Synthesis Of Environmental Responsive Block Copolymer By ATRP And Its Self-Assembly Behavior

This paper’s main work is to prepare two different macroinitiators by2-bromoisobutyryl bromide and methoxy polyethylene glycol (MPEG) with different number-average molecular weight through esterification reaction, The monomer tert-butyl methacrylate(t-BMA) and6-[4-(4-methoxy phenyl azo)phenoxy]hexyl methacrylate (AZO) introduced to the polymerization system. We obtained amphiphilic block copolymers including AB-type diblock MPEGm-b-PtBMAn and MPEGm-b-PAZOn through atom transfer radical polymerization (ATRP), the formation of copolymers were confirmed by1H NMR, GPC and FT-IR. Analysis results show that this series of block copolymer structure, controlled molecular weight and narrow molecular weight distribution. And different chain length were studied the self-assembly behavior of copolymer in aqueous solution, the pH-responsive of MPEGm-b-PMAAn and the light-responsive of MPEGm-b-PAZOn, as well as both a two-component supramolecular system. The main contents include three parts as follows:(1) With the macroinitiators prepared by2-bromoisobutyryl bromide and methoxy poly(ethylene glycol) and the monomer of t-BMA, In the catalytic system of the CuBr/PMDETA in atom transfer radical polymerization (ATRP) with bulk polymerization occurred, the AB amphiphilic block copolymer of MPEGm-b-PtMBAn is obtained. These block copolymers dissolving in cosolvent added with water by drops. In this process the micelle were formed with hydrophobic block PtBMA as the core and hydrophilic block MPEG loop chain as the corona. Using ultraviolet-visible spectrophotometer (UV-Vis) to observed the changes of the solution’s absorbance, and get the critical water content (CWC) values increases with the relative length of hydrophobic block MPEG and increases with the decrease of the solution concentration.The parents water-soluble pH-responsive block copolymers MPEGm-b-PMAAn were gaind with block of synthetic polymer MPEGm-b-PtMBAn through hydrolysis reaction. Confecting polymer aqueous solution, the solution pH adjusted in acidic aqueous which pH<4.4, carboxylic acid groups make the PMAA the protonation to become hydrophobic and the micelles liked "Core-shell" were gained, the self-assembly process by ultraviolet visible spectrophotometer (UV-Vis) monitoring. (2) With the macroinitiators were synthesized by2-bromoisobutyryl bromide and methoxy poly(ethylene glycol) and the monomer of AZO, In the catalytic system of the CuBr/PMDETA and CuCl/Me6TREN with benzene methyl ether as solvent in atom transfer radical polymerization (ATRP) with bulk polymerization occurred, the AB amphiphilic photo-responsive block copolymer of MPEGm-b-PAZOn is obtained. These block copolymers dissolving in cosolvent added with water by drops. In the system the micelle were formed with hydrophobic block PAZO as the core and hydrophilic block MPEG loop chain as the shell. Using ultraviolet-visible spectrophotometer (UV-Vis) the changes of the solution’s absorbance observed, The CWC values were decreased by the increased of the relative length of hydrophobic block PAZO and solution concentration increased.For MPEGm-b-PAZOn tetrahydrofuran solution to UV irradiation, through uv-vis spectrometer monitoring, it can be seen the characteristic peak at359nm and445nm after UV irradiation has changed, the block copolymer of MPEGm-b-PAZOn has a light responsive.(3) In selective solution, supramolecular self-assembly with the two component of MPEGm-b-PMAAn and MPEGm-b-PAZOn were occured. The changes of the supramolecular self-assembly under the solution pH change.