We report here the synthesis of a novel substituted polyvalerolactone from the renewable monomer, 4-carbomethoxyvalerolactone (CMVL, two steps from malic acid). The polymerization proceeds to high equilibrium monomer conversion to give the semicrystalline carbomethoxylated polyester with low dispersity. The material displays a glass transition temperature of -18 °C and two melting temperatures at 68 and 86 °C. This polymer can be chemically recycled by either of two independent pathways. The first (red) cleanly returns CMVL by a backbiting depolymerization from the hydroxy terminus; the second (blue) uses a base to cleave the polyester in a retro-oxa-Michael fashion. This affords a methacrylate-like monomer that we have polymerized radically to a new polymethacrylate analogue. This is a rare example of a polymer that has been shown to have two independent chemical recycling pathways leading to two different classes of monomers.
Bibliographical noteFunding Information:
Financial support for this work was provided by the Center for Sustainable Polymers at the University of Minnesota, an NSF-supported Center for Chemical Innovation (CHE-1413862). Some of the NMR data were obtained with an instrument whose purchase was enabled by the NIH Shared Instrumentation Grant program (S10OD011952). We appreciate the help of Aaron Massari (University of Minnesota) in collecting the gas-phase infrared data.