Can Be Biodegradable Polycarbonate Preparation And Properties

Polycarbonate has wide application potential such as medical and engineering materials fields as one of degradable polymer due to its biocompatability and non-toxicity. Using CO2 to synthesize aliphatic polycarbonates has great conducting significance for utilization of reproducible resource effectively and exploring green polymer field.In this paper, a new biodegradable terpolymer PPC-LA-PPO-LA was synthesized by anionic complexation, which was the terpolymerization of carbon dioxde, propylene oxide(PO) and lactide(LA) by introducing the third monomer lactide unit to insert into the backbone of poly(propylene carbonate). The structure of copolymers were characterized by FT-IR, NMR, WAXD and elemental analysis measurements. And the expected mechanism of copolymerization was proposed. Meanwhile, the effect of lactide contents on copolymer was studied. The results revealed that the degradability of copolymers was improved more with higher molar contents of LA. When the molar fraction of LA is 9.35%, the mass loss is 23% in simulated body fluid during 10 weeks. The change of molecular weight suggested surface erosion was predominant.A new computational method called nonlinear approximation method(NLA) was introduced in this work and the thermal decomposition kinetics of PPC-LA-PPO-LA was also studied. The results showed NLA method was an ideal choice for Ea calculation due to its more simple and appropriate analysis process. The average relative error was less than 6.5% when Vyazovkin model free method was chosen as the standard method. During the whole degradation process, the apparent activation values were 66.6-140.3kJ·mol-1 for PPC-LA-PPO-LA, indicating multi-step reaction process and multiple mechanisms for the pyrolysis of terpolymers.PPC-LA-PPO-LA-BSA microspheres were prepared by the W/O/W multiple emusions method in various preparation conditions.The effect of concentration of gelatin in external water phase on drug loading abilities was studied. The results indicated that the microspheres had poor drug loading and entrapment efficiency abilities due to residual impurities contained in polymer.