Synthesis of pH-sensitive poly (N,N-dimethylaminoethyl methacrylate)-grafted halloysite nanotubes for adsorption and controlled release of DPH and DS drugs

Halloysite nanotube (HNT) was functionalized with (3-Aminopropyl)triethoxysilane (APTES), alpha-bromoisobutyryl bromide (BiBB), and poly (N,N-dimethylaminoethyl methacrylate) (PDMAEMA) chains. Successful grafting of PDMAEMA by SI-ATRP method was evaluated by XPS, FTIR, TEM, and TGA. Pore volume studies were accomplished by BET, and XRD was used to study crystalline structure of nanotubes. PDMAEMA coverage is formed on the outer and inner surface and also lumen of nanotubes. Sensitivity of PDMAEMA-grafted HNTs to pH was confirmed with its solution stability evaluation and also different hydrodynamic diameters in various pH values. Finally, two samples of the neat and PDMAEMA-grafted HNTs were used as diphenhydramine hydrochloride (DPH) and diclofenac sodium salt (DS) drugs carriers and their release was investigated by varying pH using UV-spectrophotometer. Grafting of PDMAEMA chains on HNT leads to controlled release of DPH molecules. Retarded release of DS molecules from PDMAEMA-grafted HNTs at lower pH values was also observed. (C) 2015 Elsevier Ltd. All rights reserved.