剪切作用对PS-b-P2VP-b-PEO三嵌段共聚物多节状蠕虫胶束形成的影响

EFFECT OF SHEAR FLOW ON THE FORMATION OF MULTICOMPARTMENT WORMLIKE MICELLES OF PS-b-P2VP-b-PEO TRIBLOCK COPOLYMER

实验研究了剪切(搅拌)对ABC三嵌段共聚物PS720-b-P2VP200-b-PEO375在溶液中自组装形成的胶束形态的影响,研究结果表明剪切对多节状蠕虫胶束的生成和结构有着重要作用.在1500 r/min剪切速率时,嵌段共聚物自组装形成的球形胶束首先聚集形成蠕虫胶束的梭状轮廓,然后再经过不断地融合与调整形成蠕虫胶束节状部分的盘状结构,同时球的融合趋于沿着垂直于梭状结构的主轴方向(即流场方向).溶剂THF对PS嵌段充分的溶胀使得球形胶束进一步调整形成盘状结构,从而使梭状胶束聚集体顺利地向多节状蠕虫胶束过渡.通过透射电镜(TEM)和扫描电镜(SEM)对胶束形态进行表征,结果表明,多节状蠕虫胶束是剪切作用下球形胶束二次自组装的结果.

The effect of shear flow on the formation and architecture of the multicompartment wormlike micelles of PS720-b-P2VP200-b-PEO375（the subscripts indicate the numbers of the repeat units of the blocks） copolymer has been investigated by transmission electron microscopy（TEM） and field emission scanning electron microscopy（SEM）.For a system with 1 wt% copolymer concentration and 13 wt% water concentration in THF /water,the micelle morphology observed by TEM changed from spheres to shuttlelike micelle aggregates,then to multicompartment wormlike micelles and finally to spheres as the stirring rate increased from 200 r /min to 2200 r /min.It was found that the micelles would change to worms again as the stirring rate changed from 200 r /min or 2200 r /min to 1500 r /mini,ndicating that the wormlike micelles were independent on initial phases.SEM observations revealed that the wormlike micelles were composed of overlapped disks,which was also confirmed by stain technology.Further research indicated that the formation of wormlike micelles underwent three stages.The triblock copolymer first self-assembled into small spherest,hen these small spheres joined together to form intermediate shuttlelike structures and finally the spheres within the shuttlelike structures rearranged and underwent further adjustment to form the worms.Therefore,the multicompartment wormlike micelles formed as a result of secondary self-assembly of the spheres under shear flow.