Structure and mobility of poly (γ- n-alkyl-L-glutamate)s in the solid and liquid crystalline states as studied by NMR spectroscopy

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13C CP/MAS NMR and pulse 1H NMR experiments were carried out for poly(γ- n-alkyl-L-glutamate)s (PALGs) in which the number of carbon atoms of the alkyl side-chains was either odd or even, in order to elucidate the conformation, crystal structure and dynamics of the polymers. From these results, it is found that the main-chain takes an γ-helix conformation irrespective of the alkyl side-chain length. However, n-alkyl side-chains crystallize with an all-trans zigzag conformation for PALGs when the number of carbon atoms in the n-alkyl side-chains is more than 14. Further, from the pulse 1H NMR results, it is found that the 1H spin—spin relaxation time ( T 2) of the side-chains increases abruptly with an increase in temperature for PALGs with a carbon number of more than 10, which is evidence for the solvent-like nature of the side-chains in the liquid crystalline phase.