Combined main chain/side chain polymers. A new class of liquid crystalline polymers with unusual structural, thermodynamic and dynamic properties

Endres, B.; Ebert, Martina; Wendorff, Joachim H.; Reck, Bernd; Ringsdorf, Helmut

doi:10.1080/02678299008029209

Cited by 57 publications

(32 citation statements)

References 28 publications

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“…This kind of defect structure has also been reported for sterically asymmetric nonpolar LCs [12] and for comb-like LC-polymers. [13] The correlation length was calculated from the FWHM of the small angle reflex to be j % 400 Å . This value corresponds to only 10 correlated layers, a number which verifies the highly distorted state of the smectic structure.…”

Section: Characterisationmentioning

confidence: 99%

Breakdown of Layering in Frustrated Smectic‐A Elastomers

Kramer

Finkelmann

2007

Macromol. Rapid Commun.

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Smectic‐A elastomers combine the positional long‐range order of mesogenic molecules in one dimension with the rubber elasticity of a polymer network. Upon mechanical deformation, completely different responses of the phase structure have been reported. We present a highly distorted system which shows a breakdown of smectic layering but no reorientation under deformation along the layer normal, while the phase structure stays unaffected under uniaxial stress in the perpendicular direction. The thermoelastic properties, macroscopic dimensions and stress–strain behaviour are investigated parallel and perpendicular to the layer normal. SAXS measurements supply evidence for a breakdown of the macroscopically ordered layer structure indicated by the small angle intensities and correlation length, whereas the orientational order is preserved. We propose defects in the smectic layer structure to be the origin of the different responses of different smectic elastomers.magnified image

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Section: Characterisationmentioning

confidence: 99%

Breakdown of Layering in Frustrated Smectic‐A Elastomers

Kramer

Finkelmann

2007

Macromol. Rapid Commun.

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“…It has been reported that multiple-step process from smectic to isotropic transitions occurs in combined-type polymalonates having the methoxyazobenzene unit by Ringsdorf et al 2,21 In very recent years, polyketones bearing side-chain azobenzene unit were disclosed to Relationships between Structures and Liquid Crystalline and Optical Properties in Combined-type Copolyisophthalates form smectic LC phase. 29 In this way, many sidechain or combined-type polymers having the azobenzene moieties exhibit smectic phases.…”

Section: Mesomorphic Propertiesmentioning

confidence: 99%

“…1 The combined-type polymers, which have calamitic mesogens such as biphenyl, diphenyls and azobenzenes both in the side and the main chains, tend to have broader LC temperature ranges of mesophases than the parent main-chain and side-chain polymers and to show nematic phase together with smectic phases owing to the synergy effect of mesogens in the side and the main chains. 2 Researches on the combined-type LC polymers are still not adequate, 3 although a number of literatures on chemical and physical properties of main-chain and side-chain LC polymers have been reported. 4,5 On the other hand, side-chain azobenzene-containing polymers have attracted much attention because of potentials as polymers for photonics applications [7][8][9][10][11][12][13][14][15][16] in addition to LC properties.…”

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confidence: 99%

Relationships between Structures and Liquid Crystalline and Optical Properties in Combined-type Copolyisophthalates Having Nitro- and Methoxyazobenzene Units and Aliphatic Spacers in the Side Chain

Sato

Mizoi

2004

Polym J

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ABSTRACT:Combined-type thermotropic liquid crystalline (LC) homo-and copolyisophthalates having nitroand methoxyazobenzene units and three aliphatic spacers (hexamethylene, octamethylene and decamethylene) in the side chain and biphenyl unit in the main chain were prepared by melt polycondensation and relationships between polymer structures and LC and optical properties were discussed. Differential scanning calorimetry (DSC) measurements, optical texture observations using polarizing microscopy and powder X-Ray analyses indicated that the homopolyisophtalates with the nitroazobenzene unit form highly ordered smectic E phase and the other homo-and copolymers show less ordered smectic B or smectic C phase. The temperature ranges of smectic LC phases in the polymers decreased with increasing the methoxyazobenzene content. In these polymers, specific interaction such as electron donor-acceptor interaction between the nitro-and the methoxyazobenzene units plays no role in the formation and the stabilization of smectic LC phases. All the polymers displayed UV-vis absorption peak maxima on the basis of the azobenzenes or the biphenyl in solutions and in films, but no fluorescent properties were found, probably due to intraand intermolecular quenching. [DOI 10.1295/polymj.36.607] KEY WORDS Combined-type Polyisophthalate / Melt Polycondensation / Liquid Crystalline Property / Optical Property / Azobenzene / Biphenyl / Differential Scanning Calorimetry / Smectic Phase / It is well known that there are three types of polymers in thermotropic liquid crystalline (LC) polymers: (1) main-chain polymers, (2) side-chain polymers and (3) combined-type polymers.1 The combined-type polymers, which have calamitic mesogens such as biphenyl, diphenyls and azobenzenes both in the side and the main chains, tend to have broader LC temperature ranges of mesophases than the parent main-chain and side-chain polymers and to show nematic phase together with smectic phases owing to the synergy effect of mesogens in the side and the main chains.2 Researches on the combined-type LC polymers are still not adequate, 3 although a number of literatures on chemical and physical properties of main-chain and side-chain LC polymers have been reported. 4,5 On the other hand, side-chain azobenzene-containing polymers have attracted much attention because of potentials as polymers for photonics applications 7-16 in addition to LC properties. 4,17 The azobenzene derivatives have been known for displaying no photoluminescence (PL), but it has been found that the azobenzene derivatives 18 and poly(p-phenylenevinylene)s (PPV) 19 having side-chain methoxyazobenzene unit emit PL light, having very low quantum yields. 18 Our previous paper 20 has described that novel combined-type semi-rigid homopolyisophthalates having biphenyl or 2,5-diphenyl-1,3,4-thiadiazole (DTD) unit in the main chains and azobenzene moieties in the side chains are synthesized by melt polycondensation and that most of them form stable smectic LC (B, C and E) phases without showing nema...

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“…[1][2][3][4][5][6][7][8][9] In the past, many MCSCLCPs have been synthesized, and the relationship between LC behavior and structural variations has been investigated. [10][11][12][13][14][15][16][17][18][19] Generally, MCSCLCPs can be classified into two kinds according to the constitution of the backbone: one is of a nonrigid nature containing some flexible spacers, 1,3,8,11,[20][21][22][23][24] and the other is of a rigid nature without any flexible spacers.…”

Section: Introductionmentioning

confidence: 99%

Effect of flexible spacer length on the mesophase structures of main-chain/side-chain liquid crystalline polymers based on ethyl cellulose

Xiao

et al. 2010

Polym J

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Main-chain/side-chain liquid crystalline polymers (MCSCLCPs) based on ethyl cellulose (AzomEC, m¼2,4,6, where m is the length of the spacer between the main chain and mesogens) were successfully synthesized by N,N¢-dicylcohexylcarbodiimide (DCC) coupling. Molecular characterizations of the resultant polymers with different spacer lengths were performed by proton nuclear magnetic resonance, Fourier transform-infrared spectroscopy and gel permeation chromatography. The phase transitions and liquid crystalline (LC) behaviors of these polymers were investigated by differential scanning calorimetry, polarized optical microscopy and wide-angle X-ray diffraction. The results indicate that spacer length has a tremendous effect on the LC behavior of the polymer. The glass transition temperatures, phase transition temperatures and the corresponding enthalpy of transitions decreased as the flexible spacer length increased. The mesophase structures of polymers consisted of a large-scale ordered lamellar structure composed of the EC main chain and a relatively small-scale ordered structure formed by azobenzene side chains. All the polymers form a similar lamellar structure on a large scale; however, the small-scale ordered structure becomes relatively disordered, that is, from crystal (m¼2) to smectic B (m¼4) to smectic A (m¼6) at low temperatures.

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Combined main chain/side chain polymers. A new class of liquid crystalline polymers with unusual structural, thermodynamic and dynamic properties

Cited by 57 publications

References 28 publications

Breakdown of Layering in Frustrated Smectic‐A Elastomers

Breakdown of Layering in Frustrated Smectic‐A Elastomers

Relationships between Structures and Liquid Crystalline and Optical Properties in Combined-type Copolyisophthalates Having Nitro- and Methoxyazobenzene Units and Aliphatic Spacers in the Side Chain

Effect of flexible spacer length on the mesophase structures of main-chain/side-chain liquid crystalline polymers based on ethyl cellulose

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