Studies on dielectric behaviors in a series of polyalkyl-methacrylates

Ishida, Yōichi; Yamafuji, Kaoru

doi:10.1007/bf01521196

Cited by 165 publications

(103 citation statements)

References 15 publications

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“…At that temperature, we in the distribution of relaxation times. 8,32 This same broadening is observed in the a and b dielecfound that the critical pressure (point where the slope changes) in our experiment occurred at aptric relaxation spectra of polycarbonate 29 and the poly(alkyl methacrylates) 28 as temperature is proximately 1054 { 200 atm. To understand the mechanisms responsible for lowered.…”

Section: Resultssupporting

confidence: 78%

Temperature dependence of the activation volume in a nonlinear optical polymer: Evidence for chromophore reorientation induced by sub-Tg relaxations

Strutz

Brower

Hayden

1998

J. Polym. Sci. B Polym. Phys.

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Second harmonic generation (SHG) was used to measure the temperature dependence of the reorientation activation volume of 4‐(diethylamino)‐4′‐nitrotolane (DEANT) in poly(methyl methacrylate) (PMMA). The decay of the SHG signal from films of DEANT/PMMA was recorded at hydrostatic pressures up to 3060 atm and at different temperatures between 25°C below the glass transition temperature to 35°C above it. The activation volume, ΔV*αβ associated with the long range α‐type motion of the polymer remained constant at 213 ± 10 Å3 between Tg − 25°C and Tg + 10°C. At higher temperatures, ΔV*αβ decreased linearly with increasing temperature. The activation volume, ΔV*αβ, associated with short range secondary relaxations was constant over the entire temperature range with a value of 77 ± 10 Å3. The data suggest that above Tg chromophore reorientation is coupled to both the long range and local motions of the polymer; whereas, well below Tg chromophore reorientation is closely coupled to the local relaxations of the polymer. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 901–911, 1998

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Section: Resultssupporting

confidence: 78%

Temperature dependence of the activation volume in a nonlinear optical polymer: Evidence for chromophore reorientation induced by sub-Tg relaxations

Strutz

Brower

Hayden

1998

J. Polym. Sci. B Polym. Phys.

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“…Then, if z > 0 and 0 < a < 1, the series p(z;a,V)=-I ~ (-1)"r(l+na) ~r ,=, n-?.v zU~+i sin 89 -ct) (16) converges, while, if z > 0 and 1 < a < 2, 1 1)…”

Section: )mentioning

confidence: 95%

On Lévy (or stable) distributions and the Williams-Watts model of dielectric relaxation

1984

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f,~exp(_izu_[ul~)du with 0 2 since it may, for some values of z, become negative. The use of the expression exp -[t/T] ~ as a relaxation function for dynamical processes in materials was first proposed by Kohlrausch (1866). Its reciprocal plays an important role in creep phenomenon (l~ and its Fourier transform appears in investigations of response of materials to periodic driving forces (electrical and mechanical).Closed form expressions exist for (1) for few values of a other than a = 2. When a = 1 one has the Cauchy distribution Ql(z) = (1/~r)(1 + z 2) (4) Q2/3(z ) = ( 3 )l/2z-lexp( -~7z-2)W1/2,,/6 ( 2@z2 )The value of Q~ (0)

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“…[30][31][32][33][34][35][36][37][38][39][40][41][42][43] This method is sensitive to molecular fluctuations of dipoles within the system. For polymers these fluctuations are related to the molecular mobility of groups (subglass processes), segments (segmental dynamics) or the whole polymer chain as well which are show up as different relaxation processes.…”

Section: Introductionmentioning

confidence: 99%

Broadband dielectric spectroscopy on the molecular dynamics in different generations of hyperbranched polyester

Turky

Shaaban

Schoenhals

2009

J of Applied Polymer Sci

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Dielectric spectroscopy (10 À2 Hz to 10 6 Hz) was employed to investigate the molecular dynamics of hyperbranched polyesters where the number of the generation is systematically varied from 2 to 5. As a first result, the dielectric properties depends strongly on the generation of the hyperbranched polymers. For higher generations (3 to 5) at temperatures below T g two relaxation processes are observed, a c-process at lower temperatures and a b-process at higher ones. The apparent activation energies are around 100 kJ/mol which seems to be too high for truly localized processes. For the Generation 2, only the c-process is observed. For all investigated polymers the dielectric a-relaxation could not be observed because of strong conductivity effects. Therefore, the conductivity is systematically analyzed which obeys the peculiarities found to be characteristic for semiconducting disordered materials. Especially, the Barton/Nakajima/ Namikawa relationship is found to be valid.

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Studies on dielectric behaviors in a series of polyalkyl-methacrylates

Cited by 165 publications

References 15 publications

Temperature dependence of the activation volume in a nonlinear optical polymer: Evidence for chromophore reorientation induced by sub-Tg relaxations

Temperature dependence of the activation volume in a nonlinear optical polymer: Evidence for chromophore reorientation induced by sub-Tg relaxations

On Lévy (or stable) distributions and the Williams-Watts model of dielectric relaxation

Broadband dielectric spectroscopy on the molecular dynamics in different generations of hyperbranched polyester

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