Synthesis of Poly(ethylene glycol) Grafted Polyamidoamine Dendrimer Hydrogels and Their Temperature and pH Sensitive Properties

Abstract

PEG-based smart hydrogels have excellent properties and are widely used in the drug delivery, tissue engineering and other fields. In this article, a temperature responsive and pH sensitive dual responsive hydrogel which is suitable for water plugging and profile control in the Daqing oil field was prepared via graft copolymerization using polyethylene glycol (Mn = 600, 1000, and 2000) and polyamidoamine (PAMAM) as raw materials. The structure and properties of the products were characterized using infrared, 1H NMR and UV–Vis spectroscopy, end group titration, scanning electron microscopy (SEM) and swelling behavior tests. The influence of the molecular weight of the PEG precursor on the critical phase transition temperature (LCST) and pH sensitivity of the hydrogel were systematically studied. The experimental results showed that when the molecular weight of the PEG precursor was varied in the range of 600–2000, the hydrogel showed obvious temperature sensitivity and the LCST increased from 40 to 50°C. When the pH was in the range of 8–11, the hydrogel exhibited obvious pH sensitivity, swelling under alkaline conditions under acid shrinkage conditions, and the swelling ratio of the hydrogel increased upon increasing the molecular weight of the PEG precursor. The hydrogel was switched at temperatures between 10 and 60°C, pH values between 3 and 11, and the swelling behavior of the hydrogel showed good reversibility for swelling–deswelling, which provides the possibility for water plugging and profile control in an oil field. SEM showed that the hydrogels in their dry state had a spherical structure and as the molecular weight of the PEG precursor increased, the size of the spherical particles decreased and the porosity increased.