Variable-temperature FTIR studies on thermal stability of hydrogen bonding in nylon 6/mesoporous silica nanocomposite

Variable-temperature FTIR studies on thermal stability of hydrogen bonding in nylon 6/mesoporous silica nanocomposite

Polymer International 2009, 58, 503-510
Lanjie Li, Guisheng Yang

Abstract: Hydrogen bonding is very important in determining the properties of nylons. Introducing nanofillers that can form hydrogen bonds with amide groups at the interfaces may result in a different hydrogen bonding stability. Understanding the extent of the difference in hydrogen bonding between nylons and their nanocomposites and the mechanisms involved is valuable for explaining the origin of the property improvement of nanocomposites at the molecular level. Hydrogen bonding in a nylon 6/mesoporous silica nanocomposite (NMSN) was investigated using variable-temperature Fourier transform infrared spectroscopy from 30 to 240 °C, and the results were compared with those for nylon 6 (N6). Emphasis was placed on the analysis of hydrogen bonded N-H stretching and amide I modes. With increasing temperature, the hydrogen bonding in NMSN attenuated and dissociated at much lower rate than in N6. Also, the fraction of free carbonyl groups of NMSN in the melt state was much smaller than that of N6. The nanodispersion and mesoporous structure of silica were confirmed using atomic force microscopy and transmission electron microscopy. The incorporation of mesoporous silica increases considerably the thermal stability of hydrogen bonding in NMSN, which can be attributed to the interface interaction and the constraining effect of silica on the chain mobility of N6.