Title

Synthesis and Characterization of Functionalized Poly (L-lactide)-Based Materials and Lactone Polymerization Kinetics Using Real-Time ATR-FTIR Spectroscopy

Date of Award

2004

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Polymers and High Performance Materials

First Advisor

Robson F. Storey

Advisor Department

Polymers and High Performance Materials

Abstract

Functionalization of poly (L-lactide) (PLLA) was studied in order to determine potential methods to enhance its glass transition temperature and maintain polymer degradability most notably via crystallinity. The synthesis of the carboxylic acid-functionalized PLLA derivatives generally involved the addition of a moderate- to highly-reactive small molecule to a hydroxyl functionalized PLLA. Results were promising for the PLLA-succinic anhydride system at low molecular weight, but did not correlate with higher molecular weight systems. In addition, chain extension reactions performed using LDI provided polymers with pendent methyl ester functional groups that could not be converted to free carboxylic acid without degrading the PLLA backbone. Low molecular weight calcium carboxylate ionomers derived from carboxylic acid-terminated telechelic PLLA were synthesized using mild neutralization conditions at room temperature. A novel system was developed in which calcium chloride was dissolved in tetrahydrofuran or methylene chloride using 18 crown 6. Neutralization was monitored using in-situ ATR-FTIR spectroscopy by monitoring the growth of the calcium carboxylate peak ca. 1620 cm -1 . At low molecular weight, the succinic anhydride end-capped PLLA was successfully neutralized and isolated. The Tg of the isolated ionomers demonstrated an increase of ca. 10°C; however, attempts to neutralize higher molecular weight analogs failed, most likely during the work-uphsolation of the ionomer. Following this, PLLA materials carrying functional groups that, in theory, could be readily converted to carboxylic acids were generated through the synthesis of block copolymers using hydroxy-telechelic PLLA. For these materials, an ethylene glycol/stannous octoate system was used to synthesize PLLA containing hydroxyl end-groups. Two different copolymerization techniques were utilized in the synthesis of PLLA-based block copolymers. Block copolymers consisting of 5-methyl-5-benzyloxycarbonyl-1,3-dioxan-2-one (MBC) outerblocks and L-lactide innerblocks were synthesized via ring-opening polymerization using hydroxy-telechelic PLLA as a macroinitiator. (Abstract shortened by UMI.)