Studies on the thermotropic liquid crystalline polymer. VII. Synthesis and properties of photocrosslinkable poly(ether-ester) containing cinnamic group

A series of semi-aromatic poly(ether-ester)s containing cinnamic group was prepared from 4,4′-diacrylic acid-α,ω-phenoxyalkanes with diols in the presence of diphenylchlorophosphate (DPCP) and pyridine as a catalyst and solvent. The phase behavior of these polymers was studied by differential scanning calorimetry (DSC), optical polarizing microscopy equipped with a heating stage, and wide-angle x-ray diffraction (WAXD). All of the poly(ether-ester)s, except P3 , show nematic or smectic thermotropic liquid crystalline behaviour under optical polarizing microscopic observation. These polymers can undergo photocrosslinking reaction upon heating, as examined by IR, solubility, and DSC analysis. © 1993 John Wiley & Sons, Inc.     

Studies on thermotropic liquid crystalline elastomers. II. Synthesis and properties of liquid crystalline polyester elastomers

Three series of novel thermotropic liquid crystalline polyester elastomers (TLCPEEs) were prepared by direct polycondensation from terephthalic acid, polyols (M_n = 1000 or 2000), and various diols. The structures and thermal properties of the synthesized TLCPEEs were examined by FTIR spectroscopy, differential scanning calorimetry, thermal optical polarized microscopy, thermogravimetric analysis, and wide-angle x-ray diffraction. The effects of kinds and amount of diols and the molecular weight of polyols on the thermal properties of TLCPEEs were studied. By introducing long flexible spacers (PE-1000 or PE-2000) into the polymer main chain, all polymers showed two-phase morphology under the thermal optical microscopic observation. All of the synthesized polymers, except polymer P1-BPA60 and P2-BPA60, which were prepared from BPA, exhibited thermotropic liquid crystalline properties that were in the smectic phase. © 1995 John Wiley & Sons, Inc.     

Studies on thermotropic liquid crystalline polymer. XI. Effect of amide group on thermotropic liquid crystalline polymer properties

A series of poly(azomethine)s containing amide, ether, or ester groups was prepared by the condensation of dialdehydes with various diamines. The thermotropic liquid crystalline properties were examined by DSC and microscopic observations. The effects of the number and position of amide groups, which are attached to the rigid segment, on the thermotropic liquid crystalline properties of the homo-and copoly(amide-azomethine-ether)s were also investigated in this study. The copolymerization took place by changing the amount of amide group to obtain copoly(amide-azomethine) ( P13 and P14 ) which exhibit thermotropic liquid crystalline properties. The poly(azomethine)s containing ether or ester groups also exhibited thermotropic liquid crystalline properties. © 1993 John Wiley & Sons, Inc.     

Studies on thermotropic liquid crystalline polyurethanes. II. Synthesis and properties of liquid crystalline polyurethane elastomers

Three series of novel thermotropic liquid crystalline polyurethane elastomers (TLCPUEs) were studied. Hard segments were formed by using hexamethylene diisocyanate (HDI) reacted with a mesogenic unit, benzene-1,4-di(4-iminophenoxy-n-hexanol), which also acted as a chain extender. Three diols: 1,10-decanediol,poly(oxytetramethylene) glycol (PTMEG) M _n = 1000 and PTMEG M _n = 2000 were used as the soft segments. The effects of soft segments of polyurethanes on the liquid crystalline behavior were studied. Higher molecular weight TLCPUEs were obtained by adding 30?50 mol % of mesogenic segments to diisocyanates. In contrast to a conventional chain extender such as 1,2-ethylene glycol or 1,4-butyl glycol, the synthesized polyurethane elastomers exhibited a mesophase transition by using a mesogenic unit as the chain extender. Mesophase was found for all synthesized LC polyurethanes except of polymers H2-A-12 and H2-A-7. The structures and the thermal properties of all synthesized TLCPUEs were studied by using FTIR spectroscopy, wide-angle x-ray diffraction (WAXD) and DSC measurements, a polarizing microscope equipped with a heating stage, dynamic mechanical analysis (DMA), and thermogravimetric analysis (TGA). Mechanical properties were also examined by using a tensilemeter. © 1995 John Wiley & Sons, Inc.     

Random thermotropic elastomers. I. Effects of substitution and hard/soft segment lengths on properties

Syntheses of segmented copoly(ether-ester)s with (oxy-2-methyl-1,4-phenyleneoxycarbonyl-1,4-phenylene carbonyl)/(oxy-2-chloro-1,4-phenyleneoxycarbonyl-1,4-phenylene carbonyl) (methyl-/chloro-substituted) hard segments and poly(oxytetramethylene) soft segments, are reported. The methodology consisted of staged addition melt condensation of terephthaloyl chloride, poly(oxytetramethylene)glycol (POTMG; \[ \bar M_n \] = 250, 650, 1000, 2000) and methyl-/chloro-hydroquinone. Lengths of hard and soft segments were varied while the weight ratio of hard to soft segment was maintained constant. Copolymers were characterised for solubility behavior, and by infrared spectroscopy, x-ray diffraction, DSC, and polarizing microscopy. Thermal properties were found to be dependent on length of soft segment as well as on the type of substituent in the mesogenic core. In both methyl- as well as chloro-substituted copoly(ether-ester)s soft segment glass transition temperature (T_gs) was obtained between ?40 and ?50°C. All copoly(ether-ester)s are elastomeric at room temperature (25°C). These polymers exhibit thermotropic liquid crystalline behavior and were easily sheared and aligned in liquid crystalline state. © 1994 John Wiley & Sons, Inc.     

Study on the thermotropic liquid crystalline polycarbonates. IV. Synthesis and properties of liquid crystalline poly(imide-carbonate)s

Two series of novel thermotropic liquid crystalline poly(imide-carbonate)s were prepared by melt polycondensation from various arylene or alkylene bis(phenylcarbonate)s by using N,N′-bis(hydroxyethyl)pyromellitimide and N,N′-bis(hydroxypropyl)pyromellitimide as monomers. Thermotropic liquid crystalline properties were characterized by a polarizing microscope with a heating stage and a differential scanning calorimeter (DSC). Nematic melts were found for the synthesized aromatic poly(imide-carbonate)s. In order to investigate whether the pyromellitimide unit could be used as a mesogenic unit for preparing LC polymers, a series of aliphatic poly(imide-carbonate)s was prepared in this study. However, no significant LC textures were found under the observation by polarizing microscope. It was suggested that the aspect ratio of the pyromellitimide unit was too short to form liquid crystalline poly(imide-carbonate)s. In addition, it was interesting that the aliphatic poly(imide-carbonate)s with a longer spacer (n = 3) in the pyromellitimide unit showed better crystallinity. Thermostabilities of all synthesized poly(imide-carbonate)s were measured by thermogravimetric analysis (TGA). © 1994 John Wiley & Sons, Inc.     

Studies on the thermotropic liquid crystalline polymer. I. Synthesis and properties of polyamide-azomethine-ether

A series of polyamide-azomethine-ethers was prepared by condensation of 4,4′-diaminoanilide with 4,4′-diformyl-α,ω-diphenoxyalkane, 4,4′-diformyl-3,3′-methoxy-α,ω-diphenoxyalkane, and 4,4′-diformyl-3,3′-ethoxy-α,ω-diphenoxyalkane, respectively. The inherent viscosities of polymers were obviously increased when the polymers were treated by heat under nitrogen at 220°C. The thermotropic liquid crystalline properties were examined by DSC, microscope observations, and TGA. All of the polymers, except polymer A-1, exhibit thermotropic liquid crystalline properties. They also exhibit threaded and/or Schlieren textures examined by the polarizing microscope which indicate a nematic phase. In most cases, the mesophase exists up to ca. 400-460°C shown by TGA study. The mesophase cannot exist above 400-460°C because of the thermal decomposition.     

Studies on the thermotropic liquid crystalline polymer. VI. Synthesis and properties of homo- and co-poly(amide-azomethine-ether)

Two series of poly(amide-azomethine-ether)s and poly(ester-azomethine-ether)s were prepared by the condensation of dialdehydes with N,N'-bis(aminobenzamide)s and 4,4′-bis(p-aminophenyl)terephthalester, respectively. The thermotropic liquid crystalline properties were examined by DSC microscopic observations. Almost half of the synthesized polymers exhibit thermotropic liquid crystalline properties which are in the nematic phase since threaded and/or Schlieren textures are observed under polarizing microscope. The effects of the number of amide group and the nature of the nonlinear bibenzamide moiety, which link in the rigid segment, on the thermotropic liquid crystalline properties of the homo- and co-poly(amide-azomethine-ether)s were also investigated.     

Thermotropic liquid crystalline polymers with low thermal transitions. I. Low melting thermotropic liquid crystalline homo- and co-polycarbonates

Due to the particular rheological properties of thermotropic liquid crystalline polymers (TLCP), their application for imaging technology has been investigated. The first class of polymers investigated in this study are the thermotropic liquid crystalline polycarbonates prepared from the solution polycondensation of p,p-dihydroxybiphenyl with bischloroformate as the aliphatic flexible spacer. From the variety of bischloroformates employed, smectic TLCP's were generally obtained with the possible presence of a nematic mesostate. The introduction of comonomers such as substituted hydroquinones or bisphenols were found to lower both the melting transitions and mesophasic range of the TLCP. From rheological characterization, the amount of nonmesogenic moieties present in the copolycarbonates were found to correlate with the increase in the melt viscosity of TLCP.     

Studies on the thermotropic liquid crystalline polycarbonates. III. Synthesis and properties of fully aromatic liquid crystalline polycarbonates

Four series of fully aromatic thermotropic liquid crystalline polycarbonates were prepared by melt polycondensation from various novel phenylene diphenyl dicarbonates with monomers, such as hydroquinone, methylhydroquinone, chlorohydroquinone, resorcinol, bisphenol A, 4,4′-dihydroxydiphenylsulfone, or phenylhydroquinone, respectively. The thermotropic liquid crystalline properties were studied by polarizing microscope with a heating stage, differential scanning calorimeter (DSC), and wide-angle x-ray diffraction (WAXD). It was found that the nonlinearity of the carbonate group was compensated by resorcinol (1,3-phenylene unit), a bent shape unit. Nematic melts were found for the resulting polycarbonates. © 1993 John Wiley & Sons, Inc.     

Mesomorphic properties of liquid crystalline polysiloxanes and elastomers based on a tri-vinyl crosslinker

A series of crosslinked liquid crystalline polymers and the corresponding uncrosslinked liquid crystalline polymers were prepared by graft copolymerization; their liquid crystalline properties were characterized by DSC, POM and X-ray measurements. The results show that the crosslinking obtained in the isotropic state leads to a reduction of the clearing point (T_c) of the crosslinked polymers, as compared with the corresponding uncrosslinked polymers. The crosslinked polymers with low crosslinking density (P₁-P₇) exhibit nematic mesogenic phases, as do the uncrosslinked polymers. In contrast, a high crosslinking density leads to the crosslinked polymers P₈ and P₉ losing their thermotropic liquid crystalline phases; they instead exhibit stress-induced orientation.     

Flow-induced structure in a thermotropic liquid crystalline polymer as studied by SANS

Small-angle neutron scattering is utilized to determine the flow induced alignment of a model thermotropic liquid crystalline polymer (LCP) as a function of shear rate and temperature. The results demonstrate that the flow-induced structures in thermotropic liquid crystalline polymers have similarities and differences to those in lyotropic liquid crystalline polymer solutions. The shear rate dependence of the alignment shows that the flow-induced alignment correlates very well to the viscosity behavior of the LCP in the shear thinning regime, while temperature variation results in a change in the extent of alignment within the nematic phase. Relaxation results also demonstrate that the flow-induced alignment remains essentially unchanged for up to an hour after the shear field has been removed. Last, there exists a regime at low shear rate and low temperature where alignment of the LCP molecule perpendicular to the applied shear flow is stable. These results provide important experimental evidence of the molecular level changes that occur in a thermotropic liquid crystalline polymer during flow, which can be utilized to develop theoretical models and more efficiently process thermotropic polymers. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 3017–3023, 1998     

Main chain liquid crystalline ionic polymers with thermotropic and lyotropic mesophases

An ionogenic main chain liquid crystalline polymer was synthesized. In contrast to previous studies the charged sites were incorporated into the flexible spacer and not into the mesogenic group. This was done through quaternization of 1,2-bis(4-pyridylethane) with a biphenyl-4,4′-nonanoxytoluenesulphonate. The polymer displayed thermotropic and lyotropic me-sophases. The thermotropic mesophase was smectic. Organic counterions such as meth-ylsulfonates and p-toluenesulfonates were found to be favorable to the development of mesophases, due to the increased solubility and lower isotropisation temperatures, when compared to bromide counterion containing polymers. Easy supercooling, dependence on thermal history, and the development of batonnet textures on cooling from the melt were also observed. © 1995 John Wiley & Sons, Inc.     

Thermotropic liquid crystalline polymers with low thermal transitions. II. Low melting thermotropic liquid crystalline homo- and co-polyesters

Thermotropic liquid crystalline (TLC) polymers with low melt transitions are useful for imaging technologies. This is the first report describing thermotropic liquid crystalline copolyesters of low melt transitions comprised of a mesogen with up to three different spacer moieties. We have noted that the smectic mesophase range decreased with increasing amounts of different spacer moieties, without altering the isotropic transition and thereby leading to a broader nematic range. © 1995 John Wiley & Sons, Inc.     

Studies on thermotropic liquid crystalline polyphosphates containing photoreactive dual mesogens

A series of thermotropic liquid crystalline polyphosphates, containing photochromic molecules of stilbene in the backbone and substituted azobenzene in the side chain, were synthesized respectively. The inherent viscosity measurements were determined for all the polymers. The stability and char yield, T_g, T_m and T_i were investigated by thermal analysis. Polarizing optical microscopy of all the polymers exhibited birefringent melts with liquid crystalline behaviour. Variable temperature powder X-ray diffraction techniques were performed for confirmation of textures. UV-visible photolysis studies investigated the simultaneous behaviour of reactivity rates of crosslinking of stilbene units and isomerization, caused by azobenzene units in the main chain/side chain LCPs. Photoisomerization kinetics demonstrated the switching time rates for the trans-cis conversion of the azobenzene unit. A model polymer was synthesized and compared for the effect of stilbene in the main chain. Dipole moment values were calculated for the simulated low molecular mass of the pendant substituents to predict the polarity using MOPAC 3D Pro.     

Liquid crystalline polymers XII. Main chain thermotropic poly(arylidene-ether)s containing 4-tertiary-butyl-cyclohexanone moiety linked with polymethylene spacers

A new homologous series of thermally stable thermotropic liquid crystalline poly(arylidene-ether)s based on 4-tertiary-butyl-cyclohexanone moiety was synthesised by solution polycondensation of 4,4′-diformyl-α,ω-diphenoxyalkanes, I_a–f, or 4,4′-diformyl-2,2′-dimethoxy-α,ω-diphenoxyalkanes, II_a–f, with the 4-tertiary-butyl-cyclohexanone monomer. A model compound III was synthesised from the monomer with benzaldehyde and characterised by elemental and spectral analyses. The inherent viscosities of the resulting polymers were in the range of 0.18–0.92 dL/g. The mesomorphic properties of these polymers were studied as a function of the diphenoxyalkane space length. Their thermotropic liquid crystalline properties were examined by differential scanning calorimetry (DSC) and optical polarising microscopy and demonstrated that the resulting polymers form nematic mesophases over wide temperature ranges. The thermal properties of those polymers were evaluated by thermogravimetric analysis and DSC measurements and correlated to their structural units. X-ray analysis showed that polymers having some degree of crystallinity in the region 2θ = 5–60°. In addition, the morphological properties of selected examples were tested by scanning electron microscopy.     

Studies on thermotropic liquid crystalline elastomers. I. Synthesis and properties of poly (amide-ester) elastomers

Three series of novel poly(amide-ester) (PAE) elastomers were prepared by direct poly-condensation from terephthalic acid (TPA), polyols (M_n = 1000 or 2000), and various diamines. The structures and thermal properties of the synthesized PAEs were examined by FTIR spectroscopy, wide angle X-ray diffraction (WAXD), differential scanning calo-rimetry (DSC), thermal optical polarized microscopy, thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA). The effects of kinds and amount of diamines and the molecular weight of polyols on the thermal properties of PAEs were studied. By introducing long flexible spacers (PE-1000 or PE-2000) into the polymer main chain, all polymers showed two-phase morphology under the thermal optical microscopic observation. It was interesting that most of the synthesized polymers exhibited only one melting transition corresponding to the soft segments. The melting transition of hard segments could not be detected due to decomposition of the soft segments. However, a thermotropic liquid crystalline PAE (TLCPAE) prepared from methylhydroquinone and 2-chloro-5-methyl-phenylenediamine with PE-1000 could be obtained by lowering the melting transition temperature of the hard segment. © 1995 John Wiley & Sons, Inc.     

Synthesis and mesomorphic behaviour of novel chiral nematic side chain liquid crystalline polysiloxanes

A series of novel thermotropic side chain liquid crystalline polymers was synthesized by grafting copolymerization of a mesogenic monomer, 4-allyloxybenzoyl-4′?-(4-n-alkylbenzoyl)–p-benzenediol bisate and a chiral monomer, menthyl undecylenate. The mesogenic monomers exhibited nematic threadlike textures during heating and cooling. The polymers showed thermotropic liquid crystalline properties with a broad mesomorphic region over a range of 100°C. The polymers exhibited a cholesteric mesophase with a colourful Grand-Jean texture when the content of chiral units was greater than 15?mol?%; the others exhibited nematic threadlike textures. All of the polymers were thermally stable over 300°C, and most were laevorotatory as the chiral monomer.     

Designing thermotropic liquid crystalline polyazomethines based on fluorene and/or oxadiazole chromophores

The main objective of this paper was to synthesize luminescent thermotropic liquid crystalline polyazomethines containing chromophoric mesogen, which design has been addressed to optoelectronic materials. The investigation of the thermotropic behavior by three complementary methods of analyses, i.e. polarized optical microscopy, differential scanning calorimetry and wide angle X-ray diffraction, indicated a nematic mesophase for the polymers containing oxadiazole units, either alternating or random ones. A mesomorphic state maintaining the degree of order of the semicrystalline state while being viscous fluid was evidenced too. The photoluminescence spectra recorded for both polymer solutions and films exhibited a blue light emission. These results point to the possibility of obtaining monodomain or multidomain ordered thin films without grain boundaries showing good mechanical and luminescent properties.     

Studies on thermotropic liquid crystalline polymers. XV. Synthesis and properties of liquid crystalline copoly(imide-ester)s

Three series of the thermotropic liquid crystalline copoly(imide-ester)s were prepared by direct polycondensation. The first two series of the copoly(imide-ester)s were synthesized from N-(4-carboxyphenyl) trimellitimide with N,N-di(hydroxypropyl) pyromellitic diimide and various aromatic diols. The third series of copoly(imide-ester)s were prepared by N-(4-carboxyphenyl) trimellitimide with various imide-diols (methylene spacer = 2–6) and phenyl hydroquinone. The structures and thermal properties of the synthesized poly(imide-ester)s were examined by FTIR spectrum, wide-angle x-ray diffraction (WAXD), differential scanning calorimetry (DSC), thermal optical polarized microscope, and thermogravimetric analysis (TGA). The effects of the structures of the aromatic diols on the thermal properties of the resulting copoly(imide-ester)s were investigated. It was found that most of the copoly(imide-ester)s possessed excellent mesophase stabilities and thermostabilities. The mesophase stabilities of poly(imide-ester)s decreased with the increase of the size of lateral group, and the mesophase range increased with the increase of the amount of PhHQ. No significant odd-even effects were observed between the methylene spacer lengths and transition temperatures. © 1996 John Wiley & Sons, Inc.