Microscopy, optical solvent casting

Chen et al. (67) reported the use of trifluoroacetic acid (TFA) as a cosolvent with tetrahydrofuran (THF) to improve dispersion and processability of the nanocomposites. They prepared MWCNT-PMMA composite films with varying CNT content by solvent casting method using 10 vol % TFA as a co-solvent with tetrahydrofuran (THF). SEM and optical microscopy revealed a good dispersion of nanotubes in solvent and PMMA. The composites showed low percolation... 

Blends of sPP/POE were prepared by dissolving these polyolefins in xylene at about 100°C (at a polymer concentration of 2-3 wt%) and stirred thoroughly for about 1 day. Film specimens were prepared by solvent casting on optical microscope glass slides. To ensure complete removal of the solvent, the glass slides were immersed in distilled water (nonsolvent) for 1 h and then dried at the ambient temperature. Subsequently, the samples were further dried in a vacuum oven at room temperature for another 2 days. All samples were heated to 160°Cfor lOminto provide the blend with a thermal history similar to the melt-mixed samples and to further remove any residual solvent. The thickness of the blend films used for microscopy was approximately 10 pm (31). 

Polymer P25/26 self-orders in solvent-cast films, with the hackhones parallel to the substrate and a strong solvent dependence of the degree of ordering (78). Spacings of 2.2-2.G nm are observed by x-ray diffraction, indicating interdigita-tion of the dendritic side chains. P25 6 also forms thermotropic nematic liquid crystalline phases. With optical microscopy, Schlieren textures are observed for thin films cast from solution. 

Purely physical polymer blends are most commonly prepared by either mechanical mixing (melt) or dissolution in a common solvent followed by casting and solvent removal. In this study, both techniques were used the latter method was more readily applicable for film formation in small-scale laboratory batches. It was recognized that certain morphological differences between melt- and solution-fabricated polymers are often observed these include phase inversions and distortions, especially with graft and block polymers. However, casual observation by optical and electron microscopy revealed no dramatic differences between the melt- and solution-cast films, and this cannot be readily explained. 

PC (50-30)/imidized acrylate copolymer (77 % glutarimide, 19 % MMA, 3 % MAA, 2 % glutaric anhydride) (70-50) Internal mixer at 260-270 °C or solution casting/ETlK/optical microscopy/SEM/ TEM/SEC/model reactions/selective solvent extraction/comparison to blends with PMMA or with imidized acrylate copolymer cmitaining different imide levels, or no acid or anhydride/details of reaction mechanism Debier et al. 1995, 1997a, b... 

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