Multiphase biocompatible polymer blends from poly(L-lactide) and poly(methyl methacrylate)

Polymer blending provides a high-throughput method to achieve new materials with targeted properties. Thermal processing of miscible or compatibilized polymers are often preferred, but binary immiscible systems, when processed near the co-continuous composition, can provide excellent properties at lower cost and over a wider range of polymer selection.; The co-continuous region also provides novel and unusual morphologies. Such morphologies are of particular interest in the development of biomaterials, specifically tissue scaffolds and selectively resorbable materials for in-vivo tissue repair or replacement. In this thesis the binary polymer blends of poly(L-lactide) (PLLA) and poly(methyl methacrylate) (PMMA) were studied as a potential biomaterial in which the morphology and the bioresorbability can be engineered via blend processing parameters. Blends were prepared over a full range of compositions and the properties and relationships between blend phases were studied with physical and spectroscopic methods.; The blend system was found to be self-compatibilized by a in-situ generated amorphous phase that provides a linkage between the two immiscible phases. This compatibilizing phase, identified for the first time in this work, possesses a glass transition near 80°C and is generated from the PLLA and PMMA reactants. PG80 imparts synergistic biocompatibility and mechanical properties over a large range of compositions. Self-compatibilization of PLLA/PMMA blends is speculated to arise from dipole pairing of the carbonyl groups which perturbs the packing order of PLLA in blends and enable chain mobility in PMMA at a temperature much lower than its original glass transition. Thermal analysis revealed crystallinity suppression and Raman spectroscopy confirmed the diminishing of characteristic peaks in PLLA helical structure. The vibration of the carbonyl groups in blends shifts to higher wavenumber and indicates that the carbonyl double bond length is slightly shorter in blends due to changes in the local molecular environment of the carbonyl group.; The thesis has identified an interesting binary immiscible polymer blend system that demonstrates differential phase degradability that imparts significant potential for engineered biomaterials. Characterization of the physics of these polymer blends revealed a system that is self-compatibilized by an in-situ generated amorphous phase with unique properties, identified for the first time in this work.