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Special Issue "Liquid Crystalline Polymers"

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A special issue of Polymers (ISSN 2073-4360).

Deadline for manuscript submissions: closed (30 November 2011)

Special Issue Editor

Guest Editor
Dr. Patrick Keller

Institut Curie-Centre De Recherche, CNRS UMR 168, 26 rue d\'Ulm 75248 Paris Cedex 05, France
Website | E-Mail
Interests: liquid crystalline polymers and elastomers; biomimetic responsive surfaces; self-assembly; amphiphilic block copolymers; actuators

Special Issue Information

Dear Colleagues,

Classically, liquid crystalline polymers (LCPs) have been divided in lyotropic LCPs and thermotropic LCPs. Over the years, we have noticed a marked shift in the development of new LCPs, based on new potential applications in domains like actuators, organic photovoltaic or renewable energy. Beside historical families of LCPs (main-chain, side-chain, side-on, combined), new macromolecular architectures have been explored like liquid crystalline elastomers, dendritic LCPs or block copolymers. This special issue aims to provide a channel to showcase the recent developments in liquid crystalline polymer domain: synthesis, characterization, physical properties and applications.

Dr. Patrick Keller
Guest Editor

Keywords

  • main-chain LCP
  • side-chain LCP
  • jacketed LCP
  • LC elastomer
  • dendritic LCP
  • actuator
  • azo polymer
  • smart materials

Published Papers (9 papers)

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Research

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Open AccessArticle Richness of Side-Chain Liquid-Crystal Polymers: From Isotropic Phase towards the Identification of Neglected Solid-Like Properties in Liquids
Polymers 2012, 4(2), 1109-1124; doi:10.3390/polym4021109
Received: 6 March 2012 / Revised: 1 April 2012 / Accepted: 20 April 2012 / Published: 25 April 2012
Cited by 2 | PDF Full-text (393 KB) | HTML Full-text | XML Full-text
Abstract
Very few studies concern the isotropic phase of Side-Chain Liquid-Crystalline Polymers (SCLCPs). However, the interest for the isotropic phase appears particularly obvious in flow experiments. Unforeseen shear-induced nematic phases are revealed away from the N-I transition temperature. The non-equilibrium nematic phase in the
[...] Read more.
Very few studies concern the isotropic phase of Side-Chain Liquid-Crystalline Polymers (SCLCPs). However, the interest for the isotropic phase appears particularly obvious in flow experiments. Unforeseen shear-induced nematic phases are revealed away from the N-I transition temperature. The non-equilibrium nematic phase in the isotropic phase of SCLCP melts challenges the conventional timescales described in theoretical approaches and reveal very long timescales, neglected until now. This spectacular behavior is the starter of the present survey that reveals long range solid-like interactions up to the sub-millimetre scale. We address the question of the origin of this solid-like property by probing more particularly the non-equilibrium behavior of a polyacrylate substituted by a nitrobiphenyl group (PANO2). The comparison with a polybutylacrylate chain of the same degree of polymerization evidences that the solid-like response is exacerbated in SCLCPs. We conclude that the liquid crystal moieties interplay as efficient elastic connectors. Finally, we show that the “solid” character can be evidenced away from the glass transition temperature in glass formers and for the first time, in purely alkane chains above their crystallization temperature. We thus have probed collective elastic effects contained not only in the isotropic phase of SCLCPs, but also more generically in the liquid state of ordinary melts and of ordinary liquids. Full article
(This article belongs to the Special Issue Liquid Crystalline Polymers)
Open AccessArticle In Situ and Ex Situ Syntheses of Magnetic Liquid Crystalline Materials: A Comparison
Polymers 2012, 4(1), 448-462; doi:10.3390/polym4010448
Received: 19 December 2011 / Revised: 30 January 2012 / Accepted: 31 January 2012 / Published: 10 February 2012
Cited by 4 | PDF Full-text (694 KB) | HTML Full-text | XML Full-text
Abstract
Magnetic hybrid liquid crystalline composites have been obtained either by thermal decomposition of a cobalt precursor in a solution containing a liquid crystal polymer or by dispersing preformed cobalt nanorods in a liquid crystal polymer matrix. The final materials are all mesomorphous and
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Magnetic hybrid liquid crystalline composites have been obtained either by thermal decomposition of a cobalt precursor in a solution containing a liquid crystal polymer or by dispersing preformed cobalt nanorods in a liquid crystal polymer matrix. The final materials are all mesomorphous and ferromagnetic. Their magnetic characteristics are compared as a function of the synthesis method. Full article
(This article belongs to the Special Issue Liquid Crystalline Polymers)
Open AccessArticle Photomechanical Response of Composite Structures Built from Azobenzene Liquid Crystal Polymer Networks
Polymers 2011, 3(3), 1447-1457; doi:10.3390/polym3031447
Received: 1 August 2011 / Revised: 19 August 2011 / Accepted: 30 August 2011 / Published: 2 September 2011
Cited by 10 | PDF Full-text (997 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Optically directed shape adaptive responses have been sought after for many decades in photoresponsive polymeric materials. A number of recent examinations have elucidated elucidated the unique opportunities of photomechanical responses realized in azobenzene-functionalized liquid crystalline polymer networks (both elastomers and glasses). This work
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Optically directed shape adaptive responses have been sought after for many decades in photoresponsive polymeric materials. A number of recent examinations have elucidated elucidated the unique opportunities of photomechanical responses realized in azobenzene-functionalized liquid crystalline polymer networks (both elastomers and glasses). This work summarizes and contrasts the photomechanical response of glassy polydomain, monodomain, and twisted nematic azo-LCN materials to blue-green irradiation. Building from this summary, the combinatorial photomechanical response observed upon irradiation of composite cantilevers is examined. Large scale shape adaptations are realized, with novel responses that may be of potential use in future employment of these materials in actuation. Full article
(This article belongs to the Special Issue Liquid Crystalline Polymers)
Open AccessArticle Polarized Emission of Wholly Aromatic Bio-Based Copolyesters of a Liquid Crystalline Nature
Polymers 2011, 3(2), 861-874; doi:10.3390/polym3020861
Received: 31 March 2011 / Revised: 3 May 2011 / Accepted: 12 May 2011 / Published: 16 May 2011
Cited by 3 | PDF Full-text (714 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A novel thermotropic liquid crystalline polymers poly{3-benzylidene amino-4-hydroxybenzoic acid (3,4-BAHBA)-co-trans-4-hydroxycinnamic acid (4HCA: trans-coumaric acid)} (Poly(3,4-BAHBA-co-4HCA)), was synthesized by the thermal polycondensation of 4HCA and 3,4-BAHBA, which was synthesized by a reaction of 3-amino-4-hydroxybenzoic acid (3,4-AHBA) with benzaldehyde. When
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A novel thermotropic liquid crystalline polymers poly{3-benzylidene amino-4-hydroxybenzoic acid (3,4-BAHBA)-co-trans-4-hydroxycinnamic acid (4HCA: trans-coumaric acid)} (Poly(3,4-BAHBA-co-4HCA)), was synthesized by the thermal polycondensation of 4HCA and 3,4-BAHBA, which was synthesized by a reaction of 3-amino-4-hydroxybenzoic acid (3,4-AHBA) with benzaldehyde. When the 4HCA compositions of Poly(3,4-BAHBA-co-4HCA)s were above 55 mol%, the copolymers showed a nematic, liquid crystalline phase. Differential scanning calorimetry (DSC) measurements of the copolymers showed a high glass transition temperature of more than 100 °C, sufficient for use in engineering plastics. Furthermore, the copolymers showed photoluminescence in an N-methylpyrrolidone (NMP) solution under ultraviolet (UV) light with a wavelength of 365 nm. Oriented film of Poly(3,4-BAHBA-co-4HCA) with a 4HCA composition of 75 mol% emitted polarized light, which was confirmed by fluorescent spectroscopy equipped with parallel and crossed polarizers. Full article
(This article belongs to the Special Issue Liquid Crystalline Polymers)
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Open AccessArticle Mechanism Studies of LCP Synthesis
Polymers 2011, 3(2), 833-845; doi:10.3390/polym3020833
Received: 15 February 2011 / Revised: 24 March 2011 / Accepted: 22 April 2011 / Published: 4 May 2011
Cited by 3 | PDF Full-text (353 KB) | HTML Full-text | XML Full-text
Abstract
The LCP (Liquid Crystal Polymer) known as Vectra is synthesized by acidolysis of 4-hydroxybenzoic acid with 6-hydroxy-2-naphthoic acid. The apparently simple acidolysis mechanism for LCP polycondensation is in fact a complex blend of mechanisms. Kinetics of model reactions and of actual polycondensations followed
[...] Read more.
The LCP (Liquid Crystal Polymer) known as Vectra is synthesized by acidolysis of 4-hydroxybenzoic acid with 6-hydroxy-2-naphthoic acid. The apparently simple acidolysis mechanism for LCP polycondensation is in fact a complex blend of mechanisms. Kinetics of model reactions and of actual polycondensations followed second-order kinetics and their rate constants were comparable. In the latter stages, ketene loss leads to phenolic ends, while decarboxylation provides phenyl ester ends. Accordingly, the mechanism changes to phenolysis. A quinone methide intermediate may also intervene, as revealed by kinetics studies and MALDI-TOF spectroscopy. Tailor-made matrices and synthesis of alternating well-defined oligomers assisted our studies. Nucleophilic aromatic substitutions may play a role, and we speculate on possible chain polycondensation. Esterolysis may be a useful alternative to LCP synthesis. Complications caused by ketene loss can be averted by the use of methoxycarbonyloxy monomers. Full article
(This article belongs to the Special Issue Liquid Crystalline Polymers)
Open AccessArticle Structural Analysis of Aromatic Liquid Crystalline Polyesters
Polymers 2011, 3(1), 367-387; doi:10.3390/polym3010367
Received: 21 December 2010 / Revised: 13 January 2011 / Accepted: 20 January 2011 / Published: 27 January 2011
Cited by 2 | PDF Full-text (665 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Laboratory preparations of liquid crystalline prepolymers, distillates accompanying prepolymers, final polymers, and sublimates accompanying final polymers were examined. NaOD/D2O depolymerization of prepolymers and polymers back to monomers with integration of the 1H NMR spectra showed up to 6% excess of
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Laboratory preparations of liquid crystalline prepolymers, distillates accompanying prepolymers, final polymers, and sublimates accompanying final polymers were examined. NaOD/D2O depolymerization of prepolymers and polymers back to monomers with integration of the 1H NMR spectra showed up to 6% excess of carboxyls over phenol groups, caused partly by loss of the low-boiling comonomer hydroquinone through distillation during prepolymerization and leaving anhydride units in the polymer chain. ESI MS and MS/MS of hexafluoroisopropanol extracts of the prepolymer detected small molecules including some containing anhydride groups; ESI+ MS showed the presence of small cyclic oligomers. 1H NMR (including TOCSY) spectra provided more quantitative analyses of these oligomers. The final polymerization increases the length of the polymer chains and sublimes out the small oligomers. Anhydride linkages remaining in the polymer must make LCP’s more susceptible to degradation by nucleophilic reagents such as water, alkalis, and amines. Full article
(This article belongs to the Special Issue Liquid Crystalline Polymers)
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Review

Jump to: Research

Open AccessReview Current Advances in the Carbon Nanotube/Thermotropic Main-Chain Liquid Crystalline Polymer Nanocomposites and Their Blends
Polymers 2012, 4(2), 889-912; doi:10.3390/polym4020889
Received: 10 January 2012 / Revised: 12 March 2012 / Accepted: 14 March 2012 / Published: 23 March 2012
Cited by 13 | PDF Full-text (1372 KB) | HTML Full-text | XML Full-text
Abstract
Because of their extraordinary properties, such as high thermal stability, flame retardant, high chemical resistance and high mechanical strength, thermotropic liquid crystalline polymers (TLCPs) have recently gained more attention while being useful for many applications which require chemical inertness and high strength. Due
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Because of their extraordinary properties, such as high thermal stability, flame retardant, high chemical resistance and high mechanical strength, thermotropic liquid crystalline polymers (TLCPs) have recently gained more attention while being useful for many applications which require chemical inertness and high strength. Due to the recent advance in nanotechnology, TLCPs are usually compounded with nanoparticles to form particulate composites to enhance their properties, such as barrier properties, electrical properties, mechanical properties and thermal properties. Carbon-based nanofillers such as carbon nanotube (CNT), graphene and graphene oxide are the most common fillers used for the TLCP matrices. In this review, we focus on recent advances in thermotropic main-chain liquid crystalline polymer nanocomposites incorporated with CNTs. However, the biggest challenges in the preparation of CNT/TLCP nanocomposites have been shown to be inherent in the dispersion of CNTs into the TLCP matrix, the alignment and control of CNTs in the TLCP matrix and the load-transfer between the TLCP matrix and CNTs. As a result, this paper reviews recent advances in CNT/TLCP nanocomposites through enhanced dispersion of CNTs in TLCPs as well as their improved interfacial adhesion with the TLCP matrices. Case studies on the important role of chemically modified CNTs in the TLCP/thermoplastic polymer blends are also included. Full article
(This article belongs to the Special Issue Liquid Crystalline Polymers)
Open AccessReview Nanoparticle-Liquid Crystalline Elastomer Composites
Polymers 2012, 4(1), 316-340; doi:10.3390/polym4010316
Received: 30 November 2011 / Revised: 10 January 2012 / Accepted: 14 January 2012 / Published: 30 January 2012
Cited by 26 | PDF Full-text (821 KB) | HTML Full-text | XML Full-text
Abstract
Liquid crystalline elastomers (LCEs) exhibit a number of remarkable physical effects, including a uniquely high-stroke reversible mechanical actuation triggered by external stimuli. Fundamentally, all such stimuli affect the degree of liquid crystalline order in the polymer chains cross-linked into an elastic network. Heat
[...] Read more.
Liquid crystalline elastomers (LCEs) exhibit a number of remarkable physical effects, including a uniquely high-stroke reversible mechanical actuation triggered by external stimuli. Fundamentally, all such stimuli affect the degree of liquid crystalline order in the polymer chains cross-linked into an elastic network. Heat and the resulting thermal actuation act by promoting entropic disorder, as does the addition of solvents. Photo-isomerization is another mechanism of actuation, reducing the orientational order by diminishing the fraction of active rod-like mesogenic units, mostly studied for azobenzene derivatives incorporated into the LCE composition. Embedding nanoparticles provides a new, promising strategy to add functionality to LCEs and ultimately enhance their performance as sensors and actuators. The motivation for the combination of nanoparticles with LCEs is to provide better-controlled actuation stimuli, such as electric and magnetic fields, and broad-spectrum light, by selecting and configuring the appropriate nanoparticles in the LCE matrix. Here we give an overview of recent advances in this area with a focus on preparation, physical properties and actuation performance of the resultant nanocomposites. Full article
(This article belongs to the Special Issue Liquid Crystalline Polymers)
Open AccessReview Optical and Physical Applications of Photocontrollable Materials: Azobenzene-Containing and Liquid Crystalline Polymers
Polymers 2012, 4(1), 150-186; doi:10.3390/polym4010150
Received: 5 December 2011 / Revised: 28 December 2011 / Accepted: 7 January 2012 / Published: 9 January 2012
Cited by 38 | PDF Full-text (996 KB) | HTML Full-text | XML Full-text
Abstract
Photocontrol of molecular alignment is an exceptionally-intelligent and useful strategy. It enables us to control optical coefficients, peripheral molecular alignments, surface relief structure, and actuation of substances by means of photoirradiation. Azobenzene-containing polymers and functionalized liquid crystalline polymers are well-known photocontrollable materials. In
[...] Read more.
Photocontrol of molecular alignment is an exceptionally-intelligent and useful strategy. It enables us to control optical coefficients, peripheral molecular alignments, surface relief structure, and actuation of substances by means of photoirradiation. Azobenzene-containing polymers and functionalized liquid crystalline polymers are well-known photocontrollable materials. In this paper, we introduce recent applications of these materials in the fields of mechanics, self-organized structuring, mass transport, optics, and photonics. The concepts in each application are explained based on the mechanisms of photocontrol. The interesting natures of the photocontrollable materials and the conceptual applications will stimulate novel ideas for future research and development in this field. Full article
(This article belongs to the Special Issue Liquid Crystalline Polymers)

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