Aliphatic polyester block polymers constitute a highly useful and amazingly versatile class of self-assembled materials. Analogous to styrenic block polymers in both design and function, the property profiles of these degradable materials can be precisely tailored by altering the chemical structure of the components. Driven by this ideal, we have examined the impact of n-alkyl substituents on the polymerization thermodynamics and kinetics of substituted δ-valerolactone monomers and developed guiding design principles based on critical structure-property relationships in the resulting aliphatic polyesters. Under bulk room temperature conditions the polymerization rate depends strongly on substituent position and exhibits a more modest dependence on alkyl length (from -CH3 to -(CH2)8CH3). The enthalpy and entropy of polymerization are significantly influenced by substituent position, but both are largely insensitive to n-alkyl length. However, the physical properties of the resulting aliphatic polyesters depend much more on substituent length than on substituent position. Notably, we demonstrate that polymer entanglement molar mass and solubility parameter can be systematically tuned by changing the substituent length. We discuss how these key structure property relationships can be used to inform the design of advanced sustainable materials for future technologies important in the arena of environmentally friendly materials.
Bibliographical noteFunding Information:
Funding for this work was provided by the Center for Sustainable Polymers at the University of Minnesota, a National Science Foundation (NSF)-supported Center for Chemical Innovation (CHE-1413862). D.K.S. gratefully acknowledges support from the Doctoral Dissertation Fellowship awarded by the University of Minnesota Graduate School. DND-CAT is supported by the E.I. DuPont de Nemours & Co., The Dow Chemical Company, the U.S. National Science Foundation through Grant DMR-9304725, and the State of Illinois through the Department of Commerce and the Board of Higher Education Grant IBHE HECA NWU 96. Use of the APS was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract DE-AC02-06CH11357.
© 2016 American Chemical Society.