A comparative study using small-angle X-ray scattering and solid-state NMRof microdomain structures in poly(styrene-butadiene-styrene) triblock copolymers

The complementary techniques of solid-state NMR and small-angle X-ray scatt ering (SAXS) have been used to determine the microdomain structures of a se ries of commercial poly(styrene-b-butadiene-b-styrene) triblock copolymers with different molecular weights. The relative locations of multiple scatte ring peaks, indirect transform, and Pored analysis have been used to determ ine the morphology and the sizes of various domains as well as the interfac ial thickness between them. Solid-state NMR of H-1 spin diffusion measureme nts was also used to estimate the microdomain structure parameters by simul ating the spin diffusion processes with a model that considers the effects of H-1 spin-lattice relaxation. The interfacial thickness, 2 nm for all fiv e materials, and the interdomain distances, ranging from 30 to 42 nm, from NMR agree well with results from SAXS techniques. There are some discrepanc ies for some of samples regarding the domain sizes of dispersed polystyrene phases obtained from the above two techniques. These discrepancies may be mainly caused by the limited quality of the fitting procedure using indirec t transform methods.