Synthesis, Characterization, and Solution Rheology of Model Hydrophobically-Modified, Water-Soluble Ethoxylated Urethanes

Abstract

The synthesis, characterization, and solution rheology of well-characterized hydrophobically-modified, ethoxylated urethane (HEUR) water-soluble polymers are described for two types of model HEURs: linear polyloxyethylene) of M n = 26 200 with terminal hydrophobes of different sizes, and terminal hydrophobe groups separated by smaller oxyethylene spacing around a larger internal hydrophobe. In the first series, a terminal isocyanate telechelic prepolymer of poly(oxyethy1ene) is prepared and reacted with amine and alcohol containing hydrophobes of variable size. In the second, terminal hydrophobe HEURs varying in geometry around an internal hydrophobe are synthesized by a one-step addition of an ethoxylated nonylphenol surfactant to a diisocyanate or an isocyanato functional biuret or isocyanurate. Low shear rate viscosities and oscillatory responses of HEUR solutions are examined, alone and in the presence of anionic and nonionic surfactants. HEUR solutions exhibit a maximum inviscositywith increasing surfactant concentrations with both anionic and nonionic surfactants. The viscoelasticity of the solution in the area of the viscosity maximum and factors influencing the magnitude of the viscosity increase are addressed. The surfactant concentration necessary to achieve the viscosity maximum is observed to depend on the concentration and architecture of the HEUR as well as the structure of the surfactant. Differences in the phase separation behavior of aqueous solutions also are observed.

Enzyme-Catalyzed Modifications of Polysaccharides and Poly(ethylene glycol)

“…The hydrophobes associate with one another in aqueous solutions at low concentrations, and thereby increase the viscosity of the solution at low shear frequencies [21]. Examples of commercial associative thickeners include hydrophobically modified HEC (HMHEC) [22], ethoxylated urethane (HEUR) [23,24], and alkali-soluble emulsion (HASE) [25][26][27]. Enzyme catalysis can be used to put a hydrophobic unit onto a cellulose derivative.…”

Self-diffusion of hydrophobically end-capped polyethylene oxide urethane resin by using pulsed-gradient spin echo NMR spetroscopy

“…There is a delicate balance between the driving force for micellization by hydrophobes/water contacts and the penalty paid through loop formation and chain stretching in these flower-like micelles. [1][2][3][4][5][6][7] These association processes are more complex than those of traditional surfactant micelles. It is the secondary association at higher concentrations where the hydrophobic chains can bridge between neighboring micellar cores and where the hydrophilic backbone chains form loops between micelles.…”

Syneresis and Rheology Mechanisms of a Latex-HEUR Associative Thickener System

“…HEURs can be prepared from the direct addition of monoisocyanate to PEG, in which case it is called a uni-HEUR. 9 HEURs can also be prepared from the step-growth (SG) polymerization of PEG and diisocyanate. 9 Excess diisocyanate is used to control the molecular weight and to generate an isocyanatefunctionalized polymer that is then exposed to alkyl-amine or -alcohol.…”

“…9 Excess diisocyanate is used to control the molecular weight and to generate an isocyanatefunctionalized polymer that is then exposed to alkyl-amine or -alcohol. 9,[10][11][12][13][14][15][16][17][18] The resultant polymer is called a SG-HEUR. 9 Unlike uni-HEURs, the hydrophilic segment of SGHEURs consists of multiple PEG polymers that are separated by diisocyanate segments.…”

“…9 Unlike uni-HEURs, the hydrophilic segment of SGHEURs consists of multiple PEG polymers that are separated by diisocyanate segments. 9 A schematic of uni-and SG-HEURs is provided in Figure 3. The diisocyanate segments of SG-HEURs are referred to as internal hydrophobes; 9,10-18 they do not significantly contribute to the viscosity, as was shown in a fluorescence study of aqueous SG-HEUR solutions.…”