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Main chain liquid crystalline block copolymers, effects of polymer topology and flexible block structure on properties
Abstract
This thesis describes the synthesis and characterization of segmented, triblock and star block copolymers with mesogenic hard segments and long flexible spacers. This thesis explores two important aspects of structure-property relationships of phase separated block copolymers: (1) the effect of soft segment structure on the polymer thermal phase behavior; (2) the effects of hard segment structure and soft segment topology on polymer properties. The first part tests the hypothesis that the soft segment substituents that are adjacent to the hard segment lower the polymer thermal transitions temperatures. Copolymers with pentad hard segments and soft segments with varying degrees of substitution were synthesized to test this hypothesis. Pentad copolymers with completely substituted soft segments showed the lowest melting transition and exhibited no liquid crystallinity. When the substituents are separated from the hard segment, the polymer exhibits higher melting transitions and liquid crystalline behavior. In the second part, efforts were concentrated to synthesize block co-oligomers that behave as high polymers at ambient temperatures but have low melt viscosities. As part of this study, block co-oligomers with dyad esteramide and bisamide hard segments and amine terminated poly(propylene glycol)s of linear and star topologies were synthesized. The block co-oligomers showed that variations in the hard segment structure have a dramatic effect on both the melting temperature and the stability of the liquid crystalline phase. Topology of the soft segment does not effect the thermal transitions, but does affect hard segment organization. In general, star block co-oligomers showed better organization than their linear counterparts.
Subject Area
Polymer chemistry|Organic chemistry
Recommended Citation
Bhamidipati, Murty Venkata, "Main chain liquid crystalline block copolymers, effects of polymer topology and flexible block structure on properties" (1994). Doctoral Dissertations Available from Proquest. AAI9434455.
https://scholarworks.umass.edu/dissertations/AAI9434455