Research On Synthesis And Properties Of PDMS-PU/ST Composite

A series of siloxane modified polyurethane solutions were synthesized by combining prepolymerization, chain-extension, neutralization, and dispersion methods based on polyethylene glycol(PEG), polydimethylsiloxane(PDMS), isophorone diisocyanate(IPDI), triethylamine(TEA), and dimethylolpropionic acid (DMPA) as chain extender. And the optimum reaction conditions were systematically studied as well. The results showed that the optimum reaction conditions were as follows:the prepolymer temperature was70℃; the prepolymerization time was2.5h; Chain-extendering time was3h; the concentration of PDMS was less than4%; acetone as solvent was60%.PDMS-PU/ST microsphere was a new composite microsphere which was prepared by the coacervation phase separation method. The result revealed that optimum composite microsphere would be prepared when the optimal conditions of synthesizing were as follows: the mole ratio of IPDI and PEG was3:1; the optimum concentration of starch was less than8%; the PEG molecular weight was200; the concentrations of PDMS-PU/ST aqueous solution was35-40%; the concentrations of CaCl2was more than8%.The scanning electron microscopy (SEM) figures showed that composite microsphere shape was round. There are many cavums in microsphere’interior. and it was good for water resorbance and drug release. The average diameter of the composite microspheres was about2.10mm. The FTIR analysis showed that siloxane chain segments had been embedded into composite microsphere; hydroxyl association stretching vibration located at3400cm-1, and it was strengthened. It proved that there are hydrogen bonds forming in PU and ST. The swelling rate of composite microsphere increased gradually with the increase of the content of ST. The composite microsphere belonged to surface degradation,and the degradation rate can be controlled by changing the content of ST. The hemolysis rate of PDMS-PU/ST composite microsphere was less than5%, which complied with nation safety standards. It proved that the composite microspheres did not cause hemolysis.The drug-carried PDMS-PU/ST composite microsphere was prepared by coacervation phase separation method with Tetracycline Hydrochloride (TH) as drug model. The drug-loading rate increased and then balance with the increase of the drug concentration and encapsulation ratio of PU microspheres presented increasing first then decreasing tendency. The study of drug-releasing indicated that the composite microsphere can delay the releasing behavior of TH.The drug release ratio from micosohere increased with the increase of temperature and the release speed of drug increased with the mass fraction of starch. So we can control the release speed of drug by changing the mass fraction of starch.