Liquid Crystalline Silicon-Containing Polymers

Teyssié, Dominique; Boileau, Sylvie

doi:10.1007/978-94-011-3939-7_22

Cited by 6 publications

(2 citation statements)

References 93 publications

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“…Siloxane moieties (short segments, long chains, cycles) are often used in LCs as flexible spacers or as the main backbone, in combination with unnumbered mesogenic groups. The main reasons for using siloxanes instead of purely organic (hydrocarbon) counterparts derive from their bulkiness, high flexibility, chemical versatility and tendency of microphase separation [ 118 , 119 , 120 ]. Several general characteristics of the resulted LC materials are due to these specific behaviors of (poly)siloxanes: lower transition temperatures, larger mesophase range, tendency for formation of smectic mesophases and suppression of the nematic mesophase.…”

Section: Siloxane-siloxane and Siloxane-organic Copolymersmentioning

confidence: 99%

From Amorphous Silicones to Si-Containing Highly Ordered Polymers: Some Romanian Contributions in the Field

Cazacu¹,

Racleş²,

Zaltariov³

et al. 2021

Polymers

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Polydimethylsiloxane (PDMS), in spite of its well-defined helical structure, is an amorphous fluid even at extremely high molecular weights. The cause of this behavior is the high flexibility of the siloxane backbone and the lack of intermolecular interactions attributed to the presence of methyl groups. These make PDMS incompatible with almost any organic or inorganic component leading to phase separation in siloxane-siloxane copolymers containing blocks with polar organic groups and in siloxane-organic copolymers, where dimethylsiloxane segments co-exist with organic ones. Self-assembly at the micro- or nanometric scale is common in certain mixed structures, including micelles, vesicles, et cetera, manifesting reversibly in response to an external stimulus. Polymers with a very high degree of ordering in the form of high-quality crystals were obtained when siloxane/silane segments co-exist with coordinated metal blocks in the polymer chain. While in the case of coordination of secondary building units (SBUs) with siloxane ligands 1D chains are formed; when coordination is achieved in the presence of a mixture of ligands, siloxane and organic, 2D structures are formed in most cases. The Romanian research group’s results regarding these aspects are reviewed: from the synthesis of classic, amorphous silicone products, to their adaptation for use in emerging fields and to new self-assembled or highly ordered structures with properties that create perspectives for the use of silicones in hitherto unexpected areas.

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Section: Siloxane-siloxane and Siloxane-organic Copolymersmentioning

confidence: 99%

From Amorphous Silicones to Si-Containing Highly Ordered Polymers: Some Romanian Contributions in the Field

Cazacu¹,

Racleş²,

Zaltariov³

et al. 2021

Polymers

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“…HOSi(Et) 2 OSi(Et) 2 OH was constructed as a simplified model of the poly(diethylsiloxane) compound and optimized geometrically in trans-trans, trans-gauche and gauche-gauche conformations. Because ab initio MO calculations give absolute shielding values, we converted from calculated shieldings to chemical shifts using the following equation 43 for the purpose of comparison to the experimental 17 O NMR chemical shifts…”

Section: O Electric Field Gradient Componentsmentioning

confidence: 99%

Structural characterization of poly(diethylsiloxane) in the crystalline, liquid crystalline and isotropic phases by solid‐state ¹⁷O NMR spectroscopy and ab initio MO calculations

Kimura

Kanesaka

Kuroki

et al. 2004

Magnetic Reson in Chemistry

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The structure of poly(diethylsiloxane) (PDES) has been characterized using solid-state NMR of (17)O. The sample studied had a weight-average molecular weight of 2.45 x 10(5). The sample was prepared by utilizing the cationic ring-opening polymerization of (17)O-enriched hexacyclotrisiloxane. Solid-state NMR of (17)O-enriched PDES was measured on the low-temperature beta(1) phase, the high-temperature beta(2) phase, the two-phase system consisting of the liquid crystal and isotropic liquid phase and the isotropic phase. From these data, the molecular structure and dynamics of PDES in the various phases were characterized via the chemical shifts of (17)O, and electric field gradient parameters were determined from NMR and ab initio molecular orbital (MO) calculations. In addition to the solid-state NMR of (1)H, (13)C and (29)Si previously reported on these samples, knowledge of the dynamic behavior of PDES as inferred from the NMR of (17)O in the present study was enhanced significantly. Further, the potential of combining the experimental NMR of (17)O with ab initio MO calculations to characterize the dynamics of polymers containing oxygen is demonstrated.

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Synthesis and characterization of a series of smectic liquid crystalline elastomers

Zhang

Xiao

et al. 2005

J of Applied Polymer Sci

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A series of new smectic and cholesteric liquid crystalline elastomers was prepared by graft polymerization of mesogenic monomer with the chiral and nonmesogenic crosslinking agent using polymethylhydrosiloxane as backbone. The chemical structures of the monomers and polymers obtained were confirmed by Fourier transform infrared (FTIR), proton nuclear magnetic resonance spectra ( 1 H-NMR). The mesomorphic properties were investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and X-ray diffraction measurements (XRD). M 1 showed smectic (S B , S C , S A ) and nematic phases during the heating and the cooling cycles. Polymer P 0 and elastomer P 1 exhibited smectic B phase, elastomers P 2 -P 5 showed smectic A phase, P 6 and P 7 showed cholesteric phase, and P 8 displayed stress-induced birefringence. The elastomers containing less than 15 mol % M 2 displayed elasticity and reversible phase transition with wide mesophase temperature ranges. Experimental results demonstrated that the glass transition temperatures decreased first and then increased; melting temperatures and the isotropization temperatures and the mesophase temperature ranges decreased with increasing content of crosslinking unit.

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Liquid Crystalline Silicon-Containing Polymers

Cited by 6 publications

References 93 publications

From Amorphous Silicones to Si-Containing Highly Ordered Polymers: Some Romanian Contributions in the Field

From Amorphous Silicones to Si-Containing Highly Ordered Polymers: Some Romanian Contributions in the Field

Structural characterization of poly(diethylsiloxane) in the crystalline, liquid crystalline and isotropic phases by solid‐state ¹⁷O NMR spectroscopy and ab initio MO calculations

Synthesis and characterization of a series of smectic liquid crystalline elastomers

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Liquid Crystalline Silicon-Containing Polymers

Cited by 6 publications

References 93 publications

From Amorphous Silicones to Si-Containing Highly Ordered Polymers: Some Romanian Contributions in the Field

From Amorphous Silicones to Si-Containing Highly Ordered Polymers: Some Romanian Contributions in the Field

Structural characterization of poly(diethylsiloxane) in the crystalline, liquid crystalline and isotropic phases by solid‐state 17O NMR spectroscopy and ab initio MO calculations

Synthesis and characterization of a series of smectic liquid crystalline elastomers

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Product

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About

Structural characterization of poly(diethylsiloxane) in the crystalline, liquid crystalline and isotropic phases by solid‐state ¹⁷O NMR spectroscopy and ab initio MO calculations