Poly(phenyllactide): synthesis, characterization, and hydrolytic degradation.

Poly(phenyllactide) was synthesized via the ring-opening polymerization of phenyllactide, the dimer of phenyllactic acid. Phenyllactide was synthesized by two methods, the solution phase condensation of L-phenyllactic acid and by thermal cracking of low molecular weight phenyllactic acid oligomers. The poor solubility of the monomer limited solution polymerizations of phenyllactide to low yields and low molecular weights, but melt polymerization of phenyllactide with Sn(Oct)2/tert-butylbenzyl alcohol at 180 degrees C gave high molecular weight polymers in high yields. The resulting polymers were amorphous due to epimerization of approximately 10% of the stereocenters during polymerization. Poly(phenyllactide) has a glass transition temperature of 50 degrees C and degrades to monomer at 320 degrees C. Experiments run at 55 degrees C at pH 7.4 show that poly(phenyllactide) degrades at approximately 1/5 the rate of rac-polylactide.