NMR OBSERVATIONS OF ISOLATED AND STRETCHED POLYMER-CHAINS IN THEIR CRYSTALLINE INCLUSION-COMPOUNDS FORMED WITH SMALL-MOLECULE HOST CLATHRATES

Several small-molecule hosts form clathrates or inclusion compounds (I Cs) with polymers. In these polymer-ICs the guest polymer chains are c onfined to occupy narrow channels in the crystalline matrix formed by the host. The walls of the IC channels are formed entirely from the mo lecules of the host, and they serve to create a unique solid-state env ironment for the included polymer chains. Each polymer chain included in the narrow, cylindrical IC channels (ca 5.5 Angstrom A in diameter) is highly extended and also separated by the host matrix channel wall s from neighboring polymer chains. The net result is a solid-state env ironment where extended, stretched (as a consequence of being squeezed ) polymer chains reside in isolation from their neighbors inside the n arrow channels of the crystalline matrix provided by the small-molecul e host. Comparison of the behavior of isolated, stretched polymer chai ns in their crystalline ICs with observations made on ordered, bulk sa mples of the same polymer are beginning to provide some measure of the contributions made by the intrinsic nature of a confined polymer chai n and the pervasive, cooperative, interchain interactions which can co mplicate the behavior of bulk polymer samples. Just as dilute polymer solutions at the a temperature have been effectively used to model dis ordered, bulk polymer phases (both glasses and melts), polymer-ICs may be utilized to increase our understanding of the behavior of polymer chains in their ordered, bulk phases as found in crystalline and liqui d-crystalline samples. Solid-state NMR observations of polymer-ICs can provide detailed conformational and motional information concerning t he included, stretched and isolated polymer chains.