Study On The Self-Assembly Of Block Copolymer—Controlling The Orientation Of The Microdomains In PS-PMMA Films And The Application

Block copolymers (BCPs) have sparked considerable interest because the self-assembly of BCPs can lead to various ordered nanoscopic structures spontaneously. Of particular interest are block copolymer films that form cylindrical nanodomains oriented perpendicularly and spanning to both the topmost surfaces due to the potential applications in membranes with ordered structures fabrication. In this thesis, we have systematically investigated the phase behavior of thin films of polystyrene cylinder-forming polystyrene-poly(methyl methacrylate)(PS-b-PMMA) diblock copolymer. By modifying the substrates, the vertically oriented PS cylinders were obtained in the diblock copolymer thin films on the ITO, FTO glass and Si substrates respectively. Then the PMMA matrix was removed, generating PS nanopillars. This nanopillar film was used as a template to prepare TiO2rang-orderd nanoporous TiO2sel films through immersing it in a TiO2sol. Finally, the PS nanopillars were removed by sintering at high temperature and TiO2rang-ordered nanoporous films were obtained.In the part of the study on controlling the orientation of block copolymer films, we systematically investigated the influences of block copolymer film thickness, the composition and film thickness of random copolymer, the degree of polymerization of block copolymer and the method of dealing with the modified substrate on the vertical orientation of PS cylinders under the condition of thermal annealing and saturated acetone vapor annealing respectively. The results showed that:1, When the annealing time was12h, the vertically oriented polystyrene cylinders were achieved successfully using saturated acetone vapor control the orientation of micromodains in the block copolymer film due to the combined effects of the modified substrates (Si or ITO) and the acetone vapor. And when the Si substrate was modified by the hydroxyl end-functionalized random copolymer of styrene and methyl methacrylate (PS-r-PMMA-OH), the weakly variation of composition in PS-r-PMMA-OH didn’t influence the resulting vertically oriented PS cylinders. However, when the ITO conducting was modified by cross-linkable random copolymer (PG), i.e. contain some glycidyl methacrylate in PS-r-PMMA, the vertically rang-ordered micromodains can be achieved only on the thicker PG film. When increasing the block copolymer film thickness, the little orderness was found in the arrangement of vertical microdomains. In the film block copolymer with low polymerization degree, PS cylinders were more ordered than the microdomains in the high polymerization degree diblock copolymer films.2, And when the ITO substrate was modified by PS-r-PMMA-OH, the weakly variation of composition in PS-r-PMMA-OH also didn’t influence the resulting vertically oriented PS cylinders in the thermal annealing block copolymer films. When the ITO conducting was modified by PG, the orderness of the vertically oriented PS cylinder increased obviously. In the same conditions, the microdomains in block copolymer films with low polymerization degree was turned more easily than turned the microdomains in the high polymerization degree block copolymer films. The orientation of micromodains in the block copolymer films were decreased in the thick block copolymer films. In addition, when the PG modified ITO wasn’t rinsed in the toluene, the resulting orderness of the microdomains in the block copolymer film and the percentage of vertical microdomains were decreased obviously.The generating PS nanopillar by removing the PMMA matrix was used as a template to prepare TiO2rang-orderd nanoporous films by sol-gel method and the prepared TiO2rang-orderd nanoporous films were anatase. The pores size in the resulting TiO2ordered nanoporous films were uniform and long-ordered.