SYNTHESIS AND PROPERTIES OF TELECHELIC POLY(LACTIC ACID) IONOMERS

摘要

A chemical recycling process was used to synthesize ω- and α,ω-(metal carboxylate) poly(lactic acid) (PLA) ionomers. Telechelic PLAs containing carboxylic acid groups, which were neutralized with appropriate metal acetates to produce Na-, Li-, K-, Zn-, Ca- and Y-ω- and α,ω-telechelic PLA ionomers. Functionalization of the PLA was confirmed by FT-IR and ~1H-NMR. In general, the T_g and T_m of the ionomers increased with molecular weight (which also lowered the ion-concentration) and ionization of the carboxylic acid. For a fixed molecular weight, the increase in T_g and T_m were linearly dependent on the ratio of q/a, where q is the cation charge and a is its ionic radius. Crystallization behavior was dependent on the ion concentration and location of the metal ions. The presence of the ionic groups increased the modulus of the polymer and the largest changes were observed with multivalent cations. The ω-(Y carboxylate) PLA even displayed a rubber-like plateau in its softening behavior.