Guidelines To Creating a True Molecular Composite:  Inducing Miscibility in Blends by Optimizing Intermolecular Hydrogen Bonding

Blending a liquid crystalline polymer (LCP) with an amorphous polymer to create a molecular composite offers a method to utilize the desirable properties of a LCP at a more modest cost. However, very few such blends are miscible. In this paper, we describe the results of a study that seeks to correlate the extent of intermolecular hydrogen bonding between two polymers in a blend to its phase behavior. Using FT-IR to quantify the amount of intermolecular hydrogen bonding between the two polymers and DSC and optical microscopy to determine the phase behavior of these blends, the results demonstrate that the broadest miscibility window in the blends studied corresponds to the system that optimizes the extent of intermolecular hydrogen bonding. Moreover, the system that maximizes the extent of intermolecular hydrogen bonding is one where the hydrogen-bonding moieties on one of the polymers are separated out along the chain. These results therefore provide guidelines by which miscibility may be induced in polymer blends by the minor structural modification of one of the polymers.