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Suppressing the influence of humidity in protein-based materials is central to their use in a variety of applications. It is believed that protein charge plays a key role in water uptake. Therefore, in this work, whey protein was neutralized, supercharged, and superneutralized to examine the effects of protein modification on moisture absorption in protein copolymers. The charge-modified proteins were formulated into thermoset elastomers through a three-step process: methacrylation, complexation with various surfactants, and co-polymerization with n-butyl acrylate. Compatibility of the protein and hydrophobic acrylate monomer can be tuned through changes in surfactant type, ratio between surfactant and protein, and protein charge modification. Using benzalkonium chloride as the surfactant compatibilizer, elastomers with the various modified proteins were prepared using a melt polymerization approach. Acetylation and esterification of whey protein, which neutralize charged functional groups, resulted in the reduction of the proteins' water uptake relative to unmodified whey. Once incoporated into elastomers, all copolymers regardless of protein modifications have similar moisture contents. However, elastomers with superneutralized proteins demonstrated a lowered mechanical dependence on humidity, presented as a smaller change in elongation at break and tensile strength compared to a copolymer based on non-charge modified whey. This journal is

Proteins have great potential as biomass-derived feedstocks for material synthesis and can form strong materials due to their highly hydrogen-bonded nature. Elastomers comprised of proteins and a synthetic rubbery polymer were prepared by copolymerizing a methacrylated protein and a vinyl monomer, where proteins function as macro-cross-linkers and reinforcing fillers. Selecting a hydrophobic synthetic polymer block partially mitigates the moisture absorption of protein-based materials while maintaining desirable levels of mechanical properties. The use of a hydrophobic monomer is enabled by the use of surfactants that function as compatibilizers, since proteins are generally insoluble in organic solvents and vinyl monomers. Surfactants also lower the softening temperature of proteins, allowing materials to be fabricated solvent free using thermoplastic processing techniques. The preparation of a polyacrylate network toughened through incorporation of protein cross-linking domains is demonstrated using whe...

Reliable and equitable access to safe drinking water is a major and growing challenge worldwide. Membrane separations represent one of the most promising strategies for the energy-efficient purification of potential water sources. In particular, porous membranes are used for the ultrafiltration (UF) of water to remove contaminants with nanometric sizes. However, despite exhibiting excellent water permeability and solution processability, existing UF membranes contain a broad distribution of pore sizes that limit their size selectivity. To maximize the potential utility of UF membranes and allow for precise separations, improvements in the size selectivity of these systems must be achieved. Block polymers represent a potentially transformative solution, as these materials self-assemble into well-defined domains of uniform size. Several different strategies have been reported for integrating block polymers into UF membranes, and each strategy has its own set of materials and processing considerations to ensure that uniform and continuous pores are generated. This Review aims to summarize and critically analyze the chemistries, processing techniques, and properties required for the most common methods for producing porous membranes from block polymers, with a particular focus on the fundamental mechanisms underlying block polymer self-assembly and pore formation. Critical structure-property-performance metrics will be analyzed for block polymer UF membranes to understand how these membranes compare to commercial UF membranes and to identify key research areas for continued improvements. This Review is intended to inform readers of the capabilities and current challenges of block polymer UF membranes, while stimulating critical thought on strategies to advance these technologies.

Proteins are a widely available biomass source for synthesizing strong and tough engineering polymers because of their propensity to hydrogen bond, chemically stable amide backbone, and demonstrated efficacy at forming relevant material structures in nature. Because the properties of polypeptides in many ways mimic urethane bonds and hard domains, herein proteins are explored as the reinforcing component in a polyurethane-inspired elastomer. Materials are synthesized using a two-step process: first, protein is methacrylated, and then copolymerized with (meth)acrylate comonomers to link protein domains with rubbery polymer chains. This is demonstrated with water-soluble proteins, whey protein and β-lactoglobulin, and a comonomer, hydroxypropyl acrylate (HPA). The resulting elastomers are amorphous and disordered but have microphase-separated morphologies. Materials with a wide range of stiffnesses have been prepared by varying the fraction of protein macro-cross-linkers in the materials. The protein aggreg...

Bio-sourced macromolecules such as cyanophycin are an attractive source for alternative, sustainable plastics. While the chemical structure and biological function of cyanophycin have been previously investigated, its material properties remain largely unexplored. This study investigates the structural, thermal, mechanical, and solution properties of cyanophycin produced from recombinant Escherichia coli . Unplasticized, it has an elastic compression modulus of about 560 MPa and undergoes brittle failure at 78 MPa. Cyanophycin exhibits thermal stability in air up to 200 °C and does not undergo glass transition within its limit of thermal stability. The polypeptide is amorphous and has no long-range ordering in the solid state. In solution, water-soluble cyanophycin is thermoresponsive, exhibiting both upper and lower critical solution temperatures. Because the feasibility of industrial scale cyanophycin production through fermentation has been well studied, an expanded understanding of its materials properties should contribute to the development of new applications for this biopolymer.

The wide use of non-biodegradable, petroleum-based plastics raises important environmental concerns, which urges finding alternatives. In this study, an alternative way to produce polymers from a renewable source&mdash, milk proteins&mdash, was investigated with the aim of replacing polyethylene. Whey protein can be obtained from whey residual, which is a by-product in the cheese-making process. Two different sources of whey protein were tested: Whey protein isolate (WPI) containing 91% protein concentration and whey protein concentrate (WPC) containing 77% protein concentration. These were methacrylated, followed by free radical polymerization with co-polymer poly(ethylene glycol) methyl ether methacrylate (PEGMA) to obtain polymer sheets. Different protein concentrations in water (11&ndash, 14 w/v%), at two protein/PEGMA mass-ratios, 20:80 and 30:70, were tested. The polymers made from WPI and WPC at a higher protein/PEGMA ratio of 30:70 had significantly better tensile strength than the one with lower protein content, by about 1&ndash, 2 MPa (the best 30:70 sample exhibited 3.8 &plusmn, 0.2 MPa and the best 20:80 sample exhibited 1.9 &plusmn, 0.4 MPa). This indicates that the ratio between the hard (protein) and soft (copolymer PEGMA) domains induce significant changes to the tensile strengths of the polymer sheets. Thermally, the WPI-based polymer samples are stable up to 277.8 &plusmn, 6.2 &deg, C and the WPC-based samples are stable up to 273.0 &plusmn, 3.4 &deg, C.

Shifting from a fossil fuel-dependent economy to modern, sustainable development requires not only the introduction of biofuels but should also include novel and sustainable materials from renewable feedstocks. In this study, the viability of producing polyurethane-inspired elastomers manufactured through copolymerization of modified proteins from microalgae with the synthetic monomer poly(ethylene glycol) methyl ether methacrylate (PEGMA) is investigated. Techno-economic evaluation of the process reveals great potential for the technology to be economically feasible, resulting in an investment payback rate of 8.4 years under the given conditions. Sensitivity analysis shows that the process feasibility is highly dependent on the protein availability, price of copolymer, and protein concentration. Conversely, the relatively minor influence that the price of residual proteins plays in the process economics is very beneficial from the perspective of justifying algal biofuel production. A positive economic balance for the technology is achieved for a variety of different product formulations, prices, and processing techniques.