Teh-Chou Chang

New polymers of carbonic acid. XXV. Photoreactive cholesteric polycarbonates derived from 2,5-bis(4'-hydroxybenzylidene)cyclopentanone and isosorbide

Several binary copolycarbonates were prepared by polycondensation of 2,5-bis(4-hydroxybenzylidene)cyclopentanone, BHBC, with methylhydroquinone, MHQ, hydroquinone 4-hydroxybenzoate, HQHB, or isosorbide. Furthermore, five ternary copolycarbonates were prepared based on the aforementioned monomers. All polycondensations were conducted in pyridine with trichloromethyl chloroformate as condensing agent. All polycarbonates were characterized by elemental analyses, viscosity and DSC measurements, IR and 1 H- and 13 C-NMR spectroscopy, optical microscopy, and the WAXS powder pattern. All isosorbides containing binary and ternary copolycarbonates were found to form a cholesteric melt, but only three of them were capable to form a stable Grandjean texture upon shearing.

Polymers of carbonic acid. XXIV. Photoreactive, nematic or cholesteric polycarbonates derived from hydroquinone-4-hydroxybenzoate 4,4'-dihydroxychalcone and isosorbide

Numerous polycarbonates were prepared by means of “diphosgene” in pyridine using hydroquinone 4-hydroxybenzoate (HQHB) as mesogenic diphenol. In addition to the homopolycarbonate, binary copolycarbonates of HQHB and 4,4′-dihydroxychalcone (DHC) with varying molar composition were prepared. A series of ternary copolycarbonates were obtained by incorporation of isosorbide. Furthermore, an alternating copolycarbonate of HQHB and isosorbide was synthesized. All polycarbonates were characterized by inherent viscosities, elemental analyses, IR-, 1H-NMR, and 13C NMR spectroscopy, by WAXS powder patterns DSC measurements, and optical microscopy with crossed polarizers. The homopolycarbonate of HQHB and most binary copolycarbonates were semicrystalline materials forming an enantiotropic nematic melt. Particularly noteworthy is the finding that the alternating copolycarbonate of HQHB and isosorbide forms a broad cholesteric phase despite the unfavorable stereochemistry of isosorbide. The ternary copolycarbonates containing isosorbide formed a cholesteric melt and a Grandjean texture upon shearing.

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 (Mn 2,000) and PTMEG-1000 (Mn 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.

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.

Studies on thermotropic liquid crystalline polycarbonates. I: Synthesis and properties of thermotropic liquid crystalline poly(azomethine-carbonate)s

Abstract A novel diol was used as a monomer; benzene 1,4-di(4-imidophenoxy-n-hexanol), was prepared from 6-chlorohexanol with 1,4-di(4-imidohydroxyphenyl) benzene. Poly(azomethine-carbonate)s were prepared by melt polycondensation of benzene 1,4-di(4-imidophenoxy-n-hexanol) with various alkylene diphenyl dicarbonates. The inherent viscosities of the polymers were in the range 0.38−0.89 dl/g. The thermotropic liquid crystalline properties were examined by DSC and microscopy. All the polymers exhibit thermotropic liquid crystalline properties. The mesophase stabilities of poly(azomethine-carbonate)s were in the range of 60–84°. Odd-even effects were not observed between methylene spacer lengths and transition temperatures.

Studies on thermotropic liquid crystalline polymers: 4. Synthesis and properties of poly(ether ester amide)s

Abstract The thermotropic liquid crystalline behaviour of a series of aliphatic-aromatic poly(ether ester amide)s, which were prepared by direct polycondensation, was observed. Poly(ether ester amide)s I were prepared from 4,4′-diacrylic acid-α,ω-diphenoxyalkanes and 4-aminophenol or 4-amino-3-methylphenol in the presence of diphenylchlorophosphate (DPCP) and pyridine. Poly(ether ester amide)s II were prepared from 4,4′-dicarboxy-α,ω-diphenoxyalkanes and 4-aminophenol or 4-amino-3-methylphenol in the presence of DPCP and pyridine. The phase behaviour of the polymers was studied by differential scanning calorimetry and optical polarizing microscopy equipped with a heating stage. Poly(ether ester amide)s I exhibit thermotropic liquid crystalline characteristics, except in cases where methoxy or ethoxy groups were introduced into the benzene ring. All of the poly(ether ester amide)s II exhibit thermotropic liquid crystalline behaviour as observed by optical polarizing microscopy.

Studies on thermotropic liquid crystalline polymers—V. Synthesis and properties of poly(ether amide)s

Abstract Two series of poly(ether amide)s, I and II, were prepared by direct polycondensation from 4,4′-diacrylic acid-α, ω-diphenoxyalkanes and 4,4′-dicarboxyl-α, ω-diphenoxyalkanes with diamines. The phase behaviour of these polymers was studied by differential scanning calorimetry and optical polarizing microscopy using a heated stage. Poly(ether amide) IId showed thermotropic liquid crystalline behaviour by observation under the optical polarizing microscope but poly(ether amide)s I and II did not exhibit thermotropic liquid crystallinity unambiguously. It is suggested that these results are due to interchain hydrogen bonds.

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 LiCI, 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.

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(amideester)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).

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.