B段选择性成膜溶剂对ABC型氟化三嵌段共聚物氟化组分表面富集行为的影响

EFFECT OF SELECTIVE SOLVENTS FOR B BLOCK ON SURFACE SEGREGATION OF FLUORINE-CONTAINING ABC TRIBLOCK COPOLYMERS

利用ATRP技术合成聚甲基丙烯酸甲酯-b-聚甲基丙烯酸丁酯(或聚甲基丙烯酸十八烷基酯)-b-聚(甲基丙烯酸2-全氟辛基乙酯)(PMMA230-b-PBMA12(或PODMA12)-b-PFMAn)嵌段共聚物.通过X射线光电子能谱(XPS)、X射线衍射(XRD)、动态光散射(DLS)等技术研究了中间段选择性成膜溶剂对氟化三嵌段聚合物中氟化组分在表面的富集行为及影响因素.发现PBMA为中间段时,环己酮为成膜溶剂比甲苯有利于PMMA230-b-PBMA12-b-PFMA1中氟化组分向膜表面富集.当PFMA聚合度为4时,两种成膜溶剂所得膜表面氟含量基本一致.PODMA为中间段时,甲苯为成膜溶剂比环己酮有利于PMMA230-b-PODMA12-b-PFMAn中氟化组分向膜表面富集.当PFMA聚合度为4时,两种溶剂所得膜的表面氟含量差距加大.其原因是溶剂与三嵌段共聚物中间段的相容性不同,造成聚合物分子在溶液中形成胶束的稳定性有差异.在溶液固化过程,三嵌段共聚物分子在溶液中的聚集结构及其稳定性影响了氟化组分向表面富集及其有序结构的形成.

Novel ABC triblock copolymers of poly（methyl methacrylate）-b-poly（n-butyl methacrylate）（or n-octadecyl methacrylate）-b-poly（2-perfluorooctylethyl methacrylate）（PMMA230-b-PBMA12（or PODMA12）-b-PFMAn） were synthesized by atom transfer radical polymerization（ATRP）.The effect of selective solvents on surface structure of the triblock copolymers film was investigated by X-ray photoelectron spectroscopy（XPS）,X-ray diffraction（XRD） and dynamic light scattering（DLS）.The higher surface enrichment of fluorinated moieties in PMMA230-b-PBMA12-b-PFMA1 was found as the film was cast by cyclohexanone solution,compared to the film cast by toluene solution.When the length of PFMA units was about 4,the ratio of fluorine to carbon was nearly the same.As for PMMA230-b-PODMA12-b-PFMAn,the fluorinated moieties can segregate more easily on the surface as the film was cast with toluene solution,compared to the film cast from cyclohexanone solution.The reason could be attributed to the difference in compatibility between solvent and the middle block in triblock copolymers,which would affect the stability of triblock copolymers micelle in various solutions.When the solvent was the good solubility for the middle block chain,there were unstable and loose packed micellar aggregates in solution.The unstable micelle of the triblock copolymer in solution was in favor of fluorine segregation on the surface during film-formation.During film formation,the perfluoroalkyl side chains can easily segregate to the surface and be packed in a well-ordered manner,resulting in enhanced surface enrichment of fluorine element.The results suggest that copolymer solution properties,may play an important role in structure formation on the solid surface,in addition to for the molecular chain structures of copolymers.