Dr. Alan E. Tonelli (Al)
INVISTA Prof. of Fiber & Polymer Chemistry
Textile Engineering, Chemistry, and Science
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. Most recently the formation and study of molecular composites formed by the embedding of inclusion compounds formed between cyclodextrin hosts and polymer or small molecule guests into polymer fibers and films and then release and coalesence of the guest into the carrier polymer phase. 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.
We 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 ofý host CD stacks, which results in a continuous channel of ~5-8A 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. Our very recent 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 (±-CD-ICs) and pairs of side-by-side (³-CD-ICs), extended polymer chains to the necessarily cooperative motions occurring in bulk polymer 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. 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.ý For example, when polycarbonate (PC) is coalesced from its ³-CD-IC, we obtain a semicrystalline sample with a Tm elevated ~15 C above the melting temperature observed in solution-cast or high temperature annealed PC samples. This suggests a chain-extended crystalline morphology in the PC sample coalesced from its ³-CD-IC. On the other hand, when poly(ethylene terephthalate) (PET) is coalesced from its ³-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. Unlike normal PET samples, we have been unable to quench the coalesced PET rapidly from above Tm to achieve an amorphous sample. When a poly(µ-caprolactone) (PCL)-poly(L-lactic acid) (PLLA) diblock copolymer was coalesced from its ±-CD-IC, we found a significant reduction in the phase-separated morphology normally produced in solution-cast samples, as indicated by 50 and 80% reductions in the crystallinities observed for the PCL and PLLA phases, respectively, in the coalesced diblock sample. We have also created well-mixed blends of normally incompatible polymers by coalescing them from CD-ICs containing both polymer pairs. Coalescence of polymer pairs from their common CD-ICs, where chemically distinct polymers are spatially proximal, results in molecularly intimate blends, which have been demonstrated for both crystallizable polymer pairs, such as PCL/PLLA and PET/PEN (poly(ethylene-2,6-naphthalate), and the amorphous pairs PC/PS (polystyrene) and PC/PMMA [poly(methyl methacrylate)]. Finally we have found the unique morphologies created by the coalescence of homopolymers, diblock copolymer, and homopolymer pairs from their CD-ICs are stable to heat treatment for prolonged periods above their Tm's and/or Tg's. Thus we can create polymer materials with unique morphologies that are retained during normal melt processing. As a consequence, we are beginning to more fully characterize these unique and newly created, coalesced polymer samples principally by solid state NMR techniques, such as 2-D HETCOR, WIM-WISE, variable temperature 1D and 2D exchange, and CODEX experiments, which will provide measures of both the scale of mixing and the motions of their constituent polymer chains at the molecular level. Scale-up of the production of these CD-IC-coalesced polymer materials will eventually enable the determination of their bulk properties, such as permeabilities and strengths, which are presumeably distinct from and hopefully better than those of their normally produced solid samples, such as their phase-segregated blends.
Achievement of molecularily well-mixed blends composed of any two or more chemically distinct polymers, or between additives and polymers, would permit a virtually unlimited expansion of useable polymer materials. In addition to the obvious commercial significance, which would have important consequences for US industry, this development could greatly benefit society at large.
Most Recent Publications
1. Tonelli, A. E. (2012). Restructuring Polymers via Nano-Confinement and Subsequent Release . Superstructures with Cyclodextrins: Chemistry and Applications, Beilstein J. Organic Chemistry, Ritter, H., Guest Ed. . Frankfurt .
2. Williamson, B. R., Tonelli, A. E. (2012). Constrained polymer chain behavior observed in their non-stoichiometric cyclodextrin inclusion complexes. J Incl Phenom Macrocycl Chem , 72 (71) .
3. Gurarslan, A., Joijode, A., Tonelli, A. E. (2012). Polymers Coalesced from Their Cyclodextrin Inclusion Complexes: What Can They Tell Us About the Morphology of Melt-Crystallized Polymers?. J. Polym. Sci: Part B: Polym. Phys. .
4. Gurarslan, A., Shen, J., Tonelli, A. E. (2012). Behavior of Poly(e-caprolactone)s (PCLs) Coalesced from Their Stoichiometric Urea Inclusion Compounds and Their Use as Nucleants for Crystallizing PCL Melts: Dependence on PCL Molecular Weights. Macromolecukles , 45 , 2835.
5. Hunt, M. A., Villar-Rodil, S., Gomez-Fatou, M. A., Shin, I. D., Schilling, F. C., Tonelli, A. E. (2011). 13C-NMR Observed Conformations and Motions of Neat Liquid and Crystallinen-Hexatriacontane and as a Guest in the Narrow Channels of Its Inclusion Compound Formed with a-Cyclodextrin. NMR Spectroscopy of Polymers: Innovative Strategies for Complex Macromolecules, Cheng, H. N., Asakura, T., English, A. D., Eds. : Vol. 16 . Washington, D. C. : American Chemical Society.
B.S. in Chemical Engineering from the University of Kansas in 1964 and a Ph.D. in Polymer Chemistry from Stanford in 1968, where he was associated with the late Professor Paul J. Flory. He was a member of the Polymer Chemistry Research Department at AT&T Bell Laboratories, Murry Hill, N.J. for 23 years, and in 1991 joined the Fiber and Polymer Science Program in the College of Textiles at North Carolina State University in Raleigh.
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B.S. Chemical Engineering, 1964, U. of Kansas Ph.D. Chemistry, 1968, Stanford
American Chemical Society (Member) and American Physical Society (Fellow)