Thermoreversible Gelation with Two-Component Networks

Tanaka, Fumihiko; Ishida, Masahiko

doi:10.1021/ma981279v

Cited by 43 publications

(46 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The curve is a fit based on Tanaka's theory. 30 The horizontal dotted line corresponds to the critical value nfs c /ns for the appearance of a correlation hole peak as it follows from the theoretical results presented in Figure 2.…”

Section: Computer Simulation Resultsmentioning

confidence: 88%

Correlation Hole Effect in Comblike Copolymer Systems Obtained by Hydrogen Bonding between Homopolymers and End-Functionalized Oligomers

1997

View full text Add to dashboard Cite

This paper addresses concentration fluctuations in comblike copolymer systems obtained by hydrogen bonding between polymers and end-functionalized oligomers. Monodisperse block copolymer systems in the homogeneous melt exhibit small-angle X-ray scattering peaks at finite nonzero angle due to characteristic correlation hole concentration fluctuations. In comblike copolymer systems obtained by hydrogen bonding, the dominant fluctuations have been found by us to vary experimentally between conventional long wavelength fluctuations (for weak hydrogen bonding) and finite wavelength fluctuations (strong hydrogen bonding). Monte Carlo computer simulations show that both regimes occur in one and the same system depending on the temperature. The transition between both regimes is directly related to the fraction of free oligomers, which depends on the temperature and the interactions. The structure factors are analyzed in terms of the random phase approximation applied to a mixture of free oligomers and comb copolymers, using a uniform distribution of teeth along the polymer chains and a binomial distribution in the number of polymers with a given number of teeth, confirmed numerically, as input. The agreement is excellent at both high and low temperatures. hb)-R (3) E) kT[(n AB + n BC + n AC) ′ + n s (1-φ fs) ′ hb ] (4)

show abstract

Section: Computer Simulation Resultsmentioning

confidence: 88%

Correlation Hole Effect in Comblike Copolymer Systems Obtained by Hydrogen Bonding between Homopolymers and End-Functionalized Oligomers

1997

View full text Add to dashboard Cite

show abstract

“…for three combination of pairs, 20 where ∆ f 's are the standard free energy changes on bonding. To prevent gelling, we assume that the functionalities of either or both species of polymers are less than or equal to two in this section.…”

Section: Some Important Examples Of Non-gelling Associating Mixturesmentioning

confidence: 99%

Theoretical Study of Molecular Association and Thermoreversible Gelation in Polymers

Tanaka

2002

Polym J

Self Cite

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

“…Pioneering work was reported by Stockmayer, 18 who extended the statistical-mechanical theory of network-forming condensation polymers 19 to two-component condensation polymers and obtained the expressions for the weight-average molecular weight and the gel point. Recently, Tanaka and Ishida 20 combined the lattice theory of polymer solutions developed by Flory 21 and the statistical expressions for condensation polymers to construct the phase diagrams for two-component polymer networks. These phase diagrams demonstrated the solgel transition as well as the macroscopic phase separation.…”

Section: Introductionmentioning

confidence: 99%

Cascade model for coupled two‐component polymer gels

Mao

Chen

2005

J of Applied Polymer Sci

View full text Add to dashboard Cite

A cascade model for the network of coupled two-component polymer gels is presented. The network formation is assumed to be primarily due to the interaction between the functional groups of two unlike polymers. The gel modulus G versus polymer concentration C curve is constructed using the cascade formalism. The variation of G versus C curves with respect to the concentration ratio r of the two components is found to be the characteristics of mixed gels. The model parameters can be obtained by fitting G versus C curves using a nonlinear least-squares method (the gel-modulus approach). The approach is applied to the experimental data for galactomannan/xanthan and glucomannan/xanthan mixed gels. Finally we discuss the gel point predicted by the cascade model. The critical concentration C 0 for the gel point is strongly dependent on r and the functionalities for both polymers. The C 0 versus r curve is easily obtained by experiment, and can be used to evaluate the model parameters (the gel-point approach). The experimental data for galactomannan/xanthan mixed gels is tested to demonstrate the validity of the gel-point approach. The advantages and limitations of both approaches are discussed.

show abstract

Thermoreversible Gelation with Two-Component Networks

Cited by 43 publications

References 29 publications

Correlation Hole Effect in Comblike Copolymer Systems Obtained by Hydrogen Bonding between Homopolymers and End-Functionalized Oligomers

Correlation Hole Effect in Comblike Copolymer Systems Obtained by Hydrogen Bonding between Homopolymers and End-Functionalized Oligomers

Theoretical Study of Molecular Association and Thermoreversible Gelation in Polymers

Cascade model for coupled two‐component polymer gels

Contact Info

Product

Resources

About