聚(辛二酸-四甘醇酯)的合成及其微相分离结构的研究

通过熔融缩聚合成了一种新型的两亲性聚酯——聚(辛二酸-四甘醇酯)(PTEGSub),利用GPC,NMR,FTIR,TG,DSC等手段对聚合物的结构进行了表征.研究发现,在25℃时,PTEGSub在水中可以形成胶束,粒径主要集中在20～120nm之间,其临界胶束浓度(CMC)随分子量的升高而降低.通过TEM观察了在选择性溶剂中的胶束形态.利用AFM研究了PTEGSub的微相分离,发现聚合物膜中存在有球状的相分离结构.

SYNTHESIS AND MICROPHASE SEPARATION OFPOLY(TETRAETHYLENE GLYCOL SUBERATE)

A novel amphiphilic biodegradable polyester,poly(tetraethylene glycol suberate)(PTEGSub),was synthesized via melt polycondensation.The resulting polymers were characterized by GPC,NMR,FTIR,DTG and DSC measurements.These amphiphilic polymers are composed of short hydrophilic segments and short hydrophobic segments alternately along their main chains.These homopolymers with the amphiphilic monomers are just like the alternative copolymers of diacids and diols.The fact shows that 40 mg PTEGSub(M_n = 18700) could be dissolved in 100 mL deionized water.While it could be dissolved in the following solvents too:THF,chloroform,acetone,N,N-dimethylformamide(DMF),dimethyl sulfoxide(DMSO),ethyl acetate,ethylene glycol monomethyl ethyl,etc.These results support the conclusion that the polymer is amphiphilic,which could be dissolved in both hydrophilic and hydrophobic solvents.The polymers could self-assemble into polymeric micelles in water.A core-shell structure could be expected.The domains of enriched hydrophilic ethylene glycol oligomers might form a shell and the domains of enriched hydrophobic hydrocarbon ethylene chains would form a core.The diameters of the polymer micelles are mostly in the range of 20～120 nm from statistic data by DLS,although their molecular weights are different in water.This related with structure of PTEGSub whose hydrophilic segments and hydrophobic segments are short.At room temperature,the critical micelle concentrations(CMC) are 6.3×10-7,3.9×10-7,and 1.3×10-7 g/mL when their molecular weights(M_n) are 18700,33300 and 50800,respectively.CMC diminished in accordance with the increasing molecular weights of polymers.Moreover,the success of CMC determination indicates that micelles in water are core-shell structure.Micellar morphologies in different solvents were observed by TEM.The micellar morphology is different depending on solvent.In aqueous solution,most micelles are regular spherical globules.Micelles are compact and beautiful geometrical shapes could be observed.Microphase separation of PTEGSub was studied.Spheres were found on polymeric film by AFM.This profile was proved to form during solvent volatilized on the base of TEM photographs.The result is related with two factors.On one hand,phase separation is prone to take place because solubility parameters are different between hydrophilic segments and hydrophobic segments in the solvent(THF).On the other hand,there is a strong attractive interaction between ester groups of PTEGSub and silanol hydroxyls of hydrophilic mica.However,the interaction of other segments(groups) with the mica surface is weak.Thereby,phase separation is promoted.The process is going on until viscosity of solution is so great when the segments of polymers could not move.The study of microphase separation will be the foundation for the theoretical investigation in near future.