| Understanding the implications of defect structures in block copolymer (BCP) based materials is critical to realize practical applications in various emerging technologies. This thesis explores the microstructure evolution during thermal treatment in amorphous lamellar BCPs and BCP blends. A novel procedure involving film casting under controlled low-pressure conditions, reconstructive electron microscopy using serial imaging, stereology as well as pattern matching and filtering was developed to evaluate the grain growth kinetics as well as the microstructure evolution during thermal annealing. With this procedure the microstructure evolution in poly(styrene-b-isoprene) (PS-PI) as well as blends with homopolystyrene and oligo-styrene functionalized gold nanoparticles at various filling fractions was examined. Particular emphasis was on the elucidation of the texture parameters including the evolution of grain size and shape, lamellar domain orientation as well as type and extent of grain boundary structures as a function of thermal annealing times (at T=120 deg C, duration of 0, 3, and 7 days, respectively). It was found in this study that, (1) grain boundary formation can be attributed to the nucleation and growth of the microphase separated grains as well as stresses that (presumably) arise during the later stages of solvent evaporation. (2) the grain growth during thermal annealing predominantly occurs through the annealing of high angle symmetric tilt grain boundaries. (3) nano-sized additives reduce grain growth rate by stabilizing the high angle grain boundary structure. This is interpreted as a consequence of selective segregation of the fillers within grain boundary regions. In addition, with the analysis of triple junction geometry, grain boundary energy was calculated as a function of grain misorientation and determined to be strongly correlated to the angle of misorientation between adjacent grains. |
