A Novel Estimation Method of the Distribution of Carboxyl Groups Within Copolymer Particles Using Isothermal Titration Calorimeter

Summary: A novel quantitative method using isothermal titration calorimeter (ITC) for the estimation of the distribution of carboxyl groups within polymer particles has been proposed. The method has been employed to clarify the difference in the distribution between the particles prepared by batch emulsion copolymerization of styrene and methacrylic acid under inefficient and efficient stirring conditions. At inefficient stirring, monomer was floating as a layer on the aqueous medium, whereas at efficient stirring, the monomer phase was dispersed as droplets. Under inefficient stirring, methacrylic acid (MAA) polymerized faster than styrene (S) due to a slower diffusion rate of S than MAA into the aqueous medium, while under efficient stirring, S and MAA copolymerized at similar rates. ITC measurement showed that under inefficient stirring, the carboxyl groups were distributed mainly in the center of the particles, and their number decreased toward the surface. On the other hand, under efficient stirring, carboxyl groups were distributed homogeneously inside the particle.     

LixCoO2及其与LiPF6/EC+DEC电解液的热稳定性研究

使用C80微量量热仪对不同充电状态下LixCoO2的热稳定性、LixCoO2与1.0molLLiPF6EC DEC(质量比=11)电解液的热稳定性进行了研究。结果表明,LixCoO2的放热量和主放热峰温度随x值减小而增加,Li0.05CoO2在271.8℃达到放热峰,总放热量高达1575.5Jg。LixCoO2与电解液反应时,LixCoO2首先分解出的氧气使电解液氧化,同时电解液也发生分解等反应,放热峰温度随x的增大呈增大趋势,放热量随x的增大呈减少的趋势。此外,LixCoO2与电解液反应产生大量的CO2、HF等气体。