Characterization of Polymer Blends with Solid‐State NMR Spectroscopy

Abstract

Controlling the structure of complex systems of macromolecules is a common objective in current materials science research and, indeed, many investigations have been undertaken simply by the mixing of two polymers. Polymer blending offers a simple and economical means of linking the suitable properties of component polymers [1–6]. Whether a blend retains the original properties of the component polymers or demonstrates an average of their properties depends on the degree of microscopic mixing and its phase morphology [4,5]. The degree of mixing has been defined typically in terms of miscibility of molecular to macroscopic scales, the compositions of each domain, and the phase structure and domain size [7]. In the past, many instrumental methods have been applied to investigate the structures of blends, including differential scanning calorimetry (DSC) to examine miscibility, scattering measurements such as smallangle X-ray scattering (SAXS) and small-angle neutron scattering (SANS), as well as light scattering. Unfortunately, the use of only one of these method results in an incomplete understanding of a blend. Kwei and coworkers [8] were the first to use solid-state nuclear magnetic resonance (NMR) spectroscopy to examine the microstructure of a polystyrene (PS)/ poly(vinyl methyl ether) (PVME) blend, by measuring the H spin-lattice relaxation time (Tl) and spin-spin relaxation time (T2) over a wide temperature range. Nowadays, high-resolution NMR in both liquids and in solids is a widely used technique to analyze the microstructures of polymer blends. To date, several NMR techniques have been applied very effectively to examine the molecular motion, phase structure and heterogeneity of pure polymers. Heterogeneity in blends is much more distinguished compared to pure polymers, which simplifies studies of the domain morphology of the component polymers in a blend. A review of recent studies indicated that solid-state NMR spectroscopy is still an active research topic and, by including some recently developed NMR techniques, the application of solid-state NMR spectroscopy has continued to provide new 679