Reorganization of the structures, morphologies, and conformations of polymers by coalescence from their crystalline inclusion compounds formed with cyclodextrins

Abstract

AbstractWe and several other research groups have recently reported the ability of cyclodextrins (CDs) to act as hosts in the formation of inclusion compounds (ICs) with guest polymers. Polymer‐CD‐ICs are crystalline materials formed by the close packing of host CD stacks, which results in a continuous channel of ∼5‐10Å in diameter running down the interior of the CD stacks. The guest polymers are confined to the narrow, continuous CD channels, and so are necessarily highly extended and segregated from neighboring polymer chains by the walls of the CD stacks. We have shown that coalescence of guest polymers from their CD‐IC crystals can result in a significant reorganization of the structures, morphologies, and even conformations that are normally observed in their bulk samples. For example, when poly(ethylene terephthalate) (PET) is coalesced from its γ‐CD‐IC, we find that in the non‐crystalline regions of the sample the PET chains are adopting highly extended kink conformations, which result in their facile recrystallization from the melt and prevent quenching of the coalesced PET to achieve an amorphous sample during rapid cooling from above Tm. We have also created well‐mixed blends of normally incompatible polymers by coalescing them from CD‐ICs containing both polymers, where they are necessarily spatially proximal. Finally we have found the unique morphologies created by the coalescence of homopolymers, block copolymers, and homopolymer pairs from their CD‐ICs are generally stable to heat treatment for substantial periods above their Tm's and/or Tg's, and so may be thermoplastically processed without loss of the unique morphologies achieved through coalescence from their CD‐IC crystals.