Correlation between the sequence‐length distribution and structure of statistical copolymers of <scp>L</scp>‐valine and γ‐benzyl‐<scp>L</scp>‐glutamate

Abstract

Abstract Statistical copolymers were prepared from N‐carboxyanhydrides of L ‐valine and γ‐benzyl‐ L ‐glutamate in dioxan with triethylamine as an initiator. The copolymerization conversion was determined by ir spectroscopy, the copolymer composition by amino acid analysis, and the molecular weights by light scattering. The monomer reactivity ratios were found to be r Val = 0.14 and r Glu(OBzl) = 6.4. High‐molecular‐weight copolymers are formed even at low conversions. The content of β‐structure in the copolymers was estimated from the ir spectra in copolymerization mixtures. The sequence‐length distribution of L ‐valine and γ‐benzyl‐ L ‐glutamate copolymers was calculated and its dependence on copolymerization conversion is discussed. Relations between the sequence‐length distribution and the content of β‐structure were studied. It was found that the content of β‐structure in samples with the same composition is different for low‐ and high‐conversion copolymers. The formation of β‐structure in copolymers in the copolymerization mixture requires a certain minimal sequence length, which has been found to be about 6 valine units.