摘要
以醋酸乙烯酯(VAc)和丙烯酸丁酯(BA)为原料,用半连续加料法合成共聚物。研究VAc/BA共聚合的3个阶段(种子预聚合阶段、单体滴加阶段和保温熟化阶段)所得共聚物组成和微观序列结构的变化规律,采用FT-IR、13C-NMR、DSC表征聚合物的结构和玻璃化转变温度(Tg),分析聚合物共聚组成和序列结构随反应阶段的变化,采用1级Markov模型分析共聚物的序列结构分布。研究结果表明,半连续加料法制备的VAc/BA共聚物组成与序列结构在不同反应阶段存在明显变化。在预聚合阶段,单体浓度处于充溢态,聚合物中含有富BA单元的链段和富VAc单元的链段;反应进入单体滴加阶段,单体浓度处于饥饿态,生成共聚组成接近于加料比的均匀共聚物,VAc的数均序列长度(la)与BA的数均序列长度(lb)均较小。
Vinyl acetate（VAc）/butyl acrylate（BA） random copolymers have been prepared by seeded emulsion polymerization following a semi-continuous feeding method.The copolymerization process consists of three reaction stages,namely the pre-polymerization stage,monomer dropwise addition stage,and constant temperature stage.The structure and glass transition temperature（Tg） values of the copolymers obtained in the three different reaction stages were characterized by Fourier transform infrared（FT-IR） spectroscopy,13C-nuclear magnetic resonance（NMR） spectroscopy and differential scanning calorimetry（DSC） in order to analyze the composition and sequence structure of the copolymers at the three reaction stages,and the sequence distribution was calculated using the first-order Markov statistical model.The results showed that the final VAc/BA copolymer was an apparently random copolymer with a single Tg value.However,the composition and sequence structure of the copolymers changed markedly during different polymerization stages due to the changes in monomer concentration.Copolymers composed of BA-rich and VAc-rich segments,with two Tg values and a high average sequence length of BA（lb）,were the main products during the pre-polymerization stage because of the high monomer concentrations.Random VAc/BA copolymers with only one Tg value,a lower value of lb,and a lower average sequence length of VAc（la） were obtained during the monomer dropwise addition stage,where the monomer concentration was controlled by the rate of monomer addition.
出处
《北京化工大学学报（自然科学版）》
CAS
CSCD
北大核心
2011年第3期50-54,共5页
Journal of Beijing University of Chemical Technology(Natural Science Edition)
关键词
VAc/BA共聚物
种子乳液聚合
共聚物组成
序列结构
VAc/BA copolymer
seeded emulsion polymerization
copolymer composition
sequence structure
