The cyclolinear polyorganosiloxanes ‐ a new class of mesomorphic polymers

Godovsky, Yu. K.; Макарова, Н. Н.; Kuz'min, N. N.

doi:10.1002/masy.19890260110

Cited by 8 publications

(2 citation statements)

References 13 publications

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“…of the mesophase state in this case is considerably narrower (Makarova et al 1989). Hence, by changing the ratio of the methyl to phenyl groups within the cycles it is possible to regulate the stability of the mesophase and the degree of mesomorphicity.…”

Section: S E Lf-o R D E R In G Inmentioning

confidence: 91%

“…The structure of the mesophases in c l p o s s was analysed by means of the Stuart-Briegleb models and X-ray analysis (Makarova et al 1989). Analysis of the models shows that the macromolecules of cyclotetrasiloxane units can be approximated by cylinders whose diameter increases with alkyl substituents as follows: methyl, d = 11.0; ethyl, d = 13.0; and n-propyl, d 14.5 A.…”

Section: S E Lf-o R D E R In G Inmentioning

confidence: 99%

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Self-order in flexible non-mesogenic macromolecules

Godovsky

Макарова

1994

Phil. Trans. R. Soc. Lond. A

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Some very flexible linear poly(di-n-alkylsiloxane)s and cyclolinear oligo- and polyorganosiloxanes, which do not contain classical rigid rodlike or disclike mesogens, similar to other semi-organic polymers like polyphosphazenes and polysilanes, can form thermodynamically stable two-dimensionally ordered thermotropic mesophases. In many respects the mesophases in polysiloxanes resemble columnar liquid crystals which seems to be the result of the amphiphilic constitution of the polyorganosiloxanes. The origin of the mesomorphic state seems to be closely related to the competition between the interaction of the polar inorganic backbones and those of the organic side chains facilitated by the high flexibility of the inorganic main chain. Similarily to discotic liquid crystals, mesophases in polysiloxanes consist mostly of columns packed hexagonally (or closely so) with lateral long-range positional order, but with only short-range order along the columns. The unique feature of the columnar mesophases is that the axes of macromolecules lie along the column axes. The influence of molecular structure and molecular mass of linear macromolecules is discussed. It has been demonstrated that the temperature interval of mesophase stability is critically dependent on the length of the alkyl side chains. Both the process of formation of the mesophase from the isotropic melt and the crystallization of the mesophase are nucleation controlled processes, although the crystallization of the mesomorphic state is characterized by some specific features. The phase behaviour of cyclolinear polyorganosiloxanes is described with particular emphasis on the temperature stability as a function of molecular structure, tacticity, substituents and flexible spacers.

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Section: S E Lf-o R D E R In G Inmentioning

confidence: 91%

Section: S E Lf-o R D E R In G Inmentioning

confidence: 99%

Self-order in flexible non-mesogenic macromolecules

Godovsky

Макарова

1994

Phil. Trans. R. Soc. Lond. A

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Rubber‐elastic mesophase siloxane systems

Godovsky

1992

Angew. Makromol. Chem.

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Thermotropic poly(diethylsi1oxane) is a new type of the mesophase elastomers. Mechanical measurements in extension and contraction and stretching calorimetric measurements of heat and energy effects resulting from extension and contraction were combained with thermo-mechanical measurements under constant loads and opto-mechanical measurements to obtain molecular understanding of the deformational behaviour of these mesophase rubber-like materials in a wide temperature range with particular emphasis on the temperature range of the mesophase stability as a function of extension. The stress-strain curves of semi-mesomorphic films resemble the strain-strain beahaviour of crystalline polymers with a very low degree of crystallinity. During stretching of amorphous films the strain-induced mesophase occurs. The influence of stress on the temperature range of the stability of the strain-induced mesophase is very strong due to a very small heat of isotropization. The cyclic deformations of the mesophase elastomers are accompanied by the necking-renecking phenomena resulting from the strain-induced mesophase formation on stretching followed by the immediate isotropization during contraction. Some potential practical applications of the mesophase elastomers are considered.Paper presented at the meeting of the GDCh Fachgruppe 99Makromolekulare Chemie" on "Kautschukelastische Polymersystemel' in

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Cyclolinear polysiloxanes. I. Synthesis and characterization

Daum

Erdődi

Kennedy

2006

J. Polym. Sci. A Polym. Chem.

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The synthesis and characterization of two novel cyclic siloxanes, diacetoxydiethyltetramethylcyclotetrasiloxane and diacetoxytriethylpentamethylcyclopentasiloxane, and cyclolinear polymers synthesized from these monomers are presented. The cyclic siloxanes were synthesized from tetramethylcyclotetrasiloxane and pentamethylcyclopentasiloxane, respectively, by acetylation followed by ethylation. The cyclic monomers were characterized with 1 H NMR spectroscopy. Subsequently, the cyclic siloxanes were self-condensed into cyclolinear polysiloxanes and cocondensed (extended) with silanol-terminated polydimethylsiloxane into high-molecular-weight polymers containing cyclic units with linear polydimethylsiloxane spacers (extended cyclolinear polysiloxanes). The molecular weights of both the cyclolinear polysiloxanes and extended cyclolinear polysiloxanes were determined.

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The cyclolinear polyorganosiloxanes ‐ a new class of mesomorphic polymers

Abstract: A b s t r a c t -T h e p a p e r s u m m a r i z e s t h e r e c e n t a c h i e v e m e n t s

Cited by 8 publications

References 13 publications

Self-order in flexible non-mesogenic macromolecules

Self-order in flexible non-mesogenic macromolecules

Rubber‐elastic mesophase siloxane systems

Cyclolinear polysiloxanes. I. Synthesis and characterization

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