Unlike normal PET samples, we have been unable to quench the coalesced PET rapidly from above Tm to achieve an amorphous sample. On the other hand, 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 rapid recrystallization from the melt.
State vs. dmso jaikoz wilson Pc#
This suggests a chain-extended crystalline morphol-ogy in the PC sample coalesced from its γ-CD-IC. Additionally and more importantly, 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.įor example, when polycarbonate (PC) is coalesced from its γ-CD-IC, we obtain a semicryst-alline sample with a Tm elevated ~15° C above the melting temperature observed in solution-cast or high temperature annealed PC samples. We are expanding these studies to additional polymer-CD-ICs and by employing 2-D exchange NMR experiments designed to probe the specific angular distributions of conformational reorientations observed for polymer chains when segregated in their CD-IC channels and in their bulk samples. Our 13C and 1H NMR studies of polymer-CD-ICs have yielded motional parameters (relaxation times and resonance line widths) that, when compared to the same motional parameters observed on their bulk samples, reveal the inherent contribution made by single (α-CD-ICs) and pairs of side-by-side (γ-CD-ICs), extended polymer chains to the necessarily cooperative motions occurring in bulk polymer samples. 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. Polymer-CD-ICs are crystalline materials formed by the close packing of host CD stacks, which results in a continuous channel of ~5-8Ǻ in diameter running down the interior of the CD stacks. We and several other research groups have recently reported the ability of CDs to act as hosts in the formation of inclusion compounds with guest polymers. We hope this new method of fabrication will permit the delivery of various additives to polymer fibers and films which is superior to the current technologies. The formation and study of molecular composites formed by the embedding of inclusion compounds (ICs) formed between the host cyclic starches (cyclodextrins, CDs) containing 6 (α), 7 (β), and 8 (γ) glucose units and polymer or small molecule guests into polymer fibers and films followed by the release and coalesence of the guest into the carrier polymer phase has been persued. Professor Tonelli’s research interests include the conformations, configurations, and structures of synthetic and biological polymers, their determination by NMR, and establishing their effects on the physical properties of polymers.
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