Self-Diffusion Coefficients of Hydrophobic Ethoxylated Urethane Associating Polymers Using Pulsed-Gradient Spin-Echo Nuclear Magnetic Resonance

Rao, B. Lakshmana; Uemura, Yoshimitsu; Dyke, Lara; Macdonald, Peter M.

doi:10.1021/ma00106a018

Cited by 75 publications

(112 citation statements)

References 8 publications

Supporting

Mentioning

108

Contrasting

Order By: Relevance

“…where A 2τ is the echo intensity at time 2τ following the start of the PGSE pulse sequence, A 0 is the echo intensity in the absence of gradient pulses, γ is the gyromagnetic ratio of 1 H, and D is the self-diffusion coefficient. The experiment is usually performed under conditions of constant τ which means that the spin-spin relaxation (T 2 ) term A 0 = A τ = 0 exp(-2τ/T 2 ) is constant and can be ignored.…”

Section: Resultsmentioning

confidence: 99%

“…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.…”

Section: Introductionmentioning

confidence: 99%

“…[16][17][18] At steady shear, beyond a critical shear rate, they exhibit shear thinning behavior. [19][20][21][22][23][24][25] More recently, these polymers and their solutions in water have been examined by various scattering and spectroscopic techniques including dynamic and static light scattering, 3,10,[26][27][28][29][30] small angle neutron scattering, small angle x-ray scattering, 9,29,30 static and dynamic fluorescence, 3,13,14,21,31-33 PGSE-NMR, 1,12,25,34 and viscometry. 35 Since the PGSE NMR technique was first demonstrated by Stejskal and Tanner, 36 it has become a powerful technique for studying self-diffusion in polymer systems.…”

Section: Introductionmentioning

confidence: 99%

“…[37][38][39] The PGSE-NMR technique is particularly suited for measuring self-diffusion coefficients in HEUR associating polymers. 1,12,33,40,41 There are many factors that influence the self-diffusion of various diffusants in polymer systems. These factors are the polymer concentration, solvent, size and shape of the diffusant, temperature, G (gradient strength), δ (pulse length), Δ (diffusion time), byproduct and any interactions in the polymer networks.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

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

et al. 2003

View full text Add to dashboard Cite

Hydrophobically End-capped polyethylene oxide Urethane Resin(HEUR)-associating polymers, HEUR 35(8), HEUR 35 (12), and HEUR 35 (18), comprise a polyethylene oxide (PEO) having a molecular weight of 35,000 that is end capped with two C 8 H 17 , C 12 H 25 , and C 18 H 37 alkyl chains, respectively. These associating polymers were synthesized by condensation reactions with polyethylene oxides and alkyl isocyanates. The self-diffusion coefficients of HEUR-associating polymers were measured in aqueous solution by pulsed-gradient spin-echo (PGSE) nuclear magnetic resonance (NMR) spectroscopy. All polymers underwent a decrease in their mean diffusion coefficients as the concentration was increased. However, the dispersion of the diffusion coefficients, β, about the mean fluctuated with changes in concentration. The large dispersion at low concentrations of HEUR 35(8) and HEUR 35 (12) is related to the interaction between hydrophobic end groups, and the large dispersion at high concentrations of HEUR 35(18) is correlated with transient network formation. These results are valuable for predicting the associating mechanism of the large aggregates before and after their critical micelle concentration.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

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

et al. 2003

View full text Add to dashboard Cite

show abstract

“…13,69 Typical model APs that have recently been the focus of study are water-soluble polymers partially modified by hydrophobic groups. One series of APs are based on poly(ethylene oxide) chains (referred to as PEO), being modified by short alkyl chains, [70][71][72][73][74]125 propyrene oxide (or butylene oxide) chains 77 and fluorocarbon chains. [78][79][80][81] Hydrophobes are either period-ically or randomly attached on a polymer chain.…”

Section: Thermoreversible Gelation With Multiple Junctionsmentioning

confidence: 99%

Theoretical Study of Molecular Association and Thermoreversible Gelation in Polymers

Tanaka

2002

Polym J

View full text Add to dashboard Cite

ABSTRACT:This paper reviews our recent theoretical studies of molecular association and thermoreversible gelation in polymer solutions and blends. We first classify fundamental types of association, and propose their static and dynamic characterization. We then develope general theory of associating polymers to study phase transitions induced by molecular association. These transitions include macro-and microphase separation, micellization, hydration, thermoreversible gelation and liquid-crystalization. As for the origin of associative forces, we focus on hydrogen bonding and hydrophobic aggregation. Detailed study on thermoreversible gelation with multiple cross-link junctions is presented. Paying special attention to the multiplicity and sequence length of the network junctions, we derive phase diagrams with coexisting gelation and phase separation, and compare them with experimental data. Local and global structures of the gel networks are studied from molecular point of view. The theory is applied to more complex thermoreversible gels such as binary networks (interpenetrating networks, alternating networks and randomely mixed networks), hydrated networks with high-temperature gelation, gelation strongly coupled to polymer conformational transitions such as coil-to-helix transition. To study dynamics of thermoreversible gels, a simple transient network model is introduced, and creation and annihilation of junctions in the networks are theoretically described. Stationary non-linear viscosity and the dynamic mechanical moduli are calculated as functions of the shear rate, frequency and the chain disengagement rate. From the peak of the loss modulus, the lifetime τ × of the junction is estimated, and from the high frequency plateau of the storage modulus, the number of elastically effective chains in the network is found. Transient phenomena such as stress relaxation and stress overshoot are also theoretically studied. Results are compared with the recent experimental reports on the rheological study of hydrophobically modified water-soluble polymers.KEY WORDS Associating Polymers / Thermoreversible Gelation / Junction Multiplicity / Multicriticality / Transient Networks / Shear Thickening / Elastically Effective Chains / This paper reviews our recent theoretical studies of molecular association and thermoreversible gelation in polymer solutions. We introduce new theoretical frameworks to study phase transitions induced by association of polymer chains and dynamics of aggregation/dissociation processes.In most polymer blends or solutions, polymer chains carry active groups interacting with each other via strongly associative forces which are capable of forming temporal bonds. Hence description of the system in terms of van der Waals type contact energy -or χ-parameter in lattice theoretical terminology -is insufficient. These associative interactions include hydrogen bonding, ionic aggregation, electrostatic interaction, micro-crystallite formation, stereocomplex formation, solvent-complex formation, etc. Since ...

show abstract

Synthesis and properties of water soluble polyurethanes based on poly(ethylene glycol)

Doseva

Shenkov

Vasilev

et al. 2004

J of Applied Polymer Sci

View full text Add to dashboard Cite

Water soluble polyurethanes (WSPU)s have been prepared by polycondensation of isophorondiisocyanate and tolylene-2,4-diisocyanate with poly(ethylene glycol)s (PEGs) of molecular weights 400, 600, and 1,000. The physicochemical properties of the WSPUs depend on the hydrophilic-hydrophobic balance in their polymeric chain, i.e., the properties are determined by relative density of the hydrophobic diisocyanate residues in WSPU. X-ray and differential scanning calorimetry studies show that the WSPUs have a degree of crystallinity lower than that of the pure PEGs of the same molecular weights. Like the PEGs the WSPUs prepared form interpolymer complexes with polyacrylic (PAA) and polymethacrylic (PMAA) acids. These complexes are more stable than the (PEG.PAA) and (PEG. PMAA) complexes. The novel compounds can be considered as modified linear PEGs.

show abstract

Self-Diffusion Coefficients of Hydrophobic Ethoxylated Urethane Associating Polymers Using Pulsed-Gradient Spin-Echo Nuclear Magnetic Resonance

Cited by 75 publications

References 8 publications

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

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

Theoretical Study of Molecular Association and Thermoreversible Gelation in Polymers

Synthesis and properties of water soluble polyurethanes based on poly(ethylene glycol)

Contact Info

Product

Resources

About