly lower capacity retention, measuring only 28%, due to high crossover.

Surface Functionalization of Elastomers with Biopolymers

Biopolymer coatings on elastomeric surfaces have significant impact for advancements in biomedicine as they combine flexible devices with complex biological functionality. Biopolymers offer increased ability for antimicrobial coatings, sensing of relevant biological markers, and controlled drug delivery. The methodologies available to conjugate these important biopolymers to flexible elastomeric substrates are vast and rapidly evolving. This chapter aims to compile methodologies across the application space of biopolymer conjugation to elastomers. We present a guide to the field and methods ranging from surface activation and functionalization, grafting-to and grafting-from of biopolymers, and characterization of the resulting substrates.

Long-Lasting Antibacterial PDMS Surfaces Constructed from Photocuring of End-Functionalized Polymers

A challenge remains in the development of anti-infectious coatings for the inert surfaces of biomedical devices that are prone to bacterial colonization and biofilm formation. Here, a facile photocuring method to construct functionalized polymeric coatings on inert polydimethylsiloxane (PDMS) surfaces, is developed. Using atom transfer radical polymerization (ATRP) initiator bearing thymol group, hydrophilic DMAEMA and benzophenone (BP)-containing monomers are copolymerized to form polymers with end functional groups. An end-functionalized biocidal coating is then constructed on the inert PDMS surface in one step using a photocuring reaction. The functionalized PDMS surfaces show excellent antibacterial and antifouling properties, are capable of completely eradiating MRSA within ≈6 h, and effectively inhibit the growth of biofilms. In addition, they have good stability and long-lasting antibacterial activity in body fluid environments such as 0.9% saline and urine. According to bladder model experiments, the catheter's lifespan can be extended from ≈7 to 35 days by inhibiting the growth and migration of bacteria along its inner surface. The photocuring technique is therefore very promising in terms of surface functionalization of inert biomedical devices in order to minimize the spread of infection.

PEG-functionalized aliphatic polycarbonate brushes with self-polishing dynamic antifouling properties

Hydrophilic antifouling polymers provide excellent antifouling effects under usual short-term use conditions, but the long-term accumulation of contaminants causes them to lose their antifouling properties. To overcome this drawback, surface-initiated ring-opening graft polymerization (SI-ROP) was performed on the surface of the material by applying the cyclic carbide monomer 4'-(fluorosulfonyl)benzyl-5-methyl-2-oxo-1,3-dioxane-5-carboxylate (FMC), which contains a sulfonylfluoride group on the side chain, followed by a "sulfur(IV)-fluorine exchange" (SuFEx) post click modification reaction to link the hydrophilic polyethylene glycol (PEG) to the polyFMC (PFMC) brush, and a novel antifouling strategy for self-polishing dynamic antifouling surfaces was developed. The experimental results showed that the antifouling surface could effectively prevent the adsorption of proteins such as bovine serum albumin (BSA, ∼96.4%), fibrinogen (Fg, ∼87.8%) and lysozyme (Lyz ∼69.4%) as well as the adhesion of microorganisms such as the bacteria Staphylococcus aureus (S. aureus) (∼87.5%) and HeLa cells (∼67.2%). Moreover, the enzymatically self-polished surface still has excellent antifouling properties. Therefore, this modification method has potential applications in the field of biosensors and novel antifouling materials.

Surface Functionalities of Polymers for Biomaterial Applications

Changes of a material biointerface allow for specialized cell signaling and diverse biological responses. Biomaterials incorporating immobilized bioactive ligands have been widely introduced and used for tissue engineering and regenerative medicine applications in order to develop biomaterials with improved functionality. Furthermore, a variety of physical and chemical techniques have been utilized to improve biomaterial functionality, particularly at the material interface. At the interface level, the interactions between materials and cells are described. The importance of surface features in cell function is then examined, with new strategies for surface modification being highlighted in detail.

Photopatterning of PDMS Films: Challenging the Reaction between Benzophenone and Silicone Functional Groups

Direct photopatterning of PDMS (Polydimethylsiloxane) through benzophenone photo-inhibition has received great interest in recent years. Indeed, the simplicity and versatility of this technique allows for easy processing of micro-canals, or local control of PDMS mechanical properties. Surprisingly, however, the chemical reactions between silicone hydride and/or silicone vinyl groups and benzophenone have only been assessed through qualitative methods (e.g., Attenuated total reflection fourier transform infrared). In this communication, the previously proposed reaction pathways are challenged, using nuclear magnetic resonance (NMR) spectroscopy and size exclusion chromatography (SEC) monitoring. A different mechanism depicting the role of benzophenone irradiation on the polyaddition reaction of silicone formulations is proposed, and a simplified procedure involving aromatic solvent is finally disclosed.

UV-Assisted Li+-Catalyzed Radical Grafting Polymerization of Vinyl Ethers: A New Strategy for Creating Hydrolysis-Resistant and Long-Lived Polymer Brushes as a "Smart" Surface Coating

A facile synthetic route was developed to prepare a surface-grafted brush layer of poly(vinyl ethers) (PVEs) directly by a radical mechanism, with the "naked" Li⁺ acting as a catalyst. Density functional theory calculations suggested that complexation of naked Li⁺ to VEs significantly reduced the highest unoccupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) energy gap from 5.08 to 0.68 eV, providing a better prospect for electron transfer. The structure, morphology, and surface properties of grafted polymer layers were characterized using attenuated total reflection Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy, and dynamic water contact angle (DCA). Moreover, ellipsometry data indicated that the thickness of the polymer brushes was in the range of 20-60 nm, which corresponds to the grafting densities of 0.65-1.15 chain/nm², and DCA decreased from 84.4 to 45.3°. Most importantly, no hydrolysis was observed for the modified surface after 30 days of exposure to phosphate-buffered saline solution, 0.1 mol/L NaOH(eq) and 0.1 mol/L HCl(eq), demonstrating excellent hydrolysis resistance with long service life. In addition, as a proof of concept, the side hydroxyl groups of grafted PVEs provide active sites for efficient fixation of bioactive molecules, e.g., glycosaminoglycan and serum protein.

Synthesis and antifouling performance of tadpole-shaped poly(N-hydroxyethylacrylamide) coatings

Linear poly(N-hydroxyethylacrylamide) (PHEAA) is regarded as one of the most promising antifouling materials because of its excellent antifouling properties and good hemocompatibility. However, the antifouling performance of topological PHEAAs remains largely unknown. Herein, the preparation of antifouling surfaces based on a tadpole-shaped PHEAA coating is reported for the first time, and how the tadpole-shaped PHEAA architecture affects antifouling performance is investigated. It is shown that the tadpole-shaped PHEAA-modified surfaces exhibit better antifouling performance than linear copolymer precursor-modified surfaces with identical molar masses and chemical compositions. This may be primarily attributed to the presence of cyclic PHEAA head chain segments in the tadpole-shaped PHEAA copolymer, and the absence of interchain entanglements can facilitate the formation of smoother and densely packed grafts, which result in better antifouling properties.

Anti-biofouling properties of poly(dimethyl siloxane) with RAFT photopolymerized acrylate/methacrylate surface grafts against model marine organisms

Biofouling of man-made surfaces by marine organisms is a global problem with both financial and environmental consequences. However, the development of non-toxic anti-biofouling coatings is challenged by the diversity of fouling organisms. One possible solution leverages coatings composed of diverse chemical constituents. Reversible addition-fragmentation chain-transfer (RAFT) photopolymerization was used to modify poly(dimethylsiloxane) (PDMSe) surfaces with polymeric grafts composed of three successive combinations of acrylamide, acrylic acid, and hydroxyethyl methacrylate. RAFT limited conflicting variables and allowed for the effect of graft chemistry to be isolated. While all compositions enhanced the anti-biofouling performance compared with the PDMSe control, the ternary, amphiphilic copolymer was the most effective with 98% inhibition of the attachment of zoospores of the green alga Ulva linza, 94% removal of cells of the diatom Navicula incerta, and 62% removal of cells of the bacterium Cellulophaga lytica. However, none of the graft compositions tested were able to mitigate reattachment of adult barnacles, Amphibalanus amphitrite.

Engineered Chemical Nanotopographies: Reversible Addition-Fragmentation Chain-Transfer Mediated Grafting of Anisotropic Poly(acrylamide) Patterns on Poly(dimethylsiloxane) To Modulate Marine Biofouling

Effectively negating the deleterious impact of marine biofouling on the world's maritime fleet in an environmentally conscientious manner presents a difficult challenge due to a variety of factors including the complexity and diversity of fouling species and the differing surface adhesion strategies. Understanding how surface properties relate to biofouling can inform and guide the development of new antibiofouling coatings to address this challenge. Herein, we report on the development of a living photopolymerization strategy used to tailor the surface properties of silicone rubber using controlled anisotropic poly(acrylamide) patterns and the resulting antibiofouling efficacy of these surfaces against zoospores of the model marine fouling organism, Ulva linza. Chemical patterns were fabricated using reversible addition-fragmentation chain-transfer (RAFT) living polymerization in conjunction with photolithography. Pattern geometries were inspired by the physical (i.e., nonchemical) Sharklet engineered microtopography system that has been shown to be effective against the same model organism. Sharklet chemical patterns and analogous parallel channels were fabricated in sizes ranging from 2 to 10 μm in the lateral dimension with tailorable feature heights ranging from tens to hundreds of nanometers. Nonpatterned, chemically grafted poly(acrylamide) silicone surfaces inhibited algal spore attachment density by 59% compared to the silicone control; however, attachment density on chemical nanotopographies was not statistically different from the control. While these results indicate that the chemical nanotopographies chosen do not represent an effective antibiofouling coating, it was found that the Sharklet pattern geometry, when sized below the 5 μm critical attachment size of the spores, significantly reduced the algal spore density compared to the equally sized channel geometry. These results indicate that specific chemical geometry of the proper sizing can impact the behavior of the algal spores and could be used to further study the mechanistic behavior of biofouling organisms.

Insight into the Intermolecular Interaction and Free Radical Polymerizability of Methacrylates in Supercritical Carbon Dioxide

High pressure in situ Fourier transfer infrared/near infrared technology (HP FTIR/NIR) along with theoretical calculation of density functional theory (DFT) method was employed. The solvation behaviors and the free radical homopolymerization of methyl methacrylate (MMA), methacrylate acid (MAA), trifluoromethyl methacrylate (MTFMA) and trifluoromethyl methacrylate acid (TFMAA) in scCO2 were systematically investigated. Interestingly, the previously proposed mechanism of intermolecular-interaction dynamically-induced solvation effect (IDISE) of monomer in scCO2 is expected to be well verified/corroborated in view that the predicted solubility order of the monomers in scCO2 via DFT calculation is ideally consistent with that observed via HP FTIR/NIR. It is shown that MMA and MAA can be easily polymerized, while the free radical polymerizability of MTFMA is considerably poor and TFMAA cannot be polymerized via the free radical initiators. The α trifluoromethyl group (-CF3) may effectively enhance the intermolecular hydrogen bonding and restrain the diffusion of the monomer in scCO2. More importantly, the strong electron-withdrawing inductive effect of -CF3 to C=C may distinctly decrease the atomic charge of the carbon atom in the methylene (=CH2). These two factors are believed to be predominantly responsible for the significant decline of the free radical polymerizability of MTFMA and the other alkyl 2-trifluoromethacrylates in scCO2.

Thermally triggerable, anchoring block copolymers for use in aqueous inkjet printing

Towards the goal of shifting from toxic organic solvents to aqueous-based formulations in commercial inkjet printing, a series of well-defined amphiphilic block copolymers have been synthesized via RAFT polymerization.

Engineering Antifouling Conducting Polymers for Modern Biomedical Applications

Conducting polymers are considered to be favorable electrode materials for implanted biosensors and bioelectronics, because their mechanical properties are similar to those of biological tissues such as nerve and brain tissues. However, one of the primary challenges for implanted devices is to prevent the unwanted protein adhesion or cell binding within biological fluids. The nonspecific adsorption generally causes the malfunction of implanted devices, which is problematic for long-term applications. When responding to the requirements of solving the problems caused by nonspecific adsorption, an increasing number of studies on antifouling conducting polymers has been recently published. In this review, synthetic strategies for preparing antifouling conducting polymers, including direct synthesis of functional monomers and post-functionalization, are introduced. The applications of antifouling conducting polymers in modern biomedical applications are particularly highlighted. This paper presents focuses on the features of antifouling conducting polymers and the challenges of modern biomedical applications.

High-Capacity Poly(4-vinylpyridine) Grafted PolyHIPE Foams for Efficient Plutonium Separation and Purification

The use of anion-exchange resins to separate and purify plutonium from various sources represents a major bottleneck in the throughput that can be achieved when this step is part of a larger separation scheme. Slow sorption kinetics and broad elution profiles necessitate long contact times with the resin, and the recovered Pu is relatively dilute, requiring the handling of large volumes of hazardous material. In this work, high internal-phase emulsion (HIPE) foams were prepared with a comonomer containing a dormant nitroxide. Using surface-initiated nitroxide-mediated polymerization, the foam surface was decorated with a brush of poly(4-vinylpyridine), and the resulting materials were tested under controlled flow conditions as anion-exchange media for plutonium separations. It was found that the grafted foams demonstrated greater ion-exchange capacity per unit volume than a commercial resin commonly used for Pu separations and had narrower elution profiles. The ion-exchange sites (quaternized pyridine) were exposed on the surface of the large pores of the foam, resulting in convective mass transfer, the driving force for the excellent separation properties exhibited by the synthesized polyHIPE foams.