Synthesis and properties of cationic ionomers from poly(ester-urethane)s based on polylactide

l-Lactide (l-LA) was polymerized in the presence of N-methyldiethanolamine as an initiator and Sn(Oct)2 as a catalyst to give hydroxy-telechelic poly(l-lactide) (PLLA-diol) bearing a tertiary amine group at the center of the polymer chain. Successive chain extension of the PLLA-diol with hexamethylene diisocyanate afforded PLLA-based poly(ester-urethane)s (PEU) with equally spaced tertiary amine groups. Treatment of the PEU with iodomethane converted tertiary amine groups to quaternary ammonium groups to give cationic ionomers (PEU-MeI). The thermal, mechanical, hydrophilic, and biodegradation properties of the obtained polymers were investigated. The thermal properties of the PEUs and the PEU-MeIs were similar each other. The PEU-MeIs exhibited higher tensile modulus than those of the starting PEUs. The contact angles of water on the PEU-MeIs were lower than those of the PEUs with similar NMDA content indicating their higher hydrophilicity. In compost degradation tests, the PEU-MeIs showed slower degradation than those of the PEUs.