Pressure dependence of the local and global dynamics of polyisoprene

Floudas, George; Reisinger, T.

doi:10.1063/1.479774

Cited by 113 publications

(152 citation statements)

References 12 publications

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“…This equivalence of the pressure-sensitivity of τ α and τ N is unusual. Previous studies of PI 12 , PLA 80 and PPG 14 found the segmental mode to be more sensitive to pressure (although from measurements over a limited range on PPG, the opposite result, ∆V α < ∆V N , was also reported 15 ). However, such results depend upon the basis for comparison.…”

Section: Resultsmentioning

confidence: 93%

“…In Figures 8 and 9 respectively, we compare the coupling of the two modes over the same P range using published data for PPG 14 and for two different molecular weights of PI 12,81 . In each case, the slope of the curve is very close to unity, indicating that in contrast with previous conclusions, the pressure dependences of the two modes are essentially the same (i.e., ∆V α~∆ V N ), at least when compared over the same range of P. However, as discussed above, this coupling may break down very close to T g .…”

Section: Resultsmentioning

confidence: 99%

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Temperature and Density Effects on the Local Segmental and Global Chain Dynamics of Poly(oxybutylene)

Casalini

Roland

2005

Macromolecules

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Dielectric spectroscopy measurements over a broad range of temperature and pressure were carried out on poly(oxybutylene) (POB), a type-A polymer (dielectrically-active normal mode). There are three dynamic processes appearing at lower frequency, the normal and segmental relaxation modes, and a conductivity arising from ionic impurities. In combination with pressure-volume-temperature measurements, the dielectric data were used to assess the respective roles of thermal energy and density in controlling the relaxation times and their variation with T and P. We find that the local segmental and the global relaxation times are both a single function of the product of the temperature times the specific volume, with the latter raised to the power of 2.65. The fact that this scaling exponent is the same for both modes indicates they are governed by the same local friction coefficient, an idea common to most models of polymer dynamics. Nevertheless, near T g , their temperature dependences diverge. The magnitude of the scaling exponent reflects the relatively weak effect of density on the relaxation times. This is usual for polymers, as the intramolecular bonding, and thus interactions between directly bonded segments, are only weakly sensitive to pressure. This insensitivity also means that the chain end-to-end distance is invariant to P, conferring a near pressure-independence of the (density-normalized) normal mode dielectric strength.The ionic conductivity dominates the low frequency portion of the spectra. At lower temperatures and higher pressures, this conductivity becomes decoupled from the relaxation modes (different T-dependence), and exhibits a significantly weaker density effect. At frequencies higher than the structural relaxation, both an excess wing on the flank of the α-peak and a secondary relaxation are observed. From their relative sensitivities to pressure, we ascribe the former to an unresolved Johari-Goldstein (JG) relaxation, while the higher frequency peak is unrelated to the glass transition. These designations are consistent with the relaxation time calculated for the JG process. 2The dynamic properties of the POB are essentially the same as those of polypropylene glycol, in accord with their similar chemical structures. However, POB is less fragile (weaker T gnormalized temperature dependence), its relaxation times less sensitive to density changes, and facilitating the measurements herein, its normal mode has a substantially larger dielectric strength

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Section: Resultsmentioning

confidence: 93%

Section: Resultsmentioning

confidence: 99%

Temperature and Density Effects on the Local Segmental and Global Chain Dynamics of Poly(oxybutylene)

Casalini

Roland

2005

Macromolecules

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“…(9) of free volume models cannot be correct. [33], PCB54 [34], PCB42 [34], cresolphthalein-dimethylether (KDE) [8], salol [8], phenylphthaleindimethylether (PDE) [8], polypropylene oxide (PPO) [42], polymethylphenylsiloxane (PMPS) [35], o-terphenyl (OTP) [17], polyepichlorhydrin (PECh) [17], polymethyltolylsiloxane (PMTS) [36], polyvinylmethylether (PVME) [17], polyvinylacetate (PVAc) [42], polystyrene (PS) [37], PPG [38], PC [8], diglycidyl ether of bisphenol A (DGEBA) [42], 1,4-polyisoprene(PI) [39,12], poly[(phenol glycidyl ether)-co-formaldehyde] (PPGE) [42], PVAc(2) [17], polyvinylethylene (PVE) [40], 1,4-polybutadiene (PB) [17], polyethylacrylate (PEA) [37], polymethylacrylate (PMA) [17], methafluoaniline [41], PCGE [42], PMA(2) [37], polymethylmethacrylate (PMMA) [17] and polyvinylchloride (PVC) [37]. Polymer networks refer to PVE networks [43].…”

Section: Resultsmentioning

confidence: 99%

Isobaric and isochoric properties of decahydroisoquinoline, an extremely fragile glass-former

Casalini¹,

McGrath²,

Roland³

2006

Journal of Non-Crystalline Solids

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“…13,14) They investigated the dielectric behavior of PIP under in a wide range of hydrostatic pressure, up to 400 MPa, in the absence of the dilution effect.…”

Section: Neat Pressure Effectmentioning

confidence: 99%

Dielectric Behavior of cis-Polyisoprene in Carbon Dioxide under High Pressure

Inoue

Watanabe

Kihara

et al. 2007

J. Soc. Rheol., Jpn

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Dielectric measurement was conducted for cis-polyisoprene (PIP) in carbon dioxide (CO 2 ) at high pressures. CO 2 is dissolved in PIP more with increasing pressure, and this dissolution is expected to affect the chain dynamics. In our experimental window, the PIP chains having type-A dipoles parallel along their backbone exhibited the dielectric dispersion reflecting their global motion. This dispersion shifted to higher frequencies with increasing CO 2 pressure. Time -CO 2 pressure superposition was found to hold well, which suggests that the global motion of the chain is accelerated by CO 2 without any heterogeneity in space and along the chain backbone. The vertical shift factor (intensity shift factor) for this superposition gave the CO 2 concentration in PIP. The plasticizing capability of CO 2 evaluated from the horizontal shift factor (frequency shift factor) was found to be a little larger than that of tetradecane in the same range of concentration. No peculiarity was found for plasticizing ability of CO 2 even in the supercritical state (at a pressure of 10 MPa).

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Pressure dependence of the local and global dynamics of polyisoprene

Cited by 113 publications

References 12 publications

Temperature and Density Effects on the Local Segmental and Global Chain Dynamics of Poly(oxybutylene)

Temperature and Density Effects on the Local Segmental and Global Chain Dynamics of Poly(oxybutylene)

Isobaric and isochoric properties of decahydroisoquinoline, an extremely fragile glass-former

Dielectric Behavior of cis-Polyisoprene in Carbon Dioxide under High Pressure

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