Mesogen-jacketed Liquid Crystalline Research Articles

Design, synthesis and properties of mesogen jacketed liquid crystalline polymers with fluorinated triphenylene pendants

Discotic liquid crystalline polymers (DLCPs) combining the advantages of discotic liquid crystals and polymers yet have been less developed compared to the calamitic counterparts mainly due to lack of DLCP materials. Here, mesogen-jacketed liquid crystalline polymers with pendant fluorinated triphenylene were successfully synthesized via proper polymerizations of the corresponding monomers respectively. Nuclear magnetic resonance spectroscopy (both 1H NMR and 13C NMR), time-of-flight mass spectrometry (MALDI-TOF MS), Fourier transform Infrared (FT-IR) spectroscopy and other characterization methods were used to confirm the structure of the products. The mesomorphic properties of the obtained triphenylene monomers with unsaturated flexible tails and resulting polymers were investigated by polarizing optical microscopy (POM), differential scanning calorimetry (DSC), and X-ray diffractometer (XRD). The propargylene-containing monomer shows a smectic liquid crystals phase and the pentynylene monomer exhibit a highly ordered columnar helical liquid crystal phase. The three side chain polymers containing fluorinated triphenylene have good thermal stability (decomposition temperature of 350 °C or above). At the same time, the polymers prepared by the polymerization of propargylene-containing monomers have both hexagonal columnar phase (Colh) and rectangular columnar phases (Colr). The polymers with long spacer chains derived from Methyl acrylate have a hexagonal columnar structure (Colh). The fluorinated triphenylene monomers and polymers with ordered liquid crystal phases synthesized in this work provide useful inspiring for structural modifications of DLCPs and are promising for applications in organic optoelectronics.

Hierarchically Ordered Structures of Rod–Rod Block Copolymers Containing Two Mesogen-Jacketed Liquid Crystalline Polymers

In order to investigate the factors affecting the hierarchically ordered structures of the rod–rod block copolymers, SmPn based on two polynorbornene-based mesogen-jacketed liquid crystalline (LC) polymers PNb12POSS [having side-chain polyhedral oligomeric silsesquioxane (POSS) units] and PNb10PP (with a side-chain calamitic mesogen) was designed and synthesized by ring-opening metathesis polymerization, in which S and P refer to the two segments PNb12POSS and PNb10PP, respectively, whereas m and n refer to the ratios of monomer to catalyst during polymerization of PNb12POSS and PNb10PP, respectively. Investigation on the phase structures and behaviors of SmPn samples indicates that the LC and crystalline structures of the two segments are similar to their homopolymers. The PNb10PP segment forms a smectic A (SmA) phase with the ordered packing of the rod-like mesogens, and the PNb12POSS segment forms a hexagonal columnar (Colh) phase with the crystal of POSS units. The volume fraction of PNb12POSS (fPNb12POSS) plays an important role on the microphase separation of SmPn. The asymmetry between the two blocks becomes more pronounced with increasing fPNb12POSS, resulting in a larger bending curvature, and the microphase-separated structure changes from lamellar (LAM) to hexagonally packed cylinders (HEX) for S10P30, S20P30, and S30P30. Moreover, the PNb12POSS segments in S20P30 and S30P30 form Colh phases that can be clearly observed by transmission electron microscopy. However, because of the slow kinetics of the polymer chains owing to the high molecular weight and rigidity, sample S30P120 having the lowest fPNb12POSS value cannot form ordered structures, while S80P120 only forms a HEX structure lacking regularity with a size of ∼40 nm.

Phase Behavior of Phasmidic Mesogen-Jacketed Liquid Crystalline Polymers Displaying Chain Bundling

Phasmidic mesogens generally consist of a long rod core and two dendronized end-groups possessing three alkyl tails. Mesogen-jacketed liquid crystalline polymers (MJLCPs) represent an important cla...

Self-assembly and Properties of Block Copolymers Containing Mesogen-Jacketed Liquid Crystalline Polymers as Rod Blocks

Mesogen-jacketed liquid crystalline polymer (MJLCP) has attracted great attention because of its rigid conformation, facile synthesis, and structural controllability. In this feature article, the self-assembly of MJLCP-based block copolymers (BCPs) is briefly reviewed, especially the nanostructures of rod-coil diblock copolymers (diBCPs), rod-rod diBCPs, and triblock copolymers. In addition, the properties of the self-assembled BCPs are also summarized, including their applications as liquid crystalline thermoplastic elastomers and solid polymer electrolytes. The article also discusses the major challenges and future directions in the study of MJLCP-based BCPs.

Precise size control of sub-10 nm structures of cholesteryl-containing mesogen-jacketed liquid crystalline polymers

A series of mesogen-jacketed liquid crystalline polymers (MJLCPs) with polynorbornene as the main chain and cholesteryl mesogenic units at the ends of the side chain, PNbnChol (n = 1, 3, 5, which is the number of benzene rings in the rigid side-chain core), were prepared by ring-opening metathesis polymerization. The phase behaviors of the polymers were investigated by differential scanning calorimetry, polarized light microscopy, and one-dimensional/two-dimensional X-ray scattering. The polymer with one benzene as the rigid core in the side chain shows only a smectic phase with interdigitated packing of cholesteryl units at low temperatures and is amorphous at high temperatures. While polymers containing three or five benzenes in the rigid side-chain core provide two different SmA phases at different temperatures, a smectic phase with double-layer-like packing of cholesteryl units at low temperatures and the smectic phase with interdigitated packing of cholesteryl units at high temperatures. The introduction of cholesteryl to MJLCPs can fabricate precisely controlled sub-10 nm scale ordered structures that can be maintained at high temperatures.

Synthesis and Characterization of New Liquid Crystalline Thermoplastic Elastomers Containing Mesogen-Jacketed Liquid Crystalline Polymers

In order to improve the high-temperature performance of thermoplastic elastomers (TPEs), we designed and synthesized a new kind of ABA triblock copolymer containing a mesogen-jacketed liquid crystalline polymer (MJLCP), poly{2,5-bis[(4-methoxyphenyl)oxycarbonyl]styrene} (PMPCS), as the hard blocks and polybutadiene (PB) as the soft block. The triblock copolymer, PMPCS-b-PB-b-PMPCS (M-B-M), was synthesized by ring-opening metathesis polymerization in the presence of a chain transfer agent and atom transfer radical polymerization. The glass transition temperature (Tg) of the PMPCS hard block is 110–118 °C in the triblock copolymers. In addition, the liquid crystalline (LC) phase of PMPCS is stable before thermal decomposition. All the triblock copolymers form lamellar microphase-separated structures, as demonstrated by small-angle X-ray scattering and transmission electron microscopy results. The triblock copolymer (M-B-M-55) with a mass fraction of 55% of PMPCS exhibits typical properties of an LC thermopl...

Influence of the side-chain structure and molecular weight on the re-entrant behaviors of mesogen-jacketed liquid crystalline polymers

The influence of the alkyl spacer length and the terminal group volume influence on the phase behavior and structure of mesogen-jacketed liquid-crystalline polymers.

The enhancing effect of mesogen-jacketed liquid crystalline polymer PBPCS on epoxy resin

The mixtures of mesogen-jacketed liquid crystalline polymers (MJLCP) and epoxy resin (E-51) have been prepared in a certain proportion. The category of the MJLCP is poly{2, 5-bis[(4-butoxyphenyl) oxycarbonyl] styrenes} (PBPCS). Methyl tetrahydro phthalic anhydride (MeTHPA) is served as a curing agent, and N, N-dimethylbenzylamine plays the role of catalyst. Then, based on the curing process, the modified materials have been acquired by casting molding. The effect of PBPCS's improvement has been researched through the mechanical properties test, dynamic thermal mechanical test and scanning electron microscope (SEM). The results indicated that PBPCS could apparently improve the mechanical properties of resin E-51. Compared with unmodified materials, the elongation at break and the tensile strength of PBPCS have been improved remarkably through modification. Both mechanical properties of the 4wt% PBPCS/E-51/MeTHPA were enhanced by 48% and 153% separately, and the characteristics of the 3wt% one were raised by 47% and 19% respectively. Also, the ductile fracture morphology of the resins was exhibited in SEM photograph clearly.

Effects of rigid cores and flexible tails on the phase behaviors of polynorbornene-based mesogen-jacketed liquid crystalline polymers

MJLCPs with a polynorbornene main chain and different side groups have been precisely synthesized for investigating the effect of side-chain structures on the liquid crystalline phase behaviors.

Influence of the spacer length on the phase behaviors of mesogen-jacketed liquid crystalline polymers with a bulk side-chain

The alkyl spacer length influences the phase behavior and structure of mesogen-jacketed liquid-crystalline polymers with bulk side-chains.

Mesogen-Jacketed Liquid Crystalline Polymers with a Polynorbornene Main Chain: Green Synthesis and Phase Behaviors

We synthesized a new series of MJLCPs with a polynorbornene main chain, PNbnPT (n = 8, 10, 12, 14, 16, 18, which is the number of carbons in the side-chain alkyl tails), through ring-opening metathesis polymerization and investigated their phase behaviors. The monomers were facilely synthesized in satisfactory yields through a key intermediate, N-(2,5-dicarboxylphenyl)-cis-5-norbornene-exo-2,3-dicarboximide. Differential scanning calorimetry, polarized light microscopy, and wide-angle X-ray diffraction results demonstrate that the phase behavior of PNbnPT is strongly dependent on the alkyl-tail length. Polymers with relatively short alkyl tails, PNb8PT and PNb10PT, are amorphous in the whole temperature range before degradation. When the alkyl-tail length increases, PNbnPTs (n = 12, 14, 16, 18) develop into the smectic A phase, and the degree of order increases with increasing alkyl-tail length. The synthetic pathway for MJLCPs with a polynorbornene main chain in this work is more robust and greener than those reported to the best of our knowledge. And MJLCPs with a polynorbornene main chain show quite different phase behaviors compared with those with a polyethylene backbone, and they may be used to create fascinating functional materials.

Synthesis and Phase Structures of Dendronized Polymers with Dendritic Azobenzene Side Groups Based on Mesogen-Jacketed Liquid Crystalline Polymers

The first- and second-generation dendronized polymers, poly (2, 5-bis {[3, 5-di (4′-methoxy-4-oxyhexyloxy azobenzene) benzyl] oxycarbonyl} styrene) (PG1) and poly (2, 5-bis {3, 5-di [3, 5-di (4′-methoxy-4-oxyhexyloxy azobenzene) benzyl] oxycarbonyl} styrene) (PG2), were successfully synthesized, and their phase structures were investigated by differential scanning calorimetry (DSC), polarized light microscopy (PLM), and one-dimensional wide-angle X-ray diffraction (1D WAXD). The results show that the liquid crystalline (LC) phase structures of the dendronized polymers containing dendritic azobenzene side groups depend strongly on the molecular weights (MWs) and the generation of dendritic azobenzene side groups. Compared the low MWs PG2 with the low MWs PG1, the degree of order in LC phase increased with increasing the generation of dendritic azobenzene side groups.

Synthesis and phase behavior of a new 2-vinylbiphenyl-based mesogen-jacketed liquid crystalline polymer with a high glass transition temperature and low threshold molecular weight

A new mesogen-jacketed liquid crystalline (LC) polymer was synthesized by NMP. It has a high Tg and a relatively low threshold MW for LC formation.

Mesogen-jacketed liquid crystalline polymers with peripheral oligo(ethylene oxide) chains: phase structure and thermoresponsive behavior

The influence of the number and length of EO terminal groups for MJLCPs on the phase structure and thermoresponsive behavior.

Synthesis and phase structures of combined main-chain/side-chain liquid crystalline polymers with different-number azobenzene moiety in the side-chain based on mesogen-jacketed liquid crystalline polymers

Three novel combined main-chain/side-chain liquid crystalline polymers with different number of azobenzene mesogens in the side chain per repeating unit have been synthesised. These are poly(2,5-bis{[3-(4′-methoxy-4-oxyhexyloxy azobenzene)benzyl]oxycarbonyl}styrene) (denoted as PABCS), poly(2,5-bis{[3,5-di(4′-methoxy-4-oxyhexyloxy azobenzene)benzyl]oxycarbonyl}styrene) (denoted as PDABCS) and poly (2,5-bis{[3,4,5-tri(4′-methoxy-4-oxyhexyloxy azobenzene)benzyl]oxycarbonyl}styrene) (denoted as PTABCS). The chemical structure of the monomers was confirmed by 1H NMR and 13C NMR. The structural characterisation of the polymers was performed by 1H NMR and gel permeation chromatography (GPC), and the phase structures and transitions of the polymers were studied using differential scanning calorimetry (DSC), polarised light microscopy (PLM) and one-dimensional (1D) wide-angle X-ray diffraction (WAXD). The results show that the number of azobenzene mesogens in the side chain per repeating unit in the combined main-chain/side-chain liquid crystalline polymers plays an important role in dominating the phase type preferences, and the polymers exhibit more versatile and intriguing liquid crystalline properties with increasing number of azobenzene mesogens. First, the main chains of PABCS construct a 2D-centred rectangular (ΦR) scaffold and the packing of azobenzene-containing side chains inside the main-chain scaffold develops smecitc A (SmA)-like structure below isotropic temperature (Ti). Second, with increasing the number of azobenzene mesogens, the main chains of PDABCS develop a 2D-centred rectangular (ΦR) scaffold at lower temperature and a 2D hexagonal columnar (ΦH) phase at higher temperature, and the packing of side chains inside the main-chain scaffold undergoes the transition of SmA-like ↔ isotropic. Third, for PTABCS, the sequence of phase transitions followed is: 2D centred rectangular columnar phase (ΦR) scaffold of main chain and SmB-like structure of side chain ↔ 2D centred rectangular columnar phase (ΦR) scaffold of main chain and SmA-like structure of side chain ↔ 2D centred rectangular (ΦR) scaffold of main chain and isotropic side chain ↔ 2D long-range-ordered hexagonal columnar phase (ΦH) of main chain and isotropic side chain. The 2D long-range-ordered ΦH phases of the polymers PDABCS and PTABCS still remain before the samples are completely decomposed.

Synthesis and liquid crystalline behavior of 2,5-disubstituted styrene-based random copolymers: Effect of difference in length of the rigid core on the mesomorphic behavior of mesogen-jacketed liquid crystalline polymers

A series of binary copolymers, poly{2,5-bis[(4-octadecyloxyphenyl)oxycarbonyl]-styrene-co-2,5-bis[(4′-octadecyloxybiphenyl)oxycarbonyl]-styrene} (poly(M-OC18-co-M-C18)), were synthesized via free radical polymerization. The random nature of the copolymers was expected on the basis of the assumed similar reactivities because of the analogous monomers. A combination of differential scanning calorimetry (DSC), polarized optical microscopy (POM) and wide-angle X-ray diffraction (WAXD) demonstrated that phase behavior of this series of copolymers were strongly composition dependent. The P-OC18 formed smectic A phase, re-entrant isotropic phase and column nematic phase, while the P-C18 only exhibited the stable smectic A phase. The comparison between P-OC18 and P-C18 indicates that the length of the rigid core is crucial to determine the liquid crystalline (LC) structures. After copolymerization, the glass transition temperature and the phase transition temperature of the copolymers from smectic phase to isotropic phase both increased with the molar fraction of 2,5-bis[(4′-octadecyloxybiphenyl)oxycarbonyl]-styrene (M-C18) in feed. In addition, when the feed was below 0.3, a column nematic phase was observed in high temperature. Namely, simply through copolymerization, we can greatly vary LC behavior of the mesogen-jacketed liquid crystalline polymers.

Synthesis and tailoring phase behavior of mesogen jacketed liquid crystalline copolymers based on 2, 5-bis[(4-alkoxyphenyl)oxycarbonyl]styrenes

Based on 2, 5-bis[(4-alkoxyphenyl)oxycarbonyl]styrenes (M-OCm, m is the number of the carbons of alkyl tails, m = 1, 4, and 18), three series of binary copolymers with high-molecular weights, {poly(M-OC1-co-M-OC4), poly(M-OC1-co-M-OC18), and poly(M-OC4-co-M-OC18)} have been prepared via free-radical polymerization. The random nature of the copolymers was expected on the basis of the assumed similar reactivities because of the analogous monomers. The phase behaviors of copolymers were studied by DSC, POM, and one-dimensional wide-angle X-ray diffraction. The results showed that liquid crystalline (LC) phase structures of copolymers, containing smectic phase, reentrant isotropic phase, columnar phase. and isotropic phase, were strongly depended on the composition and the alkyl length due to the competing among the steric effect, the microphase separation and the driving force of the entropy. When one of them occupied a dominant position, the LC phase structure can be presented for the copolymers. Otherwise, the LC phase structure is lost despite the pair of corresponding homopolymers forming mesogenic structure. Therefore, through copolymerization, LC behavior of the mesogen-jacketed liquid crystalline polymers can be greatly varied. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2804–2816

The effects of para-, meta- and ortho-monosubstituted azobenzene moiety in the side chain on phase behavior of mesogen-jacketed liquid crystalline polymers

Three different mesogen-jacketed liquid crystalline polymers with monosubstituted azobenzene moiety in the side-chain have been studied. These are poly(2,5-bis{[para-(4′-methoxy-4-oxyhexyloxy azobenzene) benzyl] oxycarbonyl} styrene) (denoted as PPABCS), poly(2,5-bis{[meta-(4′-methoxy-4-oxyhexyloxy azobenzene) benzyl] oxycarbonyl} styrene) (denoted as PMABCS) and poly(2, 5-bis{[ortho-(4′-methoxy-4-oxyhexyloxy azobenzene) benzyl] oxycarbonyl} styrene) (denoted as POABCS). The chemical structures of the monomers were confirmed by 1H NMR, 13C NMR spectroscopy and elemental analysis. The structure characterization of the polymers was performed by 1H NMR spectroscopy and gel permeation chromatography (GPC), and the phase structures and transitions of the polymers were studied using differential scanning calorimetry (DSC), polarized light microscopy (PLM), and one- and two-dimensional (1D, 2D) wide-angle X-ray diffraction. The effects of monosubstituted azobenzene moiety in different positions on the liquid crystalline behaviors of the polymers were also investigated. The results show that the phase transitional behaviors of mesogen-jacketed liquid crystalline polymers containing monosubstituted azobenzene moiety depend strongly on the position of the substituent on the azobenzene moiety. We identify that PPABCS can form a hierarchically ordered structure with double orderings on both the nanometer and subnanometer length scales. Most likely, the thick main-chains of PPABCS obtained by “jacketing” the central rigid portion of side-chain to the polyethylene backbone construct a 2D centered rectangular scaffold. The azobenzene-containing side-chains pack inside the main-chain scaffold form smecitc A (SmA)-like structure and are perpendicular to the main-chains. We compared PPABCS with PMABCS and POABCS, and found that the hierarchically ordered structure of PMABCS was similar to that of PPABCS. It is surprising that the main-chains of POABCS also construct a 2D centered rectangular scaffold, however, the packing of azobenzene-containing side-chains inside the main-chain scaffold develops smecitc C (SmC)-like structure. Furthermore, the glass transition temperature (Tg), isotropic temperature (Ti) and liquid crystalline range (ΔT, from Tg to Ti) of the polymers decrease in the order, para > meta > ortho. It is very interesting phenomenon that the associated enthalpy changes of these polymers are also the same order, para > meta > ortho, which is different from those of MCLCPs and SCLCPs.

Influence of different linkage groups in biphenyl mesogenic core on phase behaviors of mesogen-jacketed liquid crystalline polymers

The work focuses on the design, synthesis, and characterization of a series of mesogen-jacketed liquid crystalline polymers (MJLCPs) based on the octyl substituted biphenyl mesogenic core through different linkage groups. The molecular characterizations of the polymers obtained by conventional free radical polymerization were performed with 1H NMR, gel permeation chromatography, and thermogravimetric analysis. Their thermotropic liquid crystalline (LC) behaviors were investigated in detail by a combination of various techniques, such as polarized light microscopy, differential scanning calorimetry, and 1D and 2D wide-angle X-ray diffraction. Our results showed that all the polymers were thermally stable, and their LC phases were greatly dependent on the linking groups between the biphenyl mesogenic core and terminal alkyl group substituent. Polymers with ether/ester or ether linkage group exhibited an unusual phase behavior with temperature increasing, tetragonal columnar nematic LC phase, or columnar nematic phase developed at high temperatures for the polymers transformed into amorphous phase during cooling process, showing a re-entrant phase behaviors. However, polymers with ester linkage group were not LC with temperature varied. It is illustrated that subtle changes in the molecular structure brought about tremendous variation of the LC phase properties for MJLCPs. (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 25452554

Synthesis of mesogen-jacketed liquid crystalline polymers with long symmetry mesogenic core containing two biphenyls

A series of mesogen-jacketed liquid crystalline polymers, poly {2,5-bis[(4-alkoxybiphenyl)oxycarbonyl]-styrenes} (P-Cm, m = 8, 10, 12, 14 and 18) were designed and successfully synthesized via free radical polymerization. The chemical structures of the monomers were confirmed by 1H NMR, 13C NMR and Mass Spectrometry. The molecular characterizations of the polymers were performed with 1H NMR, GPC and TGA. The phase structures and transitions of the polymers were investigated by the combination of techniques including DSC, POM, temperature-variable FT-IR spectroscopy, 1D WAXD and SAXS. The experimental results suggest that the polymers with symmetry mesogenic core containing two biphenyls can develop into a well-defined smectic A (SA) phase. This implies that MJLCPs molecules shape can be modulated from rod-like to ribbon-like by simply changing the length of the mesogenic group.