Dynamics of main-chain liquid crystalline polysiloxanes containing p-phenyleneterephthalate mesogens

Masser, Kevin A.; Patil, Harshad; Hedden, Ronald C.; Runt, James

doi:10.1016/j.jnoncrysol.2009.06.045

Cited by 3 publications

(4 citation statements)

References 33 publications

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“…In the literature, the activation energy of γ ‐relaxation is 0.43 eV . For β‐relaxation, Kremer et al report activation energies of 0.63–1.04 eV and Masser et al 0.52 eV . Activation energies that were computed for the relaxations in our samples are a bit below the ones in the literature.…”

Section: Resultscontrasting

confidence: 53%

“…Two local relaxations for MCLCP in the subglass region have been observed before; Frosini et al , Tokita and Watanabe , and Farrow et al attributed γ ‐relaxation in MCLCP with methylene sequences to motions of methylene groups. In similar systems, but without methylene sequences, the γ ‐relaxation was associated with the rotational motion of either phenyl units or alkyl/siloxane segments in the backbone of the main chain. The β‐relaxation was attributed to the rotation of the mesogenic group in the main‐chain around its long axis .…”

Section: Resultsmentioning

confidence: 99%

“…2 ) and a conductivity term ( Eq . 3 ) . The results for the time scale of the α ‐relaxation and the MWS relaxation are presented in Fig.…”

Section: Resultsmentioning

confidence: 99%

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Thermal transitions and molecular dynamics in main‐chain liquid crystalline polyester/fullerene nanocomposites

et al. 2016

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Molecular dynamics and liquid crystalline (LC) transitions in nanocomposites with main-chain liquid crystalline alkylene-aromatic polyester as a matrix and fullerene C 60 as a filler, with filler content varying from 0.3 up to 5 wt% were studied. Measurements by differential scanning calorimetry (DSC) and temperature modulated DSC techniques were performed in order to study glass transition and LC transitions. Dielectric relaxation spectroscopy (DRS) was used both to record LC transitions through isochronal measurements at four different frequencies during cooling/ heating at constant rate and to study molecular mobility through isothermal measurements in a wide temperature and frequency range, 21508C to 1908C and 10 21 to 10 6 Hz, respectively. Glass transition and LC transitions were followed for the neat matrix as well as for the nanocomposites. A moderate increase of glass transition temperature in nanocomposites was found, while the LC transitions were shifted to lower temperatures with increasing filler content. A good correlation between DSC and DRS results was found. For all the samples under study four dielectric relaxations were followed by DRS, in order of increasing temperature: two secondary relaxations, b and c, the a-relaxation related to the amorphous phase glass transition and an interfacial relaxation (Maxwell-Wagner-Sillars, MWS) due to charge accumulation at the amorphouscrystalline interface. The experimental data were analyzed in detail and the results revealed rather weak effects of fullerenes on molecular dynamics. POLYM. COMPOS., 38:E331-E341, 2017.

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Section: Resultscontrasting

confidence: 53%

Section: Resultsmentioning

confidence: 99%

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Thermal transitions and molecular dynamics in main‐chain liquid crystalline polyester/fullerene nanocomposites

et al. 2016

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“…The thermotropic liquid crystalline polymers (LCPs)have still been attracting much attention owing to their high properties, which not only improve the molecular engineering, polymer chemistry and polymer physics, polymer processing and polymer applications, but also show numerous industrial applications in such fields as blends, composite materials, membrane materials, photoelectric, military, information, print, and so on [1][2][3][4][5][6][7].…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Characterization of Thermotropic Main-Chain Liquid Crystalline Polysiloxanes Containing 1,4-butylene bi-p-hydroxybenzoate Mesogens

Gao

Sun

et al. 2011

AMR

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1,4-butylene bi-p-hydroxybenzoate (BBHB) was synthesized using methyl p-hydroxyl- benzoate and 1,4-butanediol under catalyst and stabilizer conditions; Then, the thermotropic main- chain liquid crystalline polysiloxanes (MCLCPs) with flexible spacer, were synthesized using BBHB and dimethyldiethoxysilane reagents by melting polycondensation. The chemical structures and properties were characterized by FT-IR, polarized optical microscopy (POM) and differential scanning calorimeter (DSC) respectively. It was found that MCLCPs was the type of smectic A liquid crystal, and the liquid crystal temperature ranged from 58°C to 143°C, i.e. its variationrange reached 85°C. In addition, the polysiloxane was used as the flexible main-chain and the flexible chains CH2 was embedded into the rigid structural blocks of liquid crystalline polymers, which not only decreased the melting point below the thermal decomposition temperature, but also made the clearing point and a stable liquid crystal state observed.

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Thermal stability and structural anisotropy of semiaromatic poly(ester amides) from aromatic bis(2-oxazolines) and aliphatic dicarboxylic acids

et al. 2018

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Dynamics of main-chain liquid crystalline polysiloxanes containing p-phenyleneterephthalate mesogens

Cited by 3 publications

References 33 publications

Thermal transitions and molecular dynamics in main‐chain liquid crystalline polyester/fullerene nanocomposites

Thermal transitions and molecular dynamics in main‐chain liquid crystalline polyester/fullerene nanocomposites

Synthesis and Characterization of Thermotropic Main-Chain Liquid Crystalline Polysiloxanes Containing 1,4-butylene bi-p-hydroxybenzoate Mesogens

Thermal stability and structural anisotropy of semiaromatic poly(ester amides) from aromatic bis(2-oxazolines) and aliphatic dicarboxylic acids

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