Structure and conformation of poly(ethylene glycol) in confined space of montmorillonite

Abstract

The structure and conformation of poly(ethylene glycol) (PEG) chains in the confined space of montmorillonite (MMT) were investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). A series of PEG/MMT hybrids were synthesized utilizing solution intercalation. Intercalated hybrids with monolayer and double layers of PEG chains were obtained both in Na-MMT and OMMT (DK1). However, the hydrophobic PEG chains cannot intercalate into the interlayer space of OMMT (DK4) due to the strong hydrophilic properties of DK4. There is a saturation ratio when PEG intercalated into the interlayer space of MMT. The deduced saturation ratios of PEG to Na-MMT and DK1 are 0.26 and 0.24, respectively. The structure and conformation of intercalated PEG chains exhibit different characteristics from those of the neat polymer, even more disorder in melting state. According to the results of XRD and FTIR, the structure and conformation of PEG chains in OMMT (DK1) are very similar to Na-MMT. Moreover, a possible model of PEG intercalated MMT is proposed. All PEG chains are intercalated into the interlayer spaces of MMT and form a disorder phase when PEG content is not saturated. In the cases of PEG: MMT=1:10 or 3:10 in weight, the polymer chains form one or two polymer layers. A wider monolayer form when the weight ratio of PEG/MMT is 0.2.