Comparative Broad-Band Dielectric Study on Poly(ester carbonate)s with 1,4-Cyclohexylene Linkages

Merenga, A. S.; Papadakis, C. M.; Kremer, F.; Liu, J.; Yee, Albert F.

doi:10.1021/ma000966v

Cited by 23 publications

(29 citation statements)

References 21 publications

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“…1(b)). All these results are consistent with the usual view of the c-relaxation of BPA-PC as being composed by two components [9]. Moreover, as can be seen in Fig.…”

Section: Resultssupporting

confidence: 92%

“…[9] and references therein). In this way, several molecular mechanisms for the BPA-PC secondary relaxations have been proposed.…”

Section: Introductionmentioning

confidence: 99%

“…In this way, several molecular mechanisms for the BPA-PC secondary relaxations have been proposed. Although there is not a consensus about these molecular mechanisms, what is commonly accepted is that the c-relaxation of BPA-PC consists of two very overlapped components, which would be associated with two distinct molecular motions [5][6][7]9]. Trying to gain insight into these questions, instead of modifying the polymer chemistry, our approach is modifying the molecular packing by means of mechanical deformation in order to study its influence on the secondary relaxations.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Effect of cold-drawing on the secondary dielectric relaxation of bisphenol-A polycarbonate

Mitxelena¹,

Colmenero²,

Alegría³

2005

Journal of Non-Crystalline Solids

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“…1(b)). All these results are consistent with the usual view of the c-relaxation of BPA-PC as being composed by two components [9]. Moreover, as can be seen in Fig.…”

Section: Resultssupporting

confidence: 92%

“…[9] and references therein). In this way, several molecular mechanisms for the BPA-PC secondary relaxations have been proposed.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Effect of cold-drawing on the secondary dielectric relaxation of bisphenol-A polycarbonate

Mitxelena¹,

Colmenero²,

Alegría³

2005

Journal of Non-Crystalline Solids

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“…(iii) Johari-Goldstein type β-process (secondary process in the context of dielectric relaxation) [8,9,10,11,12,13] merges into the α-relaxation around T D , extrapolating the Arrhenius-type temperature dependence below T g of the β-relaxation times [6,14,15,16,17,18,19].…”

mentioning

confidence: 99%

Merging of α and slow β relaxation in supercooled liquids

2002

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Dielectric relaxation spectroscopy (1 Hz -20 GHz) has been performed on supercooled glassformers from the temperature of glass transition (Tg) up to that of melting. Precise measurements particularly in the frequencies of MHz-order have revealed that the temperature dependences of secondary β-relaxation times deviate from the Arrhenius relation in well above Tg. Consequently, our results indicate that the β-process merges into the primary α-mode around the melting temperature, and not at the dynamical transition point T ≈ 1.2Tg.PACS numbers: 64.70. Pf, 77.22.Gm, In recent years, much of the focus on glassy dynamics has been shifting to a considerably higher temperature than T g , the glass-transition one [1,2,3,4]. The topical temperature is located around T D ≡ 1.2T g , where the dynamics of supercooled liquids has been found to change fairly. So far, there have been observed the following phenomena:(i) Rössler scaling reveals that, when cooled, the Debye-Stokes-Einstein relation becomes invalid around T D [5,6]. This indicates a change of diffusion mechanism there.(ii) Stickel analysis [7] clarifies that temperature dependence of viscosity changes around T D . Therefore, in order to fit the primary α-relaxation time τ α using the Vogel-Fulcher-Tamman (VFT) relation,the coefficients (τ 0 , C, T 0 ) have to vary at T B ≈ T D . This suggests that the mechanism of slow structural-relaxation makes some alternation there.(iii) Johari-Goldstein type β-process (secondary process in the context of dielectric relaxation) [8,9,10,11,12,13] merges into the α-relaxation around T D , extrapolating the Arrhenius-type temperature dependence below T g of the β-relaxation times [6,14,15,16,17,18,19].Theoretically, the characteristic temperature T D is thought to be comparable to T C where the idealized Mode Coupling Theory (MCT) predicts a dynamical phase transition [20]. Indeed, the above first two phenomena (i, ii) can be regarded as indicators of the dynamical transition at T C . However, the MCT is irrelevant to the third one (iii), the bifurcation of α, β-modes; even the existence of the Johari-Goldstein type β-process cannot be derived.Furthermore, from experimental aspects, while the dynamical transition phenomena (i, ii) have been confirmed from either Rössler or Stickel plot definitely, the bifurcation of (iii) is inferred from the extrapolation. Actually, however, it remains an open problem as to whether the Arrhenius behavior of the β-process persists in higher temperatures near T D : the T D -decoupling of α, β-relaxations is not conclusive.This letter thus aims to investigate the secondary β-mode in high temperatures well above T g , by carrying out precisely the broad-band measurements of dielectric relaxation. Our main result is the following: as will be seen in Figures 2 and 5, the β-relaxation times deviate from the Arrhenius relation, indicating that the β-relaxation merges into the α-mode not at T D but around the Arrhenius-VFT crossover temperature T A (generally close to the melting one) where the temperatu...

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“…As a result, the d-process is observed at temperatures 5 to 20 8C higher than the a-transition temperature. [12][13][14][20][21][22][23][24] The coexistence of the a-and d-processes in side-chain LC polymers testifies that motions of backbone and side mesogenic groups attached to backbone via a flexible methylene spacer are rather independent.…”

Section: General Features Of Dielectric Behavior Of Lc Ionomers P-limentioning

confidence: 98%

Dielectric Relaxation of Side‐Chain Liquid Crystalline Ionomers Containing Alkaline Metal Ions

Никонорова

Barmatov

Pebalk³

et al. 2005

Macro Chemistry & Physics

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Summary: Two sets of side‐chain, liquid‐crystalline ionomers based on copolymers of butyl acrylate and 4‐{[6‐(acryloyloxy)hexyl]oxy}benzoic acid containing 2.5–20 mol‐% of lithium or rubidium ions were studied. As the content of ions of alkali metals increases, segmental mobility markedly decreases. As compared with rubidium‐containing ionomers, ionomers containing lithium ions are characterized by a far more efficient decrease in their dielectric relaxation times because ionic radius of lithium ions is lower than that of rubidium ions.image

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Comparative Broad-Band Dielectric Study on Poly(ester carbonate)s with 1,4-Cyclohexylene Linkages

Cited by 23 publications

References 21 publications

Effect of cold-drawing on the secondary dielectric relaxation of bisphenol-A polycarbonate

Effect of cold-drawing on the secondary dielectric relaxation of bisphenol-A polycarbonate

Merging of α and slow β relaxation in supercooled liquids

Dielectric Relaxation of Side‐Chain Liquid Crystalline Ionomers Containing Alkaline Metal Ions

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