Hydrophobically Modified Ethoxylated Urethane Research Articles

Rheology of a spiropyran functionalized hydrophobically modified ethoxylated urethane in aqueous solution

Hydrophobically modified ethoxylated urethanes (HEURs) have been widely used as effective thickeners for improving the solution rheological properties in a variety of applications for over 40 years. We designed and prepared a novel photosensitive spiropyran-functionalized HEUR polymer (SP-HEUR), which was used to investigate the influence of hydrophobicity change of hydrophobes induced by photoisomerization of spiropyran (SP) group on the solution aggregation and rheological properties. The concentrated SP-HEUR solutions show an interesting photoresponsive rheological behavior upon alternative exposure to ultraviolet and visible light due to a reversible SP- to merocyanine-form conversion and back. A reversible rearrangement of micellar junctions through loop-bridge or bridge-loop transitions is proposed to interpret the influence of photoisomerozation of spiropyran groups on the associative structure and rheological properties of the polymer solution. This work will not only provide new insights into the...

Syneresis and rheology mechanisms of a latex-HEUR associative thickener system

This study focuses on the phase behavior, rheology, and interactions of polymer latex particles and a hydrophobically modified ethoxylated urethane (HEUR) associative thickener in water. At constant 0.25 latex particle volume fraction, increasing HEUR caused stable, followed by phase separated (syneresis), and stable mixtures as HEUR concentration increased from 0% to 2.0% (by weight) in the latex-thickener aqueous mixture. The mixtures that underwent syneresis were flocculated. The relationship between the flocculation behavior and the composition of the latex-HEUR mixtures is consistent with previous work reported by other investigators. However, detailed rheological data on systems like these that have undergone syneresis have not been reported. This paper presents detailed viscosity vs shear rate data and correlates viscosity trends with the both flocculation and syneresis behavior. The stable latex-HEUR mixtures at low HEUR levels show Newtonian or shear-thinning viscosity with well-defined low-shear Newtonian plateaus. As HEUR level is increased to levels at which syneresis is observed, erratic rheological profiles with shear thinning as well as thickening are observed. This type of shear thickening has been attributed to bridging flocculation by other investigators. When HEUR level is further increased to levels at which no syneresis is observed, low-shear Newtonian plateaus re-appeared, albeit at higher viscosities. Detailed analysis of syneresis and shear-thickening behavior of a latex-HEUR mixture containing 0.5% (by weight) HEUR showed two shear-thickening regions, one between 0.1 and 0.5 s−1 shear rate range and another between 30 and 100 s−1 shear rate range. Molecular weight distribution (MWD) of the HEUR thickener indicates that the two shear-thickening regions are related to the bi-modal nature of the thickener’s MWD.

Aggregation and Rheology of an Azobenzene-Functionalized Hydrophobically Modified Ethoxylated Urethane in Aqueous Solution

Hydrophobically modified ethoxylated urethanes (HEURs) belong to an important class of telechelic associative polymers for improving solution rheological properties. We designed and prepared a novel azobenzene end-functionalized HEUR polymer (AzoHEUR), which was used to investigate the effects of hydrophobicity change of end hydrophobes induced by photoisomerization of azobenzene on the solution aggregation and rheological properties. The concentrated AzoHEUR solutions show a reversible rheological property change upon alternative exposure to UV and visible light. We have demonstrated that a reversible change in hydrophilic–lipophilic balance of polymer followed by photoisomerization of azobenzene induces a reversible rearrangement of micellar junctions through loop–bridge or bridge–loop transitions, which reversibly changes not only the network connectivity but also the solution relaxation behavior. Moreover, a structural model is proposed to describe the rearrangement of micellar junctions induced by ph...

Highly efficient hydrophobically modified ethoxylated urethanes (HEURs) end-functionalized by two-tail dendritic hydrophobes: Synthesis, solution rheological behavior and thickening in latex

Abstract Hydrophobically modified ethoxylated urethanes (HEURs) are an important class of telechelic associative polymers with various industrial applications, in which careful control of the rheology of the solution is required. We report the synthesis of three novel HEUR polymers end-functionalized by dendritic di-substituted benzene alcohol ( HEUR-2Cn , where n is the length of hydrophobic tails) and their rheological properties in aqueous solutions and latex. The concentrated solutions of these HEURs show interesting aggregation and viscoelastic properties dependent of their hydrophobe length: a viscoelastic liquid for HEUR-2C8 , and elastic gels for both HEUR-2C12 and HEUR-2C16 due to their different relaxation behavior. Interestingly, the concentrated solutions of HEUR-2C16 form the strongest transient network with the largest number density of active micellar junctions and slowest relaxation because of its longest hydrophobe. Furthermore, these HEUR polymers have highly efficient thickening performance in latex compared with a conventional HEUR-C16 with −C 16 H 33 end group, because the dendritic two-tail hydrophobes can form more stable absorption on the surface of the latex through bridging between the latex particles than a single hydrophobe. This work opens a new perspective for highly efficient thickeners and also provides new insights into the potential of these HEUR polymers in waterborne coating, cosmetics, dyestuff, medicines and so on.

Dielectric relaxations of nanocomposites composed of HEUR polymers and magnetite nanoparticles

We investigate the dynamics of nanocomposites composed of hydrophobically modified ethoxylated urethanes (HEUR) and magnetite nanoparticles (MNPs) as dry films. We employed dielectric relaxation spectroscopy (DRS) in combination with differential scanning calorimetry (DSC) and thermally stimulated depolarization currents (TSDC). The three techniques reveal a strong heterogeneity of the matrix of the nanocomposites, consisting of (i) a crystalline poly(ethyleneoxide) PEO bulk phase, (ii) an amorphous PEO portion, and (iii) small PEO crystallites which experience different constraints than the PEO bulk phase. TSDC and DRS reveal a very high direct current (DC)-conductivity of the pure matrix, which increases with MNPs concentration. The increase of the DC-conductivity is not related to an increase of the segmental mobility, but most likely to the change of the morphology of the hydrophobic domains of the polymer matrix, due to the formation of large MNPs clusters. Indeed, the MNPs neither influence the segmental dynamics of the polymer nor the phase behavior of the polymer matrix. The addition of MNPs slightly increases the activation energy related to the γ-relaxation of the polymer. This effect might be related to the changes in nano-morphology as demonstrated by the slight increase of the degree of crystallinity. The analysis of the DRS data with the electrical modulus M″(ω) and the derivative ε″der formalism allow us to identify a low-frequency process in addition to the conductivity relaxation. This low-frequency dispersion is also revealed by TSDC. It is most likely related to the Maxwell-Wagner-Sillars relaxation, which typically occurs in systems which feature phase separation. The detailed investigation of the dielectric properties of these novel nanocomposites with increasing MNPs concentration will be useful for their practical application, for example as absorbers of electromagnetic waves.

Multi-stage freezing of HEUR polymer networks with magnetite nanoparticles.

We observe a change in the segmental dynamics of hydrogels based on hydrophobically modified ethoxylated urethanes (HEUR) when hydrophobic magnetite nanoparticles (MNPs) are embedded in the hydrogels. The dynamics of the nanocomposite hydrogels is investigated using dielectric relaxation spectroscopy (DRS) and neutron spin echo (NSE) spectroscopy. The magnetic nanoparticles within the hydrophobic domains of the HEUR polymer network increase the size of these domains and their distance. The size increase leads to a dilution of the polymers close to the hydrophobic domain, allowing higher mobility of the smallest polymer blobs close to the "center". This is reflected in the decrease of the activation energy of the β-process detected in the DRS data. The increase in distance leads to an increase of the size of the largest hydrophilic polymer blobs. Therefore, the segmental dynamics of the largest blobs is slowed down. At short time scales, i.e. 10(-9) s < τ < 10(-3) s, the suppression of the segmental dynamics is reflected in the α-relaxation processes detected in the DRS data and in the decrease of the relaxation rate Γ of the segmental motion in the NSE data with increasing concentration of magnetic nanoparticles. The stepwise (multi-stage) freezing of the small blobs is only visible for the pure hydrogel at low temperatures. On the other hand, the glass transition temperature (Tg) decreases upon increasing the MNP loading, indicating an acceleration of the segmental dynamics at long time scales (τ∼ 100 s). Therefore, it would be possible to tune the Tg of the hydrogels by varying the MNP concentration. The contribution of the static inhomogeneities to the total scattering function Sst(q) is extracted from the NSE data, revealing a more ordered gel structure than the one giving rise to the total scattering function S(q), with a relaxed correlation length ξNSE = (43 ± 5) Å which is larger than the fluctuating correlation length from a static investigation ξSANS = (17.2 ± 0.3) Å.

New Interpretation of Shear Thickening in Telechelic Associating Polymers

Shear thickening of telechelic associating polymers, particularly of hydrophobically modified ethoxylated urethanes (HEURs), is classically attributed to either non-Gaussian behavior of the chains, also called finite extensible nonlinear elasticity (FENE), or to flow-enhanced formation of network strands; however, in a recent paper [Macromolecules, 45, 888 (2012)], Suzuki et al. show that neither of the previously mentioned interpretations can hold true, as they find shear thickening while at the same time the network structure has essentially remained the equilibrium one, except for the fact that reassociation to the network of the strands that continuously detach from it is anisotropically enhanced in the shear gradient direction. In the present paper, we propose a different mechanism that might explain shear thickening, namely, the stress contribution arising from the repulsive interaction between the flowerlike micelles that are forced to interpenetrate one another by the shear flow. In support of thi...

Characterization of additives of PVAc and acrylic waterborne dispersions and paints by analytical pyrolysis–GC–MS and pyrolysis–silylation–GC–MS

Commercial formulations of poly(vinyl acetate) (PVAc) and acrylic dispersions and paints commonly used by artists include a number of additives such as surfactants, coalescing agents, defoamers and thickeners, which are designed for improving shelf-life, as well as chemical and physical properties of the resulting product. Recent studies have shown that additives present in paints play an important role in the alteration processes undergone by the painting during ageing and further in cleaning tasks planed in conservation interventions. However, the identification of additives is a difficult task due to the elusive character of these substances present at low concentration in the paint.In this context, a four-step approach is proposed that includes analysis of paint samples together with analysis of their water extracted products by pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS) and pyrolysis–silylation–gas chromatography–mass spectrometry (Py–silylation–GC–MS). This analytical strategy enables a better characterization of common additives present in commercial PVAc and acrylic paints and dispersions. In particular, the analysis of water soluble extracts, which are mainly composed by paint additives, avoids the interference of the major polymer pyrolizates. Experimental conditions concerning sample preparation and instrumental working conditions of both Py–GC techniques are optimized.Both acrylic and PVAc paints presented poly(ethylene oxide) (POE) type fragments dominating the background of their pyrograms, especially when derivatized by means of hexamethyldisilazane (HMDS). For the first time, additives such as alkyl sulfate and alkyl ether sulfate with C10 and C12 alkyl chains, poly(ethoxylate) fatty alcohol and octylphenyl poly(ethoxylate) surfactants were identified, as well as polyvinyl alcohol (PVOH) protective colloids, hydrophobically modified ethoxylated urethane (HEUR) thickeners an defoamers. Their major fragments and corresponding mass spectra are discussed.

Study of the simultaneous effects of MMT nanoclay and hydrophobically modified ethoxylated urethane (HEUR) on viscoelastic and steady shear properties of water-based acrylic resins

The storage stability of montmorillonite/acrylic resin was studied via rheological characterizations. The Na+–MMT nanoclay and a water-based acrylic resin were used for the preparation of different suspension samples. The effect of an associative polymer such as hydrophobically modified ethoxylated urethane (HEUR) in the mixture was also investigated. The result showed that the existence of an associative polymer has an influence on the stability and zero-shear viscosity of the system. In order to determine the behavior of this system under long-term storage, various rheological characterizations such as frequency sweep and rate sweep measurements were carried out. The results showed that adding the montmorillonite nanoclay and HEUR to the acrylic resin causes short- and long-term stabilities of suspensions microstructure. The required stability, a better flow, and a better structure were achieved, respectively, upon addition of an associative polymer, addition of MMT–Na+, and flow cessation.

Concentration Dependence of Nonlinear Rheological Properties of Hydrophobically Modified Ethoxylated Urethane Aqueous Solutions

For aqueous solutions of a representative telechelic polymer, hydrophobically modified ethoxylated urethane (HEUR), a recent transient network model suggested that sparse and dense HEUR networks are formed at low and high HEUR concentrations c thereby exhibiting different rheological features [Uneyama, T.; Suzuki, S.; Watanabe, H. Phys. Rev. E2012, 86, 031802]. In this study, we examined those differences for nonlinear rheological behavior of HEUR solutions (with MHEUR = 4.6 × 104 and c = 1–10 wt %) under steady shear at 25 °C to test the model. For rather dilute solutions (c ≤ 3 wt %), the steady state viscosity η exhibited crossover from the linear (zero-shear) behavior to thickening and further to thinning with increasing the shear rate γ̇, whereas the first normal stress coefficient Ψ1 remained in the linear regime up to intermediate γ̇ (where η exhibited the thickening) and then decreased with γ̇ in the thinning regime of η. In contrast, for concentrated solutions (c ≥ 4 wt %), η exhibited no thickening and a direct linear-to-thinning crossover was observed for both η and Ψ1. The critical HEUR concentration for the disappearance of the thickening of η, c* ≅ 4 wt %, was in agreement with that noted for the linear viscoelastic data, suggesting that the HEUR network structure changed from the sparse state to the dense state at c*, as considered in the above transient network model: At low c < c*, linear sequences of HEUR chains (superbridges) connected at the HEUR micellar cores would have served as effective strands to form the sparse network. Those superbridge strands dissociate and reassociate under steady shear, and the orientation of the reassociated strands should be quite sensitive to anisotropy of the spatial distribution of the cores (intra-strand dissociation sites) so that the thickening of η at intermediate γ̇ is accompanied by linear Ψ1, as deduced from the model. In contrast, at large c > c*, the dense network mainly sustained by individual HEUR chains would have been formed. For this case, the anisotropy of core distribution should less significantly affect the orientation of the created strands, which possibly erased the thickening of η at intermediate γ̇, as suggested by the model. Thus, the changes of the nonlinear behavior with c observed in this study were in harmony with the expectation from the model, lending qualitative support to the structures and dynamics of the networks considered in the model. In addition, the flow visualization using tracer particles confirmed that the flow was uniform up to the onset of thinning of η and Ψ1 (which is again in harmony with the model) and that the flow was destabilized to form shear bands in the thinning regime as similar to the behavior of a wide variety of softmatters.

Nonlinear Rheology of Telechelic Associative Polymer Networks: Shear Thickening and Thinning Behavior of Hydrophobically Modified Ethoxylated Urethane (HEUR) in Aqueous Solution

Flow behavior was examined for a 1.0 wt % aqueous solution of hydrophobically modified ethoxylated urethane (HEUR; Mw = 4.6 × 104). In the linear viscoelastic regime, the solution exhibited single-Maxwellian behavior attributable to thermal reorganization of the transient network composed of strings of HEUR flower micelles. Under shear flow at intermediate shear rates γ just above the equilibrium relaxation frequency 1/τ, the solution exhibited thickening characterized by monotonic increase of the viscosity growth function η+(t;γ) with time t above the linear η+(t) and by the steady-state viscosity η(γ) larger than the zero-shear viscosity η0. However, at those γ, the first normal stress coefficient growth function Ψ1+(t;γ) and its steady-state value Ψ1(γ) remained very close to the linear Ψ1+(t) and Ψ1,0 and exhibited no nonlinearity. In addition, the relaxation times of the viscosity and normal stress coefficient decay functions η–(t;γ) and Ψ1–(t;γ) measured after cessation of steady flow agreed...

Rheology of Aqueous Solution of Hydrophobically Modified Ethoxylated Urethane (HEUR) with Fluorescent Probes at Chain Ends: Thinning Mechanism

Nonlinear flow behavior and the corresponding fluorescent behavior were examined for a 3.0 wt% aqueous solution of hydrophobically modified ethoxylated urethane (HEUR; Mw = 1.1×105) having fluorescent pyrenyl (Py) groups at the chain ends. These end groups associated with each other to serve as cores of HEUR flower micelles, and these micelles were further connected into super-bridges to form a transient network. Correspondingly, single-Maxwellian relaxation reflecting the thermal reorganization of this network was observed in the linear viscoelastic regime. Under steady shear flow, the HEUR solution exhibited thinning of both viscosity η(γ) and first normal stress coefficient Ψ1(γ) at shear rates γ above the equilibrium relaxation frequency 1/τ. Fluorescent emission intensity IE(γ) from excimers formed by Py groups associated in a hydrophobic environment of the micellar cores and the intensity IM(γ) from dissociated Py groups (referred to as monomers) isolated in the aqueous phase were measured under flow simultaneously with η and Ψ1. The IE/IM ratio was found to decrease only slightly (by a factor of ∼4 %) on an increase of γ up to 6/τ well in the thinning regime. (For γ = 6/τ, η and Ψ1 decreased from respective zero-shear values by factors of ∼50 % and ∼75 %, respectively) Thus, the significant thinning at those γ was accompanied by a negligible change in the HEUR core structure that corresponds to just a slight shift of the association/dissociation balance of the Py groups to the dissociated state. From this result, the thinning is quite possibly attributed to flow-induced disruption of the network connectivity through conversion of the super-bridges into super-loops, both having the same core structure.

Rheology of Aqueous Solution of Hydrophobically Modified Ethoxylated Urethane (HEUR) with Fluorescent Probes at Chain Ends: Thinning Mechanism

Rheology of Aqueous Solution of Hydrophobically Modified Ethoxylated Urethane (HEUR) with Fluorescent Probes at Chain Ends: Thinning Mechanism

Investigation of the Thickening Efficiency of HEUR on the Behavior of Two Different Latex Types

Abstract A hydrophobically modified ethoxylated urethane (HEUR) as a thickener was synthesized using poly (ethylene glycol), Dicyclohexylmethane diisocyanate (H12MDI) and cethyl alcohol via step growth polymerization technique. The molecular weight of the thickener was determined by GPC, and its behavior in aqueous solution was studied. The steady shear experiments were carried out by mixture of the synthesized thickener with two resins. These resins had different nature; one with hydrophilic and the other with both hydrophilic and hydrophobic segmental structure. The result showed the type of resin can be effective in the thickening efficiency of HEUR thickener.

Study of the rheology of aqueous radiation curable polyurethane dispersions modified with associative thickeners

The chemistry of radiation curable polyurethane dispersions is outlined with an emphasis on the microstructure of the aqueous polymer dispersion and the possible interactions with associative thickeners. The steady-shear flow was studied for two model dispersions prepared from the same unsaturated polyurethane but showing significantly different particle size distributions. A hydrophobically modified ethoxylated urethane (HEUR) associative thickener with a linear structure was incorporated at different amounts to the dispersions with varying particle volume fractions. The steady-state viscosity at 25 and 10 °C was always reached quickly after instant flow rate changes so that no significant thixotropic effects were reported within the experimental timescale. Without thickener, the flow curves of the two model dispersions exhibited a Newtonian behavior except at the highest volume fractions where shear thinning became apparent. The maximum packing values determined from the Krieger–Dougherty relationship were essentially the same for the two systems. In the presence of thickener, the flow curves were characterized by a Newtonian plateau followed by a marked shear thinning region even at low particle volume fractions. This behavior typically suggests the formation of a physical network between polyurethane particles and thickener molecules partly adsorbed onto the polymer surface. The zero-shear viscosity of the two dispersions was compared with respect to: (i) particle volume fraction and (ii) particle surface area at different HEUR concentrations. At a given volume fraction, the particle size affects the viscosity of thickened models. As a corollary, a relationship is found between the particles size and the level of thickener required to reach a target viscosity. This study offers practically relevant data in terms of application conditions and provides a better insight into the thickening protocol.

Effects of nonionic surfactant on the rheological property of associative polymers in complex formulations

The rheological properties of hydrophobically modified ethoxylated urethane (HEUR) were investigated in the presence of a nonionic surfactant, polyoxyethylene stearyl ether (C 18(EO) 20). The presence of nonionic surfactants played an important role in tuning the rheological properties of HEUR aqueous solutions. Observing both plateau modulus and viscoelastic relaxation time of HEUR aqueous solutions with varying the concentration of C 18(EO) 20 allowed us to demonstrate that C 18(EO) 20 readily interacts with the hydrophobic segments of HEUR polymers, which eventually formed a strong micellar network. Moreover, the micellar network formed at a critical concentration of C 18(EO) 20, ∼0.6% w/v, was indeed stable against both ionic strength and pH in the aqueous medium and complex formulations, such as a colloid suspension and an oil-in-water emulsion, thus providing more practical applications as thickeners for a wide variety of complex formulations.

The steady state and dynamic rheological properties of telechelic associative polymer solutions

In this study, steady state, dynamic shear and normal stress differences of the polymer solutions containing telechelic hydrophobically modified ethoxylated urethane (HEUR) associative polymers have been investigated. The intermediate steady state and dynamic shear thickening were observed for both ascending and descending shear rate and frequency, respectively. The dynamic amplitude stress sweep measurements showed that maxima in G′ and G″ occurred at the frequencies of 1, 5 and 10 rad/s. At lower shear rates and frequencies, the ratio of complex viscosity to steady shear viscosity was observed to be greater than unity. This phenomenon is believed to be associated with the formation of a micro-gel like structure. The modified Cox–Merz rule (Delaware–Rutgers rule) explained the dynamic and steady state viscosity behaviors well in the shear thinning zone but not at the plateau or shear thickening regions.

Investigating the effect of hydrophobic structural parameters on the thickening properties of HEUR associative copolymers

Hydrophobically modified ethoxylated urethanes (HEUR) associative copolymers are prepared through the hydrophobic modification of polyethylene glycol based polyurethanes. These types of thickeners are categorized as anionic associative thickeners. To investigate the effect of structure of the hydrophobic groups on the thickening properties, three different hydrophobic groups were selected. These groups were comprised of cetyl alcohol (16 carbons), dodecyl alcohol (12 carbons) and a cyclic group such as cyclo hexanol. These functional groups were substituted on the identical prepolymers made from H 12MDI and polyethylene glycol. Here, three different urethane associative polymers containing hydrophobic segments and different hydrophobic groups were synthesized. The viscoelastic characteristics of all the samples were determined using a cone and plate rheometer. The viscosities of the examined HEUR samples showed both Newtonian and non-Newtonian behaviours (shear thinning and thickening) for the explored shear rates window. The steady shear viscosity results were interpreted using the theories by Raspaud [Macromolecules 27 (1994) 2956] and Semenov [Macromolecules 28 (1995) 1066]. The Cox–Merz rule happened to be applicable to these systems for the various hydrophobic ends and concentrations at lower shear rates indicating typical associative polymer behaviour. The cyclic end groups did not show viscoelasticity for the frequencies window explored. The zero shear viscosity increased by almost two orders of magnitude from HEUR-cyc to HEUR-dod and by four orders of magnitude from HEUR-cyc to HEUR-cet. The intermediate shear thickening was only observed for the concentrated HEUR-cet samples.

Steady shear viscosity study of various HEUR models with different hydrophilic and hydrophobic sizes

The influence of the hydrophilic and hydrophobic sizes in hydrophobically modified ethoxylated urethanes (HEUR) was studied through the synthesis of two series of model thickeners. The model polymers were prepared by the step-growth (S-G) polymerization of polyethylene glycol ( M n = 6000) with calculated amount of dicyclohexylmethane diisocyanate (H 12MDI). The prepolymers molecular weights were adjusted by choosing the proper molar ratio of the reactants. For the first series, the isocyanate end groups of prepolymers were reacted with cetyl alcohol, but in the second series, dodecyl alcohol was used. The synthesized models were characterized via molecular weight measurements and using an Ubbelohde capillary viscometer. The aqueous solutions of model HEUR were investigated by steady shear viscosity study. The model compounds showed excellent viscosity build up. It was found that the structural parameters have a very important effect on thickening efficiency, so that thickening efficiency increases with decreasing hydrophilic and increasing hydrophobic section sizes.

Influence of Terminal Hydrophobe Branching on the Aqueous Solution Behavior of Model Hydrophobically Modified Ethoxylated Urethane Associative Thickeners

The influence of terminal hydrophobe branching on the micellar properties of Hydrophobically modified Ethoxylated URethanes (HEURs) is addressed through fluorescence, dynamic light scattering (DLS), solution rheology, and Raman spectroscopy. Model HEURs used in this study are monodisperse and fully substituted with hydrophobic groups of different structures. Two linear hydrophobes (l-C12H25 and l-C16H33) and three branched hydrophobes [b-(C12H26), b-(C16H34), and b-(C20H42)] are coupled to the hydroxyls of POE670 and POE195 through 4,4-methylene bis(dicyclohexyl)diisocyanate (H12MDI) units. Prior low molecular weight surfactant studies observed that a CH2 group, introduced as a branch from a linear hydrophobe, contributes approximately half to the surfactant's hydrophobicity that the same CH2 unit would add to the linear chain. Within hydrophobe equivalent comparisons, greater hydrophobic domains are indicated in pyrene's I1/I3 emission ratio for the linear hydrophobe HEURs, denoting a more hydrophilic core in branched HEURs. An increase in the number of −CH2− groups notably influences aqueous solution viscosities, as expected, but among equivalent hydrocarbon comparisons, the moderate-size linear hydrophobe is more viscosifying than the branched hydrophobe at high concentrations. Viscosity increases correlate with the aggregation sizes estimated from DLS studies as aggregate sizes approach 500 nm, covering small to large hydrophobes and different oxyethylene spacer lengths. Conformational differences (Raman spectroscopy) of poly(oxyethylenes) and HEURs under stagnant and flow conditions are also examined. The presence of byproduct impurities can markedly influence these results.