Thermotropic properties and conformational studies on poly(triethylene glycol p,p'-bibenzoate) and poly(octamethylene p,p'-bibenzoate)

Pérez, Ernesto; Riande, Evaristo; Bello, A.; Benavente, Rosario; Pereña, José M.

doi:10.1021/ma00028a019

Cited by 54 publications

(42 citation statements)

References 4 publications

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“…[12] Polymers with linear methylenic spacers, (CH 2 ) n , form S A mesophases if n is even and S CA mesophases if n is odd. Moreover, S C phases have been reported for some oxymethylenic even spacers [13] and methylenic spacers with methyl substitutents. [14] In the case of quiral substituted spacers, the S C * mesophase was found.…”

Section: Introductionmentioning

confidence: 99%

Phase Behaviour of New Side‐Chain Liquid Crystalline Polyoxetanes

Martínez‐Gómez

Bello

Pérez

2005

Macro Chemistry & Physics

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Summary: The synthesis and thermal behaviour of two new polyoxetanes with side chains having a dimer structure mesogen‐spacer‐mesogen and a long terminal alkyl group are reported. The two polymers differ in the chemical structure of the central spacer. The polyoxetanes have been obtained by cationic ring‐opening polymerisation of an appropriately substituted oxetane ring. Both polyoxetanes studied exhibit liquid crystalline properties showing a similar sequence of phases. DSC and synchrotron experiments indicate that a highly ordered phase with a probable orthorhombic packing is observed at low temperature. On heating, this phase melts into a mesophase with hexagonal order within the smectic layers, which, on further heating, is transformed into a disordered smectic mesophase.

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Section: Introductionmentioning

confidence: 99%

Phase Behaviour of New Side‐Chain Liquid Crystalline Polyoxetanes

Martínez‐Gómez

Bello

Pérez

2005

Macro Chemistry & Physics

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“…A factor that can be managed is the stiffness of the molecular chains, governed by the number of conformations permitted to the chains, which can be modified by inserting side groups and/or ether groups along the spacer. The information from previous works [3][4][5][6] indicates that as a result of substituting methylenic groups by ether linkages in the spacer, the thermal transitions of thermotropic polyesters are shifted to lower temperatures, the thermodynamic behaviour becomes enantiotropic, and the rate of transformation of the mesophase into a more ordered phase is considerably decreased.…”

Section: Introductionmentioning

confidence: 99%

“…It has been proved that the thermal properties of the mesophases and their transformation rates can be controlled with suitable changes in the structure of the flexible spacer [3][4][5][6][7][8][9]. A factor that can be managed is the stiffness of the molecular chains, governed by the number of conformations permitted to the chains, which can be modified by inserting side groups and/or ether groups along the spacer.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and structural studies of poly(tetramethyleneoxypropylene p, p´-bibenzoate)

2008

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Abstract:A smectic main chain polybibenzoate has been synthesized using a mixture of the branched ether-diols: HO(CH 2 ) 4 OCH(CH 3 )CH 2 OH and HO(CH 2 ) 4 OCH 2 CH(CH 3 )OH, as flexible spacers. The mesophase has been identified as SmCalt by optical microscopy and X-ray diffraction experiments. The irregular chemical structure of the polymer, due to the asymmetry of the spacers, produce two important effects: the mesophase is stabilized and the liquid crystallization is slowed down, making possible the freezing of the amorphous glass by supercooling the isotropic melt. Therefore, both the amorphous glass and the smectic glass can be obtained and analyzed. By differential scanning calorimetric measurements it was found that the glass transition of the mesophase appears at lower temperature than the glass transition of the amorphous state. Depending on the temperature and rate of deformation, the molecular orientation in the drawn smectic phase can be perpendicular (anomalous orientation) or parallel (normal orientation) to the stretching direction (or a mixture of both orientations). The morphology of these oriented samples has been studied by scanning electron microscopy.

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“…[3,[10][11][12][13][14][15] The most noticeable characteristic of these poly(bibenzoates) with ether groups in the spacer is the considerable decrease of the rate of the mesophase-crystal transformation. Regarding the behaviour of PBs with oxyethylene spacers, it has been reported [3,12,13,16 -18] that the number of oxyethylene units in the spacer clearly affects the phase behaviour in several ways.…”

Section: Introductionmentioning

confidence: 99%

Synchrotron X‐ray and DSC Studies of the Phase Behaviour of Poly(diethylene glycol p,p′‐bibenzoate)

Pérez

Benavente

Cerrada

et al. 2003

Macro Chemistry & Physics

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Time‐resolved synchrotron X‐ray and DSC experiments were applied to investigate the phase behaviour of poly(diethylene glycol p,p′‐bibenzoate), PDEB. The DSC results are indicative of the formation of a smectic mesophase, previously identified as a SmCA type, which can be easily quenched down to room temperature. However, the synchrotron results show that the SmCA phase undergoes some kind of ordering or transformation at temperatures below 110 °C. Moreover, the annealing of PDEB at temperatures above Tg for sufficiently long times leads to the formation of a highly ordered structure, although very thin crystals and low crystallinities are obtained.Scattering profiles corresponding to sample PDEB85 in a melting experiment.magnified imageScattering profiles corresponding to sample PDEB85 in a melting experiment.

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Thermotropic properties and conformational studies on poly(triethylene glycol p,p'-bibenzoate) and poly(octamethylene p,p'-bibenzoate)

Cited by 54 publications

References 4 publications

Phase Behaviour of New Side‐Chain Liquid Crystalline Polyoxetanes

Phase Behaviour of New Side‐Chain Liquid Crystalline Polyoxetanes

Synthesis and structural studies of poly(tetramethyleneoxypropylene p, p´-bibenzoate)

Synchrotron X‐ray and DSC Studies of the Phase Behaviour of Poly(diethylene glycol p,p′‐bibenzoate)

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