A novel amphiphilic biodegradable polyester

poly(tetraethylene glycol suberate) (PTEGSub)

was synthesized viamelt 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 (Mn = 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 1.3×10-7g/mL when their molecular weights (Mn) 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.