The thioether spacer in liquid crystalline polysiloxanes with cyano- and nitrobiphenyl mesogens

Milano, J.C.; Robert, Jean Michel; Vernet, Jean-Louis; Gallot, Bernard

doi:10.1002/(sici)1521-3935(19990701)200:7<1580::aid-macp1580>3.0.co;2-a

Cited by 13 publications

(16 citation statements)

References 18 publications

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“…The DVTMS could be used but it is less efficient. [13] The progress of the reaction is followed by Gel Permeation Chromatography. At the end, an excess of 1-octene is added in order to completely eliminate the Si-H bonds still free after grafting (the average mass of polymers is close to 16 000).…”

Section: Resultsmentioning

confidence: 99%

“…They are similar to those which already were obtained with other polysiloxanes previously carried out at the laboratory. [12,13] …”

Section: Resultsmentioning

confidence: 99%

“…The SmA liquid-crystalline structure has also been specified by X-ray diffraction on the first three models of the Table 1: [13] these mesophases fine structures are of the SmAd type i.e. an interdigitated system, in the temperature range observed by DSC and MPC ( Figure 4).…”

Section: Mesomorphic Propertiesmentioning

confidence: 99%

“…[11] The first ''cyanobiphenyl'' and ''nitrobiphenyl'' liquid-crystalline polysiloxanes with thioether spacers (n ¼ 6, 8, 10 and m ¼ 2; see Figure 1) have been carried out in our laboratory. [12,13] This work enabled to develop their synthesis protocol and to prove that the thioether spacer removes the crystallization phenomenon. This concept is easily to be set up compared to the other ones.…”

Section: Introductionmentioning

confidence: 99%

“…They have been obtained by lengthening the spacer and by modifying the position of sulfur in the polymethylenic chain (m ¼ 2 and 3). This study is based on results previously obtained in our laboratory [12,13] with the goal to specify the flexibility of the thioether spacer. It will also make it possible to precise the limits of its efficiency.…”

Section: Introductionmentioning

confidence: 99%

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Synthesis and Dielectric Study of New Liquid‐crystalline Polysiloxanes Presenting a Thioether Spacer

Gilles

Milano

Vernet

2003

Macro Chemistry & Physics

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Three new cyanobiphenyl polysiloxanes presenting long thioether spacers have been carried out. This type of spacer leads to very stable liquid‐crystalline polymers at room temperature and remove the crystallinity phenomenon. Dielectric analysis results show that the thioether spacer brings much more molecular flexibility to the system.Example of an “interdigitated” structure observed by X‐ray analysis.magnified imageExample of an “interdigitated” structure observed by X‐ray analysis.

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Section: Resultsmentioning

confidence: 99%

“…They are similar to those which already were obtained with other polysiloxanes previously carried out at the laboratory. [12,13] …”

Section: Resultsmentioning

confidence: 99%

Section: Mesomorphic Propertiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Synthesis and Dielectric Study of New Liquid‐crystalline Polysiloxanes Presenting a Thioether Spacer

Gilles

Milano

Vernet

2003

Macro Chemistry & Physics

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Synthesis and thermal properties of polythioether‐based liquid‐crystalline polymers containing azobenzene in the side chain

Zhang

2009

Polymer International

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BACKGROUND: Owing to the unusual structural rearrangement of polychloromethylthiirane (PCMT) at room temperature, it has not been used as the main‐chain backbone of side‐chain liquid‐crystalline polymers (SLCPs). However, it has been observed that PCMT has a relatively stable and clear structure under special conditions. Therefore, we attempted to synthesize SLCPs using PCMT as main‐chain backbone and investigated their thermal behavior. RESULTS: New polymers, poly[1‐({(4‐methoxyazobenzene‐4′‐oxy)alkyl}thio)‐2,3‐epithiopropane], in which the number of methylene units in the alkyl group is 4, 5 or 6, were prepared by means of reactions of corresponding (4‐methoxyazobenzene‐4′‐oxy)alkylthiols with PCMT. The structures of these compounds were confirmed using elemental analysis and 1H NMR spectroscopy. The substitution ratios of the copolymers with 4, 5 and 6 methylene units in the alkyl group were 56, 75 and 80%, respectively. Differential scanning calorimetry measurements and polarized optical microscopy observations showed that the resulting copolymers exhibited thermotropic liquid‐crystalline mesomorphism with nematic phase except for the copolymer with a 56% substitution ratio. The decomposition temperature of all the synthesized copolymers was near 195 °C. CONCLUSION: This investigation has demonstrated that PCMT polymerized for 8 h has the ability to act as a suitable main‐chain backbone for SLCPs. Moreover, SLCPs could be obtained only by the reaction of PCMT with thiolate salt containing mesogenic groups. The substitution ratios increased with increasing number of methylene groups in the spacer. Copyright © 2009 Society of Chemical Industry

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Synthesis of comb‐type polycarbosilanes via nucleophilic substitution reactions on the main‐chain silicon atoms

Zhang

Park

Farmer

et al. 2003

J. Polym. Sci. A Polym. Chem.

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A series of comb-type polycarbosilanes of the type [Si(CH 3 )(OR)CH 2 ] n {where R ϭ (CH 2 ) m RЈ, RЈ ϭ OO-p-biphenylOX [X ϭ H (m ϭ 3, 6, 8, or 11) or CN (m ϭ 11)], and RЈ ϭ (CF 2 ) 7 CF 3 (m ϭ 4)} were prepared from poly(chloromethylsilylenemethylene) by reactions with the respective hydroxy-terminated side chains in the presence of triethylamine. The product side-chain polymers were typically greater than 90% substituted and, for RЈ ϭ OO-p-biphenylOX derivatives, they exhibited phase transitions between 27 and 150°C involving both crystalline and liquid-crystalline phases. The introduction of the polar p-CN substituent to the biphenyl mesogen resulted in a substantial increase in both the isotropization temperature and the liquid-crystalline phase range with respect to the corresponding unsubstituted biphenyl derivative. For R ϭ (CH 2 ) 11 OO-biphenyl side chains, an analogous side-chain liquid-crystalline (SCLC) polysiloxane derivative of the type [Si(CH 3 )(O(CH 2 ) 11 OObiphenyl)O] n was prepared by means of a catalytic dehydrogenation reaction. In contrast to the polycarbosilane bearing the same side chain, this polymer did not exhibit any liquid-crystalline phases but melted directly from a crystalline phase to an isotropic liquid at 94°C. Similar behavior was observed for the polycarbosilane with a fluorocarbon chain, for which a single transition from a crystalline phase to an isotropic liquid was observed at Ϫ0.7°C. The molecular structures of these polymers were characterized by means of gel permeation chromatography and high-resolution NMR studies, and the crystalline and liquid-crystalline phases of the SCLC polymers were identified by differential scanning calorimetry, polarized optical microscopy, and X-ray diffraction.

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The thioether spacer in liquid crystalline polysiloxanes with cyano- and nitrobiphenyl mesogens

Cited by 13 publications

References 18 publications

Synthesis and Dielectric Study of New Liquid‐crystalline Polysiloxanes Presenting a Thioether Spacer

Synthesis and Dielectric Study of New Liquid‐crystalline Polysiloxanes Presenting a Thioether Spacer

Synthesis and thermal properties of polythioether‐based liquid‐crystalline polymers containing azobenzene in the side chain

Synthesis of comb‐type polycarbosilanes via nucleophilic substitution reactions on the main‐chain silicon atoms

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