Nuclear Magnetic Relaxation of Poly(n-hexyl isocyanate) in Dilute Solution. Effects of Chain Stiffness

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Abstract

The spin–lattice relaxation time T1, spin–spin relaxation time T2, and nuclear Overhauser enhancement NOE were determined from nuclear magnetic relaxation measurements on five well-fractionated samples of poly(n-hexyl isocyanate) in the range of weight-average molecular weight Mw from 1.65×104 to 5.71×104 in n-hexane at 25 °C. It is found that T1 increases and T2 decreases monotonically with increasing Mw in the range of Mw examined, while NOE is almost independent of Mw. Such behavior may be regarded as arising from effects of chain stiffness. A comparison is then made of the present data for T1, T2, and NOE with the theory developed for the generalized Kratky–Porod (KP) wormlike chain as a special case of the helical wormlike chain, and it is shown that the theory may almost quantitatively explain the data, using the established values of the KP model parameters. A comparison is also made of the present data with the theoretical values calculated from the equations of Woessner for the equivalent, rigid prolate spheroid.

Journal

  • Polymer Journal

    Polymer Journal 37 (7), 535-540, 2005

    The Society of Polymer Science, Japan

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