Study On Synthesizing AB Block And AB_n Graft Copolymer By Mechanism Transformation

In this article, block copolymer poly(butadiene-block-2-hydroxyethyl methacrylate)(PB-b-PHEMA) and graft copolymer poly(isoprene-graft-methyl methacrylate)(PI-g-PMMA) and poly(styrene-isoprene-styrene-graft-methyl methacrylate)(SIS-g-PMMA) are synthesized by transformation of living anionic polymerization (LAP) into atom transfer radical polymerization (ATRP). Major work and conclusions are as follows:1. Firstly, the2-bromoisobutyryl-terminated macroinitiators of PB-Br with predetermined molecular weight and microstructure have been originally attempted by anionic polymerization of butadiene with n-butyllithium initiator in the solvent of cyclohexane, and then the living PB chains are extended with propylene oxide (PO) and terminated by2-bromoisobutyryl bromide (BriBBr). The prepared PB-Br has high bromine content and narrow molecular weight distribution. Then, the macroinitiators PB-Br are used to initiate the ATRP of HEMA with the ligand pentamethyldiethylenetriamine (PMDETA) and the catalyst CuCl, and therefore amphiphilic block copolymer PB-b-PHEMA is prepared. The macroinitiators PB-Br and amphiphilic block copolymer PB-b-PHEMA are characterized by Fourier Transform Infrared Spectrometer (FT-IR)、1H nuclear magnetic resonance spectroscopy (’H NMR)、differential scanning calorimeter (DSC) and Gel Permeation Chromatography (GPC). The results indicate that well-defined target products with controlled molecular weight and low molecular weight distribution are obtained. In addition, the effect of temperature and solvent on polymerization of ATRP of HEMA is investigated.2. Polyisoprene (PI) with predetermined molecular weight and microstructure is synthesized by anionic polymerization of butadiene with n-butyllithium initiator in the solvent of cyclohexane. PI is modified into epoxidized polyisoprene (EPI) with performic acid in situ from hydrogen peroxide and formic acid. Epoxy groups on the polymer were ring-opened to hydroxyl groups using an acid-catalyzed nucleophilic reaction of small amounts of water dissolved in THF. Hydroxylated polyisoprene (HPI) is esterified by2-bromoisobutyryl bromide (BriBBr) into multifunctional macroinitiator PI-Br. Then, the multifunctional macroinitiator PI-Br is used to initiate the ATRP of MMA to prepare graft copolymer PI-g-PMMA. Polymerization kinetics of the ATRP of MMA exhibits the characteristics of "living"/Controlled. Multifunctional macroinitiators PI-Br and graft copolymer PI-g-PMMA are characterized by FT-IR、1H NMR. DSC and GPC. The results indicate that well-defined target products with controlled molecular weight and low molecular weight distribution are obtained. The effect of different factors on ring opening reaction of EPI and esterification reaction of HPI is discussed respectively and the effect of solvent on polymerization of ATRP of MMA is investigated.3. Styrene-isoprene-styrene (SIS) block copolymer is modified into epoxidized styrene-isoprene-styrene (ESIS) block copolymer with performic acid generated in situ from hydrogen peroxide and formic acid. Epoxy groups on the polymer are ring-opened to hydroxyl groups using an acid-catalyzed nucleophilic reaction of small amounts of water dissolved in THF. Hydroxylated Styrene-isoprene-styrene (HSIS) block copolymer is esterified by2-bromoisobutyryl bromide (BriBBr) into multifunctional macroinitiator SIS-Br. Then, multifunctional macroinitiator SIS-Br are used to initiate the ATRP of MMA to prepare graft copolymer SIS-g-PMMA. Multifunctional macroinitiators SIS-Br and graft copolymer SIS-g-PMMA are characterized by FT-IR、1H NMR、DSC and GPC. The results indicate that well-defined target products with controlled molecular weight and low molecular weight distribution are obtained. The effect of different factors on ring opening reaction of ESIS and esterification reaction of HSIS is discussed respectively.