عنوان مقاله [English]
A route for the synthesis of an associative thickener (AT), composed of polyethylene oxide, end-capped with nonadecylamide groups, has been devised. The molecular weight of PEO was 20,000 Daltons. PEO, with
such molecular weight, was converted to a hydrophobically end-capped copolymer (hydrophobically associating nonadecanamide polyethylene oxide copolymer, POER), by three chemical reactions on its end-groups. In the first step, tosyl polyethylene oxide (Ts-PEO) was obtained from the reaction of polyethylene oxide (PEO) with tosylchloride by 95% yield. In the second step, the Ts-PEO was converted
to polyethylene oxide diamine (PEOA) by inserting ammonia gas in the solution of Ts-PEO at 0°C (90% yield). Finally, in the third step the desired associative thickener (POER) was obtained from the reaction of PEOA with nonadecanoyl chloride (90%yield). Because of chain degradation probability the reaction was carried out at the temperature lower than 45°C. Therefore, there was no chain degradation during each
reaction step. The successful conversion of hydroxyl groups was shown by viscosity behavior. This was proved by measuring the polydispersity of the reactant PEO and the product PEOR, by gel permission chromatography and comparing the viscosity of PEO with the product of the second step, polyethylene oxide diamine (POEA). The results show that through the synthetic preparation the molecular weight of the
backbone remains unchanged (~20000 D). The flow curve of a 10% aqueous solution of POER-AT shows that the solution is non-Newtonian, but the flow curve of a 10% aqueous solution of POE is a Newtonian fluid. Also the variation in viscosity of a 10% aqueous solution of POER shows that this solution is thixotropic. The effects of synthesized AT was investigated on the thickening of one formulated latex paint and
it is shown an increase in the shearing strength of the formulation.