Relationships between Diffusion and Viscoelasticity of Associative Polymer Networks

Abstract

Hydrophobically ethoxylated modified urethane (HEUR) form the flower micelles and transient network structures through the aggregation of end groups depending on the polymer concentration. The HEUR networks show the viscoelastic relaxation which is described by the Maxwell model. Although there have been many attempts to understand and predict the molecular mechanism, the full understanding remains incomplete. To understand the relaxation mechanism of associative polymers, we measured the linear viscoelasticity and the diffusibility using the fluorescence recovery after photobleaching method. With increasing the polymer concentration, the self-diffusion coefficient decreased, while the relaxation time increased, suggesting that the viscoelastic relaxation is correlated with the diffusion of the polymers. The calculated diffusion distance of the HEUR chains within the viscoelastic relaxation time is 100 times larger than the size of a HEUR chain. This significant deviation suggests that some of the HEUR chains diffuse quickly through the unimer and flower micelles at low concentrations and through the recombination process of the network strands at high concentrations.

Rheological Test for the Homogeneity of Aqueous Blends of Associative Polymer Network and Entangled Linear Polymer

“…Here, G N,H is the modulus and τ H is the relaxation time of the transient network of HEUR. This result is consistent with the previous studies 1,5,[8][9][10]15) , and can be explained in the framework of the classical transient network theory 17,18) . The theoretical models for transient networks assume that the viscoelastic relaxation is caused by the detachment of the bridged chains from the hydrophobically associated cores.…”

“…A hydrophobically modified ethoxylated urethane sample was kindly supplied by ADEKA. Its characterization details have been reported previously 10) . The weight average molar mass, M w , and the polydispersity index represented by the ratio of the weight to number averaged molar masses (M w /M n ) were M w = 3.5 × 10 4 g/mol and M w /M n = 3.7, respectively.…”

“…HEUR is one of telechelic type associative polymers and has been widely used as rheology modifiers in water-born coatings [1][2][3][4] . Because of their unique association structure and rheological behaviors, many studies have been pursued to understand the relationship between their structure and rheological properties 1,[5][6][7][8][9][10] . For the industrial application of HEURs, the control of viscoelastic profiles under elongational and shear flows in both linear and nonlinear regions is needed 4) .…”

Orientational Dynamics of Magnetic Iron Oxide Nanoparticles in a Hydrogel: Observation by Magnetic Linear Dichroism under Oscillating Field

“…The HEUR molecule consists of the hydrophilic main chain of polyethylene oxide (PEO) and hydrophobic terminals of 2-decyl-tetradecane. The molecular mass ( M w ) was 3.5 × 10 4 g mol –1 , and the dispersity index ( M w / M n ) was 3.7 . The minimum gelation concentration of HEUR ( C HEUR *), above which a continuous transient network is formed by hydrophobic interaction (Figure e), is 0.8 wt %.…”

Dynamic Light Scattering Study on Particle Diffusion in Slide-Ring Gels: Enhanced Fluctuation of Sliding Networks

“…Q is given by the following equation: (7) where λ is the wavelength of the incident laser, n is the refractive index of the solvent (n = 1.33 for water), and θ is the scattering angle. The relaxation time of the silica particle has a distribution represented by β silica , and the average relaxation time <τ silica > was calculated from the following equation 25,26) :…”