Mesogen-jacketed Liquid Crystal Polymers Research Articles

Helical columnar phase of mesogen-jacketed liquid crystal polymers for efficient circularly polarized luminescence

A copolymerization strategy for preparing mesogen-jacketed liquid crystal polymers with stable and good circularly polarized luminescence was developed in this paper.

Synthesis and properties of long-lived room-temperature phosphorescent liquid crystal polymers based on “Jacketing” effect

Polymerization is one of the most widely used strategies to achiever RTP. To date, various polymer-based RTP materials have been reported. However, how to improve the phosphorescence lifetime of polymer-based RTP materials still needs to be further researched. In this article, we proposed a new strategy to realize long-lived room-temperature phosphorescence by utilizing the “jacketing” effect of mesogen-jacketed liquid crystal polymers. Two polymers PMJ0DFM and PMJ6DFM with different flexible spacer length were synthesized, and their liquid crystal phase structures and photo-physical properties were systematically investigated. PMJ0DFM formed columnar nematic phase while PMJ6DFM formed a more ordered hexagonal columnar phase liquid crystal. For PMJ0DFM without spacer length, due to the strong “Jacketing” effect, the thermal motion of the chromophore was suppressed, and it was also more conducive to the aggregation and planarization of the chromophores. Therefore, PMJ0DFM film showed longer phosphorescence lifetime and more red-shifted phosphorescence spectrum than PMJ6DFM film. The phosphorescence lifetimes of PMJ0DFM and PMJ6DFM were 355 ms and 247 ms, respectively. In addition, we also explored their application in linearly polarized luminescent materials. When oriented, PMJ0DFM and PMJ6DFM film could emit efficient linearly polarized room temperature phosphorescence.

Recent progress of functional mesogen-jacketed liquid crystal polymers

Recent progress of functional mesogen-jacketed liquid crystal polymers

Steric hindrance effect on thermo-responsive behaviors of well-defined water-soluble semi-rigid polymers

Three series of water-soluble semi-rigid thermo-responsive polymers with well-defined molecular weights based on mesogen-jacketed liquid crystal polymers, poly[bis(N-(2-hydroxypropyl) pyrrolidone) 2-vinylterephthalate] [P(2-HPPVTA)], poly[bis(N-(1-methyl-2-hydroxyethyl) pyrrolidone) 2-vinylterephthalate] [P(1-M-2-HEPVTA)] and poly[bis(N-hydroxypropyl pyrrolidone) 2-vinylterephthalate] (PHPPVTA) have been synthesized via reversible addition-fragmentation chain transfer polymerization. The steric hindrance effects on liquid crystalline property and thermo-responsive behaviors of semi-rigid water-soluble polymers (P(2-HPPVTA), P(1-M-2-HEPVTA), and PHPPVTA) were carefully investigated. From molecular structure, the steric hindrance of P(1-M-2-HEPVTA) is stronger than that of P(2-HPPVTA). Polarized light microscope and one-dimensional wide-angle X-ray diffraction revealed that both the P(2-HPPVTA) and P(1-M-2-HEPVTA) display a columnar nematic phase, indicating that the steric hindrance effect do not affect liquid crystalline behavior of the polymers. The dynamic light scattering results demonstrated that P(1-M-2-HEPVTA) exhibited lower cloud point compared with that of P(2-HPPVTA) at the same mass concentration and the same molecular weight. The more significant molecular weight and concentration dependence on cloud point have been observed in P(2-HPPVTA) solution than in P(1-M-2-HEPVTA) solution. We also discovered that the cloud points of both P(2-HPPVTA) and P(1-M-2-HEPVTA) solution are lower in D2O than in H2O. It is noted that the cloud point of PM-2 is 9.9 °C lower in D2O than in H2O, much less pronounced than the cloud point difference of PH-2. The differences of thermo-responsive behaviors between P(2-HPPVTA) and P(1-M-2-HEPVTA) were resulted from the steric hindrance effect existed in their side groups. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3429–3438

Unusual effect of molecular weight and concentration on thermoresponsive behaviors of well‐defined water‐soluble semirigid polymers

AbstractA series of water‐soluble semirigid thermoresponsive polymers with well‐defined molecular weights based on mesogen‐jacketed liquid crystal polymers (MJLCPs), poly[bis(N‐hydroxyisopropyl pyrrolidone) 2‐vinylterephthalate] (PHIPPVTA) have been synthesized via reversible addition fragmentation chain transfer (RAFT) polymerization. Dynamic light scattering (DLS) revealed that the novel monomer and polymers have thermoresponsive properties with cloud point in the range between 10 and 90 °C. The cloud point was increased by 56.2 °C when the polymer molecular weight increased from 0.47 × 104 g mol−1 to 3.69 × 104 g mol−1. In addition, the cloud point of PHIPPVTA was decreased by 18.8 °C with the increase of polymer concentration from 5 to 10 mg mL−1. A slight increase (0.1–3.5 °C) of cloud point has been observed after knocking off the end‐groups of PHIPPVTA. Moreover, the cloud point of polymer increased with increasing of its molecular weight with or without the trithiocarbonate end‐groups, which showed the opposite trend comparing with other thermoresponsive polymers with flexible backbones. These polymers show a dramatic solvent isotopic effect that the cloud point in D2O was lower than in H2O. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Synthesis and phase behaviour of a poly{2,5-bis[(p-ethoxyphenoxy) carbonyl] benzyl acrylate}-based mesogen-jacketed liquid crystalline copolymer

Mesogen-jacketed liquid crystal polymers have attracted considerable interest in recent years. In this paper, a series of poly (PEPCS)-based mesogen-jacketed liquid crystal copolymers (MJLCPs) with a different 4-hydroxybutyl acrylate (HEA) content has been synthesised and characterised using Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC) and polarising optical microscopy (POM). The hydroxyl groups are attached to the backbone in the PEPCS-co-HEA copolymers to facilitate further chemical crosslinking. These PEPCS-based MJLCPs show a reversible phase transition when the HEA content is lower than 30 wt%. Tg and Ti shift to lower temperatures as the HEA content increases. POM studies reveal that the PEPCS and PEPCS-co-HEA copolymers all show a transition from the nematic to isotropic phase on heating and from the isotropic to nematic phase on cooling. Below Tg , the long range orientational ordering of the mesogenic units is fixed.

Novel semirigid water-soluble thermoresponsive polymers based on mesogen-jacketed liquid crystal polymers

Two novel semirigid smart polymers based on mesogen-jacketed liquid crystal polymers were successfully synthesized via free radical polymerization, which showed both characteristic liquid crystal properties of mesogen-jacketed liquid crystal polymers and remarkably reversible thermoresponsive phase transition behaviors.

SHAPE MEMROY EFFECT OF MESOGEN-JACKEDTED LIQUID CRYSTAL POLYMER FIBER

The shape memory effect of poly2,5-bis[(4-butoxyphenyl)oxycarbonyl]-styrenes(PBPCS),one of the classical mesogen jacketed liquid crystal polymers(MJLCPs),fiber was studied by dynamic mechanical analysis(DMA).According to the results,the outstanding shape recovery ability of PBPCS fiber was found.The reversion rate of PBPCS fiber was improved with the increase of temperature apparently when it was above T_g(106.7℃).Especially when temperature above 145℃,the rate of shape recovery was the best.The time of recovery from 400% draw ratio to origin length was about 9 min.The repeatability of shape memory was good in 5 repeated times.2-Dimensional wide angle X-ray diffraction(2D WAXD)experiments showed the diameter of helical cylindrical blocks changed from 2.5 nm to 2.4 nm after deformation.This result indicated that the helical main-chain of PBPCS was in a more straight conformation.So,there would be a certain inner stress in the molecular chain,namely the shape memory force(F_ sm).It was about 1.6 MPa.There was no stable and memory phase structure of traditional shape memory polymers(SMP)in PBPCS because it was an amorphous polymer.The reason of PBPCS fiber with the shape memory effect is its special helical molecular chain structure just as a spring,say,the flexible polystyrene main chain makes PBPCS fiber present a good strain reversion ability,and the mesogenic effect of side chains makes the fiber keep its original dimension.

Design, synthesis, and characterization of a combined main‐chain/side‐chain liquid crystalline polymer based on mesogen‐jacketed liquid crystal polymer via atom transfer radical polymerization

AbstractA novel combined main‐chain/side‐chain liquid crystalline polymer based on mesogen‐jacketed liquid crystal polymers (MJLCPs) containing two biphenyls per mesogenic core of MJLCPs main chain, poly(2,5‐bis{[6‐(4‐butoxy‐4′‐oxy‐biphenyl)hexyl]oxycarbonyl}styrene) (P1–P8) was successfully synthesized via atom transfer radical polymerization (ATRP). The chemical structure of the monomer was confirmed by elemental analysis, 1H NMR, and 13C NMR. The molecular characterizations of the polymer with different molecular weights (P1–P8) were performed with 1H NMR, gel permeation chromatography (GPC), and thermogravimetric analysis (TGA). Their phase transitions and liquid‐crystalline behaviors of the polymers were investigated by differential scanning calorimetry (DSC) and polarized optical microscope (POM). We found that the polymers P1–P8 exhibited similar behavior with three different liquid crystalline phases upon heating to or cooling in addition to isotropic state, which should be related to the complex liquid crystal property of the side‐chain and the main‐chain. Moreover, the transition temperatures of liquid crystalline phases of P1–P8 are found to be dependent on the molecular weight. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7310–7320, 2008

Synthesis and Characterization of Branched Mesogen-Jacketed Liquid Crystal Polymers Based on 2,5-Bis[(4‘-methoxyphenyl)oxycarbonyl]styrene and 4-Chloromethylstyrene

A series of branched mesogen-jacketed liquid crystal polymers were synthesized via atom transfer radical copolymerization of mesogenic 2,5-bis[(4‘-methoxyphenyl)oxycarbonyl]styrene (MPCS) and nonmesogenic 4-chloromethylstyrene (CMS) catalyzed by the CuCl/CuCl2/bipyridine complex in anisole solution at 110 °C. During the early period of polymerization, CMS acted mainly as an initiator to induce the polymerization of MPCS. The molecular weights (MWs) of the resultant polymers increased linearly with monomer conversion and showed a symmetrical and relatively narrow distribution. With the proceeding of polymerization, MWs changed from monomodal to multimodal distribution, indicating the formation of branched structure through the action of vinyl group of CMS. This mechanism was also supported by the increased chain density estimated by a combination of gel permeation chromatography and laser light scattering, end-group analysis, and the reactivity ratios of two monomers (rMPCS = 0.71, rCMS = 0.10). The thermotropic properties of the copolymers strongly relied on the feed ratio of MPCS to CMS and MW. The feed ratio of MPCS to CMS should be at least 30 with high enough MW. For the copolymer obtained at the feed ratio of 32, the minimum Mn,GPC was 1.21 × 104 Da to achieve a mesophase. Although linear poly{2,5-bis[(4‘-methoxyphenyl)oxycarbonyl]styrene} displayed columnar nematic phase (ΦN) and hexatic columnar nematic phase (ΦHN) depending on MW, the branched polymer showed just a ΦN phase, indicating the remarkable depressing effect of the branched structure on the mesomorphic property.

Restudy of the unusual phase behavior of the mesogen-jacketed liquid crystal polymers

A series of poly{2,5-bis[(4-butoxyphenyl)-oxycarbonyl]styrenes} (PBPCS) with low molecular weight distribution was synthesized by atom transfer radical polymerization (ATRP). The mesomorphic properties were investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and rheometer. PBPCS showed the phase transition from isotropic into liquid crystal (LC) phase, and the LC phase formed at high temperature and disappeared in the subsequent cooling procedure. Using the WAXD fiber pattern, the phase structure of the PBPCS at higher temperature showed hexagonal columnar nematic phase. Experimental results demonstrated that the driving force of the entropy is an important factor during the unusual LC phase formation of PBPCS.

Influence of molecular weight on liquid crystalline behavior of linear and star mesogen‐jacketed liquid crystal polymers

AbstractA series of novel multi‐armed (di‐, tri‐ and tetra‐armed) mesogen‐jacketed liquid crystal polymers (MJLCPs) were synthesized by atom transfer radical polymerization (ATRP) of {2,5‐bis[(4‐methoxyphenyl)oxycarbonyl]styrene}(MPCS) using di‐, tri‐ and tetrafunctional initiator, respectively. The results show that the number average molecular weight (Mn,GPC) was increased versus monomer conversion, and the polydispersities were quite narrow (<1.19), which is the characteristic of controlled polymerization. The chemical structures of these multi‐armed mesogen‐jacketed liquid crystal polymers were confirmed by 1H NMR. The liquid crystalline behavior of these multi‐armed MJLCPs with arms ranging from two to four was studied by differential scanning calorimetry (DSC), polarized optical microscopy (POM) and wide‐angle X‐ray diffraction (WAXD). It was found that liquid crystalline phases appeared simply when the number molecular weights (Mn,GPC) of these multi‐armed MJLCPs was higher than a certain critical values, that is, Mn,GPC > 1.87 × 104 g/mol, 1.84 × 104 g/mol, 2.69 × 104 and 3.68 × 104 g/mol, which were initiated by coil difunctional initiator, hard difunctional initiator, trifunctional initiator and tetrafunctional initiator, respectively. All the liquid crystalline phase was found to be stable up to the decomposition temperature of these multi‐armed MJLCPs. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3232–3244, 2005

Synthesis and characterization of four-armed star mesogen-jacketed liquid crystal polymer

The synthesis of four-armed star mesogen-jacketed liquid crystal polymer was achieved by atom transfer radical polymerization in chlorobenzene solution using pentaerythritol terakis(2-bromoisobutyrate) (PT-Br) as an initiator and CuBr/sparteine complex as a catalyst. The results show that the number average molecular weigh is creased linearly vs. monomer conversion, and that the polydispersities were quite narrow (<1.19), which is the character of controlled polymerization. The structure was experimentally confirmed by 1H NMR. The liquid-crystalline behavior of the four-armed star polymer was studied using DSC and POM. Only the polymer with a M n,GPC beyond 3.68×10 4 g/mol formed a liquid crystalline phase which was quite stable with a high clearing point.

Effects of molecular weight on liquid-crystalline behavior of a mesogen-jacketed liquid crystal polymer synthesized by atom transfer radical polymerization

The synthesis of poly{2,5-bis[(4-methoxyphenyl)oxycarbonyl]styrene} (PMPCS) with different molecular weight and low polydispersity was achieved by atom transfer radical polymerization in methoxybenzene solution using 1-bromoethylbenzene as an initiator and CuBr/sparteine complex as a catalyst. The concentration of the living centers throughout the polymerization was found to be constant. The liquid-crystalline behavior of the polymers with Mn ranging from 3800 to 17,400g/mol was studied using DSC and POM. Only the polymers with Mn beyond 10,200g/mol formed a liquid-crystalline phase, which was quite stable with a high clearing point (higher than the decomposition temperature of the polymer).

Atom-Transfer Radical Polymerization to Synthesize Novel Liquid Crystalline Diblock Copolymers with Polystyrene and Mesogen-jacketed Liquid Crystal Polymer Segments

The synthesis of a series of new rod-coil diblock copolymers with different molecular weights and low polydispersity was achieved by atom transfer radical polymerization. The block architecture (coil-conformation of styrene segment and rigid-rod conformation of 2,5-bis[(4-methoxyphenyl)-oxycarbonyl]styrene segment) of the diblock copolymers was experimentally confirmed by proton nuclear magnetic resonance ( 1 H NMR) and differential scanning calorimetry (DSC). The liquid crystalline behavior of the copolymers was studied using DSC and a polarized optical microscope (POM). It was found that the liquid crystalline behavior was dependent on the molecular-weight of the rigid segment. Only those copolymers with Mn of the rigid block beyond 9,300 g/mol could form liquid crystalline phases above the glass transition temperature of the rigid block.

Synthesis and polymerization of 2,5-Bis(4′-alkoxy-phenyl)styrene for mesogen-jacketed liquid crystal polymers

A series of novel reactive liquid crystals, 2,5-bis(4'-alkoxy-phenyl)styrene, was designed and synthesized to prepare stereoregular mesogen-jacketed liquid crystal polymers (MJLCPs). These monomers are different from their analogous studied previously in that they do not contain polar linkages such as ester or/and amide group and therefore are expected to polymerize easily both by radical and ionic polymerization. The preliminary studies show that the resulting polymers have higher glass transition temperature (Tg) and much better thermal stability than their analogous.

Nitroxide-mediated ?living? free radical synthesis of novel rod-coil diblock copolymers with polystyrene and mesogen-jacketed liquid-crystal polymer segments

Nitroxide-mediated ?living? free radical synthesis of novel rod-coil diblock copolymers with polystyrene and mesogen-jacketed liquid-crystal polymer segments

Synthesis and Characterization of A New Series of “Mesogen-Jacketed Liquid Crystal Polymers” Based on the Newly Synthesized Vinylterephthalic Acid

The synthesis and characterization of a new series of mesogen-jacketed liquid crystal polymers, poly{2,5-bis[(para-substituted phenyl)oxycarbonyl]styrene}s, based on 2-vinylterephthalic acid are reported. These polymers formed very stable liquid crystal phases above the glass transition temperatures. A brief comparison of the properties of the new polymers with those of some previously reported counterparts is included.

Mesogen-jacketed Liquid Crystal Polymers With Mesogens of Aromatic Amide Structure

The synthesis and property of a new series of mesogen-jacketed liquid crystal are reported. These polymers have aromatic amide structures as the mesogenic groups and are represented by poly-2,5-bis(4-methoxy- benzamido)styrene. The preliminary study on properties shows that the polymers have very high glass transition temperatures as well as very low critical concentrations for the formation of the lyotropic liquid crystal phase. The results indicate a high degree of chain rigidity. However, the liquid crystalline order of molecular organization in bulk samples disappears upon heating to the glass transition temperature as revealed by polarizing microscopy and by X-ray diffractometer. Therefore, the liquid crystalline order of these polymers forms only through solution but not through heating. This behavior is different from that of the previously studied poly-2,5-bis[(4-methoxybenzoyl)oxy]styrene and its homologs. The latter polymers are liquid crystals both lyotropically and thermotropically. © 1997 John Wiley & Sons, Ltd.

Restudy of the Old Poly-2,5-di(benzoyloxy)styrene as a New Liquid Crystal Polymer

Abstract The 40 year old polymer, poly-2,5-di(benzoyloxy)styrene, has been restudied from the view point of the “mesogen-jacketed liquid crystal polymer.” This old polymer was synthesized in 1952 as a precursor of an electron exchange polymer and is now found to be thermotropically liquid crystalline, from which the characteristic banded texture of rigid and semi-rigid liquid crystal polymers may be obtained. The monomer of this polymer, 2,5-di(benzoyloxy)styrene, was then also not realized as liquid crystalline, is now found to be liquid crystalline forming too. This finding offers probably the first example of liquid crystal rigid rod-like molecules with lateral but without terminal substitutions. The synthesis and primary characterization of a series of the closely related polymers poly-2,5-bis[(4-substituted-benzoyl)oxy styrenes are also reported.