Liquid Crystalline Type Order in Polydiethylsiloxane

Beatty, C. L.; Pochan, J. M.; Froix, Michael F.; Hinman, D. D.

doi:10.1021/ma60046a031

Cited by 82 publications

(19 citation statements)

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“…Desper and Schneider 12) have found that upon heating some crystalline polyphosphazenes are transformed into a roesomorphic phase. Later, a similar mesophase was found in linear -polydiethylsiloxanes by Beatty and co-workers 13). For this mesophase they used the term "viscocrystalline".…”

Section: Instroduction Classification Of the Mesomorphic Statessupporting

confidence: 55%

“…One of them (rather narrow and very intensive) is near 29 = 8 to 12°, and the second one with a wide maximum is near 29 = 16 to 25°. The fact that there is one sharp X-ray maximum supported by optical and NMR data, has led Beatty et al 13) to the conclusion that POES can exist in the mesomorphic state. The structure of the mesophase was identified by Tsvankin et al 30) whoobtained a well-oriented mesomorphic structure by stretching a slightly crosslinked POES film five to six times its original length at room temperature (Fig.…”

Section: Structure and Morphologymentioning

confidence: 99%

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Thermotropic Mesophases in Element-Organic Polymers

Godovsky

Папков

Dušek³

1989

Speciality Polymers/Polymer Physics

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This review is primarily concerned with mesomorphic behaviour of element-organic polymers, such as linear and cyclolinear polyorganosiloxanes and linear polyphosphazenes. These polymers can form thermotropic mesophases without any mesogens. Recent development in thermodynamics, kinetics, structure and morphology, elasticity and thermoelasticity and some other properties are considered. The influence of the molecular structure and molecular weight of linear macromolecules on the ability to form the mesophases and their temperature stability is discussed. The phase behaviour of cyclolinear polyorganosiloxanes is described with special emphases on the temperature stability of the mesophases as a function of molecular structure, tacticity, substituents and flexible spacers. The state of order of polyorganosiloxanes is analysed in comparison to mesophase states of linear and cyclic low molecular siloxanes. The Iyotropic mesophase behaviour of the ladder polyorganosiloxanes is also examined briefly.

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Section: Instroduction Classification Of the Mesomorphic Statessupporting

confidence: 55%

Section: Structure and Morphologymentioning

confidence: 99%

Thermotropic Mesophases in Element-Organic Polymers

Godovsky

Папков

Dušek³

1989

Speciality Polymers/Polymer Physics

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“…In particular, their applications in severe environments, especially in low‐temperature regions, have become broader in recent years. Poly(diethylsiloxane) stands out among all other poly(diorganosiloxane)s in that it has, so far, the lowest glass‐transition temperature ( T g ): −138 °C,2, 3 although its low‐temperature use as an elastomer is limited by its crystallization at temperatures near −73 °C and a mesomorphic phase transition at approximately 20 °C 4–7. Previous studies on poly(diethylsiloxane) copolymers mainly focused on copolymers bearing two kinds of units, including the introduction of diphenylsiloxane (Ph 2 SiO), 3,3,3‐trifluoropropylmethylsiloxane, ethylphenylsiloxane, or methylphenylsiloxane (MePhSiO)8, 9 into the poly(diethylsiloxane) backbone to disrupt the crystallization.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and characterization of poly(diethylsiloxane) and its copolymers with different diorganosiloxane units

Liu

Yang

Zhang

et al. 2003

J. Polym. Sci. A Polym. Chem.

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Poly(diethylsiloxane) and its copolymers with various kinds of R 1 R 2 SiO (R 1 ϭ R 2 ϭ methyl or phenyl, or R 1 ϭ methyl and R 2 ϭ phenyl) units have been prepared by the equilibrium polymerization of cyclosiloxanes. All the polymers have been characterized by 1 H and 29 Si NMR, gel permeation chromatography, differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA) measurements. The results indicate that a random distribution of different units has been obtained in the structures of copolymers containing 50 mol % diethylsiloxane units content. DSC and DMA show that the presence of 2.5 mol % diphenylsiloxane units or 5.0 mol % methylphenylsiloxane units in the copolymer can disrupt the crystallinity and lead to noncrystalline copolymers with low glass-transition temperatures (ranging from Ϫ133 to Ϫ137°C according to DSC).

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“…In addition, molecular mechanics calculations suggested details about the nature of the low-energy rotational isomers [12]. Beyond the condis state a,"viscous crystalline" or "liquid crystalline" state with only slightly different entropy and enthalpy than the liquid was reported, up to about 310 K [13]. Its nature is still not fully understood, but may be caused by a temperature-dependent fraction of rigid chain segments caused by intramolecular steric hindrance [12].…”

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confidence: 99%

The thermal properties of polysiloxanes poly(dimethyl siloxane) and poly(diethyl siloxane)

Varma‐Nair

Wesson

Wunderlich

1989

Journal of Thermal Analysis

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New measurements and literature data on polysiloxanes covering heat capacities, transition parameters, enthalpies, entropies and Gibbs energies are presented and critically reviewed. The ATHAS computation method is used to bring heat capacities into agreement with an approximate frequency spectrum. The various crystal and mesophases are discussed. The ATHAS (1990) recommended data are as follows: For poly(dimethyl siloxane) the glass transition is at 146 K with an increase in heat capacity of 29.24 J/(K mol). The completely crystalline sample melts at about 219 K with a heat of fusion of 2.75 kJ/mol. For poly(diethyl siloxane) the glass transition is at 135 K with an increase in heat capacity of 34.48 J/(K mol). The completely crystalline sample changes to a condis crystal at 206.7 K with a heat of disordering of 2.72 kJ/mol. The transition to a poorly characterized "viscous crystal" with thermodynamic properties close to the melt occurs at 282.7 K with an enthalpy of transition of 1.84 kJ/mol. Final fusion occurs'at 308.5 K and a small endotherm of about 231 J/tool. Tables of heat capacities, enthalpies, entropies and Gibbs energies are given from 0 K to 550 K.Of the poiysiloxanes only poly(dimethyl siloxane), PDMS, and poly(diethyl siloxane), PDES, have found major attention. In the 1980 ATHAS data bank of heat capacities of macromolecules [1] only few data on semicrystalline PDMS and PDES could be presented [2]. The follow-up analyses and fitting of the data in the solid state to approximate vibrational frequency spectra done with many other polymers [3] could not be carried out before because of lack of data and understanding of the phase behaviour. This paper, largely based on the experimental work of one of us (J.P.W.) [4] and the continuing A THA S collection of thermal data, brings PDMS and PDES into the group of close to 100 well characterized polymers [5].

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Liquid Crystalline Type Order in Polydiethylsiloxane

Abstract: The potential constants need to characterize the interactions between chlorine atoms ((A/r12) -(C/r6)) are A = 2,95 X 106 kcal Á12 and C -

Cited by 82 publications

References 2 publications

Thermotropic Mesophases in Element-Organic Polymers

Thermotropic Mesophases in Element-Organic Polymers

Synthesis and characterization of poly(diethylsiloxane) and its copolymers with different diorganosiloxane units

The thermal properties of polysiloxanes poly(dimethyl siloxane) and poly(diethyl siloxane)

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