Adsorption of polyamine, polyacrylic acid and polyethylene glycol on montmorillonite: An in situ study using ATR-FTIR

Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and X-ray diffraction (XRD) have been employed to investigate the adsorption of water soluble polymers from aqueous solution onto a clay mineral surface in situ, to gain an understanding of the interactions occurring at the microscopic level in water based muds (WBM). The water soluble polymers studied were; polyethylene glycol (PEG) (molecular weight, M(W), 300 and 1000) (neutral), polyamine (FL15) (M(W) 5000) (cationic) and polyacrylic acid, PAA, (M(W) 2000) (charge dependant on pH) to establish the effect of polymer charge on the nature and extent of adsorption. XRD and ATR-FTIR spectroscopy have shown that water soluble polymers adsorb onto clay dispersions and are stable when deposited as thin solid films. XRD indicates that PEG stacks as either one or two layers whereas PAA and FL15 are restricted to a single layer between the clay lamellae. ATR-FTIR spectroscopy showed that FL15 penetrated the Na-SWy-1 films which contained low loadings of PEG without displacing any of the resident PEG. When a bilayer of PEG was present, FL15 did not penetrate into the film. Both PAA and PEG adsorbed onto FL15 loaded Na-SWy-1 films irrespective of FL15 loading or the molecular weight of the PEG. ATR-FTIR indicated that significant adsorption occurred in under 30 s and the adsorption rate was not influenced by the presence of a second polymer preloaded into the clay.