Transient inhomogeneities in polymeric liquids and solutions: characterization by static and dynamic light scattering

Koch, T.; Strobl, G.; Stühn, Bernd

doi:10.1016/0032-3861(93)90452-g

Cited by 14 publications

(14 citation statements)

References 5 publications

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“…Since we observed the heterogeneities in all studied solutions, and there in a reproducible manner, we feel that this might be the case. In an earlier work 9 we found that the heterogeneity scattering vanished after months; however, the chemical stability cannot be insured over such a long time, and this might change the behavior. The samples used by Brown in his studies 4 obviously didn't show the heterogeneity scattering, thus enabling the observation of the qindependent network reorganization modes.…”

Section: Discussionmentioning

confidence: 76%

Large-Scale Heterogeneities in Entangled Polymer Solutions. Light-Scattering Study on Polystyrene in Toluene

1997

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Static and dynamic low-angle light-scattering experiments carried out on semidilute and moderately concentrated solutions of polystyrene in toluene provide evidence for the existence of heterogeneities in the entanglement network with correlation lengths of several hundred nanometers. The slow mode showing up in the correlograms in addition to the gel mode reflects the diffusive motion of these chain associations. The tendency to form associations increases with the solute concentration and with decreasing temperature. The observations indicate that the reptation time does not represent the longest relaxation time in the system; a complete reorganization of the entanglement network requires a much longer period.

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Section: Discussionmentioning

confidence: 76%

Large-Scale Heterogeneities in Entangled Polymer Solutions. Light-Scattering Study on Polystyrene in Toluene

1997

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“…[9][10][11][12] For example, Koch et al 10 found that the slow mode of short polyisoprene and polystyrene chains in semidilute solutions was diffusive, i.e., Γ s ∝ q 2 , supported by other similar results. 1, 11 Brown et al 1 and Burchard 13 suggested that the dissolution process might result in an inhomogeneous network-like structure, or in other words, the overlapping of polymer chains in semidilute solution might lead to some "transient clusters".…”

Section: Introductionmentioning

confidence: 78%

Effects of Temperature and Swelling on Chain Dynamics during the Sol−Gel Transition

Ngai

Chen

2004

Macromolecules

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The UV-irradiation-induced [2 + 2] photocycloaddition of 7-methacryloyloxy-4-methylcoumarin attached to PMMA can transfer a semidilute solution to a homogeneous and speckle-free chemical gel. It allows us to study the effect of temperature on the chain dynamics at each stage of the sol-gel transition by laser light scattering. The fast and slow relaxation modes in semidilute solution are preserved in the resultant gel. For the fast mode, the characteristic decay time 〈τ c〉f and its related scattering intensity 〈I〉fast are nearly temperature-independent because it is related to the motions of the subchains ("blobs") between two cross-linked points. In contrast, 〈τc〉s and 〈I〉slow increase as the temperature decreases from 40 to 10°C, which cannot be attributed to the chain conformation because chloroform remains a good solvent in this temperature range. The increase of 〈I〉 slow is because the lights scattered from the segments of different chains are more correlated at lower temperatures (higher viscosity). This study further supports that the slow mode is due to the density fluctuation. Moreover, the scattering vector (q) dependence of 〈τ c〉f and 〈τc〉s shows that as the temperature decreases, the scaling exponent Rf in 1/〈τc〉f ∼ q R f increases from 2.0 to 2.4, but Rs in 1/〈τc〉s ∼ q R s decreases from 3.0 to 2.2, which can be related to the decrease of static correlation length. The swelling of the resultant gel shows a similar effect as the increase of the temperature.

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“…To treat dynamical properties at arbitrary times, generalized transport functions are introduced. A straightforward generalization of eq 5 leads to the definition of a generalized time-dependent "frequency matrix" Q(q,t) by j¡Kq,t) = -Q(q,tH{q,t) (8) If the matrix ( , ) is approximately constant over a certain range of time, the mathematical procedure mentioned in the preceding section can be used to evaluate the decay rates relevant for this specific time domain. This is of special importance in the short-time or in the long-time limit.…”

Section: Dynamics At Arbitrary Timesmentioning

confidence: 99%

Collective Diffusion in Polymer Solutions

Genz¹

1994

Macromolecules

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The decay of concentration fluctuations in polymer solutions is investigated. Starting from a microscopic basis, a theoretical framework is developed to describe so-called memory effects leading to additional slow modes. The theory is formulated for a multicomponent system. These general results are applied to a homopolymer-solvent system. With respect to the interpretation of dynamic light scattering the behavior at small scattering vectors q is relevant. In this case, an approximately diffusive decay mode and slower, approximately q-independent modes related to viscoelastic properties are predicted at higher polymer concentrations. The relation to typical experimental results and to the theory recently presented by Wang is discussed.

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Transient inhomogeneities in polymeric liquids and solutions: characterization by static and dynamic light scattering

Cited by 14 publications

References 5 publications

Large-Scale Heterogeneities in Entangled Polymer Solutions. Light-Scattering Study on Polystyrene in Toluene

Large-Scale Heterogeneities in Entangled Polymer Solutions. Light-Scattering Study on Polystyrene in Toluene

Effects of Temperature and Swelling on Chain Dynamics during the Sol−Gel Transition

Collective Diffusion in Polymer Solutions

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