Local polymer and solvent dynamics in Aroclor solutions: implications for solvent modification

Gisser, Daniel J.; Ediger, M. D.

doi:10.1021/ma00030a013

Cited by 36 publications

(37 citation statements)

References 15 publications

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“…It is well known that the presence of polymer chains in solution modifies the solvent dynamics and that the extent and sign of this modification depend on the polymer/solvent system. 26,28,31,32,51 In the case of finite concentration solutions, although PI causes the relaxation time of Aroclor to shift to shorter times (higher frequencies), the effect of PS is of the opposite sign and larger in magnitude, shifting the frequency dependence of Aroclor to lower frequencies. At the same time, the relaxation times for the global motion polymer contribution to the PS/Aroclor solution properties shift even further, thus enhancing the high-frequency plateau ( s / N becomes larger).…”

Section: ϫ8mentioning

confidence: 99%

Apparent relaxation‐time spectrum cutoff in dilute polymer solutions: An effect of solvent dynamics

Peterson

Echeverría

Hahn

et al. 2001

J Polym Sci B Polym Phys

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ABSTRACT:The apparent short time cutoff of the relaxation-time spectrum at surprisingly long times for polymers in solution is a well known but not yet understood observation. To elucidate its origins we revisit viscoelastic and oscillatory flow birefringence data for solutions and melts of two linear polymers (polystyrene and polyisoprene) and present new measurements of oscillatory flow birefringence of the latter. Previous measurements have suggested that the "flexibility" of both polymers in solution is smaller than in the melt on the basis of the breadth of the relaxation-time spectrum of the solution as compared with that of the melt. Our new measurements have explored a higher effective frequency range than was previously possible. This has allowed us to observe the effect of the rotational relaxation time of the solvent on the dynamics of the solution at high frequencies. To obtain the polymer global motion contribution, one now needs to subtract from the solution properties a frequencydependent complex solvating environment contribution. We show that the decrease in apparent "flexibility" for solutions arises from the presence of a solvent that exhibits a rotational relaxation time and thus simple viscoelastic behavior somewhat near the frequency window of the experiment. Although recent predictions of a model for a chain in a solvent with a single relaxation time are in qualitative agreement with our results, our data suggest that the solution results may reflect the influence of solvent on the development of the "entropic spring" forces at short times.

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Section: ϫ8mentioning

confidence: 99%

Apparent relaxation‐time spectrum cutoff in dilute polymer solutions: An effect of solvent dynamics

Peterson

Echeverría

Hahn

et al. 2001

J Polym Sci B Polym Phys

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“…There has been long-standing interest in modifying the dynamics of small molecules by the addition of polymers. [1][2][3] Both the sign and the magnitude of the change in the solvent's viscosity and relaxation times reflect changes in the motion of solvent molecules residing in the vicinity of dissolved polymer chains.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of aroclor and its modification by dissolved polystyrene

Casalini

Santangelo

Roland

2002

The Journal of Chemical Physics

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Dynamic mechanical spectroscopy, dielectric spectroscopy, and viscosity measurements were carried out on Aroclor 1254 ͑PCB54͒, a chlorinated biphenyl. The temperature dependences of both the dielectric relaxation times and the viscosity depart from a single Vogel-Fulcher behavior, at a temperature, T B , equal to 294 K. The ratio of this characteristic temperature to T g (ϭ246 K) is close to that found previously for other Aroclors, having different chlorine levels. The shapes of the dielectric and mechanical relaxation functions were equivalent, yielding a value for the Kohlrausch stretch exponent equal to 0.62 5 at T g. However, the relaxation times for the dielectric modulus were substantially larger than the viscosity and mechanical relaxation times. The respective temperature dependences of the viscosity and the dielectric relaxation times, although similar, deviated from the Debye-Stokes relation with decreasing temperature. The temperature associated with this deviation is somewhat higher than T B , and coincides with the temperature at which the relaxation function approaches Debye behavior. These phenomena all reflect the alleviation at high temperature of intermolecular constraints on the dynamics. The addition of high molecular weight polystyrene ͑PS-90k͒ to the PCB54 had an almost negligible effect on the dielectric relaxation times, notwithstanding that the polystyrene's glass temperature is 130 degrees higher than T g for PCB54. The PS-90k exerted a more significant effect on the mechanical relaxation times of the PCB54. However, the modification of the Aroclor dynamics is still orders of magnitude less than the effect of the dissolved PS-90k on the relaxation times of an oligomeric PS ͑PS-o͒. This low molecular weight PS has a T g identical to that of the PCB54. The dramatic difference between the effect of added polymer on the dynamics of Aroclor versus PS-o can be ascribed to differences in their capacity for intermolecular coupling with the PS-90k solute.

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“…Further, it has become evident that the solvent rotational mobility and local friction coefficient can be significantly altered with the addition of small amounts of polymer [2][3][4]. In a solvent-rich mixture, it is expected that addition of a higher Tg polymer will slow the reorientational relaxation time of the solvent, while the addition of a lower Tg polymer will decrease the solvent relaxation time.…”

Section: Introductionmentioning

confidence: 99%

Dielectric and mechanical relaxation in PMPS, BMC and their mixtures

Santangelo

Roland

Ngai

et al. 1994

Journal of Non-Crystalline Solids

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Dielectric and dynamical mechanical measurements have been performed on mixtures of the small molecule glassforming liquid 1,1-bis(p-methoxyphenyl) cyclohexane (BMC) with poly(methylphenylsiloxane) (PMPS). Earlier measurements had indicated that the BMC dynamics are modified in a very interesting way by the presence of the polymer, despite the equivalence of their glass transition temperatures, Tg. By varying the molecular weight of the polymer (and hence Tg), the BMC mobility is anomalously enhanced in mixtures of high Tg PMPS. An interpretation for these results based on the coupling model of relaxation is suggested.

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Local polymer and solvent dynamics in Aroclor solutions: implications for solvent modification

Cited by 36 publications

References 15 publications

Apparent relaxation‐time spectrum cutoff in dilute polymer solutions: An effect of solvent dynamics

Apparent relaxation‐time spectrum cutoff in dilute polymer solutions: An effect of solvent dynamics

Dynamics of aroclor and its modification by dissolved polystyrene

Dielectric and mechanical relaxation in PMPS, BMC and their mixtures

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