Estimation of Effective Crosslink Density in Poly(N-hydroxyalkyl L-glutamine) Hydrogels

Abstract

Four kinds of poly(N-hydroxyalkyl L-glutamine) hydrogels, PHEG, PHPG, PHBG and PHPeG, were prepared by aminolysis of poly(γ-benzyl L-glutamate) (PBLG) membranes with corresponding aminoalcohols, such as 2-amino-1-ethanol (E), 3-amino-1-propanol (P), 4-amino-1-butanol (B), and 5-amino-1-pentanol (Pe), together with a crosslinking agent octamethylenediamine (OMDA). Effective crosslink density was estimated on the basis of rubber elasticity theory. This estimation was limited to hydrogels which contain random coil polypeptides. The effective crosslink density was shown to be proportional to the ratio of OMDA to amino alcohol. It was found that relative reactivities of OMDA with PBLG are dependent on the alkyl chain lengths of the coexisting aminoalcohols. The order of effective crosslink density was PHBG>PHPG>PHEG, when the same content of OMDA was used.