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Solid‐state modifications of poly(γ‐ethyl‐ L ‐glutamate)
Author(s) -
Sasaki Shintaro,
Miyamoto Misao,
Nakamura Takao,
Uematsu Ichitaro
Publication year - 1978
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.1978.360171117
Subject(s) - tetragonal crystal system , chemistry , crystallography , hexagonal crystal system , annealing (glass) , solvent , solid state , chloroform , residue (chemistry) , molecule , helix (gastropod) , stereochemistry , crystal structure , materials science , organic chemistry , ecology , snail , composite material , biology
Several modification of the arrangements of α‐helical molecules were found in the solid films of poly (γ‐ethyl‐ L ‐glutamate), depending on the casting solvent and the temperature. The helical conformation is somewhat looser than the normal 18‐residue, 5‐turn α‐helix. Using x‐ray diffraction, the types of molecular arrangements were classified into tetragonal, pseudohexagonal, and hexagonal ones. Tetragonal packing was observed in the filmm (form T) prepared by casting the solution in trifluorethanol or dichlorethane. The sample obtained from chloroform solution is a well‐ordered, pseudohexagonal modification (form I). Forms I and T change into a poorly crystalline form III by annealing at temperatures above 130° C. It is particularly noteworthy that the less‐ordered form III exhibits a thermoreversible transition around 110°C into a well‐ordered form H with the hexagonal molecular packing.