Study On Structure And Self-assembly Behavior Of Gradient Copolymer

The gradient copolymers of p-chlorostyrene(p-ClSt)and methyl acrylate(MA) were synthesized using atom transfer radical polymerization(ATRP),which were catalyzed by CuBr/N,N,N',N",N"-pentamethyldiethylenetriamine(PMDETA)in bulk at 90℃.The results of copolymerization kinetics show that the copolymerzation are "living",because plots of ln([M]_o/[M])verse time and M^?_n verse monomer conversion were linear.The monomer reactivity ratios(r_s=1.2 r_A=0.09)were obtained from ¹HNMR spectra using Mayo-Lewis equation by integral method.A series of gradient copolymers were obtained due to the difference of reactivity ratios and initial feed composition.¹³C NMR was used to characterize the structure of gradient copolymers at different conversions.The triad sequences were determined using the C1 ipso region(aromatic C1 carbon)and the carbonyl resonance frequencies from the spectra.A parameter,gradient index(I),was proposed to characterize the gradient structure of the gradient copolymers for the first time.All kinds of gradient copolymers were characterized by the gradient index(I),and the result show it is suitable for characterize the gradient structure of the gradient copolymers.The self-assembly behavior of polymers is an attractive field which is developing full of vitality in recent years.The amphiphilic polymers formed specific structure through the equilibrium of hydrophobic and hydrophilic effectiveness.These micelles have special functions and can be widely applied in biology,pharmacy,catalyst,and other fields.Recently,much attention have been focused on the amphiphilic block polymers,but studies of amiphiphilic gradient have not been reported.In this thesis, the self-assembly behavior of amphiphilic gradient copolymers in selective solvents was systemically investigated.The regular and reverse micelles were obtained in selective solvents by two methods due to gradient copolymers' property of high p-ClSt content during initial stage and high AA content at the end stage.The size of micelles were studied by dynamic light scattering(DLS)and the morphologies of micelles in aqueous solution were observed by transmission electron microscope (TEM)and atomic force microscopy(AFM).As AA content in gradient copolymer increased,the micelles' hydrodynamic diameter increased correspondingly in aqueous solution,whereas it decreased in nonpolar solution.Furthermore,as the polymer concentration increased in the solution,the morphology of micelles changed progressively from sphere to rod.It is believed that this is the first observation of morphologies of the global and rod-like micelles which were prepared from amphiphilic gradient copolymers.