Study On Disassembly Behavior Of Crystalline Micelles Of PCL-b-PDM Block Copolymers

Recently,crystallization-driven self-assembly of block copolymers has gained great attentions because of its unique characteristics and advantages.The shape of crystalline micelles of BCPs can be regulated by changing crystallization conditions as well as cha:in structure.In this reseach,we studied the morphology of poly(?-caprolactone)-b-poly((dimethylamino)ethyl methacrylate)(PCL-b-PDM)crystalline micelles and its disassembly behavior with transmission electron microscopy(TEM)as the main characterization tool.Firstly,the effect of adding n-hexanol on the morphological transition of PCL-b-PDM lamellar crystalline micelles in the aqueous solutionwas investigated.It was found that the addition of n-hexanol could induce specific disassembly of PCL-b-PDM lamellar crystalline micelles into cylinders.The disassembly was probably caused by the moderate hydrogen-bonding interaction between the PCL crystals in the micellar core and the additive n-hexanol.The disassembly rate was quite slow and a certain amount of n-hexanol was required for complete disassembly.The PCL crystals were partially cleaved along the(200)crystal plane in the presence of n-hexanol.To our best knowledge,this is the first report on specific disassembly of lamellar crystalline micelles into cylinders so far.Secondly,the effect of altering the selective solvent on the morphological transition of PCL-b-PDM lamellar crystalline micelles in the methanol solution was investigated.Besides,the corona chains were quaternized with bromide reagents in order to investigate the effect of structure-changing of the corona chain on morphology of crystalline micelles.It was found that a small amount of water could trigger the disassembly of PCL-b-PDM lamellar crystalline micelles into cylinders but full disassembly couldn't be achieved.The quaternization could depress the disassembly caused by alteration of the selective solvent from methanol into aqueous solution.