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

Abstract

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.