Stability of organically modified montmorillonites and their polystyrene nanocomposites after prolonged thermal treatment

作者：Frankowski David J; Capracotta Michael D; Martin James D; Khan Saad A; Spontak Richard J^*

来源：Chemistry of Materials, 2007, 19(11): 2757-2767.

DOI：10.1021/cm061953k

Melt intercalation of montmorillonite (MMT) into polymeric matrices to improve the mechanical properties of polymers has evolved into a subject of tremendous fundamental and technological interest. The thermal treatment experienced during processing or end use can substantially affect the clay and diminish the target properties of polymer/clay nanocomposites (NCs) because of deintercalation or degradation of surface modifiers. In this work, changes in morphology, chemistry, and thermal stability of organically modified (OM) MMT after annealing in O-2-rich and N-2 environments are investigated. Degradation of the alkyl ammonium cation occurs at temperatures as low as 105 degrees C upon prolonged exposure in an O-2-rich environment. X-ray diffractometry (XRD) performed in situ establishes the response of two OM-MMTs to elevated temperatures at short times, whereas ex situ XRD provides insight into high-temperature exposure at long times. Active sites on the silicate surfaces are found to induce scission of, as well as chemical interaction with, the chains comprising a polystyrene (PS) matrix. Size-exclusion chromatography indicates that PS chain scission occurs primarily after relatively short annealing times, whereas branching and cross-linking are more prevalent after long exposure times in an O-2-rich environment.

• 出版日期2007-5-29