用含氟丙烯酸酯无规共聚物制备超疏水膜

用微乳液聚合法制备了丙烯酸全氟烷基乙酯和甲基丙烯酸甲酯的无规共聚物,并对其进行了表征.采用溶剂挥发成膜法一步制备了具有超疏水性的该聚合物膜,水滴在该聚合物膜上的静态接触角可达151°~160°,滚动角小于3°.通过扫描电子显微镜观察发现该聚合物膜表面分布了许多乳突状突起和微孔洞,并具有微米和纳米尺度相结合的复合杂化结构.该类超疏水表面的形成是由适度粗糙的表面和低表面能相互结合引起的.探讨了该类超疏水膜的形成机理.

PREPARATION OF SUPER-HYDROPHOBIC FILMS WITH PERFLUOROALKYLETHYL ACRYLATE RANDOM COPOLYMERS

Super-hydrophobic surfaces have attracted significant attention recently,and various preparing methods have been reported,such as sol-gel method,plasma etching,phase separation,template-based extrusion and so on.Besides them,the solvent evaporation-phase separation was a relatively simple one,but only polymers with particular structure,such as block copolymers and polymer blends,were successfully applied by this method,Moreover,some complicate post-procedures or rigorous special environments were often essential.Herein we reported a simple way to facile a super-hydrophobic surface of random copolymers just by one-step casting the polymer solution onto a solid surface.The films had many micro- and nano-scale convexities and grooves with multiplex structures distributed on the surface,which appeared like a lotus leaf surface.The micro-scale roughness and low surface energy together endowed the films excellent super-hydrophobic ability even without further modification.The water contact angle was about 155°～160°, and the sliding angle was less than 3°.The random copolymers of metharcylate (MMA) and perfluoroalkylethyl acrylate (FMA) were synthesized by micro-emulsion polymerization.The polymerization was carried out with sodium dodecylsulfate-C_7F_ 15 COONH_4-n-butanol as emulsifier,K_2S_2O_8-NaHSO_3-CuSO_4 redox as initiator.The emulsion was poured into excess methanol and washed by water.Then the polymer was purified several times by dissolving in acetone and precipitation by methanol.The copolymers were characterized by ~1H-NMR,FTIR,GPC and fluorine element analysis.Super-hydrophobic films were prepared by a one-step casting process.First,the copolymers were dissolved in F-113 to form homogeneous solutions,and then cast on 2 cm× 2 cm clean glass plates at pre-set temperatures in windtight environment.When the solvent was evaporated,super-hydrophobic films were formed.It was found that when a good solvent of PMMA was used,such as tetrahydrofuran (THF),acetone,etc.,or the mixed solvents of THF-F113,acetone-F113 etc., a smooth surface with water contact angles less than 130° was obtained.A super-hydrophobic film could not gotten at these cases.It was regarded that the movement and interpretation of copolymer segments had dominative effects on the films morphology.The concentration of the polymer solution had great effect on the morphology of the films prepared.The casting solution concentration should be in an appropriate scale,the best concentration (c) was about 5×10~ -3 g/mL≤c≤c_0,where c_0 was the critical concentration of copolymer in F113.What was more,the temperature and pressure should also be proper.The possible reason of leading to the super-hydrophobic properties of these films was due to the combination of micro- and nano-scale binary roughness and low surface energy.The mechanism of forming these films based on the micelle aggregation model and was further discussed in this paper.These special films with both many convexities and grooves were formed because of the intrinsic properties of the random copolymer and a proper solution concentration as well as the forming conditions.In conclusion,using F113 as solvent,PFMA-PFMA random copolymers can facile super-hydrophobic surfaces by the solvent evaporation-phase separation method.