| 초록 |
The effects of the stereospecificity of polymer chain and of the interaction inpolypropylene solutions on the relation between liquid-liquid phase separation andcrystallization were investigated by using an isotactic polypropylene (i-PP) and asyndiotactic polypropylene (s-PP) of high stereoregularity and of similar molar mass,with dialkyl phthalate as a solvent. A series of dialkyl phthalates with a differentnumber of carbon atoms in the alkyl chain, was employed to control the interactionbetween polymer and solvent. Phase transition temperatures were measured by opticalmicroscopy with a hot-stage. Liquid-liquid phase separation in the system of i-PP anddihexyl phthalate occurred below crystal melting. However liquid demixing temperaturefor the s-PP system in the same solvent was elevated much above its meltingtransition temperature due to decreased melting point and increased liquid demixingtemperature. The reduced solubility of s-PP is primarily attributed to enhancedhydrophobicity arising from alternate positioning of methyl groups along the polymerchain. As the length of the alkyl chain in phthalate increases, liquid-liquid phaseseparation temperature decreases significantly and melting point does slightly, resultingin liquid demixing temperature shifted below melting point for the solution of s-PP anddinonyl phthalate.
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