Polymerization In Liquid Crystals Research Articles

Preparation of magneto-electro-optically active polymer using Fe ionic liquid as electro-magnetic dopant

In this research, we report the synthesis of conjugated polymers with magnetism. Electrochemical polymerization in liquid crystal was conducted with 1-butyl-3-methylimidazolium tetrachloroferrate (BMITF), which is a paramagnetic character having a large magnetic susceptibility, as a supporting salt. The polymer films thus obtained had magnetism because BMITF remains in the films as a dopant. Poly(2,2′-bithiophene) and poly(bis-(3,4-ethylenedioxythiophene)) were prepared in nematic or cholesteric liquid crystal with BMITF by electrochemical polymerization. Transcription of the liquid crystal structure was succeeded with a small amount of BMITF. Blush or fingerprint structures were confirmed by polarizing optical microscopy observation. The addition of the excess amount of BMITF broke the structure of the liquid crystal. Poly(2,2′-bithiophene) transcribed the cholesteric liquid crystal structure showed a negative Cotton effect, indicating with left-handed helical structure. Poly(bis-(3,4-ethylenedioxythiophene)) transcribed the cholesteric liquid crystal structure showed a positive Cotton effect, indicating the polymer forms a right-handed helical structure. The X-ray photoelectron spectroscopy measurements, confirming the existence of Fe element in the polymers thus obtained. From the electron spin resonance measurements, the polymers thus obtained showed magnetic activity. This method affords facile synthesis of conjugated polymers with magnetism.

Preparation of helical liquid crystal electrolyte with L-isoleucine derivatives and molecular asymmetric imprinting polymerization in liquid crystal to produce electro-optically coloration active polymers having chiral charge carrier chiralions

Molecular asymmetric imprinting polymerization in the cholesteric liquid crystal was carried out. An L-isoleucine derivative with fluorine was synthesized for a chiral inducer to induce the cholesteric liquid crystal from the nematic liquid crystal. A substance with multiple asymmetric centers can be obtained conveniently to use amino acid as chiral substance. The L-isoleucine derivative induced helical structure for 4-cyano-4'-hexylbiphenyl (6CB). Electrochemical preparation of π-conjugated polymers was carried out in the cholesteric liquid crystal. Fingerprint texture derived from the cholesteric liquid crystal was transcribed to the polymers. UV-vis and circular dichroism (CD) spectra of oxidized (doped) for and reduced (dedoped) form of the polymer were measured. Electrochemical polymerization in the helical liquid crystal produced the molecular aggregation imprinted chiral polymers, which have liquid crystal-like aggregation form, chirality with no stereogenic center via formation of polymer atropisomer, and electrochemical driven change in optical activity, as a form of electro-optically coloration active polymers. Finally, the polarons and bipolarons are in the form of chiral structure. These charge carriers in the polymers can be determined as chiral charge carrier “chiralions”.

(Digital Presentation) Electrochemical Polymerization of Thiophene in Cholesteric Liquid Crystal with Vitamins

Vitamins are natural compounds which is important for biological reactions. Vitamin C (ascorbic acid) is a water-soluble substance, while Vitamin E (tocopherol) is a soluble material in organic solvents. Further, antioxidant action can affect for metabolism in biological system. Vitamin E has three asymmetric centers in the molecular structure. In the liquid crystal technology, nematic liquid crystal is simple and high fluidity similar to isotopic liquid. Addition of small amount of chiral compounds to nematic liquid crystal can induce cholesteric liquid crystal. This is another chiral and helical version of nematic liquid crystal. In this study, we employed vitamin E as a chiral inducer to nematic liquid crystal for formation of helical liquid crystal system. Electrochemical polymerization is a convenient method for preparation of electroactive polymer deposited on an electrode in the form of thin film. Electrochemical polymerization in LC provides some interesting phenomena. First, electrochemical polymerization in liquid crystal allows the resultant to imprint morphology of molecular aggregation structure from molecular level to macroscopic level of liquid crystal. Second, electrochemical polymerization produces electroactive polymer with dynamically color change upon electrochemical redox process, which character can be applied for electrochemical driven display. Third, electrochemical charge and discharge provides voltaic storage function for the resultant polymer. Thus, electrochemical technique and polymer chemistry, such a brilliant combination produces electro-optic character. Recently, electrochemical polymerization in helical liquid crystal system has been performed. The electrochemical polymerization employs cholesteric liquid crystal as an electrolyte for polymerization. Cholesteric liquid crystal can be prepared by mix of nematic liquid crystal and chiral compounds. We employ synthetic compound as a chiral inducer. Here, we use vitamin E as chiral inducer to nematic liquid crystal preparation of cholesteric liquid crystal electrolyte solution for electrochemical polymerization. Observation of optical texture of the cholesteric liquid crystal electrolyte containing tetrabutylammonium perchlorate (TBAP) as a supporting salt showed fingerprint texture, which is characteristic of cholesteric liquid crystal.Next, electrochemical polymerization in cholesteric liquid crystal induced by vitamin E was carried out. We employed constant voltage electrochemical polymerization to ITO (indium–tin-oxide) coated glass slides were sandwiched via insulator tetrafluoroethylene as a spacer, and the choleretic liquid crystal electrolyte contained monomer (2,2′-bithiophene) was charged with pipette before application of voltage for electrochemical polymerization. The entire polymerization cell was heated to change the liquid crystal to isotropic phase. Then, gradually cooled to room temperature, and the isotopic phase was changed to cholesteric liquid crystal phase with iridescence. After confirming the electrolyte showed liquid crystal phase, constant voltage of 6 V across the sandwiched cell for 60 min was applied. Then, the polymerization cell was de-assembled and washed wish a large volume of organic solvent to remove the liquid crystal electrolyte solution, oligomer, and residual monomer. The polymer film thus prepared was deposited on cathode. This is quite interesting phenomena because electrochemical polymerization is generally occurred at the anode with oxidation. However, this result indicates that electrochemical polymerization in liquid crystal at cathode is possible. Cathodic electrochemical polymerization has been reported for dibromo aromatic compound or unsaturated aliphatic compounds. However, cathodic electrochemical polymerization of aromatic compounds with no halogen group has been few reported.The polymer shows electronic optical transition in visible range due to development of p-conjugated system and absorption at long wave lengths due to doping band accompany by generation on polaron (radical cation). The electrochemical character of the resultant polymer was examined using cyclic voltammetry (CV). The CV measurements were achieved in a monomer-free 0.1-M TBAP−acetonitrile solution at the scan rates of 10 mVs−1. The potential was calculated using a reference of silver/silver ion (Ag/Ag+) electrode. The oxidation and reduction signals are observed during the oxidation and reduction processes. The result showed the resultant polymer has good redox property. The resultant polymer shows no CD signal from short to long wavelengths, indicating no optical activity. However, the polymer shows the similar optical texture to that of liquid crystal electrolyte under the polarizing optical microscopy observations, implying the fingerprint texture of the polymer as macroscopic transcription of the liquid crystal structure may not contribute optical active property. Transcription from liquid crystal environment may not always occurs from molecular level to macroscopic level in the polymerization in liquid crystal. The polymer prepared in this study has no hierarchal structure from molecular level to the higher level, indicating macroscopic morphological imprinting in the polymerization is not essential condition for imprinting from the molecular level.

Reaction field induction self-amplification optical activity during polymerization in liquid crystal

A monomer having both chiral induction from nematic liquid crystal (LC) to cholesteric LC and polymerization activity was prepared. Addition of the compound to nematic LC induced the formation of a cholesteric liquid crystal in its chiral form. Subsequent electrochemical polymerization of the monomer produced an optically active polymer with a helical structure as confirmed by circular dichroism (CD) and optical rotatory dispersion measurements. While, the addition of the chiral monomer to an isotropic non-LC solution, and subsequent polymerization resulted a product with no clear optical activity. These results suggest that polymerization of the monomer in a cholesteric environment allows the formation of a polymer with high optical activity. Morphological imprinting from the matrix LC was confirmed by surface observation through polarizing optical microscopy. The chiral monomer changes the surrounding environment to grow into a more highly ordered helical structure. The matrix LC as the environment amplifies the optical activity with helical growth of the monomer during polymerization.

Conjugated Polymer Films Having a Uniaxial Molecular Orientation and Network Structure Prepared by Electrochemical Polymerization in Liquid Crystals.

A new method for fabricating conjugated polymer films was developed using electrochemical polymerization in liquid crystals and magnetic orientation. A uniaxial main chain orientation and a crosslinked network structure were achieved with this method. By employing eight types of monomers, the influence of the crosslinking for the film was investigated. The crosslinking was found to improve the solvent resistance of the conjugated polymer films. This new method is expected to be useful in various applications, such as high-powered organic electronic devices with durability.

Polymerization of furan by a sequential liquid crystal W-STEP method

Chemical oxidative oligomerization of furan as a monomer in helical twisted liquid crystal field and subsequently electrochemical polymerization were carried out with convenient one-pot process, referred to as double step (W-STEP) polymerization in liquid crystal. The pre-alignment of linear formed oligo-furan in the liquid crystal matrix and electrochemical polymerization affords to yield electo-optically active π-conjugate polymer with beautiful finger print pattern.

Chemical-Electrochemical Sequential Double-Step Polymerization in Liquid Crystal Allows for Imprinting of 3D Molecular Assembly Form Showing Electro-Chiroptical Effect

Chiroptical polypyrrole (PPy) film was prepared by sequential reaction of chemical oligomerization with FeCl3 and subsequent electrochemical polymerization in a cholesteric liquid crystal (CLC) con...

Precipitation polymerization in liquid crystals to prepare uniform epoxy microspheres

In this paper, uniform epoxy resin polymer microspheres (EMs) with controllable diameters and a narrow size distribution were prepared by precipitation polymerization using liquid crystals (LCs) as the solvent. The effects of the LC solvents on the morphologies of the resultant epoxy resin were thoroughly investigated. It was found that the formation of uniform EMs is sensitive to the properties of the LCs solvents. Uniform EMs can be obtained when the solubility parameters (δ) of the used solvent range from 20.59 to 21.29 (cal/cm3)1/2 and its dispersion terms (δd) are in the range of 19.87–20.89 (cal/cm3)1/2. Apart from the effects of solvents, the size of the as-made EMs can be further regulated from 2.6 μm to 10.1 μm by controlling the reactivity of epoxy monomers and the functionality of thiol hardeners. Moreover, we demonstrated that carbonizing the EMs can directly produce uniform carbon microspheres (CMs) with smooth surface. This work enlightens a new way for the preparation of EMs through precipitation polymerization in LCs solvent.

Electrochemical Preparation of Electro-active Polymers having Nitrogen Atom

New functions of polymer film can be developed by using template. We synthesized polypyrrole (PPy) as a conducting polymer in liquid crystal electrolyte solution. The liquid crystal electrolyte solution for the electrochemical polymerization contains monomer, electrolyte, and matrix liquid crystal. The electrochemical polymerization in liquid crystal was simply performed by using sandwich cell electrochemical polymerization method, which we have originally developed. Application of constant voltage between the two electrodes produces a solid polymer film at anode side through electrochemical oxidation polymerization process. Polarizing optical microscopy observation revealed that the polymer film thus obtained show beautiful optical texture like liquid crystal. The surface texture was derived from molecular structure transcription from the liquid crystal electrolyte solution. The transcription is occurred from molecular level to macroscopic level. Infrared absorption spectroscopy measurements, UV-Vis absorption measurements confirm that the polymer film is exactly pi-conjugated film, although the optical structure is very similar to that of liquid crystal. Furthermore, the polymer film can be tuned its color via electrochemical redox reaction (doping-dedoping). Therefore, the polymer has both liquid crystal order and electro-active property. Lyotropic liquid crystals have good affinity with water, and form crystal like aggregation structure via a self-assembly. Lyotropic liquid crystal shows variety in liquid crystal type, such as columnar phase, smectic phase, nematic phase, and cholesteric phase. In this research, we employed lyotropic liquid crystals for electrolyte solution. Columnar liquid crystals have paid attention as an electrical conduction materials having good carrier mobility. Therefore, the polymer thus prepared can be expected to show structure based unique electrical conduction function through columnar form produced by the transcription from the liquid crystal electrolyte solution in the electrochemical polymerization. Cholesteric liquid crystals show chiral aggregation form. The polymer prepared in cholesteric liquid crystal shows fingerprint texture under the observation of polarizing optical microscope, and optical rotation and circular dichroism. The optical rotation angle can be controlled with electrochemical redox reaction. In this presentation, we report, 1) Preparation of liquid crystal electrolyte solution and characterization 2) Electrochemical polymerization 3) Spectroelectrochemistry. This research can be involved molecularly imprinting (MIP) [3,4]. We discuss the method of electrochemical polymerization, functions, and future prospective of the polymer films prepared in liquid crystals based on electrochemistry.

Light driven asymmetric polymerization: an approach for tele-control reaction

Chiroptical activity tuning polymerization in liquid crystal (LC) electrolyte solution under irradiation of UV or Vis light was performed.

A computer simulation study of the influence of a liquid crystal medium on polymerization

We present a simple molecular level model based on Gay-Berne monomers linked by finitely extendable nonlinear elastic potential bonds for describing main chain polymerization in liquid crystals. We apply the model to study the influence that the order of the medium has on the characteristics of the chains obtained. We find that the chains prepared from the nematic are actually straighter than those obtained from a polymerization in the isotropic phase and that they are characterized by a small number of hairpins as experimentally observed.

Direct synthesis of aligned cis-rich polyacetylene films using low-temperature nematic liquid crystals

Liquid crystal polymerization method has been extended so as to cover synthesis of cis-rich polyacetylene films with high alignment. Three kinds of liquid crystal mixtures which maintain nematic phase at lower temperature than 0 °C have been developed by using a series of liquid crystals of phenylcyclohexane derivatives because of their well-confirmed inertness towards Ti(OBu) 4 - AlEt 3 catalyst. It has been implied from DSC measurements that catalyst solutions using three, five and six component systems permit low-temperature polymerizations ranging from −20 to −30 °C, from −40 to −60 °C and from −10 to −45 °C, respectively. Polyacetylene films synthesized by using five and six component liquid crystals with and without an external magnetic force have high cis contents of 85 – 94 %. High alignment of fibril morphology of the films has also been confirmed through SEM observations. Measurements of electrical conductivity of the films upon iodine doping yielded a maximum conductivity of 1.6 × 10 4 S/cm and electrical anisotropy of 7.0.

Highly Conducting Polyacetylene Films Prepared in a Liquid Crystal Solvent

Polyacetylene films prepared by the liquid crystal polymerization method with gravity flow technique are investigated through measurements of scanning electron micrographs, polarized infrared absorption spectra, and electrical conductivities. It is explored that the films have significant orientation of conjugated polyene chains along fibril alignment, and that upon doping by I2 or AsF5 they exhibit the highest electrical conductivity among those reported so far. By taking account of both morphological structure and activation energy for electrical conduction, the high conductivity is rationalized with preferential increase of parallel fraction of fibril achieved in the highly oriented polyacetylene films.

Highly conductive polyacetylene film prepared by the liquid crystal polymerization method under magnetic field

Advanced synthetic method of highly oriented polyacetylene film has been developed by applying magnetic force into a polymerization system consisting of nematic liquid crystals. Polymerizations were carried out at 10 – 13°C in order to keep the nematic phase under magnetic field of 2 – 14 kGauss. Polyacetylene films prepared showed high alignment of fibrils, providing not only crucial infrared dichroism in polarized infrared absorption spectra, but also the highest value of electrical conductivity with 10 4 S/cm order upon iodine doping.

Polymerization in liquid crystal — XVII. Effect of flexible substituents in the mesogenic side-chain on the behaviour of mesogenic polymers

Nine monomers, derivatives of the phenyl ester of acryloyloxybenzoic acid with general ▪ were synthesized; X was -(CH 2) 6O-, -(CH 2) 2O- or nothing; R was -O(CH 2) 4H, -OCH 3, or -H. Polymers from all the monomers were studied by polarization microscopy, differential scanning calorimetry and mechanical relaxation spectroscopy. It was established that transition temperatures of the polymers, as plotted against the chain length of the spacer as well as of the p-alkoxy substituent, were monotonous functions tending to limiting values. A nematic state was found only for the polymer from p-butoxyphenyl- p′-acryloyloxy hexoxybenzoate.

Polymerization in liquid crystal — XVIII. Effect of the polyethyleneoxide main chain on the properties of polymers containing mesogenic groups in the side chain

The effect of the main chain on the mesomorphic properties was studied on the basis of the three-component thermodynamic model of polymers containing mesogenic groups in the side chain. Poly(ethylene oxide) oligomers substituted with mesogenic groups were prepared by reacting epichlorohydrin with mesogenic molecules. It was established that the glass transition temperatures of these oligomeric products were markedly reduced in comparison to polyacrylates containing the same rigid core. The relatively flexible main chain increases the clearing point relative to that of the monomer. Clearing point rises with length of the main chain. A flexible main chain suppresses the vibration of the rigid cores thus increasing the thermal stability of the mesomorphic structure. No explanation was found for the exothermic latent heat of 170 J/g observed during the first melting of the cholesteryl succinyl epoxypropionate oligomers and polymers.

Molecular Optics: Nonlinear Optical Processes in Organic and Polymer Crystals

Abstract Physical studies of nonlinear optical properties of organic and polymer structures have demonstrated exceptionally large second and third order nonlinear optical responses that are important to the fields of nonlinear optics and optical device technologies. These unusual responses have been exhibited by a large number of structures, phases, and states that include organic solids and films, single crystal polymers, Langmuir-Blodgett films, liquid crystals, and liquid crystal polymers. Experimental and theoretical studies of such systems have achieved significant advances in the understanding of these exceptional macroscopic nonlinear optical responses based on theoretically calculated microscopic electronic mechanisms, especially the role of electron-electron correlations and highly charge correlated electron excited states. Combined theory and experiment has led to the recent discovery of liquid crystal polymerization of divinyldiacetylene monomers to form highly conjugated liquid crystal polymer...

Polymerization in liquid crystals. XIII. Copolymerization of mesogenic monomers

Polymerization in liquid crystals. XIII. Copolymerization of mesogenic monomers

Polymerization in liquid crystals—IX: Structural investigations of copolymers containing p-methyl- p′-acryloyloxy azoxybenzene and cholesterylvinyl succinate

Structure of copolymers of p-methyl- p′-acryloyloxy azoxybenzene (MAAB) with cholesterylvinyl succinate (CVS) was studied by small- and wide-angle X-ray diffractometry, DSC, polarizing microscopy, and thermomechanical methods. The copolymers were found to be anisotropic non-crystalline substances in which the radial distribution of the radius of gyration of inhomogeneities corresponds to that of the diameter of the molecules determined by GPC. Both phase transition temperatures and clearing points of copolymers show a minimum as functions of the composition. On both sides of this minimum, the copolymers have different structures. At higher MAAB contents, the copolymer structure is similar to that of polyMAAB; at lower MAAB concentrations, alternating copolymer is formed similar in structure to polyCVS. For identification of the structures, copolymer/comonomer phase diagrams were also investigated.

Polymerization in liquid crystals—XI: Copolymerization of N-acryloyl piperidine with cholesteryl acrylate and phenyl- p-acryloyloxy benzoate

N-acryloyl piperidine (AP) was copolymerized with mesogenic monomers [such as cholesteryl acrylate (CA) and phenyl- p-acryloyloxy benzoate (PAB)] in isotropic solution using radical initiation (A AP = 1.1, r CA = 0.16, and r AP = 0.81, r PAB = 0.16. The copolymers are anisotropic having minimum values of transition and clearing points with composition. The composition corresponding to the minimum is a boundary between two structures as indicated by wide-angle X-ray scattering. Distribution of the gyration radii determined by GPC in tetrahydrofuran is identical to that of solid polymers measured by small-angle X-ray scattering, except that the average value of the latter is about 10 −6 cm less than that of the former. It was established that AP as a non-mesogenic comonomer did not suppress the mesomorphism of the copolymer and in fact formed mesomorphic homopolymers. In the solid polymer, the macromolecule which is anisotropic in geometry was found to form the structural unit having a minimum of the melting and clearing point with composition, as for a eutectic system.