Impact of Chain Length on Release Behavior of Modified Polyethylene Glycol Intercalated-Montmorillonite Nanocomposite

A new drug delivery nanocomposite system was prepared from sodium montmorillonite (Na⁺Mt) intercalated with modified polyethylene glycol (PEG). PEGs of different molecular weights (400, 4000, and 8000) were modified with glycidyltrimethylammonium chloride (GTMAC) to provide terminal quaternary ammonium sites capable for attaching with Mt or other materials through ion exchange. The modified PEG-GTMAC derivatives were reacted in excess amount with Na⁺Mt through ion exchange. The remaining quaternary sites were used for the attachment of sodium diclofenac as a model drug. The structures of the prepared clay-modified PEG-diclofenac systems were characterized using Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The release behavior of diclofenac from the different nanocomposites was studied at different pH values. With regard to the PEG chain length, the drug release increased with increasing PEG molecular weight (GCDIII > GCD-III > GCDII > GCDI). The kinetics of the release models was discussed using Korsmeyer-Peppas, Higuchi, and zero- and first-order models. The results of the kinetics study revealed that modified samples with PEG 400 and PEG 4000 (GCD-I and GCDII) exhibited non-Fickian diffusion (anomalous transport) while modified samples with PEG 8000 (GCDIII) exhibited super case-II transport.