Graft copolymerization of 2-(dimethylamino)ethyl methacrylate onto potato starch was carried out in an aqueous medium using a potassium permanganate/sulfuric acid initiation system. The grafting percentage and grafting efficiency were determined as functions of the concentrations of potassium permanganate, sulfuric acid and the monomer, and also polymerization temperature and time. The IR spectrum of the graft copolymer showed the peaks characteristic of the grafted chains. The grafting percentage and grafting efficiency increased and then decreased with increasing the concentrations of potassium permanganate, sulfuric acid, and the monomer, as well as polymerization temperature. The grafting reaction was characterized by an initial fast rate followed a lower rate which leveled off after a certain time. The overall activation energy for the grafting was estimated to be 66.9 kJ/mol.

Novel ampholytic grafted polysaccharides were prepared by grafting the Zwitterionic monomer 2-(2-methacryloethyldimethylammonio) ethanoate onto hydroxyethyl cellulose. Ethylenediamine tetraacetic acid was used in combination with ceric ammonium nitrate as the redox initiator. The effects of various factors such as initiator amount, monomer concentration, reaction temperature and time on the grafting were studied and the optimum reaction conditions to obtain maximum degree of grafting were found. The resulted graft copolymer was characterized by IR and thermal analyses.

In an attempt to develop an environmentally friendly, multifunctional mud additive for oilfield drilling treatment, new water‐soluble grafted starches with amphoteric character were prepared by grafting the mixed monomer system of 2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid (AMPS) and 2‐(dimethylamino)ethyl methacrylate (DMAEM) onto naturally occurring potato starch, and characterized by IR and composition analyses. Their structure‐property relationships with respect to the hydration suppression of the swellable clay and the control of mud rheology were studied with the help of clay hydration‐swelling test, mud rheology test, and SEM observation. It has been found that the grafting of DMAEM enhances the inhibition effectiveness of clay hydration‐swelling and that the grafting of AMPS increases the viscosity of the treated muds and the tolerance to added salt. Compared with the partially hydrolyzed polyacrylamide with a degree of hydrolysis of 16%, a typical polymeric additive used in current drilling fluids, such grafted starch with suitable grafting percentage and composition has some distinct advantages in the formulation of water‐based drilling muds.Swelling percentage (Sp) of the clay pellets as a function of hydration time (t) in water and various sample solutions.magnified imageSwelling percentage (Sp) of the clay pellets as a function of hydration time (t) in water and various sample solutions.

The study was undertaken to investigate the hydration suppression of swellable clay by water‐soluble graft terpolymers of potato starch with the mixed monomer system of acrylamide and 2‐(dimethylamino)ethyl methacrylate. It was found that the grafted starches investigated suppress the clay hydration‐swelling more effectively than a partially hydrolyzed polyacrylamide with a degree of hydrolysis of 16 %, a typical inhibitive polymer used in current drilling fluids. Besides, an increase in the grafting extent or concentration of the grafted starches results in enhanced hydration‐suppression efficiency. The starch graft terpolymer with a grafting extent of 120 %, applied at a concentration of 0.6 % (w/w) gives a suppression efficiency of 64.8 % toward the swelling of clay that had been hydrated for 24 h. The interaction of the terpolymer with the clay particles was discussed with the help of SEM observation.