Synthesis in inverse emulsion and properties of water‐soluble associating polymers

Abstract

An inverse, free-radical emulsion polymerization technique was designed for the preparation of copolymers of acrylamide and sodium acrylate modified with low amounts (Ͻ0.5 mol %) of a series of amphiphilic comonomers, the isooctylphenoxypoly(oxyethylene)(n) methacrylates (1 Յ n Յ 12). The products of the reaction were hydrophobically modified water-soluble polymers (HMWSPs) of high molecular weight encapsulated within water droplets dispersed in an organic medium. Kinetic studies showed that the full-conversion samples were rather homogeneous in composition because of the specificity of the process. A mechanistic scheme is proposed that accounts for the incorporation level of the amphiphilic comonomer as a function of its hydrophile-lipophile balance and the nature of the redox initiator (hydrophilic or lipophilic). The rheological properties of the HMWSPs in aqueous solutions were investigated as a function of the comonomer content and the nature of the initiator with steady-flow experiments. The thickening properties were directly correlated to the conditions of synthesis and were optimal when the initiator and the amphiphilic comonomer were located in two distinct phases. A maximum in viscosity was observed for a hydrophobe content of about 0.3 mol %. An examination of the viscosity as a function of the shear rate and time showed that these solutions had all the characteristics of associating polymers. The complex rheological behavior was the result of the balance between interchain and intrachain hydrophobic liaisons and the kinetics of disorganization and reorganization of the network structure.

Synthesis in inverse emulsion and associating behavior of hydrophobically modified polyacrylamides

“…The polymerizations were carried out at 18 ± 1°C except for diPh‐2–CUM‐O, for which a higher temperature (45°C) is required to solubilize the hydrophobic comonomer in the oil phase. The details of the experimental procedure of the polymerization were presented in a previous study 21. Recall that the final latex was diluted twofold with hexane and poured into an excess of methanol.…”

“…The details of the experimental procedure of the polymerization were presented in a previous study. 21 Recall that the final latex was diluted twofold with hexane and poured into an excess of methanol. The precipitated polymer was recovered by centrifugation and then repeatedly washed under stirring with the following solvents: methanol, isopropanol, and acetone.…”

Inverse Miniemulsion Polymerization of Unsaturated Monomers

“…Pabon et al [79] showed that the use of an inverse (mini)emulsion polymerization route allows one to increase considerably the solid contents in the final products (up to 25 wt %). The associative copolymers were formed of an acrylamide/sodium acrylate backbone hydrophobically modified with small amounts (~ 0.5 mol %) of a series of amphiphilic comonomers, isooctylphenoxy-poly(oxyethylene)(n) methacrylates (with 1 < n < 12.5).…”

“…Pabon et al have extended the inverse miniemulsion polymerization technique to the synthesis of hydrophobically modified water-soluble polymers (HMWSPs) [79]. The hydrophilic backbone of the copolymers was formed from an acrylamide/sodium acrylate (AAm/NaA) mixture.…”

Preparation of highly concentrated inverse emulsions of acrylamide‐based anionic copolymers as efficient water rheological modifiers

“…The production of acrylic polymers by inverse emulsion polymerization has several advantages such as easy handling and fast water redispersion for specific uses such as thickening agents. 8,9 In addition, the inverse emulsion polymerization technique results in high molecular weight polymers that overcome the problems associated with the high viscosity levels reached during bulk, solution or dispersion polymerization approaches. 10 However, if the amount of active material in the final product is not sufficiently high, various drawbacks, such as the expensive transportation costs, may limit their market.…”