Optimizing hydrogen-bonding in creating miscible liquid crystalline polymer blends by structural modification of the blend components

Our recent experimental results have shown that a miscible blend containing a liquid crystalline polymer (LCP) and an amorphous copolymer, both capable of self-association and interassociation by hydrogen-bonding, can be created by slight structural modification of the amorphous polymer. The results also show that an optimum amount of intermolecular H-bonding can be formed in the blend by systematically varying the distance between the hydrogen-bonding groups on the copolymer chain. It was found that the system with the optimum amount of intermolecular hydrogen-bonding is also the system with the broadest miscibility window. In this paper, this work is extended by examining the effect of elimination of self-associating hydrogen bonds in the LCP on the intermolecular hydrogen-bonding and on the phase behavior of these blends. FTIR and phase behavior results show that this modification results in increased intermolecular hydrogen-bonding and a broader miscibility window than the blend that contains the original liquid crystalline polymer. In agreement with our previous results, the optimum amount of intermolecular H-bonding is formed in the blend by systematically varying the distance between the hydrogen-bonding groups on the amorphous copolymer. DSC and optical microscopy correlate these data to the blend phase behavior to show that the optimum amount of intermolecular hydrogen-bonding correlates to the system with the broadest miscibility window. Finally, thermodynamic analysis of these blends provides insight and guidelines regarding the applicability of this scheme to create a miscibility window in other polymer blends.