Self-assembly Of Nanomicelles And Preparation Of Thermo-responsive Superhydrophobic TiO₂/Poly（N-isopropylacrylamide） Microspheres Based On ATRP

Nanotechnology was widely applied in surface science in recent years. The contentsof surface science at the nanoscale are self-assembly in the surface or interface ofmaterials and design machining at micro/nano scale. The functional surface showsspecial performance including mechanical, electrical, thermotic, optical and magnetic,and is widely used in information and telecommunication technology, optics,electronics, energy and measurement and control technology. It is important todevelop nano-materials surface science that enlarging the implementation methods ofnano-surfaces，further extending the compounding between nano-materials surfacescience and traditional surface science，and broadening the industrial application ofnano-material. This paper contain two directions of surface science,evaporation-induced self-assembly on the various substrates and preparation ofthermo-responsive superhydrophobic TiO₂/Poly（N-isopropylacrylamide） microspheres.Both of two are based on surface science.Polystyrene-block-Poly （acrylic acid）（PSt-b-PAA） is a typical amphiphilic blockcopolymer that was synthesized via atom transfer radical polymerization （ATRP）.Then the polymer as prepared self-assembled into cubic nanomicelles in THF/watermixed solution. The core-shell micelles consist of a core formed by the insoluble PSblock and a shell of the soluble PAA block swollen in water. In the next step, thenanomicelle solution with a small quantity of tetrahydrofuran （THF） or N,N-dimethylformamide （DMF） which plays a role of additive was dropped on thevarious substrates such as glass slip, silicon wafer and aluminium sheet. And themethod of solvent evaporation-induced self-assembly was used to aggregate thenanomicelle. Depending on the kind of additive, the temperature and the substrate, themorphologies of the orderly aggregates were varied from flower-like to rodlike onglass slip or silicon wafer. Also some irregular aggregates appear on aluminium sheet.Moreover, a possible mechanism was proposed.For the past few years, environmental responsive superhydrophobic surfaces withwater contact angle change with stimuli have received a lot of research attention，dueto their important applications ranging from self-cleaning materials to microfluidicdevices and biomaterials. Here our experimental strategy is modifying low surfaceenergy stuff on the rough surface, a facile method that combined sol-gel and surface-initiated ATRP to produce thermo-responsive superhydrophobic TiO₂/Poly（N-isopropylacrylamide） microspheres with core-shell structure was reported. Theas-prepared particles have been characterized by scanning electron microscopy,transmission electron microscopy, thermal gravimetric analysis, FT-IR analysis, anddynamic light scattering. The surface coated with microspheres show hydrophilicproperties （CA=90.5±2.3°） at27°C, it changes to superhydrophobicity（CA=150.2±2.3°） while the temperature rises up to42°C. This performance isattributed to lower critical solution temperature （LCST） phenomenon of Poly（N-isopropylacrylamide）. Five cycles measurements of water droplet reversible switchbetween hydrophilicity and superhydrophobicity were demonstratedtemperature-responsive surface property. The mechanism has been discussed in lightof the Wenzel model and Cassie model.