Associating water soluble polymers

Li (2007) observed that the adsorption of a hydrophobically associating water-soluble polymer, AP-2, did not follow the Langmuir-type isotherm. Figure 5.37 shows that the adsorption increased to a maximum and then decreased as the polymer concentration was increased. The reason is probably that the hydrophobic polymer has an adsorption layer of multiple molecules on rock surfaces. When the polymer concentration is increased, the adsorption layer becomes thicker because of more adsorption. When the polymer concentration is further increased, the molecular interaction in the liquid is stronger than that between the adsorbed molecules and rock surfaces. Then the adsorbed molecules may leave the rock surfaces and redissolve into the liquid. Thus, the adsorption decreases. 

Rheology modification Clays, amide modified alkyds, hydrophobically associating water soluble polymers, cellulosics, titanium chelates... 

Aubry, T. and M. Moan (1996). Influence of a nonionic surfactant on the rheology of a hydrophobically associating water soluble polymer. Journal of Rheology 40(3) 441-448 (1978 present). 

Yabin, N., Jian, P., Zhuoyan, Z., Guijiang, W., Guanghua, S., and Lijun, S. 2001. Research on Hydrophobically Associating Water-Soluble Polymer Used for EPR. Paper SPE 65378 presented at the SPE International Symposium on Pilfield Chemistry, Houston, 13-16 February. DPI 10.2118/65378-MS. 

Synthesis and Characterization of Hydrophobically Associating Water-Soluble Polymers... 

Hydrophobically associating water-soluble polymers are of interest because of their unusual properties in solution. Even small levels of hydrophobic groups on water-soluble polymer backbones can have a profound effect on aqueous solution rheology. For example, solutions of such polymers show enhanced viscosification efficiency, shear-thickening rheology, as well as improved shear and salt stability [1-19]. 

Nevertheless, hydrophobically associating water-soluble polymers present challenges to both the synthetic and characterization chemists. Hydrophobically associating water soluble polymers are often difficult to synthesize because of problems associated with mixing oil-soluble and water-soluble reagents/ monomers. Similarly, since only small levels of hydrophobe are needed for rheology control, characterization of hydrophobe contents often stretch the detection limits of conventional polymer characterization methods. 

The solution properties of polymeric amphiphilic molecules are strongly influenced by molecular aggregation and have been a subject of widespread research [4-19]. These polymers contain a major amount of polar, water-soluble groups and a minor amount of nonpolar hydrocarbon chains. The amphiphilic nature of these structures causes polymer aggregation in aqueous media which results in unique and useful solution properties. This chapter describes the solution properties of hydrophobically associating water-soluble polymers. In addition, the relationship between these properties and performance attributes in a variety of technological applications will be described. 

Hydrophobically associating water soluble polymers can be prepared either by copolymerization of a hydrophilic and a hydrophobic monomer or by modification of a precursor water-soluble polymer. A typical example of materials prepared by the first method is the hydrophobic derivatives of polyacrylamide (PAM) [10-15]. The copolymerization occurs in the presence of a surfactant in order to increase the solubility of the hydrophobic component in the water and the resulting polymers exhibit a rather block structure the hydrophobic groups have a rather block distribution on the PAM chain [10, 13-15]. The size of the hydrophobic blocks can be controlled by the quantity of the surfactant added (see also the contribution of Prof. McCormick group in this book). Unfortunately this copolymerization technique does not allow the simultaneous control of all the molecular parameters (i.e. polymer molecular weight, degree of modification and alkyl group distribution). 

For instance, the use of hydrophobically associating water-soluble polymers is a new approach to aqueous fluid mobility control over the last few years [4-9]. Much of this research has focussed on the synthesis of copolymers of acrylamide and comonomers containing long hydrocarbon chains such as laurylacrylate or -methacrylate and N-alkyl acrylamides [8]. Other approaches to this problem have included the synthesis of cellulose-based water-soluble polymers substituted with long hydrocarbon chains [7]. 

Associating water soluble polymers were derived from a precursor chain, poly(acrylic acid) in its sodium form. Two different precursor batches were used they had an average molecular weight of 150.000 and 225.000 according to the supplier (Polysciences Inc, Warrington, PA). SEC analyses... 

In the below described experiments, the adamantyl substituted poiy[7V-tris (hydroxymethyl) methyl] acrylamide (poiymer A) and P-CD polymer were used as two self-associating water soluble polymers, and the drug naproxen served as a blocker of their association [25]. Polymer A substituted with adamantyl units and P-CD polymer obtained by crosslinking with EP were mixed to give an inciusion complex in the form of a gei. Upon introduction of a drug molecule, e.g. naproxen which is able to fill the P-CD cavities, the expulsion of adamantyl unit occurs this behavior leads to disruption of association of polymer A with P-CD polymer, and to inhibition of the gel formation. 

The first criterion was associated with improved secondary and tertiary petroleum recovery processes. This is the justification for the patent appHcations issued to the Dow (50) and Exxon (51) corporations. The additional costs of production and the increased adsorption of such modified water-soluble polymers are detrimental to the commercial appHcation of such polymers and even the academic studies in this area have decreased in recent years. 

Chain-Growth Associative Thickeners. Preparation of hydrophobically modified, water-soluble polymer in aqueous media by a chain-growth mechanism presents a unique challenge in that the hydrophobically modified monomers are surface active and form micelles (50). Although the initiation and propagation occurs primarily in the aqueous phase, when the propagating radical enters the micelle the hydrophobically modified monomers then polymerize in blocks. In addition, the hydrophobically modified monomer possesses a different reactivity ratio (42) than the unmodified monomer, and the composition of the polymer chain therefore varies considerably with conversion (57). The most extensively studied monomer of this class has been acrylamide, but there have been others such as the modification of PVAlc. Pyridine (58) was one of the first chain-growth polymers to be hydrophobically modified. This modification is a post-polymerization alkylation reaction and produces a random distribution of hydrophobic units. 

J. Bock and co-workers, "Hydrophobically Associating Polymers," ia G. A. Stahl and D. N. Schul2, eds., Water-Soluble Polymers for Petroleum Recorey, Plenum Press, New York, 1988, pp. 147—160. 

Other. A large variety of additives are used in paper-coatiag colors primarily to modify the physical properties of the colors (102). At high soHds concentrations in water, mineral pigment particles tend to associate and form viscous pastes. Dispersants (qv) are used to prevent this and to provide low viscosity slurries. Common dispersants include polyphosphates and sodium polyacrylate [9003-04-7]. Various water-soluble polymers are added to coatiag colors and act as water-retention agents and as rheology modifiers. 

Resin Solubilizers. In general, water-soluble resins ate amine salts of acidic polymers. Water-soluble coatings formulated with AMP-95 and DMAMP-80 exhibit superior performance (15,16) (see Water-SOLUBLE polymers). AMP-95, used in conjunction with associative thickeners (17) or hydroxy-ethylceUulose, provides for the most efficient utilization of such thickeners. It also is the neutralizer of choice for use with hair spray resins. 

A theoretical prediction of water-soluble polymer solutions is difficult to obtain due to their ability to build up aggregations and associations. A prediction of the viscosity yield is much easier to observe for solutions of synthetic polystyrene due to its simple solution structure. These solutions have been well characterized in other studies [19-23] concerning their chemical composition, molar mass and sample polydispersity. 

When a water-soluble polymer is dissolved in water, a complex network is formed that includes the polymer backbone, free water, and water in various degrees of bonding to the polymer. Depending on the concentration of polymer, its molecular weight, and several other factors, the network of polymer and bound water can assume the volume of the solution. This, of course, leads to the high viscosity that these solutions develop. The volume occupied by the polymer and the associated water in the system are said to be the hydrodynamic volume. As this volume increases because of increases in molecular weight or in the water shell surrounding the molecule, the viscosity of the solution increases. 

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