Abstract:ABSTRACT:Two new liquid crystalline polysiloxanes with very wide mesomorphic temperature range have been prepared. One containing 4-[(S)-2-methyl-l-butoxy]phenyl 4-hexanyloxybiphenyl-4'-carboxylate side groups displays enantiotropic smectic A, chiral smectic C and smectic B phases. The other containing (S)-2-methyl-l-butyl 6-(4-undecanyloxybiphenyl-4'-carbonyloxy)-2-naphthalenecarboxylate side groups exhibits only an enantiotropic cholesteric phase. Both mesomorphic polysiloxanes were used as stationary phases… Show more
“…4-Allyloxybiphenyl-4′-carboxylic acid, 4-hydroxyphenyl-4′-allyloxybenzoate, and 4-(6-acryloyloxyhexyloxy)benzoic acid were prepared according to the literature procedures reported. [30][31][32] Cholesteryl 4-Allyloxybiphenyl-4′-carboxylate (M1). First, 2.54 g (0.01 mol) of 4-allyloxybiphenyl-4′-carboxylic acid was reacted at 60 °C with 15 mL of thionyl chloride containing a few drops of N,N-dimethylfomamide (DMF) for 3 h, and then the excess thionyl chloride was removed under reduced pressure to give the corresponding acid chloride.…”
Section: Methodsmentioning
confidence: 99%
“…The synthesis of the olefinic monomers is shown in Schemes and . 4-Allyloxybiphenyl-4‘-carboxylic acid, 4-hydroxyphenyl-4‘-allyloxybenzoate, and 4-(6-acryloyloxyhexyloxy)benzoic acid were prepared according to the literature procedures reported. − 1 Synthetic Route of Cholesteric Monomer 2 Synthetic Route of Cross-Linking Monomer…”
The synthesis of the two monomers M 1 and M2 and a series of new side-chain cholesteric liquid crystalline elastomers P2-P8 is presented. The chemical structures of the monomers and elastomers obtained were confirmed by FTIR or 1 H NMR spectroscopy. The cross-link density of the elastomers was determined by swelling experiments. The mesomorphic properties were investigated by differential scanning calorimetry (DSC), thermogravimetric analyses (TGA), polarizing optical microscopy (POM), and X-ray diffraction (XRD) measurements. Monomer M 1 showed a cholesteric phase, and M2 revealed smectic and nematic phases. The effect of the cross-link density on the phase behavior of P2-P8 is discussed. Elastomers P2-P6 containing less than 12 mol % of the cross-linking units displayed elasticity, reversible liquid crystalline phase transition, wide mesophase temperature ranges, and high thermal stability. Elastomer P 7 displayed stress-induced birefringence, and P8 showed only elasticity with no other texture. Experimental results demonstrated that the glass transition temperatures increased, and the isotropization temperatures and the mesophase temperature ranges of P 2-P6 decreased with increasing cross-link density.
“…4-Allyloxybiphenyl-4′-carboxylic acid, 4-hydroxyphenyl-4′-allyloxybenzoate, and 4-(6-acryloyloxyhexyloxy)benzoic acid were prepared according to the literature procedures reported. [30][31][32] Cholesteryl 4-Allyloxybiphenyl-4′-carboxylate (M1). First, 2.54 g (0.01 mol) of 4-allyloxybiphenyl-4′-carboxylic acid was reacted at 60 °C with 15 mL of thionyl chloride containing a few drops of N,N-dimethylfomamide (DMF) for 3 h, and then the excess thionyl chloride was removed under reduced pressure to give the corresponding acid chloride.…”
Section: Methodsmentioning
confidence: 99%
“…The synthesis of the olefinic monomers is shown in Schemes and . 4-Allyloxybiphenyl-4‘-carboxylic acid, 4-hydroxyphenyl-4‘-allyloxybenzoate, and 4-(6-acryloyloxyhexyloxy)benzoic acid were prepared according to the literature procedures reported. − 1 Synthetic Route of Cholesteric Monomer 2 Synthetic Route of Cross-Linking Monomer…”
The synthesis of the two monomers M 1 and M2 and a series of new side-chain cholesteric liquid crystalline elastomers P2-P8 is presented. The chemical structures of the monomers and elastomers obtained were confirmed by FTIR or 1 H NMR spectroscopy. The cross-link density of the elastomers was determined by swelling experiments. The mesomorphic properties were investigated by differential scanning calorimetry (DSC), thermogravimetric analyses (TGA), polarizing optical microscopy (POM), and X-ray diffraction (XRD) measurements. Monomer M 1 showed a cholesteric phase, and M2 revealed smectic and nematic phases. The effect of the cross-link density on the phase behavior of P2-P8 is discussed. Elastomers P2-P6 containing less than 12 mol % of the cross-linking units displayed elasticity, reversible liquid crystalline phase transition, wide mesophase temperature ranges, and high thermal stability. Elastomer P 7 displayed stress-induced birefringence, and P8 showed only elasticity with no other texture. Experimental results demonstrated that the glass transition temperatures increased, and the isotropization temperatures and the mesophase temperature ranges of P 2-P6 decreased with increasing cross-link density.
“…Diblock Copolymer Preparations. 21 (v) r-Methacryloxypropyl-ω-carboxylate-Poly(dimethylsiloxane)-b-poly-(ethylene oxide) ( 14). The homopolymers are coupled by a hydrosilylation reaction.…”
Novel short chain R,ω-heterotelechelic amphiphilic poly(dimethylsiloxane)-b-poly(ethylene oxide) diblock copolymers (PDMS-PEO) with total molecular weights below 10 000 g/mol are synthesized, characterized, and used as basic constituent parts for functionalized nanoparticles. The self-assembly of the amphiphilic diblock copolymer in water as a solvent selective for the PEO block leads to the formation of spherical and cylindrical micellar structures with diameters between 10 and 25 nm. The core of the micelles is built of the hydrophobic PDMS chains, whereas the corona is set up by the hydrophilic PEO blocks. By using R,ω-heterotelechelic diblock copolymers, it is possible to fix the core of the micelles by cross-linking of the PDMS-sided (R) methacrylic end groups. The resulting nanoparticles possess the PEO-sided (ω) functional end groups introduced during the synthesis of the amphiphilic diblock copolymer. In the present study, these functionalities are hydrophilic, uncharged hydroxy end groups (-OH), hydrophilic, charged carboxylate (-COOH) end groups, or hydrophobic benzylic end groups (-CH 2C6H5).
“…Since then, a great deal of attention has been paid to the separation properties of this relatively wide group of substances [3,4], used mainly as stationary phases in packed columns. Liquid crystals have been used as stationary phase [5][6][7][8][9][10][11][12][13][14][15][16] in GC to separate a variety of compounds including isomeric mixtures which cannot be separated on conventional stationary phases. Conventional stationary phase separation of analytes is based on differences in vapor pressures of the solutes and/or differences in solubility arising from specific energetic interactions.…”
A novel series of side-chain liquid crystalline copolysiloxanes containing [S]-1-(2-naphthyl) ethyl 6-[4-(10-undecen-1-yloxy) biphenyl-4 -carbonyloxy]-2-naphthoate mesogenic and 4-biphenyl 4 -allyloxybenzoate mesogenic side groups in the backbone and side chains liquid crystalline copolymers were prepared and evaluated as possible stationary phases for gas chromatography capillary columns. All copolymers display enantiotropic cholesteric phases. These mesomorphic polysiloxanes specimens with the widest temperature range were used as the stationary phase in a gas chromatography capillary column, and it showed good thermal and physical stability, excellent chemical inertness, and unique separation properties for polycyclic aromatic compounds. These cholesteric LC copolysiloxane stationary phases show much better separation effect for the polycyclic aromatic compound than those of the nematic and smectic LC copolysiloxanes.
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