Effect of groups at α-position and side-chain structure of comonomers on surface free energy and surface reorganization of fluorinated methacrylate copolymer

Abstract

Surface free energy and surface reorganization, two essential properties for low surface free energy materials, have been researched by studying the effects of the groups (H or CH3) at α-position and the side-chain structures (flexible or rigid) of alkyl (meth)acrylate on a series of fluorinated copolymers poly (perfluorohexylethyl methacrylate)-co-poly [alkyl (meth)acrylate]. The static contact angle, X-ray photoelectron spectroscopy (XPS), and surface tension studies indicate that both the groups at α-position and the side-chain structures of alkyl (meth)acrylate can significantly influence the arrangement of perfluoroalkyl chains at the interface, resulting in different fluorine-enriched concentrations on the interface, which will finally affect the surface free energy of the copolymer. The dynamic contact angle measurement shows that the surface reorganization of the fluorinated chains are directly associated with the Tg of these copolymers, and decrease with the increasing Tg. All these results show that the copolymers containing H at the α-position and flexible side-chain in comonomer have lower surface free energy and higher surface reorganization, while the steric hindrance effects of α-methyl groups and/or rigid side-chain in comonomer allow the copolymers having higher surface free energy and lower surface reorganization.