Biodegradable polymers derived from renewable resources: Highly branched copolymers of itaconic anhydride

Date of Completion

January 2000

Keywords

Chemistry, Polymer|Environmental Sciences|Engineering, Environmental|Engineering, Materials Science

Degree

Ph.D.

Abstract

In an effort to design cyclic anhydride containing polymers that are derived from renewable resources and have biodegradable characteristics, three copolymer systems using itaconic anhydride have been studied. Two of the systems were copolymers with stearate based monomers; vinyl stearate and stearyl methacrylate, while the third was a copolymer with a methacrylate terminated poly (lactic acid) (PLA) macromonomer. For the stearate systems, stearyl methacrylate showed good copolymerization with equal conversions for both monomers. On the other hand vinyl stearate did not show as good results due to its decreased reactivity, which resulted in a copolymer highly enriched in itaconic anhydride with significant amounts of unreacted vinyl stearate under all copolymer compositions. These differing results were confirmed through analysis of reactivity ratios showing a results that are more favorable for copolymerization for the methacrylate system. Copolymers from both systems showed single melting transitions in a precarious range of 45–50°C arising from the stearyl side groups, though after quenching from the melt this shifted to below room temperature. Anhydride retention was confirmed through structural analysis. ^ Similar to the stearyl methacrylate system, methacrylate terminated PLA macromonomers were copolymerized with itaconic anhydride. PLA's acceptance as a biodegradable material derived from renewable resources, make it a viable choice, with which to design anhydride containing copolymers. Good copolymerization was shown for all compositions studied with retention of the anhydride, though at high itaconic anhydride concentrations conversions were reduced significantly. Copolymers showed glass transition temperatures ranging from 32°C for 85 mole % PLA macromonomer to 73°C for 85 mole % itaconic anhydride. ^ An effort to produce PLA macromonomers through a process of chemical recycling commercial PLA was also undertaken. Promising results were obtained showing similar properties to macromonomers produced through the ring opening polymerization with significant gains in time from 12–24h for the polymerization to 0.5–1h for recycling. Broadening this process to other biodegradable polyesters of poly (caprolactone) (PCL) and poly (hydroxy butyric acid– co-hydroxy valeric acid) (Biopol) showed good results with PCL, though poor results were obtained with Biopol arising from its decreased thermal stability. ^

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