Linear Polyurethanes Made from Threitol: Acetalized and Hydroxylated Polymers

A set of novel linear polyurethanes was synthesized by reaction in solution of 1,6-hexamethylene diisocyanate (HDI) or, 4,4'-methylene-bis(phenyl diisocyanate) with 2,3-acetalized threitols, specifically, 2,3-O-methylidene-L-threitol and 2,3-O-isopropylidene-D-threitol. The polyurethanes containing acetalized threitols had weight-average molecular weights between 40,000 and 65,000 Da. Most of them were amorphous and they displayed T-g higher than their unsubstituted analogs. Deprotection of acetalized polyurethanes by treatment with acid allowed preparing semicrystalline polyurethanes bearing two free hydroxyl groups in the repeating unit. The crystalline structure and crystallizability of the hydroxylated polyurethane made from HDI were investigated taken as reference the polyurethane made from 1,4-butanediol and HDI. The hydrolytic degradability of threitol derived polyurethanes was comparatively evaluated under a variety of conditions. Highest degradation rates were obtained upon incubation at pH 10 at temperatures above T-g, the aliphatic hydroxylated polyurethane being the fastest degrading compound. (C) 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7996-8012, 2008