A preliminary correlation between macroscopic and microscopic polymer properties: Dynamic storage modulus vs. CPMAS NMR cross polarization rates

Abstract

SynopsisA correlation has been established between the dynamic storage modulus ( E ' ) and the mean cross polarization time constants (Tm) for a set of five morphologically diverse polymers, including one a t two temperatures and one at two plasticizer concentrations. The correlation is only possible when the TCH values for all of the motional environments within the polymers are considered. An inversion recovery cross polarization (IRCP) NMR technique is used to obtain motional and morphological information from the main chain carbons of each polymer. After comparing simpiified correlation functions for the two parameters, an experimental relationship between them is established that suggests that TCH and E' are both modulated by a similar distribution of molecular motions. INTRODUCTIONCorrelations between macroscopic physical properties of polymers and solidstate NMR relaxation parameters have been slow to develop despite ongoing efforts. Schaefer and co-workers' were previously successful at making a general correlation between the impact resistance and CP / MAS relaxation constants of several glassy polymers. However, to the best of our knowledge, no one has attempted a correlation based on a simple comparison of the motional models that describe either the macroscopic properties of interest (such as E') or microscopic relaxation constants (such as TCH ).Correlations of this type could potentially be valuable to scientists that are interested in studying polymer structure-property relationships. Here we attempted to establish a correlation between dynamic storage modulus (E') and the average cross polarization constant ( T c H ) with this purpose in mind. BACKGROUND

Studies of polymer mobility in composite blends of poly(vinyl butyral) and alumina

“…[6][7][8] Given that T C H is weighted by near static motional c o m p~n e n t s ,~~'~ it appears to be particularly sensitive to motions that are likely to influence the response of materials to mechanical deformations at low strain rates or at low-strain amplitudes during low-frequency dynamic experiments. Previous work on alumina-filled polystyrene systems has shown that IRCP can be used to determine the relative contribution of the polymer phase to the macro-scopic dynamic mechanical behavior of the composite."…”

Condition monitoring of a thermally aged hydroxy‐terminated polybutadiene (HTPB)/isophorone diisocyanate (IPDI) elastomer by nuclear magnetic resonance cross‐polarization recovery times

“…Parker et al 4 and Marcinko et al 5,6 recognized that the 13 C CP recovery time, T cp , is sensitive to the low-frequency long-range cooperative motions of a polymer. These motions are expected to be more closely related to the mechanical properties of a material.…”

“…This result is consistent with a reduction in the tensile elongation at break of HTPB with aging time. 1 Parker et al 4 used Maxwell's model for viscoelastic materials to derive a relationship between Young's modulus and T cp . They showed that the modulus was related to a complex quantity involving (T cp ) 2 and the measurement frequency of Young's modulus.…”

“…Parker et al 4 and Marcinko et al 5,6 have shown that the 13 C cross-polarization (CP) time constant, T cp , can be a sensitive probe of mechanical properties for a wide range of polymers. T cp is a function of the low frequency motions that characterize long-range cooperative processes that are closely related to the mechanical properties of the polymer.…”

Molecular Correlations to Macroscopic Wood Performance Using CP/MAS NMR

“…More recently it has been shown that crosspolarization measurements can be used to study the motional and morphological heterogeneities in solid polymers (Cory and Ritchey 1989;Parker et al 1989). With this technique, Parker et al (1990Parker et al ( , 1993 and Marcinko et al (1992Marcinko et al ( , 1994 have established a correlation between dynamic storage modulus (E') and the mean cross-polarization time constant, <T C H>, for a wide variety of synthetic polymers. This more recent correlation employs an inversion recovery cross-polarization, IRCP, pulse.…”