Synthesis and characterization of thermotropic liquid crystalline poly(ester‐imide‐ketone)

A series of poly(ester imide ketone)s derived from N,N′‐hexane‐1,6‐diylbis(trimellitimide), 4,4′‐dihydroxybenzophenone, and p‐hydroxybenzoic acid (PHB) were synthesized by the direct polycondensation method in benzene sulfonyl chloride, dimethylformamide, and pyridine with varied PHB contents. The liquid crystalline behavior and thermal properties of the poly(ester imide ketone)s were characterized by polarized‐light microscopy, wide‐angle X‐ray diffraction, thermogravimetric analysis, differential scanning calorimetry, and temperature‐modulated differential scanning calorimetry (MDSC). The results showed that the synthesized polymers possessed a nematic thermotropic liquid crystalline characteristic and high thermal stability. The liquid crystalline polymers, with a PHB content ranging from 0 to 50 mol %, exhibited multiple phase transitions as evidenced by the MDSC results. A transitional smectic phase from solid state to nematic thermotropic liquid crystalline state was observed, and a transition model is proposed. Under certain conditions, the polymer with 33 mol % PHB content showed two significantly different liquid crystalline textures. This type of liquid crystalline polymer exhibited excellent fiber forming. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1045–1052, 2003     

Synthesis and mesomorphic properties of a new side‐chain,chiral smectic,liquid‐crystalline elastomer

The synthesis of the new chiral monomer 4‐(10‐undecylen‐1‐yloxy)biphenyl‐4′‐[(S)‐2‐methyl‐1‐bu‐ toxy]benzoate (M₁), the nematic crosslinking agent biphenyl 4,4′‐bis(10‐undecylen‐1‐yloxybenzoate) (M₂), and the corresponding liquid‐crystalline elastomer is described. The chemical structures of the chiral monomer and crosslinking agent have been characterized with Fourier transform infrared, elemental analyses, and proton and carbon‐13 nuclear magnetic resonance spectra. The mesomorphic properties have been investigated with differential scanning calorimetry, polarizing optical microscopy, and X‐ray diffraction. Monomer M₁ shows different smectic phases (smectic A, chiral smectic C, and smectic B) and a cholesteric phase, and M₂ exhibits a nematic phase. The liquid‐crystalline elastomer shows smectic A and chiral smectic C phases. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4234–4239, 2006     

Synthesis and photoluminescence property of polyacetylenes containing liquid crystalline side groups

A series of new side-chain liquid crystalline (LC) polyacetylenes containing 4-(trans-n-alkylcyclohexanylcarbonyloxy)phenyl 4-alkynyloxybenzoate side groups were synthesized by using [Rh(nbd)Cl]₂, WCl₆ and MoCl₅ as polymerization catalysts. The synthesized polymers were characterized by differential scanning calorimetry, optical microscopy and X-ray diffraction measurements. The monomers showed a nematic phase while all polymers revealed the nematic, smectic A and smectic C phases. X-ray diffraction measurements proved that all the polymers show an interdigitated bilayer structure. The optical properties of the polymers were investigated by UV-vis and photoluminescent spectroscopies. The polymer films emitted green-blue photoluminescence at about 500 nm.     

Simulation study on the liquid‐crystalline ordering and fluidity of energetic diblock copolymers based on poly[3,3‐bis(azidomethyl) oxetane]

The liquid‐crystalline ordering and fluidity of energetic diblock copolymers based on poly[3,3‐bis(azidomethyl) oxetane] (BAMO) and 3‐nitratomethyl‐3′‐methyloxetane (NMMO) were investigated by the dissipative particle dynamics method. The results show that these copolymers, with moderate BAMO block lengths (x's), experienced the disorder, nematic, and smectic phases with decreasing temperature. The nematic phase was suppressed when the rod length was too long or short. After the formation of the smectic phase, the fluidity had a sharp decline. The temperature forming the smectic phase was defined as the order–disorder transition temperature (T_ODT) and depended strongly on x. A simple scaling rule, T_ODT ≈ e^?x, between T_ODT and x was constructed. The effect of the soft NMMO block fraction on the fluidity emerged before the formation of the smectic phase. These results can help researchers design and synthesize new energetic copolymers with an appropriate melting temperature range for use as binders of solid propellants. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis and characterization of side‐chain liquid‐crystalline ionomers containing quaternary ammonium salt groups

A series of thermotropic side‐chain liquid‐crystalline ionomers (LCIs) containing 4‐(4‐alkoxybenzyloxy)‐4′‐allyloxybiphenyl (M) as mesogenic units and allyl triethylammonium bromide (ATAB) as nonmesogenic units were synthesized by graft copolymerization upon polymethylhydrosiloxane. The chemical structures of the polymers were confirmed by IR spectroscopy. DSC was used to measure the thermal properties of these polymers. The mesogenic properties were characterized by polarizing optical microscopy, DSC, and X‐ray diffraction. Homopolymers without ionic groups exhibit smectic and nematic mesophases. The nematic mesophases of the ionomers disappear and the mesomorphic temperature ranges decrease with increasing concentration of ionic units. The influence of the alkoxy chain length on clearing temperature (T_c) values of ionomers clearly shows an odd‐even effect, similar to that of other side‐chain liquid‐crystalline polymers. The mesomorphic temperature ranges increase with increasing alkoxy chain length when the number of alkoxy carbon is over 3. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2879–2886, 2003     

Thermotropic,side-chain ordered polymeric coatings: gas permeability switching via a thermal stimulus

Rapid access to large areas of stimuli-responsive materials is attractive in the field of membrane science for purification systems and molecular valves. Thermotropic liquid crystalline (LC) systems show sharp property changes through the smectic–LC transition induced by temperature. Comparison of similar amorphous and liquid crystalline systems allows for the elucidation of the characteristics of the LC phase. Lightly crosslinked C₆F₁₃ and C₈F₁₇ perfluorinated side-chain acrylate networks were UV cured as thin films resulting in amorphous and thermotropic liquid crystalline thin films, respectively. Thermal and morphological characterization indicates a restructuring of the liquid crystalline phase through the isotropic transition giving rise to an increase in transport and free volume properties. The amorphous film showed no dramatic change in transport or free volume properties.     

Novel cellulose derivatives. I. Liquid crystal phase formation in tri-O-α-naphthylmethyl cellulose solutions

Tri-O-α-naphthylmethyl cellulose was prepared by homogeneous phase reaction using SO₂–diethylamine (DEA)–dimethyl sulfoxide (DMSO) as the solvent system. Observations made by dynamic mechanical spectrometry and by cross-polarized optical microscopy revealed liquid crystalline behavior for the concentrated solutions of tri-O-α-naphthylmethyl cellulose in dimethylacetamide (DMAc). Experimental and calculated (predicted) critical volume fraction of the derivative, V^c_p, did not show agreement. It is determined that V^c_p is affected by bulky substituents on the cellulose backbone to some extent. © 1993 John Wiley & Sons, Inc.     

Phase identifications and monotropic transition behaviors in a thermotropic main-chain liquid crystalline polyether

A thermotropic liquid crystalline (LC) polyether was synthesized by condensation polymerization of 1-(4-hydroxyphenyl-2-(2-methyl-4-hydroxypheyl)ethane) and α,ω-dibromononane, and abbreviated as MBPE-9. Multiple phase transitions were found via differential scanning calorimetry (DSC) upon heating and cooling. Based on wide-angle X-ray diffraction (WAXD) and polarized light microscopy (PLM) experiments, two monotropic LC nematic (N) and smectic phases and three crystalline (orthorhombic K₁, triclinic K₂ and triclinic K₃) phases were identified. A study on kinetics showed that only when the N phase formation rate was faster than the crystallization rate of K₁ phase which directly grew from the melt, the presence of the N phase could accelerate both the overall crystallization and the linear crystal growth rates of K₁ phase. In a narrow temperature region, two distinct crystal growth rates could be observed: one was directly from the isotropic melt, and another was from the N phase.     

Preparation of novel liquid crystalline polymeric film material and its photoinduced alignment behavior

Two kinds of novel oxetane monomers, containing biphenyl, flexible spacer and cinnamoyl group, were synthesized. The liquid crystal phase behavior of the corresponding polymers was investigated and isotropic–nematic, nematic–smectic and smectic–crystal transitions were identified during cooling. Both polymers exhibited clear fan texture morphology under a polarized optical microscope. Irradiation of a polymer film with linearly polarized UV light led to cycloaddition of the cinnamoyl groups, causing simultaneous alignment of the liquid crystal unit.     

Main‐chain liquid‐crystalline ionomers bearing potassium sulfonate groups

A series of thermotropic main‐chain liquid‐crystalline (LC) ionomers were prepared, which contained potassium sulfonate groups pendent to the chains. The polymers were prepared in an esterifying reaction with potassium ion contents ranging between 0 and 3.9 wt %. The content of potassium ion was characterized by spectrophotometric analysis with sodium tetraphenylboron as the titrant. Chemical structures were determined by various experimental techniques including Fourier transform IR spectroscopy and ¹H‐NMR. LC properties were characterized by differential scanning calorimetry, polarizing optical microscopy, and X‐rays. All of the polymers displayed nematic or smectic mesophases. With increasing potassium sulfonate ionic concentration in the polymers, the melting temperatures and isotropic transition temperatures changed little, whereas the temperature of the smectic A–nematic phase transition increased. The ionic aggregation was tangled with the rigid mesogenic groups of LC segments to form multiple block domains, leading the soft main chains to fold and form a lamellar structure due to their electrostatic interactions. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2021–2026, 2005     

Synthesis,Characterization and Texture Observations of Calamitic Liquid Crystalline Compounds

Several divinylic mesogenic monomers were synthesized based on coupling the monomer 4-(4-pentenyloxy)benzoic acid with chlorohydroquinone, 2,5-dihydroxy- acetophenone, methylhydroquinone or 2-methoxyhydroquinone. This resulted in novel mesogens of phenylene esters with different lateral substituent groups. The effect of the lateral substituent group on the thermotropic phase behavior for these liquid crystalline compounds was investigated using DSC and optical polarized microscopy. All the mesogens proved to have a wide nematic liquid crystalline range. Only the phenylene ester, which has a methoxy lateral substituent, exhibited both nematic and smectic phases. Structural confirmation of all new derivatives was accomplished by ¹H- and ¹³C-NMR spectroscopic analysis, along with CH elemental analysis.     

Preparation of Tri-O-alkylcellulose by the use of a nonaqueous cellulose solvent and their physical characteristics

Tri-O-methyl-, -ethyl-, -n-propyl-, -n-butyl-, -n-pentyl-, -iso-amyl-, -n-hexyl-, -n-heptyl-, -n-octyl-, -n-decyl-, and -3-phenoxypropyl-celluloses have been prepared with powdered sodium hydroxide and the corresponding alkyl iodides or bromides in one of nonaqueous cellulose solvents, SO₂-diethylamine-dimethylsulfoxide. These new tri-O-alkylcelluloses were characterized by infrared spectra, ¹³C-NMR spectra, and optical rotations. The first six tri-O-alkylcelluloses described above were obtained as white powders and most of them (tri-O-methyl-, -ethyl-, -n-propyl-, and -n-pentyl-celluloses) showed thermotropic liquid crystals due to smetic or short pitch cholesteric phases. On the other hand, the latter five derivatives were obtained as gummy solids even at room temperature, and easily showed lyotropic liquid crystals in their concentrated chloroform solutions due to choresteric phases. some of these tri-O-alkyl-celluloses (tri-O-methyl-, -ethyl-, -n-propyl-, and -n-butyl-celluloses) were characterized by differential scanning calorimetric and X-ray diffractometric analyses.     

Side‐chain copolymers containing smectic monomer and chiral reagent—Synthesis and characterization

A series of new chiral side‐chain liquid‐crystalline polymers were prepared containing smectic‐nematic monomer and nonmesogenic chiral monomer. All polymers were synthesized by graft polymerization using polymethylhydrosiloxane as backbone. The mesomorphic properties were investigated by differential scanning calorimetry, polarizing optical microscopy, thermogravimetric analyses, and X‐ray diffraction measurements. The chemical structures of the monomers and polymers obtained were confirmed by Fourier transform infrared, proton nuclear magnetic resonance spectra (¹H NMR). M₁ showed smectic (S_B, S_C) and nematic phase on the heating and the cooling cycle. Polymers P₀–P₂ were in chiral smectic A phase, while P₃–P₅ were in cholesteric phase, P₆ has bad LC properties, and P₇ has no LC properties. Experimental results demonstrated that nonmesogenic chiral moiety and LC mesogenic with long carbochain offered the possibility of application because of its lower glass transition temperature, and the glass transition temperatures and isotropization temperatures and the ranges of the mesophase temperature reduced with increasing the contents of chiral agent. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis and thermal transitional properties of side-chain liquid crystalline polyacrylates containing para-nitroazobenzene as mesogenic groups

The synthesis and characterization of side-chain liquid crystalline (LC) polyacrylates containing para-nitroazobenzene (Pn) as mesogenic groups were described. Homopolymers with 3 and 4 carbon atoms in the spacers were non-LC polymer; for homopolymers with 6 carbon atoms in the spacer, nematic LC behavior was observed. Copolymers with acrylic acid as one componenet exhibited an S_Ad phase according to the WAXD results which showed the d/l of 1.4–1.54 for the copolymers with 3,4 and 6 carbon atoms in the spacers. Considering the molecular structure as well as the WAXD results of the copolymers, the possible molecular arrangement in the smectic S_Ad phase was proposed, in which the smectic layers were composed of the antiparallel mesogens and the antiparallel arrangement was considered to be enhanced due to the H bond between  COOH and  NO₂. The stress-induced orientational phenomena of Pn in the LC states was also discussed. © 1996 John Wiley & Sons, Inc.     

Synthesis and characterization of a series of smectic liquid crystalline elastomers

A series of new smectic and cholesteric liquid crystalline elastomers was prepared by graft polymerization of mesogenic monomer with the chiral and nonmesogenic crosslinking agent using polymethylhydrosiloxane as backbone. The chemical structures of the monomers and polymers obtained were confirmed by Fourier transform infrared (FTIR), proton nuclear magnetic resonance spectra (¹H‐NMR). The mesomorphic properties were investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and X‐ray diffraction measurements (XRD). M₁ showed smectic (S_B, S_C, S_A) and nematic phases during the heating and the cooling cycles. Polymer P₀ and elastomer P₁ exhibited smectic B phase, elastomers P₂–P₅ showed smectic A phase, P₆ and P₇ showed cholesteric phase, and P₈ displayed stress‐induced birefringence. The elastomers containing less than 15 mol % M₂ displayed elasticity and reversible phase transition with wide mesophase temperature ranges. Experimental results demonstrated that the glass transition temperatures decreased first and then increased; melting temperatures and the isotropization temperatures and the mesophase temperature ranges decreased with increasing content of crosslinking unit. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 498–506, 2005     

Synthesis and properties of photochromic cholesteric liquid crystalline polysiloxane containing chiral mesogens and azobenzene photochromic groups

A series of novel thermotropic side‐chain liquid crystalline polymers(P₀–P₁₂) were synthesized by grafting copolymerization of mesogenic monomer cholesteryl undecylenate (M1) and photochromic monomer 4‐allyoxy‐4′‐nitroazobenzene (M2) on polymethylhydrosiloxane. The chemical structures of polymers were characterized by infrared (IR) and ultraviolet (UV) spectroscopy. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to measure the thermal properties of those polymers, and the mesogenic properties were characterized by polarized optical micrograph, DSC, wide‐angle X‐ray diffraction and small‐angle X‐ray scattering. The glass transition temperatures (T_gs) of the polymers increased from P₀ to P₄ and decreased from P₅ to P₁₂. The clearing point temperatures (T_is) of the polymers P₁–P₁₂ were lower than that of P₀, but increased from P₁ to P₄ and decreased from P₅ to P₁₂. They showed thermotropic liquid crystalline properties in a broad mesogenic region at temperatures >100°C. The polymers P₀–P₈ exhibited a cholesteric mesophase with oily streaks and lined texture, and polymers P₉–P₁₂ showed a chiral smectic mesogenic phase with a layered texture. All of the polymers were thermally stable to ～ 320°C. The UV‐induced trans–cis photoisomerization was investigated for the azo monomer and polymers P₈ and P₁₂. The solution of the azo monomer and liquid crystalline polymers P₈ and P₁₂ can undergo photoisomerization, and the environments of the azo group were responsible for the aforementioned photochemical process. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2155–2162, 2002     

Preparation and properties of azobenzene-containing amphiphilic miktoarm star polymers

Summary A series of novel miktoarm star polymers composed of a poly(ethylene oxide) (PEO) and two side-chain liquid crystalline azobenzene-containing polymethacrylate (PEO-(PMMAZO)₂) were prepared using atom transfer radical polymerization (ATRP). Bifunctional macroinitiator PEO-Br₂ was synthesized by condensation reaction in two steps and characterized by ¹H NMR, ¹³C NMR and IR. Kinetic study showed that it was a first order reaction referred to the monomer MMAZO, namely, 6-(4-methoxy-4’-oxy-azobenzene)hexyl methacrylate. The liquid crystalline behaviors of the miktoarm star polymers were studied by differential scanning calorimetry (DSC) and polarized optical microscope (POM). They exhibited smectic and nematic mesophases when Mn was beyond 9.4×10³ g/mol. The phase transition temperatures of the smectic and nematic phases increased while the melting temperature of PEO decreased with increasing molecular weight of the LC block. Compared with diblock polymer PEO-PMMAZO, the melting temperature of PEO in miktoarm star polymer decreased more rapidly.     

Investigation of the electrothermo-optical effect of a smectic LCP–nematic LC–chiral dopant ternary composite system based on SA ↔ N* phase transition

A sharp change in transmittance from a transparent state to a light scattering one within a tiny temperature range is induced accompanied with the heat-induced phase transition from a smectic-A (S_A) phase to a chiral nematic (N*) one in a side-chain smectic-A liquid crystalline polymer (S_ALCP)–low-molecular-weight nematic liquid crystal (NLC)–chiral dopant ternary composite system with a homeotropic boundary condition. By adjusting the polymer ratio, an induced N* phase exhibiting strong light scattering over a wide temperature region has been obtained. The resulting scattering texture retained in the S_A phase due to fast cooling from the N* phase can be rather stable and can be easily erased by cooling slowly from the N* phase to the S_A phase after the scattering texture being heated into the N* phase again or by application of an alternating current electric field on the scattering texture directly. Based on these characteristics, it is very possible that this composite system will be used as a novel thermal addressed liquid crystal display material with respect to a fast response, a high contrast, and a durable memory effect. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 623–631, 1999     

Permeation of carbon dioxide in a thermotropic liquid-crystalline polyester

The transport properties of a thermotropic liquid crystalline polyester have been analyzed using carbon dioxide as permeant. Carbon dioxide, in the analyzed range of temperature and pressure, gives some information on the phase organization of the system. The structural model compatible with the transport behavior assumes the presence of a disordered phase within the well-ordered liquid crystalline domains. The same structural model was previously suggested on the basis of the transport behavior of methylene chloride vapors in nematic and smectic liquid-crystalline polymers.