Synthesis And Solution Self-assembly Of Polyethylene-block-poly(methyl Methacrylate)

Because of the simple structure and strong crystallinity of polyethylene,polyethylene-based block polymers exhibit some special self-assembled morphologies.The aim of this paper is to investigate the effect of crystalltion-driven force on the morphology of micelles during the self-assembly of polyethylene group block copolymers in selective solvents.The full text is divided into three parts:1.Three polyethylene-block-poly(methyl methacrylate)(PE_n-b-PMMA_m)crystalline-coil copolymers with very similar block mass ratios(r=M_PE/M_PMMA=1)but different molar masses were synthesized.The molecular weight,the molecular structure and the thermal properties of copolymers were characterized by gel permeation chromatography(GPC),thermogravimetric analysis(TGA),proton nuclear magnetic resonance(¹H-NMR),fourier transform infrared spectroscopies(FTIR),and differential scanning calorimetry(DSC),respectively.The self-assembly behavior of polymer in toluene solution was studied by changing the cooling rate.The experiment results shown that the cooling rate could affect the crystallization-driven force of copolymers,which made a big difference in the size of micelles.2.The self-assembly behavior of three copolymers with different molar masses in toluene solution was studied by changing the crystallization temperature.The experiment results shown that the initial large compound micelles were decomposed into small micelles,then crystallized and assembled into fusiform aggregates due to the change of solubility and crystallization with the decrease of crystallization temperature.In addition,molar masses may affect the stability and decomposition temperature of large compound micelles.3.The self-assembly behavior of copolymers in chloroform/tolution mixed solution and DMF solution were studied by changing the solvent properties.The experoment results shown that the interface energy of the small micelles increased,and more small micelles gathered together with the increase of chloroform ratio.So the size of fusiform aggregates increased,the crystallization weakened,and the main reason for aggregation into fusiform aggregates was no longer crystallization.In the more polar DMF,the size of columnar micelles changes significantly by the combined action of micellization and crystallization with the decrease of temperature,while the molar masses may affect the solubility of the copolymers and the difficulty of micelle growth.In summary,three polyethylene-block-poly(methyl methacrylate)crystalline-coil copolymers with very similar block mass ratios(r=M_PE/M_PMMA=1)but different molar masses were synthesized.The effect of crystallization on the morphology of micelles was discussed by changing the cooling rate,crystallization temperature and solvent properties in different selective solvents.