Surface modification of montmorillonite and application to the preparation of polybutadiene/montmorillonite nanocomposites

Hydrophobic organic montmorillonite (OMMT) which exists as stable dispersions in cyclohexane has been prepared by the combined modification of quaternary ammonium salts and coupling agents, and polybutadiene (PB)/OMMT nanocomposites (NCs) were successfully synthesized by in situ living anionic polymerization. The results showed that the interlayer spacing of OMMT increased dramatically on increasing the length of the long alkyl chain of C12, C16, C18 and C22 in n-alkyltrimethylammonium ions and the number of long alkyl chains of 1C16, 2C16 and 3C16 in hexadecylmethylammonium ions. The interlayer spacings reached 4.9 and 5.07 nm, respectively, when C22 and 3C16 were used. The dispersion of MMT intercalated by quaternary ammonium salts was improved significantly after surface modification by different coupling agents, and the OMMTs could be disperses stably in cyclohexane for at least 72 h. In addition, the coupling agents did not change the inherent intercalation structure of OMMT. The results from a kinetic study and 1H NMR analysis indicated that the incorporation of OMMT had little influence on the living polymerization and PB microstructure (proportions of 1,2- and 1,4-units) when the OMMT content was below 3 wt%. However, the OMMT modified by different coupling agents had some influence on the molecular weight distribution. The results from transmission electron microscopy and X-ray diffraction revealed that exfoliated structures of clay were obtained for all NCs. Furthermore, the results of differential scanning calorimetry and thermogravimetric analysis indicated that Tg and Tdc of NCs were increased compared to those of PB. Copyright © 2006 Society of Chemical Industry