University of Connecticut |
Polymer Program SeminarFrom Waste Cellulose to Functional Polycarbonates Friday, April 28, 2006 11:00 am , IMS Room 20 A process for the commercial production of diphenolic acid [4-(bis (hydroxyphenyl))pentanoic acid, DPA] in good yield from cellulose-rich sources such as wood, paper, sewage sludge, paper mill sludge and food processing waste via levulinic acid has been developed*. Materials derived from this monomer such as polycarbonate homo- and copolymers (with bis-phenol A, BPA) have been prepared and their properties have been studied. The influence of copolymer composition on thermal properties of these materials has been determined. Blends of polycarbonates from BPA and from DPA appear to be compatible with each other. Soluble but highly branched polyester can be prepared from bis-acetoxy DPA by a thermally induced polycondensation interchange reaction with the elimination of acetic acid. Extremely high apparent molecular weights are attainable in this way. Further reaction yields very high molecular weight crosslinked materials. The preparation of the t-butyl ester of DPA enables the formation of homo- and co-polycarbonates in which the blocking group can be removed to give free carboxyl groups along the polymer backbone. Such materials exhibit classic polyelectrolyte behavior. The sodium salt of the homo polycarbonate carboxylate is surprisingly stable to hydrolysis in alkaline solutions. Neutralization of the carboxyl groups with polyvalent counter ions leads to crosslinked gels. The carboxyl groups can also serve as the locus for grafting reactions leading to materials with unusual properties. *In the vein of: "When Nature gives you lemons, don't whimper or despair. For so it goes, and always has -- lemons are a dare. Rise up to face them, to use them, or to share, Dare to make lemonade, each time and everywhere."
|