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.     

Studies on thermotropic liquid crystalline polymers. XIV. Synthesis and properties of liquid crystalline poly(imide-ester)s by the direct polycondensation

A series of semi-aromatic poly(imide-ester)s were prepared by the direct polycondensation of N-(4-carboxyphenyl) trimellitimide or N-(3-carboxyphenyl) trimellitimide with various pyromellitic diimide diols containing methylene spacer = 2–6, respectively. The effect of the amount of LiCl, pyridine, and the kinds of condensation agents on the direct polycondensation were studied. 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 microscopic observation, and thermogravimetric analysis (TGA). It is found that P1 series [derived from N-(4-carboxyphenyl) trimellitimide] with even number methylene spacer (n = 4, 6) exhibit smectic mesophase, but P2 series [derived from N-(3-carboxyphenyl) trimellitimide] do not show LC phase. © 1996 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.     

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 polycarbonates. II. Synthesis and properties of fully aromatic liquid crystalline polycarbonates

Four series of fully aromatic polycarbonates were prepared by using melt polycondensation from various novel phenylene diphenyl dicarbonates: 1,4-phenylenc diphenyl dicarbonate, 1,3-phenylene diphenyl dicarbonate, methyl-1,4-phenylene diphenyl dicarbonate, and chloro-1,4-phenylene diphenyl dicarbonate with various diols—4,4′-biphenyl diol, hydroquinone, 2,7-naphthalene diol and 1,5-naphthalene diol, respectively. The thermotropic liquid crystalline properties of synthesized polycarbonates were investigated by: (1) examination of the melt birefringence and stir opalescence by a polarizing microscope equipped with a heating stage, (2) characterization by a differential scanning calorimeter (DSC), and (3) analysis of the wide angle x-ray diffraction. It was found that the 1,3-phenylene unit is compensated for the nonlinearity of the carbonate group, and polycarbonates which contain this bent shape unit showed excellent wide mesophase transition in this study. © 1993 John Wiley & Sons, Inc.     

Studies on the thermotropic liquid-crystalline polymer. IX. Synthesis and properties of crosslinkable copoly(amide-ester)s containing conjugated double bonds

Four series of copoly(amide-ester)s containing conjugated double bonds were prepared by using direct polycondensation in the presence of diphenylchlorophosphate (DPCP) and pyridine. Series I–III were prepared from para, meta-aminophenol, or their mixture with p-phenylene bis(acrylic acid) (PPBA), p-carboxylic cinnamic acid (PCCA), and stilbenedicarboxylic acid (SDBA), respectively. Series IV was prepared from a mixture of aminophenols [2-methyl 4-aminophenol (MePAP) and m-aminophenol (MAP)] with a mixture of diacids (PPBA and SDBA). Thermotropic liquid-crystalline behavior of these polymers was studied by differential scanning calorimetry (DSC), and optical polarizing microscopy equipped with a heating stage. Series I , series II , and P40–P100 of series IV could undergo crosslinking reaction by heating. However, series III could undergo crosslinking reaction only by photoirradiation upon heating. After crosslinking reaction occurred, the properties of these polymers were also examined by DSC, TGA, WAXD, and IR. The synthesized polymers could be crosslinked in the liquid-crystalline phase with retention of the order in the final crosslinked solid. © 1993 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.     

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 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.     

Studies on thermotropic liquid crystalline polyurethanes. III. Synthesis and properties of polyurethane elastomers by using various mesogenic units as chain extender

Four series of thermotropic polyurethane elastomers (TPUEs) were synthesized in this study. The hard segments were formed by using 4,4′-methylenedicyclohexyl diisocyanate (H₁₂MDI) reacted with various mesogenic units, such as benzene-1,4-di(4-iminophenoxy-n-hexanol), benzene-1,4-di(4-iminophenol), and 3,3′-(4,4′-biphenylene)dipropanol, which also acted as the chain extender. Poly(oxytetramethylene)glycols (PTMEGs), PTMEG-2000 (M_n 2,000) and PTMEG-1000 (M_n 1,000) were used as a soft segment. The structures of all synthesized thermotropic liquid crystalline polyurethanes (TLCPUs) were characterized by FTIR spectroscopy. The effects of mesogenic units on the LC properties and elastic behaviors of LCPUs were studied. It was difficult to show LC behaviors for the PU elastomers derived from the mesogenic units with a lower aspect ratio, such as 3,3′-(4,4′-biphenylene)dipropanol, or the long soft segments, PTMEG-2000. In addition, these PU elastomers show better elastic properties by using a higher aspect ratio mesogenic unit as the chain extender, such as benzene-1,4-di(4-iminophenoxy-n-hexanol and benzene-1,4-di(4-imino-phenol)). The thermal properties were investigated by DSC measurements, thermal optical polarized microscopy, wide angle X-ray diffraction, dynamic mechanical analysis, and thermogravimetric analysis. The mechanical properties were measured by a tensilemeter. © 1996 John Wiley & Sons, Inc.     

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.     

Studies on the thermotropic liquid crystalline polymer. XII. Synthesis and properties of crosslinkable thermotropic liquid crystalline homo- and copoly(ether-ester)s

A series of crosslinkable thermotropic liquid crystalline poly(ether-ester)s and copoly(ether-ester)s was prepared. All of the polymers were crosslinked by thermal treatment or photo-irradiation upon heating. The thermal stability and thermal crosslinking reaction of these polymers were investigated. These polymers also could be crosslinked by copolymerization with vinyl monomers, such as styrene or methyl methacrylate. The crosslinked polymers exhibited thermotropic liquid crystalline behavior after softening by heating. The phase behavior of linear polymers and crosslinked polymers was studied by differential scanning calorimetry (DSC) and an optical polarizing microscope equipped with a heating stage. © 1995 John Wiley & Sons, Inc.     

Synthesis,structure and properties of new chiral liquid crystalline monomers and homopolysiloxanes containing menthyl groups

The synthesis is described of four new chiral liquid crystalline monomers (M₂–M₅ ) and their corresponding side‐chain homopolysiloxanes (P₂–P₅ ) containing menthyl groups. Chemical structures were characterised using FT‐IR or ¹H NMR spectra, and specific optical rotations were evaluated with a polarimeter. The phase behaviour and mesomorphic properties of the new compounds were investigated by differential scanning calorimetry, thermogravimetric analysis, polarising optical microscopy, UV/visible/NIR spectrocopy and X‐ray diffraction. The monomers and homopolymers with more aryl segments showed noticeably lower specific optical rotation value. The monomers M₂–M₅ formed a cholesteric or blue phase when a flexible spacer was inserted between the rigid mesogenic core and the terminal menthyl groups by reducing the steric effect. M₂–M₅ revealed enantiotropic cholesteric phase. Moreover, M₂ also exhibited a monotropic smectic A (SmA) phase, and M₄ also exhibited a cubic blue phase on cooling. The selective reflection of light shifted to the long wavelength region with increasing rigidity of the mesogenic core for M₂–M₅ . P₂–P₅ exhibited SmA phases, and the mesogenic moieties were ordered in smectic orientation with their centres of gravity in planes. Melting or glass transition temperature and the clearing temperature increased, and the mesophase temperature range widened with increasing rigidity of the mesogenic core.     

Studies on the thermotropic liquid-crystalline polymer. VIII. Synthesis and properties of fully aromatic poly(ester)s and poly(amide-ester)s containing p-phenylene diacrylic group

Three series of polymers containing p-phenylene diacrylic group were prepared by direct polycondensation in the presence of diphenylchlorophosphate and pyridine. Series I was prepared from p-phenylene bis(acrylic acid) with various hydroquinones. Series II was prepared from p-phenylene bis (β-cyano acrylic acid) with methylhydroquinone. Series III was prepared from 3-methyl-4-aminophenol with p-phenylene bis(acrylic acid) or p-phenylene bis(β-cyano acrylic acid), respectively. 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). It was found that these polymers, except IIIb , exhibit thermotropic liquid-crystalline properties and show threaded or Schlieren texture under the optical polarizing microscopic observation. Furthermore, the melting temperatures of these polymers were decreased in the range of 254–354°C by incorporating with p-phenylene diacrylic group into the main chain. © 1993 John Wiley & Sons, Inc.     

Synthesis and characterization of novel thermotropic liquid crystalline copoly(ester imide)s

Novel liquid crystalline copoly(ester imide)s were synthesized via polyesterification of triethyleneglycol bis(4-carboxyphenyl) ether ( 1e ), diacetoxybiphenyl, and diacids with imide moieties. The effects of composition on the changes of T_g, T_m, and T_i were examined by global TSC and DSC. Thermal gravimetric analyses (TGA) found that 4a–d and 5a–g possess higher thermal stability. Strong stir opalescence phenomenon and observations from polarized optical microscopy identified that 2b–e and 3a–d possess the typical schlieren texture of an enantiotropic nematic mesophase. The birefrigent melts of 4a–d and 5a–g, however, displayed particular liquid crystalline behavior. Copolymers with higher aromatic imide ring content ( 4a–d, 5a–g ) form a layered structure and an enantiotropic smectic mesophase in the melting state. The melt viscosity of the semetic mesophase was higher than the nematic mesophase which was observed by capillary rheometer. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1791–1803, 1998     

Synthesis and properties of cholesteric liquid crystalline elastomers

The synthesis of new side-chain cholesteric liquid crystalline elastomers, containing the flexible non-mesogenic crosslinking agent M-1 and the cholesteric monomer M-2, is described by a one-step hydrosilication reaction. The chemical structures of the monomers and network polymers obtained were confirmed by FT-IR spectroscopy. Their mesogenic properties and phase behavior were investigated by differential scanning calorimetry, polarizing optical microscopy, and x-ray diffraction measurements. The influence of the crosslinking units on the phase behavior is discussed. The network polymers showed elasticity, reversible phase transitions, and cholesteric Grandjean texture. The experimental results demonstrated that the glass transition temperatures and isotropization temperatures of network elastomers decreased as the concentration of crosslinking units was increased, but the cholesteric phase was not disturbed.     

Studies on thermotropic liquid crystalline polymers. XVI. Synthesis and properties of fully aromatic poly(amide-ester)s with naphthalene structures

A series of novel, fully aromatic high-molecular-weight poly(amide-ester)s was prepared by the direct polycondensation from terephthalic acid (TPA) and 2,6-naphthalene dicarboxlic acid (NDC) with various aromatic diols and diamines in the presence of diphenyl chlorophosphate (DPCP), LiCl, and pyridine. The structures and thermal properties of these synthesized poly(amide-ester)s were examined by FTIR, wide-angle x-ray diffraction (WAXD), differential scanning calorimetry (DSC), thermal polarized optical microscope, thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA). The effects of the kinds of the aromatic diols and diamines (bisphenyl units, naphthalene, and (un)substituted phenylene structures) on the thermal properties of the synthesized poly(amide-ester)s were investigated in this study. Strong interchain interactions were induced by using a 50:50 molar ratio of the amide groups to the ester groups, and, thus, no LC properties but good thermal stabilities were found in all of the synthesized poly(amide-ester)s containing naphthalene, substituted hydroquinone, or bisphenol segments in this study. However, another series of poly(amide-ester)s with a molar ratio of diamine to diol of 20:80 exhibited excellent mesophase stabilities, with various molar ratio of terephthalic acid (TPA) to 2,6-naphthalene dicarboxlic acid (NDC). © 1996 John Wiley & Sons, Inc.     

Thermotropic liquid crystalline polyester nanocomposites via in situ intercalation polycondensation

A thermotropic liquid crystalline polyester (TLCP)/organoclay nanocomposite was synthesized via in situ intercalation polycondensation of diethyl‐2,5‐dihexyloxyterephthalic acid and 4,4′‐biphenol in the presence of organically modified montmorillonite (MMT). The organoclay, C18‐MMT, was prepared by the ion exchange of Na⁺‐MMT with octadecylamine chloride (C18‐Cl^?). TLCP/C18‐MMT nanocomposites were prepared to examine the variations of the thermal properties, morphology, and liquid crystalline phases of the nanocomposites with clay content in the range of 0–7 wt%. It was found that the addition of only a small amount of organoclay was sufficient to improve the thermal behavior of the TLCP hybrids, with maximum enhancement being observed at 1 wt% C18‐MMT. Copyright © 2008 John Wiley & Sons, Ltd.     

Studies on the synthesis and properties of thermotropic liquid crystalline polycarbonates. VII. Liquid crystalline polycarbonates and poly(ester‐carbonate)s derived from various mesogenic groups

Three series of thermotropic liquid crystalline polycarbonates and poly(ester‐carbonate)s were prepared by solution polycondensation of 4,4′‐biphenyldiol (BP), 4′‐hydroxybiphenyl‐4‐hydroxybenzoate (HHB), or 4‐hydroxyphenyl‐4″‐hydroxybiphenyl‐4′‐carboxylate (HHBP), as mesogenic unit, with 1,10‐bis(p‐hydroxybiphenoxy)decane (N10), bisphenol A (BPA), 4,4′‐dihydroxy‐diphenyl ether (BPO), 4,4′‐[phenylbis(oxy)]bisphenol (BPOO), methylhydroquinone (MeHQ), or phenylhydroquinone (PhHQ). One series of cholesteric poly(ester‐carbonate)s were also prepared by using HHBP, the aromatic diols mentioned above and isosorbide as the chiral moiety. All polycondensations were implemented in pyridine by using triphosgene as the condensation agent. The synthesized polycarbonates were characterized by viscometer, FTIR, DSC, TGA measurements, polarizing microscopy equipped with a heating stage, and WAXD powder pattern. In this study, it was found that the liquid crystalline properties of polycarbonates strongly rely on the mesogenic unit applied. HHBP‐series exhibits a wide temperature region of liquid crystalline (LC) phase even with 50% of bisphenol A (BPA), which is a V‐shaped structure and usually destroys liquid crystalline properties. In addition, homopolycarbonate with HHBP structure possesses extraordinarily low phase‐transition temperature and wide liquid crystalline phase range, due to its asymmetric structure. This asymmetric structure results in head‐to‐tail, head‐to‐head, and tail‐to‐tail random conformation of polymer chain. The isosorbide containing poly(ester‐carbonate)s formed cholesteric phase, which showed homogeneous blue, green, or red Grandjean texture upon shearing in molten state and the Grandjean texture could be frozen easily while quenching the sample to the room temperature. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1852–1860, 2000     

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.