Synthesis Of Photo-sensitivity Amphiphilic Block Copolymer By ATRP And Its Micellization

Atom transfer radical polymerization (ATRP) is a new effective method to preparecontrolled well-defined block copolymers .Two different amphiphilic block copolymers withthe photo-sensitive property of PFMnC-b-PMAA and PFMnC-b-PEG-b-PFMnC were preparedin two different ways by ATRP. Therefore, amphiphilic block copolymer's micellization wasinvestigated through self-assembly in water.The caprolactone-modified acrylates (FMn) are a series of novel monomer in bothstructure and character, which have different number of ε-caprolactone unit that can bedegradated.Series of photo-sensitive macromonomer FMnC (n=1~5) were synthesized byacylation reaction of FMn with cinnamyl choride.Halogen-terminated PFMnC-Br was synthesized by atom transfer radical polymerizationof photo-sensitive macromonomer FMnC using ethyl-α-bromopropionate (EPN-Br) as initiatorand CuCl/ N,N,N′,N″N″-pentamethyldiethylenetriamine (PMDETA) complex as the catalystsystem. PFMnC-Br was used as macroinitiator to initiate the ATRP of t-butylmethacrylate(t-BMA), thus PFMnC-b-P(t-BMA) with narrow distribution was obtained. After hydrolyzationand acidition, the amphiphilic diblock copolymers PFMnC-b-PMAA was prepared. Thestructures and properties of the resulted products were characterized by using IR, UV, 1H-NMRand GPC. The rule of the polymerization of ATRP was discussed in detail. The results showthat the process may be a "living/controlled" polymerization. The copolymers form sphericalmicelles in water with PFMnC chain as the core and PMAA chain as the corona. Furthermore,the effects of the ratio of PFMnC to PMAA , the n value of monomer FMnC , the concentrationof polymer solution, the ratio of selective solvents, pH value and the ionic strength on thesizes of micelles were investigated by dynamic laser light scattering(DLS).A series of PEG macroinitiators (Br-PEG-Br) were prepared by the reaction betweenmonodisperse PEG and 2-bromoisobutyryl bromide, and the synthesis of the ABA-typeamphiphilic triblock copolymers with the photo-sensitive property (PFM1C-b-PEG-b-PFM1C)via atom transfer radical polymerization with CuCl/ PMDETA complex as the catalyst systemwas studied .The results showed that the number average molecular weight is close to thetheoretical value ,which is characteristic of the living polymerization . At last ,the micellizationof PFM1C-b-PEG-b-PFM1C in water and some factors that influenced the micellization werestudied by DLS.The results show that the triblock copolymer could self-assemble intonanometer micelles with narrow distribution, and of the cross-linked micelles is smallerthan that of uncross-linked micelles .