Chemistry, Functionality, and Coating Performance of Biobased Copolycarbonates from 1,4:3,6-Dianhydrohexitols

Biobased polycarbonates were synthesized from 1,4:3,6-dianhydro-D-glucitol, 1,4:3,6-dianhydro-L-iditol, and 1,4:3,6-dianhydro-D-mannitol as the principal diols, using different types of carbonyl sources. The (co)polycarbonates resulting from polycondensation reactions in solution using triphosgene consisted of several types of polymer chains with respect to chain topology (e. g., linear or cyclic chains) and end-group structure (e. g., hydroxyl, chloroformate or alkyl chloride end-groups). The introduction of flexible comonomers seemed to increase the amount of cyclic structures in the product mixtures. The melt polymerization of diphenyl carbonate with 1,4:3,6-dianhydrohexitols required high reaction temperatures and led to almost exclusively hydroxy-functional poly(1,4:3,6-dianhydrohexitol carbonate)s. Copolymerizing the 1,4:3,6-dianhydrohexitols with 1,3-propanediol and diphenyl carbonate at high temperature resulted in the partial loss of 1,3-propanediol. On the other hand, by melt polycondensation of 1,4:3,6-dianhydrohexitol-based bis(phenyl carbonate) monomers in combination with primary diols and/or triols, the insertion of the primary alcohols could be achieved in a more controlled way. OH-functional materials were prepared, having suitable molecular weights, T(g) values, thermal stability, and melt viscosity profiles for (powder) coating applications. These functional biobased (co)polycarbonates were cured with polyisocyanate curing agents, resulting in colorless to pale yellow transparent, glossy coatings with good mechanical performance and solvent resistance. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 1450-1463, 2011