Structural characteristics and interfacial relaxation of nanocomposites based on polystyrene and modified layered double hydroxides

Nanocomposites based on polystyrene (PS) and organically modified MgAl-layered double hydroxides (O-LDHs) were prepared via in situ free radical polymerization. The modification of LDH by sodium dodecylbenzenesulfonate (SDBS) led to a nearly complete substitution of original NO3− in LDH intergallery and an enlarged interlayer distance. The structural changes of LDH layers before and after preparation of nanocomposite samples were well investigated, and the corresponding mechanism diagram was proposed to visually describe the results. X-ray diffraction (XRD) and transmission electron microscopy (TEM) showed that O-LDH was homogeneously distributed in the PS matrix as stacks with an intercalated structure. The tan δ spectra of nanocomposites revealed that there were two kinds of relaxation in PS/O-LDH nanocomposites. The second of relatively low intensity located at the temperature is higher than the main relaxation (glass transition of PS matrix), corresponding to motions of the PS chains confined by O-LDH particle surfaces. According to the stack structure and dispersion behavior of O-LDH layers in the PS matrix, a three-layer model was introduced to explain the two relaxations in PS/O-LDH nanocomposites.