Control of Film Morphologies in Self-Assembly of High-Mw PS-PMMA Block Copolymers

• Main Authors: Teng-yi Wang, 王騰逸
• Other Authors: Y.W. Chiang
• Format: Others
• Language: en_US
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/26132187897235058051

碩士 === 國立中山大學 === 材料與光電科學學系研究所 === 101 === Control of film morphologies to generate one-dimensional (1D) or three-dimensional (3D) polymeric photonic crystals from self-assembly of high-Mw polystyrene-b-polymethylmethacrylate (PS-PMMA) block copolymers (BCPs) is conducted in this study. Microphase-separated lamellar and gyroid phases can be observed in the bulk samples of high-Mw PS-PMMA BCP by transmission electron microscopy (TEM). Disordered morphologies are observed in the as-spun PS-PMMA thin films from poor solvents for PMMA (i.e. benzene, toluene, and divinylbenzene) due to fast evaporation of solvents. After solvent annealing by benzene, PMMA micelles in a PS matrix can be obtained. By contrast, coexistence of parallel and perpendicular lamellar microstructures is found in the PS-PMMA thin film after solvent annealing by neutral dichloromethane. In contrast to as-spun disordered morphologies from PMMA poor solvents, microphase-separated bicontinuous or lamellar microstructures are observed in the as-spun PS-PMMA thin films from PS-selective 1,1,2-trichloroethane or chloroform. After solvent annealing by neutral dichloromethane or 1,2-dichloroethane, the improvement of the lateral arrangement for the gyroid phase can be found. Also, a phase transition from the as-spun bicontinuous to lamellar microstructures are obtained using PS-selective solvents such as chloroform and 1,1,2-trichloroethane for annealing. Except for solvent-induced microstructural orientation, large-area and well-oriented lamellar microstructures parallel to the substrate can be successfully carried out in the PS-PMMA thick film by shear-induced orientation. Accordingly, 1D BCP photonic crystals are fabricated from the self-assembly of the lamella-forming PS-PMMA. The red- and blue-shifting reflectivity bands of the 1D BCP photonic crystals can be stimulated by the swelling and de-swelling of the microdomain driven by solvent vapor, revealing the reversible solvatochromic behavior. Also, the complexation of PMMA with metal salts is performed in the high-Mw PS-PMMA BCP. After complexation, the increase of segregation strength of microphase segregation and the decrease of the refractive index contrast may give rise to the formation of strong-segregated lamellar microstructures with sharp reflectivity bandwidth in the metal-complexed PS-PMMA. As a result, the solvent-responsive 1D BCP photonic reflectors with tunable bandwidth can be successfully carried out in the PS-PMMA BCP films having well-aligned microstructural orientation by solvent- and shear-induced orientation.