Novel linear fluoro-silicon-containing pentablock copolymers: synthesis and their properties as coating materials

Abstract

A series of linear fluorosilicone pentablock copolymers consisting of poly(dimethylsiloxane) (PDMS), poly(methyl methacrylate) (PMMA) and poly(dodecafluoroheptyl methacrylate) (PDFHM), named as PDMS-b-(PMMA-b-PDFHM)₂, have been synthesized by ATRP and their thermal properties, self-assembly behavior in different solutions and surface features of films have been systematically investigated. TGA measurements reflect that the thermal stability of PDMS-b-(PMMA-b-PDFHM)₂ is enhanced by the middle-block PDMS. TEM observation and DLS analysis reveal that PDMS-b-(PMMA-b-PDFHM)₂ is able to self-assemble into unimers in both chloroform and dioxane solutions, and spherical micelles with a core–corona structure in chloroform, oblate spheroidal micelles with a multilayer core–corona structure in dioxane. The diameters of micelles in the dioxane solution are larger, while the concentrations of unimers in the chloroform solution are higher. SCA, QCM-D and XPS measurements have confirmed that the unimers play a dominant role in governing the surface properties of PDMS-b-(PMMA-b-PDFHM)₂ films. In the case of PDMS-b-(PMMA-b-PDFHM)₂ with a PMMA/PDMS weight ratio of 10 : 1 and 20%wt of DFHM content, the film cast from chloroform solution has a lower surface free energy of 16.8 mN m⁻¹, lower adsorbed amounts of 8.6 × 10⁴ ng cm⁻² for water and 6.6 × 10⁴ ng cm⁻² for hexadecane, and higher surface stability. Such excellent thermal and surface properties demonstrate that this novel pentablock copolymer PDMS-b-(PMMA-b-PDFHM)₂ is a promising candidate as a coating material.