Abstract
Copoly(alkyl(ethyl or methyl)-L-aspartate-benzyl-L-aspartate) alkylated less than 20% (e.g., E-1) transformed at 127°C into the ω helix accompanied by the incorporation of a small amount of alkyl-L-aspartate into the ω helix of the benzyl-L-aspartate. Only the benzyl-L-aspartate of copolyaspartates with alkylation from 20 to 60% transformed into the ω helix in the temperature range from 100 to 130°C, and the rest of the alkyl-L-aspartate still remaining in the α helix form. That is, copolyaspartates exist as mixtures of the α helix and the ω helix and packing modes of helices must change in the temperature range from 100 to 130°C. It was found that the formation of the stacks between benzyl and ethyl or methyl groups could not take place, in contrast to the formation of stacks between benzyl and butyl groups. For alkylation more than 60%, benzyl-L-aspartate did not form either ω helices nor stacks and thus there was no α–ω transition. All copolyaspartates synthesized here transformed into the β form in the vicinity of 200°C. Copolyaspartate with alkylation at about 80% exhibited a much higher transition temperature than poly(β-benzyl-L-aspartate). The α helices of poly(β-ethyl-L-aspartate) and poly(β-methyl-L-aspartate) are thus considered much more stable than the ω helix of poly(β-benzyl-L-aspartate).
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Tsujita, Y., Fukagawa, M. & Uematsu, I. The Structure and Properties of Copolyaspartate II. Copoly(ethyl-L-aspartate-benzyl-L-aspartate) and Copoly(methyl-L-aspartate-benzyl-L-aspartate). Polym J 14, 781–788 (1982). https://doi.org/10.1295/polymj.14.781
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DOI: https://doi.org/10.1295/polymj.14.781