SYNTHESIS AND CHARACTERIZATION OF ALIPHATIC POLYCARBONATEDIOLS

Two kinds of aliphatic polycarbonate diols were synthesized by carbonate interchange reaction of aliphatic diols (1,4 butanediol and 1,6 hexanediol) with diethyl carbonate. The process of synthesis can be divided into three steps: first, reflux for 2 h~3 h; second, distillation of by product, ethanol; third, reaction in vacuum for 1 h~2 h. During reflux reaction in a flask soaked in a 160 ℃ oil bath, the temperature of the reactant gradually self decreased due to the formation of low boiling point by product, ethanol. With the removing of ethanol out of the reaction system in the second step, the flask inner temperature self increased reaching to the oil temperature. The third step of synthesis was carried out under 160 ℃~180 ℃ and about 6665 Pa. The choice and content of catalyst had great effects on the rate of reaction. Sodium ethylate was the better catalyst than butyl titanate. The best content of sodium ethylate was 0.25% ~ 0.50% by mass of aliphatic diols (1,4 butanediol or 1,6 hexanediol). The hydroxyl functionalities of all polycarbonates were about 2 according to the absolute molecular weights by ice point decrease and hydroxyl values by endgroup titration. The chemical structures of aliphatic polycarbonatediols were determined and confirmed by FT IR, 1H NMR and elemental analysis.