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The determination of polymer structure and dynamics via inversion recovery cross polarization NMR

Hedrick, David Paul
http://rave.ohiolink.edu/etdc/view?acc_num=case1056485161

Abstract Details

1992, Doctor of Philosophy, Case Western Reserve University, Chemistry.
Nuclear Magnetic Resonance (NMR) spectroscopy was used to study the structure and dynamics of polymer systems. In particular, solid state 13C relaxation techniques were used to study the molecular motions of various polymer systems in at least three frequency regimes. The interpretation of previous and current results from a recently developed relaxation technique, namely Inversion Recovery Cross Polarization (IRCP) NMR, were evaluated in terms of new findings that have helped elucidate cross polarization dynamics. A cyclo-aliphatic polyurethane sample that was made up of a poly(tetramethylene oxide) (PTMO) soft segment and a 1,4-cyclohexane diisocyanate/1,4-cyclohexane dimethanol hard segment was studied using variable temperature solid state 13C NMR relaxation techniques. Carbon resolved proton T1ρ and IRCP resolved cross polarization (TCH) time constants were found to be sensitive to changes in the polymer molecular motions that resulted from a change in morphology as a function of temperature. The effect of PTMO molecular weight was also determined for two polymers with PTMO number average molecular weights (Mn) of 1000 and 2000. Solid and solution state 13C NMR spectroscopy was used to determine the structure of a series of copolymers formed via a ceric ion initiated graft polymerization reaction with polyvinyl alcohol (PVA). Inversion recovery cross polarization, T CH, as well as proton and carbon rotating frame spin-lattice relaxation times were measured. Proton T1ρ values were used to determine miscibility, where T CH and carbon T1ρ values were found to reflect changes which result from differences in polymer chain conformations and packing. The graft site between a graft copolymer of PVA and polyvinyl acetate (PVAc) was elucidated via 13C solution state NMR. Thermal results, as measured by DSC, and solid state relaxation times supported the proposed chemical structure of the graft site. 13C NMR relaxation parameters were used to compare the motional characteristics of di-n-hexyladipate (DHA) in solution and in the solid matrix of poly(vinylbutyral-co-vinyl alcohol) (PVB). The intramolecular motional behavior of DHA was found to be inherently anisotropic as seen from T1 relaxation experiments in solution, while in both scalar decoupled "solid solution" and solid state cross polarization experiments intramolecular motion appears to be more homogeneous. The motional behavior of methylene carbons is generally most inhibited near the DHA ester positions as indicated by shorter T1 values. IRCP experiments on DHA in the PVB matrix have been used to study the heterogeneity of near static motions. Bi-exponential relaxation decays were found to be most pronounced for carbons near the ester position. This relaxation behavior is consistent with the existence of intermolecular heterogeneities which result from the phase separated plasticizer domains.
William Ritchey (Advisor)
188 p.
Chemistry, Polymer
determination polymer structure dynamics inversion recovery cross polarization NMR

Recommended Citations

Citations

  • Hedrick, D. P. (1992). The determination of polymer structure and dynamics via inversion recovery cross polarization NMR [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1056485161

    APA Style (7th edition)

  • Hedrick, David. The determination of polymer structure and dynamics via inversion recovery cross polarization NMR. 1992. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1056485161.

    MLA Style (8th edition)

  • Hedrick, David. "The determination of polymer structure and dynamics via inversion recovery cross polarization NMR." Doctoral dissertation, Case Western Reserve University, 1992. http://rave.ohiolink.edu/etdc/view?acc_num=case1056485161

    Chicago Manual of Style (17th edition)

case1056485161
590
© 1992, all rights reserved.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.