1. |
The Slightly-Bending-Rod Model of Nematic Polymers |
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Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals,
Volume 266,
Issue 1,
1995,
Page 1-8
Francesco Greco,
Giuseppe Marrucci,
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摘要:
A simple model for stiff polymers is here proposed to describe the flow behavior in the nematic phase. The model relaxes the usual assumption of a complete rigidity of the rodlike molecule. The dynamical equation is tractable if the molecular bending motion is much faster than rotation of the molecular axis.
ISSN:1058-725X
DOI:10.1080/10587259508033627
出版商:Taylor & Francis Group
年代:1995
数据来源: Taylor
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2. |
Liquid Crystalline Epoxy Thermosets |
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Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals,
Volume 266,
Issue 1,
1995,
Page 9-22
M. Giamberjni,
E. Amendola,
C. Carfagna,
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摘要:
Rigid rod epoxy compounds can be cured in liquid crystalline structure. The so obtained networks exhibit better mechanical properties with respect to the isotropic ones. The mesogenic character of the epoxy compounds appears more crucial than the molecular geometry of the curing agent in developing liquid crystallinity. The curing temperature plays an important role in affecting the state of order of the thermosets.
ISSN:1058-725X
DOI:10.1080/10587259508033628
出版商:Taylor & Francis Group
年代:1995
数据来源: Taylor
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3. |
Miscibility and Liquid Crystal Behaviour of P-Azoxy Anisole in Polymer Blends |
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Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals,
Volume 266,
Issue 1,
1995,
Page 23-33
Mariano Pracella,
Bruno Bresci,
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摘要:
The phase behaviour of two polymer/liquid crystal blends has been investigated by DSC and optical microscopy. In one case, blends of poly(octadecylethylene) (POE) and p-azoxyanisole (PAA) are found almost immiscible below the isotropization temperature of the liquid crystal. The crystallization process of PAA in the blends takes place with a sporadic growth of dendritic structures determined by the dispersion of the nematic phase in the molten polymer. In the other case, blends of poly(biphenylyloxyexylacrylate) (PBHA) and PAA display a different phase behaviour indicating partial miscibility of the two components at temperatures above the melting point of the polymer. At high concentrations of PAA a nematic phase dispersed in a isotropic liquid mixture of polymer and liquid crystal is observed. These results are accounted for by the different side-chain structure of the polymer components.
ISSN:1058-725X
DOI:10.1080/10587259508033629
出版商:Taylor & Francis Group
年代:1995
数据来源: Taylor
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4. |
Characterization of Phthalocyanine Langmuir-Blodgett Films by Optical Dichroism and Resonance Raman Scattering |
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Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals,
Volume 266,
Issue 1,
1995,
Page 35-45
R. Capelletti,
M.P. Fontana,
C.A. Nicolae,
R. Paradiso,
R. Bonnett,
R.F. Wilkins,
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摘要:
In this Paper we report optical dichroism and polarized resonance Raman scattering measurements on Langmuir-Blodgett layers of tetra tertiary butyl monosulphonic acid of phthalocyanine (tBPcSA). These measurements were performed to determine molecular alignment and local ordering in our samples, using surface enhanced optical and Raman spectroscopy. Thus our L-B layers were deposited on rough thin (50 Å) Ag island films. We found that the surface enhancement effects dominated the optical behaviour of our samples, making it more difficult to extract the desired information on molecular orientation. At the same time, we found that tBPcSA L-B layers can be a good system to study resonance effects and to test the reliability of the structural information obtainable by optical spectroscopic techniques.
ISSN:1058-725X
DOI:10.1080/10587259508033630
出版商:Taylor & Francis Group
年代:1995
数据来源: Taylor
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5. |
Main Chain Order and Dynamics in a Liquid Crystalline Side-Group Polymer |
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Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals,
Volume 266,
Issue 1,
1995,
Page 47-58
Guido Germano,
CarloAlberto Veracini,
Christine Boeffel,
HansWolfgang Spiess,
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摘要:
The orientational distribution function for the C-CD3bond on the perdeuterated polymethacrylate chain of a liquid-crystalline side group polymer was determined in the frozen SAphase by solid-state2H NMR. The results are compared with the ones of two similar systems recently reported. The slow chain dynamics above the glass transition was studied via 2D2H NMR, which indicates a diffusive motion constrained by the partial orientational order of the mesophase.
ISSN:1058-725X
DOI:10.1080/10587259508033631
出版商:Taylor & Francis Group
年代:1995
数据来源: Taylor
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6. |
The Nucleating Effect of a Semiflexible Liquid-Crystalline Polymer for the Crystallization of Poly(Phenylene Sulfide) |
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Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals,
Volume 266,
Issue 1,
1995,
Page 59-72
Massimo Paci,
Perluigi Magagnini,
Ugo Pedretii,
Arnaldo Roggero,
FrancescoP.La Mantia,
LiliaI. Minkova,
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摘要:
Blends of poly(phenylene sulfide) and a semiflexible liquid-crystalline polymer have been prepared, in the whole range of concentration, by melt mixing. The effect of the LCP phase on the crystallization of PPS has been studied by non-isothermal and isothermal calorimetry. It has been found that the addition of only 2-5% LCP into PPS strongly increases the crystallization rate of the latter polymer. This effect has been interpreted as the result of an increased nucleation density. The morphology of the blends, studied by scanning electron microscopy, has shown that the two polymers are incompatible, although the phase dispersion is good. Under elongational flow, the dispersed phase shows a distinct tendency toward fibrillation.
ISSN:1058-725X
DOI:10.1080/10587259508033632
出版商:Taylor & Francis Group
年代:1995
数据来源: Taylor
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7. |
Microscopic and Collective Dynamics in Supercooled Polymeric Liquid Crystals: Dependence on the Thermal History |
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Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals,
Volume 266,
Issue 1,
1995,
Page 73-83
L. Andreozzi,
E. Chiellini,
M. Giordano,
D. Leporini,
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摘要:
The reorientation process of a probe molecule in a supercooled polymeric liquid crystal has been studied by non linear Electron Spin Resonance. The temperature dependence of the correlation time of the spinning motion of the probe τ∥and the collective viscoelastic relaxation, as given by dynamic-mechanical measurements, have been compared. In amorphous samples the Williams-Landel-Ferry law is observed, which in annealed samples is replaced by a dual Arrhenius law broken at the glass transition. A scaling law τ∥∝ ηξ, η being the polymer viscosity, is found in both amorphous (ξ = 4.7 10−2± 2.8 10−3) and partly crystalline samples (ξ = 5.9 10−2± 6.5 10−3).
ISSN:1058-725X
DOI:10.1080/10587259508033633
出版商:Taylor & Francis Group
年代:1995
数据来源: Taylor
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8. |
Intermittency at the DSM1-DSM2 Transition in Nematic Liquid Crystal Films |
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Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals,
Volume 266,
Issue 1,
1995,
Page 85-98
N. Scaramuzza,
C. Versace,
V. Carbone,
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摘要:
In this letter we report on the turbulence to turbulence transition, which occurs in a homogeneously oriented nematic liquid crystal (NLC) film under the action of an external alternate voltage. Our observation show that the transition is characterized by a NLC-substrate anchoring breaking, which results in the on set of the twist distortion of the molecular director field. We give the characterization of the different dynamic regimes in terms of the probability distribution functions (PDF's) of the director field curvature energy. The PDF's, which are undoubtedly non-gaussian, indicate that, in both turbulent regimes, the curvature energy is highly intermittent.
ISSN:1058-725X
DOI:10.1080/10587259508033634
出版商:Taylor & Francis Group
年代:1995
数据来源: Taylor
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9. |
Liquid Crystalline Behaviour of Polymer Networks Based on Segmented Chain Mesogenic Polymers |
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Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals,
Volume 266,
Issue 1,
1995,
Page 99-109
Gabriele Aurino,
Ugo Caruso,
Stefania Pragliola,
Antonio Roviello,
Augusto Sirigu,
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摘要:
The synthesis of some crosslinked polymers based on a segmented-chain polymeric mesogen containing variable amounts of a side chain substituent is reported. The unswollen networks show thermotropic mesomorphism of nematic character whose stability decreases with increasing substitution and crosslink density. Depending on the same parameters, the swollen networks may show optical anisotropy at room temperature whose origin is attributed to phase separation
ISSN:1058-725X
DOI:10.1080/10587259508033635
出版商:Taylor & Francis Group
年代:1995
数据来源: Taylor
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10. |
Cholesteric Textures of Aqueous Hydroxypropylcellulose Solutions |
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Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals,
Volume 266,
Issue 1,
1995,
Page 111-119
S. Guido,
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摘要:
Liquid crystalline textures exhibited by aqueous solutions of hydroxypropylcellulose were investigated by video-enhanced contrast polarized light microscopy. For the first time in this particular system, typical cholesteric structures, such as oily streaks and fingerprint lines, were resolved in close detail by light microscopy. Biphasic separation was observed even in samples of concentration well above the critical value generally accepted for mesophase formation at room temperature (∼40% wt). The dependence of the helical pitch on polymer concentration was also studied, by Fourier transforming images of the cholesteric textures.
ISSN:1058-725X
DOI:10.1080/10587259508033636
出版商:Taylor & Francis Group
年代:1995
数据来源: Taylor
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