Degradable Thermosets from Sugar-Derived Dilactones

Using the sugar derivatives glucarodilactone and mannarodilactone, two new dimethacrylate monomers (GDMA and MDMA) were synthesized by a tin-catalyzed alcohol-isocyanate coupling between the dilactones and isocyanatoethyl methacrylate. GDMA was polymerized using thermally initiated free radical polymerization at 135 degrees C in the presence of dicumyl peroxide as an initiator. The fractional conversion of methacrylate groups in PGDMA was determined by FT-IR to be 0.64, within the typical range of poly(dimethacrylates). Tensile testing of PGDMA demonstrated the stiff but brittle nature of this material and the modulus was shown to be similar to that reported for commercially available poly(dimethacrylates) from rigid monomers. The hydrolytic stability of PGDMA was investigated by submersing polymer samples in acidic, neutral, and basic aqueous environments. PGDMA degraded to water-soluble components after 17 days in 1 M NaOH but remained stable under acidic and neutral conditions. Solvent casting a mixture of GDMA, MDMA, and benzoyl peroxide followed by thermal curing at 95 C gave clear P(GDMA-co-MDMA) (3:2) coatings. These coatings showed similar hydrolytic stability to the bulk PGDMA material. GDMA and methyl methacrylate (MMA) were used to synthesize P(GDMA-co-MMA) microspheres by precipitation polymerization in THF. These particles were characterized by dynamic light scattering (DLS) in THF and in the dry state by scanning electron microscopy. Optimization of polymerization conditions yielded 730 nm diameter particles with a spherical morphology and low dispersity as determined by DLS.