Properties of hydrophobically associating polyacrylamides: influence of the method of synthesis

Abstract

Hydrophobically modified water-soluble polymers have been prepared by radial copolymerization of acrylamide and ethylphenylacrylamide as the hydrophobic comonomer.Three methods of synthesis in aqueous media have been investigated: (i) a "micellar" process in which the presence of a surfactant ensures the solubilization of the hydrophobic monomer; (ii) a "homogeneous" process wherein a miscible cosolvent is used; (iii) a "heterogeneous" process, without additive to solubilize the insoluble monomer. The properties of the copolymers in dilute and semidilute aqueous solutions strongly depend on the conditions of the synthesis.Copolymers prepared by the homogeneous and heterogeneous processes behave like homopolyacrylamide; i.e., hydrophobic interactions do not occur significantly. Copolymers obtained by micellar copolymerization exhibit improved thickening properties due to intermolecular hydrophobic associations. These differences can be directly related to the copolymer microstructure, i.e., to a random or blocky distribution of the hydrophobic units. The blockiness of the copolymer can be adjusted by varying the [hydrophobe]/[micelle] ratio at a constant hydrophobe level. Thus, it is possible to control the association degree and therefore the rheological properties. Fluorescence studies, using pyrene as a probe, reveal the formation of hydrophobic microdomains which corroborate the rheological results.

Rheological properties of multisticker associative polyelectrolytes in semidilute aqueous solutions

“…10,42 The polymerization procedure was similar to that described elsewhere. 49,50 The monomer concentration in the feed was kept at 2 wt %, and the initiator concentration was set to 0.8 mol % with respect to the monomer feed. Such a high initiator concentration was required 53,62 because of the rather low dissociation constant of ACVA at 50°C (k d,50°C Ϸ 3 ϫ 10 Ϫ6 s…”

“…It has been inferred from photophysical and rheological experiments that the length of these hydrophobic segments corresponds roughly to the average number of hydrophobic monomers per micelle (N H ). 18,[43][44][45][46][47][48][49][50][51] It has also been clearly established that the thickening efficiency is directly related to the polymer microstructure: the longer the hydrophobic blocks, the greater the thickening efficiency at a constant level of hydrophobe incorporation. 48 -53 In this report, we describe the micellar synthesis and aqueous solution properties of multiblock polyelectrolytes of AM, sodium 2-acrylamido-2-methylpropanesulfonate (NaAMPS), and N,N-dihexylacrylamide (DiHexAM).…”

Synthesis and association behavior of cationic amphiphilic copolymers consisting of quaternary ammonium and nonionic surfactant moieties

“…[28][29][30] Thus, to obtain a statistical copolymer, copolymerization was conducted in an ethanol solution using AIBN as illustrated in Scheme 1 where x in P-ATMAC/DEmMA(x) denotes the mol % content of DEmMA in feed.…”

Metastable state of amphiphilic polysaccharide solutions

“…Depending on their hydrophilic-lipophilic balance, i.e., on both the extent and the length of hydrophobic substitution, water-soluble amphiphilic polymers can behave as polysoaps [1][2] and/or associating polymers [3][4][5]. They possess properties superior to those of conventional hydrophilic polymers.…”