Detailed investigation on polycarbonate synthesis and molecular design of novel liquid crystalline polycarbonates in scCO2 media /
Çalık, Müge Yeşim (2006) Detailed investigation on polycarbonate synthesis and molecular design of novel liquid crystalline polycarbonates in scCO2 media /. [Thesis]
In the first part of this study, the experimental demonstration of a novel and environmentally benign supercritical carbon dioxide (scCO2) technique that yields polycarbonates in a single-step reaction, have been reported. Different chiral and racemic epoxy monomers have been copolymerized and some detailed micro and macro structure investigations have been conducted. By these examinations, it is aimed to say more about the modes of the ring opening of epoxides in scCO2 media in coordination with the utilized catalyst as well as the tacticity and the microstructure of the resultant polymers. In the second part, optically active side chain liquid crystalline polycarbonates having no spacer unit and its homologue with six spacer unit have been synthesized under scCO2 conditions. The obtained polymers are worthwhile since they are highly stereoregular and can find applications in an enlarged mesomorphic temperature range compared to their acrylic analogues. The synthesized materials were characterized by IR, 1H-NMR and 13C-NMR while the thermal properties were measured by DSC. Polarized optical micrograph and wide angle X-ray diffraction were used for the mesogenic property characterization of the copolymers. The DSC analyses of the copolymers indicate that the Ti values do not change dramatically, whereas a pronounced decrease in Tg values are observed from that of their acrylic analogues. Hence, the obtained polymers exhibit another practical benefit by widening the mesomorphic temperature range. This study is the insightful combination of material processing and chemical design that elucidates the advantages of scCO2 application in terms of liquid crystallinity and the tacticity of the obtained polymers.
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