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Storrs, CT, United States

Zhu Y.,5 North Eagleville Road | Otley M.T.,5 North Eagleville Road | Zhang X.,Polymer Program | Li M.,Polymer Program | And 4 more authors.
Journal of Materials Chemistry C | Year: 2014

Utilizing the in situ method, we report the fabrication of flexible electrochromic (EC) devices in a one-step lamination procedure. In this study, electrochromic device performance was enhanced via the use of new gel polymer electrolyte (GPE) materials based on poly(ethylene glycol) (PEG) derivatives. PEG serves as the polymer matrix in electrochromic devices (ECDs) that provides not only mechanical stability, but also a wide potential window and compatibility with a variety of salts. Poly(ethylene glycol) dimethacrylate (PEGDMA) in conjunction with poly(ethylene glycol) methyl ether acrylate (PEGMA), containing lithium trifluoromethanesulfonate (LiTRIF) as the salt and propylene carbonate (PC) as a plasticizer; we investigated various electrolyte parameters, including salt loading, the mono/di-functional PEG ratio, and the plasticizer to PEG ratio. Optimized gel systems exceed the mechanical flexibility of indium tin oxide (ITO) coated polyethylene terephthalate (PET) substrates in their sustainable minimum bending radius of curvature, exhibit an ionic conductivity up to 1.36 × 10-3 S cm-1, and yield electrochromic devices (ECDs) with photopic contrasts as high as 53% (without background correction) using poly(2,2-dimethyl-3,4-propylenedioxythiophene) (PProDOT-Me2) as the standard electrochromic material. In addition to ionic conductivity, the crosslink density of the GPEs was found to have an important effect on the photopic contrast of the resultant ECDs. Using these results, 110 cm2 flexible patterned EC displays were assembled as a demonstration of their potential in real world applications. © The Royal Society of Chemistry 2014. Source

Riccardi C.M.,5 North Eagleville Road | Riccardi C.M.,University of Connecticut | Cole K.S.,5 North Eagleville Road | Benson K.R.,5 North Eagleville Road | And 10 more authors.
Bioconjugate Chemistry | Year: 2014

Several key properties of catalase such as thermal stability, resistance to protease degradation, and resistance to ascorbate inhibition were improved, while retaining its structure and activity, by conjugation to poly(acrylic acid) (PAA, Mw 8000) via carbodiimide chemistry where the amine groups on the protein are appended to the carboxyl groups of the polymer. Catalase conjugation was examined at three different pH values (pH 5.0, 6.0, and 7.0) and at three distinct mole ratios (1:100, 1:500, and 1:1000) of catalase to PAA at each reaction pH. The corresponding products are labeled as Cat-PAA(x)-y, where x is the protein to polymer mole ratio and y is the pH used for the synthesis. The coupling reaction consumed about 60-70% of the primary amines on the catalase; all samples were completely water-soluble and formed nanogels, as evidenced by gel electrophoresis and electron microscopy. The UV circular dichroism (CD) spectra indicated substantial retention of protein secondary structure for all samples, which increased to 100% with increasing pH of the synthesis and polymer mole fraction. Soret CD bands of all samples indicated loss of ∼50% of band intensities, independent of the reaction pH. Catalytic activities of the conjugates increased with increasing synthesis pH, where 55-80% and 90-100% activity was retained for all samples synthesized at pH 5.0 and pH 7.0, respectively, and the Km or Vmax values of Cat-PAA(100)-7 did not differ significantly from those of the free enzyme. All conjugates synthesized at pH 7.0 were thermally stable even when heated to ∼85-90 °C, while native catalase denatured between 55 and 65 °C. All conjugates retained 40-90% of their original activities even after storing for 10 weeks at 8 °C, while unmodified catalase lost all of its activity within 2 weeks, under similar storage conditions. Interestingly, PAA surrounding catalase limited access to the enzyme from large molecules like proteases and significantly increased resistance to trypsin digestion compared to unmodified catalase. Similarly, negatively charged PAA surrounding the catalase in these conjugates protected the enzyme against inhibition by negatively charged inhibitors such as ascorbate. While Cat-PAA(100)-7 did not show any inhibition by ascorbate in the presence of 270 μ1/4M ascorbate, unmodified catalase lost ∼70% of its activity under similar conditions. This simple, facile, and rational methodology produced thermostable, storable catalase that is also protected from protease digestion and ascorbate inhibition and most likely prevented the dissociation of the multimer. Using synthetic polymers to protect and improve enzyme properties could be an attractive approach for making "Stable-on-the-Table" enzymes, as a viable alternative to protein engineering. © 2014 American Chemical Society. Source

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