Mesogen-jacketed Liquid Crystalline Polymers Research Articles

New Morphologies and Phase Transitions of Rod–Coil Dendritic–Linear Block Copolymers Depending on Dendron Generation and Preparation Procedure

Amphiphilic rod–coil dendritic–linear block copolymers PEG(Gm)-b-PMPCS (where m is the number of dendron generation, and m = 1, 2, 3) composed of a semirigid Percec-type dendron with hydrophilic poly(ethylene glycol) (PEG) tails and a rod-like mesogen-jacketed liquid crystalline polymer, poly{2,5-bis[(4′-methoxy-phenyl)oxycarbonyl]styrene} (PMPCS), were successfully prepared. The self-assembled structures undergo a transition from vesicles through large compound vesicles (LCVs) to short cylindrical micelles with increasing dendron generation. PEG(G2)-b-PMPCS forms stable LCVs with porous surfaces of a narrow size distribution in a mixed solvent of tetrahydrofuran and water. The formation mechanism of the supramolecular structure with nano- and microsized scales is studied through changing the rate of water addition. It is composed of two steps: morphological transformation and vesicles fusion or differentiation. Vesicles are precursors for LCVs regardless of what the initial morphology is. However, the fi...

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 behavior of mesogen-jacketed liquid crystalline polymer with triphenylene discotic liquid crystal mesogen unit in side chains

Phase behavior of mesogen-jacketed liquid crystalline polymer with triphenylene discotic liquid crystal mesogen unit.

Ordered nanostructures at two different length scales mediated by temperature: A triphenylene‐containing mesogen‐jacketed liquid crystalline polymer with a long spacer

ABSTRACTA mesogen‐jacketed liquid crystalline polymer (MJLCP) containing triphenylene (Tp) moieties in the side chains with 12 methylene units as spacers (denoted as PP12V) was synthesized. Its liquid crystalline (LC) phase behavior was studied with a combination of solution 1H NMR, solid‐state NMR, gel permeation chromatography, thermogravimetric analysis, polarized light microscopy, differential scanning calorimetry, and one‐ and two‐dimensional wide‐angle X‐ray diffraction. By simply varying the temperature, two ordered nanostructures at sub‐10‐nm length scales originating from two LC building blocks were obtained in one polymer. The low‐temperature phase of the polymer is a hexagonal columnar phase (ΦH, a = 2.06 nm) self‐organized by Tp discotic mesogens. The high‐temperature phase is a nematic columnar phase with a larger dimension (a′ = 4.07 nm) developed by the rod‐like supramolecular mesogen—the MJLCP chain as a whole. A re‐entrant isotropic phase is found in the medium temperature range. Partially homeotropic alignment of the polymer can be achieved when treated with an electric field, with the polymer in the ΦH phase developed by the Tp moieties. The incorporation of Tp moieties through relatively long spacers (12 methylene units) disrupts the ordered packing of the MJLCP at low temperatures, which is the first case for main‐chain/side‐chain combined LC polymers with MJLCPs as the main‐chain LC building block to the best of our knowledge. The relationship of the molecular structure and the novel phase behavior of PP12V has implications in the design of LC polymers containing nanobuilding blocks toward constructing ordered nanostructures at different length scales. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 295–304

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.

Mesogen-jacketed liquid crystalline polymers and elastomers bearing polynorbornene backbone

This manuscript describes a series of mesogen-jacketed liquid crystalline polymers (MJLCPs) and elastomers (MJLCEs) bearing a novel polynorbornene backbone, onto which the liquid crystalline mesogen is laterally attached by a single covalent bond without spacers. The side-on mesogenic monomers are synthesized via palladium-catalyzed exo-hydroarylation of norbornadiene, and then polymerized using a Grubbs' catalyst initiated ring opening metathesis polymerization (ROMP) method. MJLCEs are prepared by mixing the MJLCPs with bifunctional benzophenone cross-linkers, pulling fibers to achieve a fine alignment, and crosslinking under UV illumination. Their mesomorphic, thermo-actuation and mechanical properties are studied in detail by a combination of 1H NMR, gel permeation chromatography, thermogravimetric analysis, differential scanning calorimetry, polarized optical microscopy, X-ray diffraction and dynamic mechanical analysis. These newly designed polymers can decouple the dynamics of the very bulky and rigid polynorbornene main chain and the mesogenic side groups to achieve liquid crystallinity, only if the length of alkoxy terminal chains of the mesogens is long enough (the number of the carbons in the alkoxy group, n > 9). Moreover, interesting external force induced reversible thermal-actuation behaviors of smectic MJLCEs are observed and analyzed as well.

Influence of fluorinated substituent and terminal length on phase behavior of mesogen‐jacketed liquid crystalline polymers with a biphenyl mesogen

AbstractA series of mesogen‐jacketed liquid crystalline polymers, poly{2,2,3,3,4,4,4‐heptafluorobutyl 4′‐hydroxy‐2‐vinylbiphenyl‐4‐carboxylate} (PF3Cm, where m is the number of carbon atoms in the alkoxy groups, and m = 1, 4, 6, and 8), the side chain of which contains a biphenyl core with a fluorocarbon substituent at one end and an alkoxy unit of varying length on the other end, were designed and successfully synthesized via atom transfer radical polymerization. For comparison, poly{butyl 4′‐hydroxy‐2‐vinylbiphenyl‐4‐carboxylate} (PC4Cm), similar to PF3Cm but with a butyl group instead of the fluorocarbon substituent, was also prepared. Differential scanning calorimetric results reveal that the glass transition temperatures (Tgs) of the two series of polymers decrease as m increases and Tgs of the fluorocarbon‐substituted polymers are higher than those of the corresponding butyl‐substituted polymers. Wide‐angle X‐ray diffraction measurements show that the mesophase structures of these polymers are dependent on the number of the carbon atoms in the fluorocarbon substituent and the property of the other terminal substituent. Polymers with fluorocarbon substituents enter into columnar nematic phases when m ≥ 4, whereas the polymer PF3C1 exhibits no liquid crystallinity. For polymers with butyl substituents, columnar nematic phases form when the number of carbon atoms at both ends of the side chain is not equal at high temperatures and disappear after the polymers are cooled to ambient temperature. However, when the polymer has the same number of carbon atoms at both ends of the side chain, a hexagonal columnar phase develops, and this phase remains after the polymer is cooled. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

Influence of alkoxy tail length on the self‐organization of hairy‐rod polymers based on mesogen‐jacketed liquid crystalline polymers

AbstractA series of hairy‐rod polymers, poly{2,5‐bis[(4‐alkoxyphenyl)oxycarbonyl]styrenes} (P‐OCm, m = 1, 2, 4, 6, 8, 10, 12, 14, 16, and 18) were designed and successfully synthesized via free radical polymerization. The chemical structure of the monomers was confirmed by elemental analysis, 1H NMR and 13C NMR. The molecular characterizations of the polymers were performed with 1H NMR and gel permeation chromatography. The phase structures and transitions of the polymers were investigated by the combination of techniques including differential scanning calorimetry, wide‐angle X‐ray diffraction, polarized optical microscopy, and rheological measurement. The experimental results revealed that the self‐assembly behaviors of P‐OCm changed with the increase in m. First, the P‐OCm (m = 1, 2) showed only a stable liquid crystalline phase above Tg. Second, with the increasing length of alkoxy tails, the P‐OCm (m = 4, 6, 8) presented a re‐entrant isotropic phase above Tg and a liquid crystalline phase at higher temperature. Third, the P‐OCm (m = 10, 12, 14, 16, 18) exhibited an unusual re‐entrant isotropic phase which was separating SmA (in low temperature) and columnar phases (in high temperature). It was the first time that mesogen‐jacketed liquid crystalline polymers formed smectic phase, re‐entrant isotropic phase, and columnar phases in one polymer due to the microphase separation and the driving force of the entropy. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Side-chain jacketing effect and mesogen-jacketed liquid crystalline polymers

Side-chain liquid crystalline polymers (LCPs) with the mesogens either terminally or laterally attached to the backbone are usually synthesized based on the concept of “flexible spacer”. The insertion of spacers with reasonable lengths between the backbone and mesogens can effectively decouple dynamics of backbone and mesogen, and thus facilitate ordered packing of side-chains. In contrast to that, the molecular design of mesogen-jacketed liquid crystalline polymers (MJLCPs), which belong to the catalog of laterally attached side-chain LCP, attempts to take the advantage of the coupling of side-chain and backbone. At the chemical structure level, the feature MJLCP is that the relatively bulky side-groups such as calamitic mesogens are linked to the backbone through a very short linkage or even a single carbon-carbon band. This arrangement of side-chains can cause significant “jacketing” effect, forcing the backbone to well extend. In this review, we discuss the “jacketing” effect, the special chain conformations of MJLCP due to the “jacketing” effect, and also the liquid crystalline phase structures of MJLCP. We demonstrate that the shape and dimension of MJLCP can be tuned upon using the “jacketing” effect. Furthermore, MJLCP can be used as rod-like component in block copolymers and also as main-chain part in combined main-chain/side-chain LCPs, which can render interesting hierarchical supramolecular orderings.

Competition and Promotion between Two Different Liquid-Crystalline Building Blocks: Mesogen-Jacketed Liquid-Crystalline Polymers and Triphenylene Discotic Liquid Crystals

Mesogen-jacketed liquid-crystalline polymers (MJLCPs) containing two triphenylene (Tp) units in the side chains, denoted as PPnV (n = 3 or 6, which is the number of the methylene units between the terephthalate core and Tp moieties in the side chains), were synthesized through conventional free radical polymerization, and the phase behaviors of these new combined main-chain/side-chain liquid-crystalline (LC) polymers were investigated. The chemical structures of the monomers were confirmed by elemental analysis, high-resolution mass spectrometry, and 1H/13C NMR. The molecular characterizations of the polymers were performed with 1H NMR, gel permeation chromatography, and thermogravimetric analysis. LC behaviors of the polymers were investigated by differential scanning calorimetry (DSC), polarized light microscopy, and wide-angle X-ray diffraction (WAXD). Both polymers exhibit excellent thermal stabilities. DSC and WAXD results indicate that covalently incorporating Tp discotic liquid crystals has a treme...

Synthesis and Characterization of Mesogen-Jacketed Liquid Crystalline Polymers through Hydrogen-Bonding

In an attempt to construct mesogen-jacketed liquid crystalline polymers through noncovalent interactions, poly(2-vinylbenzene-1,4-dioic acid) and five series of pyridine derivatives were synthesized as hydrogen-bonding donor and acceptors, respectively. The structures of the compounds were confirmed by 1H NMR, FT-IR, and gel permeation chromatography. A series of complexes with the same degree of polymerization and polydispersity were obtained by mixing the hydrogen-bonding donor and acceptors. The hydrogen-bonds were confirmed by FT-IR spectra. We found that the rigidity and structures of pyridine derivatives and the strength of the hydrogen-bonding all influenced the liquid crystalline behaviors of the resulting complexes. Smectic A and columnar nematic phases were observed in complexes PPANCx and PPANNEC, respectively.

Mesogen-jacketed liquid crystalline polymers: from molecular design to polymer light-emitting diode applications

This critical review covers the recent progress in the chemical structure design and light-emitting performance evaluation of electroluminescent mesogen-jacketed liquid crystalline polymers (MJLCPs). By applying the concept of MJLCPs, two main chromophoric building units, electron-transporting and hole-transporting units with large steric hindrance, are attached to the backbones solely or together. We highlight the structure–properties–performance relationships of electroluminescent MJLCPs. Device performances can be enhanced by the “jacketing effect”, which inhibits the aggregation of conjugated structures, fluorescence quenching, and excimer formation.

SYNTHESIS AND CHARACERIZATION OF A SERIES OF MESOGEN-JACKETED LIQUID CRYATALLINE POLYMERS WITH LONG MESOGENIC SIDE CHAINS

A series of mesogen-jacketed liquid crystalline polymers,poly[2,5-(4′-alkoxybi-phenyloxycarbonyl) styrene](PnCbiPCS,n=4,6,8,10,14) with long mesogenic side chains,were prepared by atom transfer radical polymerization(ATRP).Molecular weights and molecular weight distributions of the polymers were measured by gel permeation chromatography(GPC).The liquid crystalline(LC) behavior was studied by a combination of differential scanning calorimetry(DSC),thermogravimetric analysis(TGA),polarized light microscopy(PLM),one-dimensional(1D) and two-dimensional(2D) wide-angle X-ray diffraction(WAXD),and small-angle X-ray scattering(SAXS).All the polymers had good thermal stablility and exhibited stable LC properties,and no isotropization temperatures were observed before the onset temperatures of thermal decomposition.1D SAXS and WAXD studies revealed that PnCbiPCS could form smectic structures with the long mesogenic side chains aligned parallel to each other.The d-spacings increased with increasing aliphatic tails.2D WAXD results showed that the sheared samples exhibited Smectic A structures with the layer normal perpendicular to the shear direction.Comparing with the results of poly{2,5-bis[(para-substituted phenyl)oxycarbonyl]styrene}s,one may indicate that the length of the mesogenic group is crucial in determining the LC structure.

Synthesis and properties of mesogen‐jacketed liquid crystalline polymers containing biphenyl mesogen with asymmetric substitutions

AbstractThis work focuses on the design, synthesis, and characterization of a series of mesogen‐jacketed liquid crystalline polymers (MJLCPs), poly(alkyl 4′‐(octyloxy)‐2‐vinylbiphenyl‐4‐carboxylate) (pVBP(m,8), m = 1, 2, 4, 6, 8, 10, 12). For the first time, we realized asymmetric substitutions in the mesogens of MJLCPs. The polymers obtained by conventional free radical polymerization were investigated in detail by a combination of various techniques, such as differential scanning calorimetry, wide‐angle X‐ray diffraction, and polarized light microscopy. Our results showed that all the polymers were thermally stable, and their glass transition temperatures decreased when m increased. The liquid crystalline (LC) phases that developed at high temperatures and disappeared at low temperatures were strongly dependent on the difference in lengths of alkyl groups on the 4 and 4′ substitution positions of the side‐chain biphenyl. While polymer pVBP(1,8) was not liquid crystalline, columnar liquid crystalline phases were observed for all other pVBP(m,8) (m = 2, 4, 6, 8, 10, 12) polymers. Polymer pVBP(8,8) showed a tetragonal columnar nematic liquid crystalline phase, and the other LC polymers exhibited columnar nematic phases. In additions, the smaller the difference in the lengths of the terminal alkyls, the easier the development of the liquid crystalline phase. Birefringence measurements showed that solution‐cast polymer films exhibited moderately high positive birefringence values, indicating potential applications as optical compensation films for liquid crystal displays. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011