Synthesis and characterization of amphiphilic poly(2-ethyl-2-oxazoline)/poly(epsilon-caprolactone) alternating multiblock copolymers

Abstract

Novel amphiphilic alternating multiblock copolymers were synthesized by the polycondensation reaction of alpha,omega-dihydroxypoly(2-ethyl-2-oxazoline) (HO-PEtOz-OH) with alpha,omega-dicarboxypoly(epsilon-caprolactone) (HOOC-PCL-COOH) by varying the block composition. The phase transition and swelling behaviors of multiblock copolymer hydrogels depending on temperature changes were investigated in aqueous media. The crystalline melting of PCL domain and the hydrophobic interaction within the gel could be correlated with the phase transition. Thermosensitive swelling behaviors of hydrogels were investigated in response to temperature changes. The hydrogels exhibited reversible swelling-shrinking behavior, where the higher swelling ratios were obtained at the lower temperature. The higher swelling ratios were obtained for hydrogel containing longer PEtOz blocks, and swelling capacity could be controlled by adjusting the block composition. In mechanical tests, the dried gels and hydrogels of multiblock copolymers prepared from longer oligomeric PCL exhibited maximum strengths in the range of 10.6-12.5 and 3.2-7.3 MPa, and ultimate elongation up to 880-930 and 320-1000%, respectively. (C) 2000 Elsevier Science Ltd. All rights reserved.