Acid-initiated polymerization of epsilon-caprolactone under microwave irradiation and its application in the preparation of drug controlled release system.

Acid-initiated ring-opening polymerization (ROP) of epsilon-caprolactone (epsilon-CL) was conducted under microwave irradiation (MI) at 2.45 GHz. At this frequency, metallic catalysts were no longer necessary. The effects of microwave power, irradiation time, epsilon-CL: acid molar ratio and acidity of acid on the polymerization were investigated. Both the rate of polymerization and the molar mass of polymer obtained were enhanced in comparison with conventional thermal method. Poly(epsilon-caprolactone) (PCL) with weight-average molar mass (Mw) over 12000 g/mol and Mw/Mn below 1.6 was synthesized in the presence of carboxylic acids such as maleic acid (MA), succinic acid (SA) and adipic acid (AA). The polymerization was also carried out when the monomer contained a certain amount of ibuprofen (IBU), by which, the IBU-PCL controlled release system was prepared directly. The release of IBU from the system was sustained from 12 h to 9 days with IBU content in weight increasing from 5 to 20%. It seems that this is a promising method to prepare drug controlled release systems.