Phase behaviour and electro-optical response of systems composed of nematic liquid crystals and poly (2-ethylhexylacrylate)

Experimental studies of phase diagram and morphology of mixtures composed of linear poly(2-ethylhexylacrylate) (poly-2EHA) of molecular weight M_w = 92000g/mol and E7, an eutectic blend of nematic liquid crystals (LCs), were performed. The latter consists of four cyanoparaphenylenes, i.e. 4-cyano-4?-n-pentyl-biphenyl (5CB), 4-cyano-4?-n-heptyl-biphenyl (7CB), 4-cyano-4?-n-oxyoctyl-biphenyl (8OCB) and 4-cyano-4?’-n-pentyl-p-biphenyl (5CT). Thermal properties of the poly-2EHA/E7 system were studied by differential scanning calorimetry and the sample morphologies were investigated by optical microscopy. Phase diagram analysis revealed an increase of the nematic–isotropic transition temperature when E7 was added to poly-2EHA, compared to pure E7. This effect, related to a preferential miscibility phenomenon of E7 components towards poly-2EHA, was evidenced by gas chromatography analysis coupled to mass spectrometry, allowing to qualify and quantify the content of phase separated LC domains. Thermograms of model LC mixtures including 5CB, 7CB, 8OCB and 5CT, which correspond to their composition in segregated LC domains of poly-2EHA/E7, present strong deviations from eutectic behaviour. In order to access the impact of such variations for practical applications, such a model LC mixture was introduced in photochemically crosslinked 2-EHA (polycross-2EHA). Surprisingly, the electro-optical response of the obtained polycross-2EHA/LC films was considerably improved compared to the original polycross-2EHA/E7 system.     

Solubility effects of multicomponent liquid crystal blends towards poly (n-butyl-acrylate)

Blends composed of isotropic linear poly (n-butylacrylate) of molecular weight M _w?=?112,000 g mol^?1 and the commercial four-component nematic low molecular weight liquid crystal (LC) mixture E7 exhibit a strong shift of the single nematic–isotropic transition temperature T _NI compared to that of the pure LCs, which was evidenced by using two complementary experimental techniques: differential scanning calorimetry (DSC) and high-performance liquid chromatography. The first one provides direct information about phase behaviour and variation of T _NI of the polymer/LC blends, whereas the second one consists of analysing qualitatively and quantitatively the composition of millimetre-sized segregated LC domains in the two-phase region of the phase diagram.

In order to understand the origin of the unusual phase behaviour, several LC blends were prepared by modifying the concentration of the four single LC components that are present in the eutectic E7 mixture, following the results from the previous chromatographic analysis. These model blends were investigated by DSC measurements, showing that the variation, particularly of the terphenyl LC compound concentration, plays a determining role for the phase behaviour of the LC mixture and the shift of T _NI.     

The nematic-isotropic two phase region in mixtures of quasi-spherical solutes in alkylcyanobiphenyls: An E.S.R. study using tempone as probe

The transitional behaviour of binary mixtures, each containing a non-mesomorphic quasi-spherical solute at a low mole fraction in a nematogenic solvent, has been investigated by E.S.R. spectroscopy using 4-oxo-2,2,6,6-tetramethyl-4-piperidinyl-1-oxy (tempone) as a spin probe. This approach makes use of the smaller coupling constant obtained for the spin probe in the orientationally ordered nematic phase relative to that obtained in the isotropic phase. The solutes included Et₄C (tetraethylmethane) and R ₄Sn (R = C^b2bH₅, n-C_{3 H 7} and nC_b4H₉). The solvents were 4-n-pentyl-4′-cyanobiphenyl (5CB) 4-n-hexyl-4′-cyanobiphenyl (6CB) and 4-n-heptyl-4′-cyanobiphenyl (7CB). This fast approach compares favourably with other studies. In addition it provides the tempone spectral parameter, f, which is a relative measure of the fraction of the nematic phase at different temperatures within the two phase region.     

Phase equilibrium of poly(n-butyl acrylate) and E7

The experimental equilibrium phase diagram of mixtures of linear poly(n-butyl acrylate) of molecular mass M_w = 112000 g mol^-1 and the low molecular mass LC mixture E7 has been established using polarized optical microscopy and light scattering techniques. The diagram is found to be reminiscent of an upper critical solution temperature system. Two independent series of samples with the same composition were studied, yielding consistent results. A region of nematic and isotropic coexisting phases and a region of a single isotropic phase were identified in the composition-temperature phase diagram. The results were analysed within a theoretical model combining the Flory-Huggins lattice theory for isotropic mixing and the Maier-Saupe theory for nematic ordering. Interestingly, no region of isotropic coexisting phases was observed in our experiments. This is probably due to the fact that the nematic interaction overwhelms the isotropic interaction in the region where (I + I) coexisting phases could appear. A preferential solubility of certain constituents of the LC mixture in the polymer could possibly be a reason for this behaviour.     

Side group functionalized liquid crystalline polymers and blends VIII. Nematic and SmAre phase formation in hydrogen-bonded blends of smectic side group LC polymers and a low molar mass dopant

Hydrogen-bonded blends based on smectic side group functionalized LC copolymers containing 4-alkyloxybenzoic acid fragments (proton donor) and a non-mesogenic low molecular mass dopant 4-cyanophenyl pyridine-4-carboxylate or 4-methoxyphenyl-d₄ pyridine-4-carboxylate (proton acceptor) were obtained. The blends containing 10-35 mol % of low molecular weight dopant form nematic (I-N-SmA) or re-entrant SmA phases (I-SmA-N-SmAre). The temperature dependence of the order parameter S, the birefringence Δn, and the splay K ₁ and bend K ₃ elastic constants of the nematic phase were studied by ²H NMR spectroscopy and the Fréedericksz method of threshold transitions in a magnetic field. A mechanism for the destruction of the SmA phase and the formation of the nematic phase in the hydrogen-bonded blends is suggested.     

Cyanobiphenyl-based liquid crystal dimers and the twist-bend nematic phase

ABSTRACT

The synthesis and characterisation of several members of the 1,ω-bis(4-cyanobiphenyl-4′-yl) alkane (CBnCB) and the 1-(4-cyanobiphenyl-4′-yloxy)-ω-(4-cyanobiphenyl-4′-yl) alkane (CBnOCB) homologous series are reported. The new odd members described CB5CB, CB13CB, CB4OCB, CB8OCB and CB10OCB all exhibit twist-bend nematic and nematic phases. The members of these series already reported in literature, CB7CB, CB9CB, CB11CB and CB6OCB, were also prepared in order to allow for a direct comparison of their transitional properties. The properties of these dimers are also compared to those of the corresponding members of the 1,ω-bis(4-cyanobiphenyl-4,-yloxy) alkanes (CBOnOCB). For any given total spacer length, for odd members of these series, the nematic–isotropic transition temperatures and associated entropy changes are greatest for the CBOnOCB dimer and lowest for the CBnCB dimer. These trends are understood in terms of molecular shape. For short spacer lengths, the twist-bend nematic–nematic transition temperature (T_NTBN) is higher for the CBnOCB series than for the CBnCB series but this is reversed as the spacer length increases. Of the CBOnOCB dimers, a virtual value of T_NTBN was estimated for CBO3OCB and T_NTBN was measured for CBO5OCB. These values are considerably lower than those observed for the corresponding members of the CBnCB or CBnOCB series. The dependence of T_NTBN on molecular structure is discussed not only in terms of the molecular curvature but also in the ability of the molecules to pack efficiently. As the temperature range of the preceding nematic phase increases, so the twist-bend nematic–nematic transition entropy change decreases and the transition approaches second order for the longer spacers. For comparative purposes, the transitional behaviour of the even-membered dimers CB6CB, CB5OCB and CBO4OCB is reported and differences accounted for in terms of molecular shape.     

Equilibrium phase diagram of polystyrene and 8CB

The experimental equilibrium phase diagram of a mixture of linear polystyrene of molecular weight M_w = 44,000 g/mol and 4‐cyano‐4′‐n‐octyl‐biphenyl (8CB) is established. The three transitions smectic A‐nematic, nematic‐isotropic, and isotropic‐isotropic are observed. The first two are observed both by optical microscopy and differential scanning calorimetry (DSC) while the isotropic‐isotropic transition could be seen only via optical microscopy. Two series of samples with the same compositions were independently prepared and yielded consistent results both by microscopy and DSC. Measurements of sample compositions with less than 50 weight % of 8CB were influenced by the vicinity of the glass transition temperature (T_g) of the polymer in the mixture. This quantity is also determined by DSC as a function of composition. A single T_g is observed, which decreases with composition of the LC. Other thermodynamic quantities such as the enthalpy variations of LC in the nematic‐isotropic transition and the fraction of LC contained in the droplets are also considered. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1841–1848, 1999     

Synthesis of side‐chain liquid‐crystalline homopolymers and triblock copolymers with p‐methoxyazobenzene moieties and poly(ethylene glycol) as coil segments by atom transfer radical polymerization and their thermotropic phase behavior

A series of side‐chain liquid‐crystalline (LC) homopolymers of poly[6‐(4‐methoxy‐4′‐oxy‐azobenzene) hexyl methacrylate] with different degrees of polymerization were synthesized by atom transfer radical polymerization (ATRP), which were prepared with a wide range of number‐average molecular weights from 5.1 × 10³ to 20.6 × 10³ with narrow polydispersities of around 1.17. Thermal investigation showed that the homopolymers exhibit two mesophases, a smectic phase, and a nematic phase, and the phase‐transition temperatures of the homopolymers increase clearly with increasing molecular weights. A series of novel LC coil triblock copolymers with narrow polydispersities was synthesized by ATRP, and their thermotropic phase behavior was investigated with differential scanning calorimetry and polarized optical microscopy. The LC coil triblocks were designed to have an LC conformation of poly[6‐(4‐methoxy‐4′‐oxy‐azobenzene) hexyl methacrylate] with a wide range of molecular weights from 3.5 × 10³ to 1.7 × 10⁴ and the coil conformation of poly(ethylene glycol) (PEG) (number‐average molecular weight: 6000 or 12,000) segment. Their characterization was investigated with ¹H NMR, Fourier transform infrared spectra, and gel permeation chromatography. Triblock copolymers exhibited a crystalline phase, a smectic phase, and a nematic phase. The phase‐transition temperatures from the smectic to nematic phase and from the nematic to isotropic phase increased, and the crystallization of PEG depressed with increasing molecular weight of the LC block. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2854–2864, 2003     

Azobenzene-based liquid crystal dimers and the twist-bend nematic phase

ABSTRACT

The synthesis and characterisation of two new sets of non-symmetric liquid crystal dimers is reported, the 1-(4-substitutedazobenzene-4′-yloxy)-6-(4-cyanobiphenyl-4′-yl)hexanes (CB6OABX) and 1-(4-substitutedazobenzene-4′-yloxy)-6-(4-cyanobiphenyl-4′-yloxy)pentanes (CBO5OABX). The terminal substituents are methyl, methoxy, butyl, butyloxy, nitrile and nitro. All the CB6OABX dimers exhibit twist-bend nematic (N_TB) and nematic (N) phases. The CBO5OABX dimers also all show an N phase but only the butyl and butyloxy homologues exhibit the N_TB phase. The transitional behaviour of the non-symmetric dimers is compared to that of the corresponding symmetric dimers, the 1,5-bis(4-substitutedazobenzene-4′-yloxy)pentanes (XABO5OABX) and either 1,7-bis(4-cyanobiphenyl-4′-yl)heptane or 1,5-bis(4-cyanobiphenyl-4′-yloxy)pentane. The XABO5OABX dimers all show a nematic phase and in addition, the butyl homologue exhibits a smectic A phase. The difference in transitional behaviour between the CB6OABX and CBO5OABX dimers is attributed to the difference in their molecular shapes arising from different bond angles between the para axis of the cyanobiphenyl unit and the first bond in the spacer. Specifically, the all-trans conformation of a CBO5OABX dimer is more linear than that of the corresponding CB6OABX dimer. Differences within each set of dimers are attributed to changes in the average molecular shape and the strength of the mixed mesogen interaction on varying the terminal group. Crystal structures are reported for CB6OABOMe, CBO5OABNO₂ and MeOABO5OABOMe.     

Blue phase stability of n-OCB homologue chiral nematic liquid crystal mixtures

Blue phase (BP) stability of a chiral nematic liquid crystal (LC) mixture is dependent upon chemical structure as well as physical properties. In this study, the blue phase temperature range dependent on alkyl chain length was investigated in order to evaluate the relationship between blue phase stability and the molecular structures of four kinds of 4-n-alkyloxy-4'-cyanobiphenyl (n-OCB) homologue chiral nematic LC mixtures composed of rod-like nematic LCs. It was confirmed that the blue phase temperature range was strongly dependent upon the molecular parity, K ₃₃/K ₁₁ and the helical twist power of the n-OCB homologues chiral nematic LC mixtures.     

A carbon-13 study of relaxation in the mesophases of 5O·7 and the 5CB homologous series

Abstract

Carbon-13 spin-lattice relaxation times of the protonated ring carbons have been measured at 22·6 MHz in the nematic and all four smectic phases of 5O·7 (4-n-pentyloxybenzylidene-4′-n-heptylaniline). Dong has obtained the deuterium spectral densities J ₁ and J ₂ at 15·4MHz for the deuterated aniline ring of 5O·7-d ₄, and has presented and applied a theory in which the spectral densities are expressed in terms of the diffusion constants D∥ and D?. His results are used to calculate ¹³C relaxation times from the spectral densities J ₀, J ₁ and J ₂. The calculated ¹³C spin-lattice relaxation times are then compared with our experimental values to test the theory. The ¹³C spin-lattice relaxation times of all the resolved resonances in the various phases of the first four members of the 5CB homologous series have been published previously. Dong has also published an analysis of 5CB deuterium data, and we use his results for the diffusion constants D∥ and D? to calculate ¹³C relaxation times of the protonated aromatic carbons of 5CB, 6CB, 7CB and 8CB. The ¹³C relaxation times of the unprotonated aromatic carbons of the 5CB series are calculated in the manner of Wittebort et al., but using the spectral density expressions developed by Dong. The calculated ¹³C spin-lattice relaxation times of the 5CB homologous series are then compared with our experimental values to test the theory for the protonated and unprotonated ring carbons.     

Synthesis of novel multi-arm star azobenzene side-chain liquid crystalline copolymers with a hyperbranched core

A series of novel multi-arm star side-chain liquid crystalline (LC) copolymers with hyperbranched core moieties were synthesized by atom transfer radical polymerization (ATRP) using a multi-functional hyperbranched polyether as the initiator and chlorobenzene as the solvent. The multi-functional hyperbranched polyether initiator was prepared from poly(3-ethyl-3-(hydroxymethyl)oxetane) (PEHO) and 2-bromo-2-methylpropionyl bromide. The azobenzene side-chain liquid crystalline arms were designed to have an LC conformation of poly[6-(4-methoxy-4^′-oxy-azobenzene)hexyl methacrylate] with different molecular weights. Their characterization was performed with ¹H NMR, size exclusion chromatograph (SEC), differential scanning calorimetry (DSC) and thermal polarized optical microscopy (POM). The multi-arm star side-chain liquid crystalline copolymers exhibited a smectic and a nematic phase, and the phase transition temperatures from the smectic to the nematic phase and from the nematic to isotropic phase increased with increasing the molecular weight of the multi-arm star side-chain liquid crystalline copolymers from 1.78 × 10⁴ to 9.07 × 10⁴.     

Molecular ordering in microconfined liquid crystals: An infrared linear dichroism study

Abstract

The molecular arrangement of 5CB confined within the cylindrical pores of Anopore membranes was characterized by means of the IR-order parameter obtained from linear dichroism measurements of selected IR absorption bands. The treatment of the experimental data includes a local field correction extended to the twisted nematic configuration, yielding order parameters increased by about 30% in comparison with the uncorrected data. The nematic director of 5CB aligns along the pore axes, whereas in lecithin coated Anopore channels, the local nematic director is oriented approximately radially due to the perpendicular anchoring of the 5CB molecules at the pore wall. Doping of 5CB with the chiral agent CB15 yields local nematic directors tilted with respect to the pore axes. The average tilt angle increases up to about 40° at a fraction of CB15, x _cb15 = 0.25 (w/w). These results are discussed in terms of the conical helicoidal and alternatively the radially twisted axial arrangement of the LC molecules within submicrometer cylindrical cavities.     

Viscoelastic properties of dilute nematic mixtures containing cyclic and hyperbranched liquid crystal polymers dissolved in a nematic solvent

The twist and bend viscosities of dilute solutions of cyclic and hyperbranched liquid crystal polymers (LCP) dissolved in low molar mass nematic solvents were determined via dynamic light scattering analysis. These results were compared to those of linear chains with similar chemical repeat structures. The nematic solvent used was 4′-pentyloxy-4-cyanobiphenyl (50CB). The cyclic LCP oligomers, Cy TPB10, have a mesogenic group, 1-(4-hydroxy-4′-biphenyl)-2-(4-hydroxyphenyl) butane, separated by flexible decamethylene spacers. The twist viscosity of the cyclic Cy-TPB10 oligomers increases with molecular weight more strongly than the linear, TPB-10, suggesting that the hydrodynamic behavior of Cy-TPB10 is closer to that of a rigid rod than TPB10. Surprisingly, the intrinsic bend viscosity [η_bend] of Cy-TPB10 decreases with molecular weight, in contrast to the positive dependence for linear TPB10. This may reflect the higher strain energy in the smaller ring sizes. The hyperbranched LCP, TPD-b-8, is also based on the mesogen 10-bromo-1-(4-hydroxy-4′-biphenyl)-2(4-hydroxyphenyl) decane but with octyl groups at the chain ends. We compare the viscoelastic behavior of dilute nematic solutions of TPD-b-8 in 50CB against that of a linear main-chain LCP, TPB7, with the same mesogenic group but with heptamethylene spacers. The viscometric properties of TPD-b-8/50CB and TPB7/50CB are quite different. The results suggest that each chain is prolate (i. e., R_∥ > R_⊥) but that TPD-b-8 has a smaller chain anisotropy than that of TPB7. © 1995 John Wiley & Sons, Inc.     

The twist-bend nematic phase: translational self-diffusion and biaxiality studied by 1H nuclear magnetic resonance diffusometry

ABSTRACT

Recently, there has been a surge of interest in mesogens exhibiting the twist-bend nematic (N_TB) phase that is shown to be chiral even though formed by effectively achiral molecules. Although it now seems to be clear that the N_TB phase in the bulk is formed by degenerate domains having opposite handedness, the presence of a supramolecular heliconical structure proposed in the Dozov model has been contradicted by the Hoffmann et al. model in which the heliconical arrangement is replaced by a polar nematic phase. The evidence in support of this is that the quadrupolar splitting tensor measured in various experiments is uniaxial and not biaxial as expected for the twist-bend nematic structure. In this debate, among other evidence, the molecular translational diffusion, and its magnitude with respect to that in the nematic phase above the N_TB phase, has also been invoked to eliminate or to confirm one model or the other. We attempt to resolve this issue by reporting the first measurements of the translational self-diffusion coefficients in the nematic and twist-bend nematic phases formed 1″,7″-bis-4-(4′-cyanobiphenyl-4′-yl) heptane (CB7CB). Such measurements certainly appear to resolve the differences between the two models in favour of that for the classic twist-bend nematic phase.     

Synthesis of novel three‐arm star azo side‐chain liquid crystalline polymer via ATRP and photoinduced surface relief gratings

A three‐arm star azo side‐chain liquid crystalline (LC) homopolymer, poly[6‐(4‐methoxy‐4‐oxy‐azobenzene) hexyl methacrylate] (PMMAZO), was synthesized by atom transfer radical polymerization (ATRP) method. The polymerization of 6‐(4‐methoxy‐4‐oxy‐azobenzene) hexyl methacrylate proceeded in a controlled/“living” way. A series of three‐arm star LC block copolymers (PMMAZO‐b‐PMMA) were also synthesized. The polymers were characterized by ¹H NMR, gel permeation chromatograph, and UV–vis spectra, respectively. The both polymers of PMMAZO and copolymers of PMMAZO‐b‐PMMA exhibited a smetic phase and a nematic phase. As concern to the PMMAZO, the glass‐transition temperature (T_g) and phase‐transition temperature from the smetic to nematic phase and from the nematic to isotropic phase increased with the increase of molecular weight (M_n(GPC)) of PMMAZO. The phase transition temperature of the block copolymers, PMMAZO‐b‐PMMA, with the same PMMA block was similar to that of PMMAZO. However, the T_g of the PMMAZO‐b‐PMMA decreased at low azo content and then increased with the increasing M_n(GPC) when azo content was above 61.3%. With illumination of linearly polarized Kr⁺ laser beam at modest intensities (35 mW/cm²), significant surface relief gratings formed on PMMAZO films with different molecular weights were observed. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 777–789, 2008     

Structure-property relationships in azobenzene-based twist-bend nematogens

ABSTRACT

The synthesis and characterisation of a new set of azobenzene-based non-symmetric liquid crystal dimers, the 1-(4-substitutedazobenzene-4?-yloxy)-6-(4-methoxybiphenyl-4?-yl)hexanes (MeOB6OABX), that exhibit the twist-bend nematic phase, N_TB, is described. The terminal substituents are methyl, methoxy, ethyl, butyl, butoxy, and nitrile. All six dimers exhibit both the N_TB and conventional nematic, N, phases. The identification of the N_TB phase was performed using polarised light microscopy and confirmed for binary mixtures with a standard twist-bend nematogen 1,7-bis-4-(4?-cyanobiphenyl) heptane (CB7CB). The transitional behaviour of the MeOB6OABX dimers is compared with that of the corresponding ether-linked 1-(4-substitutedazobenzene-4?-yloxy)-6-(4-methoxybiphenyl-4?-yloxy)pentanes, MeOBO5OABX, all of which exhibit a conventional nematic phase. In addition, the nitrile-substituted MeOBO5OABCN shows the N_TB phase. The behaviour of these non-symmetric dimers is also compared to that of the corresponding symmetric dimers. Differences in the transitional properties between these sets of new materials are accounted for in terms of not only molecular shape but also other factors including the strength of the mixed mesogen interaction.     

Calorimetric studies of poly (2-phenoxyethylacrylate)/5CB mixtures

The thermophysical properties of mixtures of poly (2-phenoxyethylacrylate) and 4-cyano-4′-pentyl-biphenyl, 5CB, are investigated using polarizing optical microscopy (POM) and differential scanning calorimetry (DSC). The polymer has a molar mass M _w = 181 000 g mol ^-1 the low molecular mass liquid crystal exhibits a nematic to isotropic transition at 35.3°C and crystallizes below 23°C. The phase diagram exhibits miscibility gaps in certain regions of temperature and composition where coexisting nematic and isotropic phases are found. From a practical point of view when considering the electro-optical applications of these systems, it proves to be useful to know precisely the amount of small liquid crystal molecules dissolved in the polymer matrix and the concentration of polymer in the nematic phase. The former quantity has a mechanical impact due to a plasticizing effect, an optical impact since it changes the polymer refractive index, while the polymer in the nematic phase shifts the transition temperatures influencing the electro-optical response of the liquid crystal. The present work addresses these important aspects using POM and DSC.     

Tunable backflow in chiral nematic liquid crystals via twist-bend nematogens and surface-localised in-situ polymer protrusions

Dynamic electro-optic response of the liquid crystal (LC) director shows a backflow effect that is manifested as an optical bounce in chiral nematic LCs (N*LC) during field-induced homeotropic-twisted transition. The bend elastic constant (K₃₃) strongly influences the dynamics of backflow at the N*LC in homeotropic-twisted transition. The cyanobiphenyl LC dimers – CB7CB, CB9CB and CB11CB – possess a unique characteristic of inherent bend molecular configuration that lowers K₃₃. With the modulation of the effective K₃₃ in dimer-doped N*LCs, we report the tunability of the optical bounce that decreases with the increase in the length of flexible spacers in LC dimers. The doped LC dimers with short spacer lengths not only generate a strong backflow with an enhanced twist degeneracy of the LC director across the cell, but also prolong the time of disappearance of the optical bounce. Furthermore, we demonstrate the suppression of the optical bounce with surface localised polymer protrusions having 50–100 nm diameters, which allow faster dynamic relaxation process and reduced backflow. We envision a novel design of a tunable microfluidic device for precise flow control of organic or inorganic matter in LC medium that exploits the tunable backflow in LC dimer-doped N*LCs.     

Investigation of surface anchoring strength and pretilt angle in NLC on rubbed polythiophene surfaces with alkyl chain lengths

A high pretilt angle for the nematic liquid crystal, 4-n-pentyl-4'-cyanobiphenyl (5CB), was observed on rubbed polythiophene (PTP) surfaces having alkyl chains with more than ten carbon atoms. We consider that this is due to a surface-excluded volume effect caused by the long alkyl chains between the LC molecules and the PTP surfaces. The polar anchoring strength in 5CB on rubbed PTP surfaces with long alkyl chains has also been successfully evaluated. The extrapolation length d_e of 5CB increases with increasing alkyl chain lengths above the seven carbons of alkyl chain R7; that is, it may be attributed to the high pretilt angle. An extrapolation length of 5 nm is observed in 5CB for the seven carbons alkyl chain R7 on the PTP surface; this indicates high anchoring strength.