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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

Correlations between the macroscopic bulk polymer properties storage modulus (E′) and loss modulus (E″) and the microscopic property of cross‐polarization as represented by the time constant TCH have been established for a series of polyurethane elastomers. The dependence of E′, E″, and TCH as a function of molecular weight, rigid domain concentration, and temperature are graphically presented as a series of log plots. An experimental relationship is presented that shows that the distribution of motions of the flexible domains appears to be the major factor in the success of these correlations.

Abstract. Hybrid thin films containing nano-sized inorganic domains were synthesized from UV-curable acrylate-modified waterborne polyurethane (WPU-AC) and monodispersed colloidal silica with coupling agent. The coupling agent, 3-(trimethoxysilyl)propyl methacrylate (MSMA), was bonded onto colloidal silica first, and then mixed with WPU-AC to form a precursor solution. This precursor was spin coated, dried and UV-cured to generate the hybrid films. The silica content in the hybrid thin films was varied from 0 to 30 wt%. Experimental results showed the aggregation of silica particles in the hybrid films. Thus, the silica domain in the hybrid films was varied from 30 to 50 nm by the different ratios of MSMAsilica to WPU-AC. The prepared hybrid films from the crosslinked WPU-AC/MSMA-silica showed much better thermal stability and mechanical properties than pure WPU-AC.

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