Regio-Random Clemmensen Reduction Of Biodegradable Polyesters For Photochemically Triggered 3d Printing

A zinc/acetic acid-mediated Clemmensen reduction coupled with sonication affords a time-dependent regio-random reduction of degradable poly(propylene maleate) oligomers to poly(propylene fumarate-co-propylene succinate) co-polymers. Characterization by H-1 and C-13 NMR spectroscopy, size exclusion chromatography, UV-vis spectroscopy, differential scanning calorimetry, and rheology demonstrates that the solvent used for the reduction can be tuned to afford copolymers with random succinate content not previously accessible without chain scission. These copolymers show lower molar extinction coefficients and reduced viscosities compared to previous unsaturated analogues. Together these features afford faster and improved 3D-printability using stereolithographic conditions. The variation in network properties, succinate stoichiometry, and polymer mass fraction allow the mechanical properties of the photochemically printed structures to be tuned widely.