Microwave‐assisted ring‐opening copolymerization and property of polycarbonates

Recently, the microwave-assisted heating method has become a commonly used and environmentally friendly heating technology in the field of organic and polymeric synthetic chemistry. A series of poly(5,5-dimethyl trimethylenecarbonate-co-2-phenyl-5,5-bis[oxymethyl] trimethylenecarbonate) (P[DTC-co-PTC]) were synthesized by microwave-assisted ring-opening polymerization of 5,5-dimethyl trimethylene carbonate (DTC) and 2-phenyl-5,5-bis(oxymethyl) trimethylene carbonate (PTC) using tin(II) 2-ethylhexanoate and aluminum isopropoxidase, the catalysts. These co-polycarbonates were further reduced by a palladium-carbon catalyst (Pd/C catalyst, 10%) to make partly deprotected polycarbonates (HPDPC). These two co-polycarbonates were characterized by gel permeation chromatography, (HNMR)-H-1, Fourier transform infrared spectroscopy, UV, differential scanning calorimetry, and automatic contact-angle measurements. The influences of the microwave irradiation time, microwave power, monomer feed molar ratio, different catalysts, and monomer/catalyst feed molar ratio on the molecular weights of co-polycarbonates were also investigated. In vitro water absorption, degradation and drug release tests indicated that partly deprotected co-polycarbonate HPDPC possessed greater hydrophilicity, faster degradation rate, and faster drug release rate than that of corresponding P(DTC-co-PTC). Therefore, microwave-assisted polymerization is a clean and cheap heating method and can be used for ring-opening copolymerization of carbonates, which enhances the hydrophilicity and biodegradation rate of aliphatic polycarbonates.