Synthesis and Characterization of Biopolymer Composites and their Inorganic Hosts

Abstract

Biopolymers are biodegradable and biocompatible materials obtained from renewable sources. These polymers could have an increased impact in consumer or health applications, given a larger, more flexible range of physical properties. Targeting enhanced properties through the design of organic-inorganic hybrids requires novel synthesis routes. An in-situ polymer composite that differs from hybrids generated by simple mixing of the organic and inorganic phases, has been demonstrated here. A known ring opening polymerization catalyst was incorporated within the channels of mesoporous hosts (e.g. MCM-41). A combination of elemental, solid-state NMR, BET nitrogen adsorption, and microscopy experiments indicated that the stannous octoate catalyst was supported inside the host channels, and that a charged framework is not required for its incorporation. These Sn(Oct)2 supported mesoporous catalysts were used to prepare poly(d,l-lactide) composites. Multiple experiments, including solid state NMR, BET nitrogen adsorption, and calorimetric analysis, gave evidence that the resulting polymer forms inside the host channels. In this way, an organic-inorganic composite which grows out of the crystallites is generated in-situ. Additionally, the acid catalyzed condensation polymerization of lactic acid with micro/mesoporous materials was investigated. Results suggest that Al-SBA-15 is a potential catalyst for this type of polymerization. This approach is desirable, since the generated organic-inorganic composite would contain no impurities (i.e. metal catalysts).