Thermo-responsive stick-slip behavior of advancing water contact angle on the surfaces of poly(N-isopropylacrylamide)-grafted polypropylene membranes  

作　　者：WAN LingShu,MENG XiangLin,YANG YunFeng,TIAN Jing & XU ZhiKang Key Laboratory of Macromolecular Synthesis and Functionalization,Ministry of Education Department of Polymer Science and Engineering,Zhejiang University,Hangzhou 310027,China 

出　　处：《Science China Chemistry》2010年第1期183-189,289,共8页中国科学（化学英文版）

基　　金：support from the National Natural Science Foundation of China for Distinguished Young Scholars (Grant No.50625309);The Zhejiang Provincial Natural Science Foundation of China (Grant No.Z406260);supports from the National Postdoctoral Science Foundation of China (Grant Nos.20070421172 & 20081466)

摘　　要：Wettability of a solid surface is highly important to its practical application,especially for the surface that shows thermoresponsive properties.In this paper,we describe a thermo-responsive stick-slip behavior of water droplets on the surfaces of poly(N-isopropylacrylamide)(PNIPAM)-grafted polypropylene membranes.Field emission scanning electron microscope(FESEM) images elucidate that the morphology of PNIPAM-grafted membrane surface is thermo-responsive,i.e.,the surface becomes rougher above the lower critical solution temperature(LCST) of PNIPAM.On the surface of nascent polypropylene membranes,the water droplet shows a smooth motion resulting in advancing and receding water contact angles of 111° and ～65°,respectively.On the PNIPAM-grafted membrane surfaces,the water droplet shows a stick-slip pattern above the LCST,whereas it advances smoothly below the LCST.This phenomenon is reproducible and can be ascribed to the energy barriers enhanced by the shrink of PNIPAM chains above the LCST.We also find that the slip contact angle decreases from 102° to 92° after several stick-slip cycles.This decrease is attributed to the water adsorption on the grafted PNIPAM layer,which is confirmed by the continuous decrease of the receding water contact angle.Wettability of a solid surface is highly important to its practical application,especially for the surface that shows thermoresponsive properties.In this paper,we describe a thermo-responsive stick-slip behavior of water droplets on the surfaces of poly(N-isopropylacrylamide)(PNIPAM)-grafted polypropylene membranes.Field emission scanning electron microscope(FESEM) images elucidate that the morphology of PNIPAM-grafted membrane surface is thermo-responsive,i.e.,the surface becomes rougher above the lower critical solution temperature(LCST) of PNIPAM.On the surface of nascent polypropylene membranes,the water droplet shows a smooth motion resulting in advancing and receding water contact angles of 111° and ～65°,respectively.On the PNIPAM-grafted membrane surfaces,the water droplet shows a stick-slip pattern above the LCST,whereas it advances smoothly below the LCST.This phenomenon is reproducible and can be ascribed to the energy barriers enhanced by the shrink of PNIPAM chains above the LCST.We also find that the slip contact angle decreases from 102° to 92° after several stick-slip cycles.This decrease is attributed to the water adsorption on the grafted PNIPAM layer,which is confirmed by the continuous decrease of the receding water contact angle.

关 键 词：STICK-SLIP BEHAVIOR water contact ANGLE THERMO-RESPONSIVE surface poly(N-isopropylacrylamide) POLYPROPYLENE MEMBRANE 

分 类 号：TQ320.721[化学工程—合成树脂塑料工业]