writer：Chen Huiqin,Zhou Gengbing,Cai Zhiqi,Pi Pihui,Wen Xiufang,Zheng Dafeng,Cheng Jiang,Yang Zhuoru
keywords：Fluorinated acrylate copolymers, Crystallization,Surface wetting properties, Hydrophobicity and oleophobicity
source：期刊
specific source：ACTA POLYMERICA SINICA期: 12 页: 1454-1460
Issue time：2011年
A series of fluorinated acrylate copolymers were synthesized via free radical copolymerization by using monomers of 2-(perflurooctyl) ethyl methacrylate (FOEMA) and n-alkyl acrylates (RAs) (n = 4, 8, 12, 16, 18) with various lengths of side chains. The crystalline behavior of the copolymers was characterized by X-ray diffraction (XRD) and differential scanning calorimetry (DSC). It is found that the crystallization of acrylate copolymers is in close connection with the side-chain length of acrylates. The copolymers crystallized at room temperature when the side-chain length number n was 16 or 18, however, no crystallization was observed for the copolymers with n less than 16 under the same condition. The crystallization enthalpy changes of RA-co-FOEMA copolymers were determined from the DSC thermograms. The copolymer with n = 16 has the minimum entropy change at constant pressure compared with other three crystallized copolymers through thermodynamic calculation, which indicated this copolymer was the most ordered one. The F/C atomic ratios and composition of functional groups on the surfaces of RA/FOEMA copolymer films were determined by multifunctional photoelectron spectroscopy (XPS), and the static contact angles of n-hexadecane and water on films were measured. The F/C ratios increased from 0. 39 to 0. 71 with increase in the side-chain length of RA/FOEMA copolymers. When n was 16 or 18, the copolymers demonstrated much more composition of non-polar groups (-CF, and -CF(2)) and fewer polar groups (-C=O and -C-O-C=O) on the film surfaces, leading to the rapid increase in the n-hexadecane static contact angles on the films of copolymers. It may suggest that crystallization of hydrocarbon side-chain of copolymers can promote fluorinated component to migrate to the polymer-air interface during the process of film forming and hence improve the hydrophobicity and oleophobicity of the films.