The development of tunable and degradable crosslinked-polyanhydride networks from renewably derived itaconic anhydrides and multifunctional thiols is presented. Itaconic acid was initially converted to ethyl itaconic anhydride and isoamyl itaconic anhydrideviaa two-step synthetic procedure on hundred-gram scale with minimal purification. Dinorbornene-functionalized derivatives were preparedviacycloaddition chemistry, and photoinitiated thiol-ene polymerization reactions were explored using commercially available tetra- and hexa-functional thiols, all using solvent-free syntheses. The thiol-ene reaction kinetics of different monomer compositions were characterized by real-time Fourier transform infrared (RT-FTIR) spectroscopy, with the norbornene functionalized derivatives exhibiting the highest reactivity towards thiol-ene photopolymerizations. The thermal and mechanical characteristics of the thermosets were analyzed and the viscoelastic behavior was investigated by dynamic mechanical analysis to understand the influence of the ester functionality and choice of crosslinker on the material properties. The anhydride backbone was found to be susceptible to controlled degradation under physiologically-(phosphate-buffered saline) and environmentally-relevant (artificial seawater) testing conditions over a period of 60 days at 50 °C. This work demonstrates that itaconic acid may be a useful feedstock in the generation of degradable polyanhydride networksviathiol-ene photopolymerization.
Bibliographical noteFunding Information:
This work was supported by the National Science Foundation under the Center for Sustainable Polymers (CHE-1901635) and by the National Science Foundation Graduate Research Fellowship Program (to C. M. Lau) under Grant no. DGE-1348264. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.