(289h) Biobased Polymers from Multicomponent Mixtures for Tuning Properties and Reducing Costs

Economic challenges continue to hamper the adoption of biobased polymers as alternatives to traditional, yet unsustainable, petroleum-based plastics.  Generally, renewable polymers are too expensive due to the significant separation steps required to make purified monomer streams.  In this work, we suggest that materials with reproducible thermal characteristics can be synthesized in a controlled and predictable manner from batches of monomers with complex and somewhat variable compositions, such as minimally processed bio-oils.  The approach of polymerizing complex mixtures should help mitigate separations costs.  We demonstrate this idea through a model system of monomers that can be derived from pyrolyzed Kraft lignin bio-oils and fatty alcohols.  The polymers are synthesized by reversible addition–fragmentation chain-transfer (RAFT) polymerization, which enables subsequent chain-extension and the generation of self-assembling block polymers for thermoplastic elastomer applications.  Kinetic parameters for the multicomponent RAFT polymerizations (chain-transfer coefficients and propagation rate constants) are predicted using kinetic data from corresponding homopolymerizations, reactivity ratios, and feed compositions.  Glass transition and thermal degradation temperatures of the resulting polymers also are shown to be predictable and adjustable prior to polymerization.  Together, this work provides a unique path forward for economically viable biobased materials by demonstrating that for synthetic and behavior control, polymers need not be limited to systems composed of only a few chemically distinct monomer types.