Polarizing Microscope Observations Research Articles

Lamellar Thickening in Isotactic Polypropylene with High Tacticity Crystallized at High Temperature

Crystallization behavior of isotactic polypropylene (iPP) with extremely high isotacticity has been studied over a very wide range of crystallization temperature Tc (145 °C ≤ Tc ≤ 166 °C). Optical polarized microscopy observation reveals that morphologies obtained before and after Tc = 157.0 °C are different in nature. Differential scanning calorimetric measurement shows that the melting temperature (Tm) increases significantly with increase of both Tc and crystallization time t. A sudden jump in the slope of Tm versus log t plot is observed at Tc = 157.0 °C, which suggests a kind of order−disorder transition taking place at high Tc (≥157.0 °C) to allow better chain sliding diffusion. Such a disordering has been confirmed by means of X-ray measurements and will be reported in another paper of this series. It was also convinced that annealing at high temperature subsequent to lower temperature crystallization promotes much more rapid lamellar thickening than crystallization alone does at the same high temperature. The lamellar thickness is determined by transmission electron microscopy and also shows a discontinuous upward shift at Tc = 157.0 °C. The lamella with the thickness up to 66 nm is reported for the first time.

Thermotropic Liquid-Crystalline Polymers Having Five-Membered Heterocycles as Mesogens V. Relationship between Polymer Structure and Thermotropic Liquid-Crystallinity in Semi-Rigid Polyesters Composed of Twin 2-Phenyl-1,3,4-thiadiazoles Having Central Aliphatic Chains

Semi-rigid polyesters based on twin biphenyl analogues of 1,3,4-thiadiazole (2-phenyl-1,3,4-thiadiazoles) with hepta- and octamethylene chains in the central part were synthesized by melt polycondensation of bismethyl ester derivatives of twin 2-phenyl-1,3,4-thiadiazole with α, ω-alkylenediols and dioxydialcohol derivatives of biphenyl. The relationship between polymer structure and thermotropic liquid-crystallinity (LC) was investigated by differential scanning calorimetry (DSC), polarizing microscope observations, miscibility tests and temperature-dependent X-ray analysis. All the polymers derived from α, ω-alkylenediols appeared to form enantiotropic or monotropic nematic phase independent of the lengths of aliphatic chains. Among the polyesters containing the biphenyl unit, most polymers with octamethylene segment between the twin 2-phenyl-1,3,4-thiadiazoles showed the nematic phase, but polymers composed of the twin biphenyl analogue having the central heptamethylene chain had no LC melts.

Thermotropic semi-rigid copoly(imide-carbonate)s composed of 3,4,3",4"-p-terphenyltetracarboxdi-imide and 3,4,3',4'-biphenyltetracarboxdi-imide rings

New semi-rigid copoly(imide-carbonate)s composed of 3,4,3",4"-p-terphenyltetracarboxdi-imide and 3,4,3',4'-biphenyltetracarboxdi-imide units and neighbouring homologous penta- and hexa-methylene spacer chains were prepared by melt polycondensation; the relationships between polymer structure and liquid crystalline (LC) properties are discussed. Differential scanning calorimetry measurements, polarizing microscope observations, miscibility tests and variable temperature X-ray analyses suggest that the 3,4,3",4"-p-terphenyltetracarboxdi-imide-rich copolymers form thermotropic LC nematic and smectic phases, but the 3,4,3',4'-biphenyltetracarboxdi-imide-rich copolymers are amorphous and have no LC melts. Therefore, the presence of 3,4,3",4"-p-terphenyltetracarboxdi-imide units confers good mesogenic properties.

Artificial Chitin Spherulites Composed of Single Crystalline Ribbons of α-Chitin via Enzymatic Polymerization

A crystalline product of artificial chitin by chitinase-catalyzed polymerization of a chitobiose oxazoline derivative was investigated by using optical microscopy in combination with TEM and SEM techniques. Platelike single crystals of α-chitin were first formed. The crystals were gradually shaped into ribbons by the rapid growth along the a axis with the crystalline thickness being ca. 10 nm. The α-chitin ribbons then aggregated to form bundlelike or dendritic assemblies as the ribbon concentration in solution increased. They grew into spherulites by splaying and branching, which displayed birefringence with a Maltese cross by polarization microscopic observation. The present artificial chitin spherulite, in which a number of α-chitin ribbons radiated from a common center, is completely different from the helicoidal textures composed of α-chitin microfibrils which have been known so far as a typical three-dimensional organization of chitin.

Novel Photoalignment Materials for Liquid Crystals Based on Modified Polysiloxane

Novel photosensitive alignment materials based on allyl-cinnamate-grafted methyl hydrogen polysiloxane fluid (MHPF) were used in fabricating liquid crystal (LC) cells by sandwiching nematic LC molecules between two indium-tin-oxide (ITO) patterned substrates. The LC aligning ability of this kind of alignment layer, fabricated by linearly polarized UV-induced polymerization (LPP), was characterized based on polarizing microscopic and conoscopic observations. The influences of the thickness of LPP films, LC materials, different end groups, baking conditions and exposure conditions on the alignment and thermal stability are discussed in detail. The results confirmed that the photoalignment films exhibited not only good aligning ability but also excellent thermal stability.

Chirality Dependence of Molecular Alignment under a High Magnetic Field in an Antiferroelectric Liquid Crystal MHPOBC

We observed the molecular alignment in each smectic phase of an antiferroelectric liquid crystal MHPOBC under a high magnetic field using a polarizing microscope observation. The alignment in the SmC(*) phase depends on the chirality; In a racemic mixture, the molecules align parallel to the field, while the molecules tilt with respect to the field in a high optical purity compound because of the helix. On the other hand, the molecular alignment in the bulk state of the SmCA(*) phase was independent of the optical purity and the smectic layer becomes normal to the field because of the macroscopic magnetic anisotropy of an anticlinic molecular structure in SmCA(*).

Transient Periodical Structure at Polarization Reversal in Ferroelectric Liquid Crystals

Switching mechanism of thick cell of ferroelectric liquid crystals has been studied by means of light scattering measurement and polarizing microscope observation adopting stroboscopic technique. The transmitted light through the cell at the instant of polarity reversal of applied voltage has been diffracted by the formation of periodical stripe texture. This transient stripe texture has a tilt from the smectic layer. The period of the transient stripe texture is independent of temperature and depends on applied voltage. The oblique angle from smectic layer depends on applied voltage.

Single-crystal growth of aluminum tungstate–scandium tungstate solid solution samples by the modified Czochralski method

Single crystals of the aluminum tungstate–scandium tungstate solid solution were grown by the modified Czochralski (CZ) method. The crystals obtained were transparent and shown to have satisfactory quality by polarizing microscope observations. The single crystals were demonstrated to contain both Al and Sc elements by electron probe microanalysis (EPMA) measurements and the Al : Sc trivalent cation ratio in the solid solution was precisely determined to be 8.5 : 1.5 from the lattice parameters obtained by the X-ray powder diffraction analysis.

Estimation of Cooling Time of Electrofusion Jointing in PE Pipes for Gas Distribution.

From the viewpoint of work efficiency, the post-fusion cooling time of EF joints should be reduced. However, insufficient cooling time can lead to poor joint performance. To estimate what is a sufficient cooling time, this study evaluates three types of gas pipes, buried after three different cooling times following fusion, and studies the relationship between the cooling time and the EF joint performance. Evaluation items include the deformation, degree of crystallinity, polarized microscope observation, tensile strength, tensile creep strength, TEM observation, and fusion simulation. The results show only a slight difference regarding the degree of crystallinity, tensile strength, and TEM observation, while a distinct difference was observed regarding tensile creep strength. The fused zones were subjected to a temperature profile during the cooling process determined by simulation. The results showed that these three fused zones have different states (melting state, semi-solid, or solid state) at the moment when the weight of soil acts on the fused zones. By the deformation of the fused zone during the cooling process, the crystal condition changed. It is said that the difference of the crystal condition of the fusion zone is the main factor affecting the tensile creep strength.

DNA-Drug Interaction Measurements Using Surface Plasmon Resonance

The interactions of the drugs 2,7-bis[(diethylamino)-ethoxy]-fluoren-9-one dihydrochloride (Tilorone). 2,7 bis[(dipropylamino)-acetamido]-fluoren-9-one dihydrochloride (FA-2). 2′- (4-hydroxyphenyi)-5-(4-methyl-1 -piperazinyl)-2,5′-bi-1 H-benzimidazole trihydrochloride (Hoechst 33258) and hematoporphyrin IX derivative (HPD) with synthetic self-complementary DNA (36-b.p.; 5′-biotin-spacer-[d(CGCTATATAGCG)]3-3′) were studied by SPR (Surface Plasmon Resonance). Monolayers of biotinylated DNA were immobilized on a streptavidin-dextran-gold triple-layer. Small portions of the drugs (approximately 30 pmol/ml) were injected in continuous flow. The mass corresponded to the amount of the bound molecules. Injections of 50 mM sodium hydroxide pulses separated the DNA double strands, releasing the effector molecules. Subsequent treatments with the effectors gave reproducible results. The maximum interaction between drug and DNA was observed in the case of Tilorone. 41 molecules could bind to the 36-b.p. DNA duplex. To investigate the microscopic behavior in condensed nucleic acid phases, SFM (Scanning Force Microscopy)-imaging and polarizing microscopic observations of DNA-effector complexes were carried out. Supplementary UV-absorption thermal denaturation curves of DNA with the above-mentioned effectors in dilute solutions were measured. As an additional aid to understand the geometries of DNA-drug interactions, computer simulations were performed and compared with the experimental data.

Polyesters containing sulfur. VI. Synthesis and characterization of polyesters from naphthalene‐1,4‐ or naphthalene‐1,5‐bis(methylthioacetic acid) and aliphatic diols

Two series of new linear polyesters containing sulfur in the main chain were obtained by melt polycondensation of naphthalene-1,4-bis(methylthioacetic acid) (N-1,4-BMTAA) or naphthalene-1,5-bis(methylthioacetic acid) (N-1,5-BMTAA) with some aliphatic diols using a 0.05 molar excess of diol. Softening temperatures ranging from 55 to 130°C, reduced viscosities in the range of 0.15–0.39 dL/g, and low-molecular weights were their characteristic. The structure and thermal properties of all polyesters were examined by using elemental analysis, FT-IR and 1H-NMR spectroscopy, X-ray diffraction analysis, differential thermal analysis (DTA), thermogravimetric analysis (TGA), and differential scanning calorymetry (DSC). The kinetics of polyester formation by uncatalyzed melt polycondensation was studied in a model system: N-1,4-BMTAA or N-1,5-BMTAA and 2,2′-oxydiethanol (ODE) at 150, 160, and 170°C. Reaction rate constants (k3) and activation parameters (ΔG‡, ΔH‡, ΔS‡) from carboxyl group loss were determined using classical kinetic methods. Hydroxyl-terminated polyesters derived from 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol were used for preparation of the polyurethanes by melt polyaddition with hexamethylene diisocyanate (HDI). They were characterized by reduced viscosity, FT-IR spectroscopy, X-ray diffraction analysis, TGA, DSC, polarizing microscope observation, and hardness and tensile properties. The resulting polyurethanes behave like high-elasticity thermoplastic elastomers, except the one derived from N-1,5-BMTAA and 1,6-hexanediol-based polyester. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2359–2369, 1998

Polyesters containing sulfur. VI. Synthesis and characterization of polyesters from naphthalene-1,4- or naphthalene-1,5-bis(methylthioacetic acid) and aliphatic diols

Two series of new linear polyesters containing sulfur in the main chain were obtained by melt polycondensation of naphthalene-1,4-bis(methylthioacetic acid) (N-1,4-BMTAA) or naphthalene-1,5-bis(methylthioacetic acid) (N-1,5-BMTAA) with some aliphatic diols using a 0.05 molar excess of diol. Softening temperatures ranging from 55 to 130°C, reduced viscosities in the range of 0.15-0.39 dL/g, and low-molecular weights were their characteristic. The structure and thermal properties of all polyesters were examined by using elemental analysis, FT-IR and 1 H-NMR spectroscopy, X-ray diffraction analysis, differential thermal analysis (DTA), thermogravimetric analysis (TGA), and differential scanning calorymetry (DSC). The kinetics of polyester formation by uncatalyzed melt polycondensation was studied in a model system: N-1,4-BMTAA or N-1,5-BMTAA and 2,2'-oxydiethanol (ODE) at 150, 160, and 170°C. Reaction rate constants (k 3 ) and activation parameters (ΔG , ΔH , ΔS ) from carboxyl group loss were determined using classical kinetic methods. Hydroxyl-terminated polyesters derived from 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol were used for preparation of the polyurethanes by melt polyaddition with hexamethylene diisocyanate (HDI). They were characterized by reduced viscosity, FT-IR spectroscopy, X-ray diffraction analysis, TGA, DSC, polarizing microscope observation, and hardness and tensile properties. The resulting polyurethanes behave like high-elasticity thermoplastic elastomers, except the one derived from N-1,5-BMTAA and 1,6-hexanediol-based polyester.

Liquid Crystalline Phase Transition in Hexakis(4-(N-(41-alkoxyphenyl)iminomethyl)phenoxy)cyclotriphosphazene

A new series of cyclotriphosphazenes bearing Schiff bases with different carbon number alkoxy end groups(HAICP) in the side chains were synthesized and their phase transitions and liquid crystallinity were studied using DSC measurements and polarizing microscope observations. We found a monotropic Sml phase for n = 3 and an enantiotropic Sml phase for n = 4 −5, enantiotropic Sml, SmC and SmA phases for n = 6 – 7, enantiotropic SmC and SmA phases for n = 8 – 10, and enantiotropic Sm2, SmC and SmA phases for n=11 and 12 in the HAICP series. The Sml phase is a low-order uniaxial smectic phase and Sm2 phase is a low-order biaxial smectic phase. The melting point decreased with an increase in the end alkoxy carbon number, n, of the cyclotriphosphazenes, but the clearing point decreased with an increase in n. As a result, the mesomophic region expands with an increase in n. The melting and clearing points do not show clear odd-even effects, which is caused by the peculiar shape of the cyclotriphosphazenes.

Light Refraction at the Interface between Coexisting Phases of KHCO3

Polarizing microscope observations of ferroelastic domains which coexist with the monoclinic phase in as-grown KHCO 3 crystals below T c = 318 K are reported. The nature as well as the orientation of the phase boundary are predicted in the frame of the theory of Domain-wall orientations in ferroelastics assuming that the domains are triclinic. Specific light refraction experiments at this interface are carried on and analytical expressions between the angles of incidence and of refraction are established using crystal optics. From measurements of these angles, the orientation of the phase boundary is derived with a precision of about 0.2 degree. The excellent agreement between this orientation and the one predicted from the lattice parameters of the two phases shows that the boundary corresponds to a ferroelastic Domain-wall of the W ′ -type and that the observed domains well consist of a triclinic phase.

Boundary condition effects on field-induced deformation modes in polymer dispersed liquid crystals

Electric field-induced deformation modes, which are considered one of the causes of the hysteresis in the V-T response of polymer dispersed liquid crystal (PDLC), were investigated. We constructed model PDLC cells with varied alignment treatments at the interface of the liquid crystal droplets. The electric field-induced deformation modes of the liquid crystals in the model cells were analyzed by polarized microscope observations. Our results suggested a possible way to hysteresis-free PDLC devices.

Semirigid Homo- and Copoly(Imide-Carbonate)s Based on 3,4,3″,4″ -p-Terphenyltetracarboxdiimide

Novel thermotropic liquid crystalline (LC) semirigid homo- and copoly(imidecarbonate)s composed of a 3, 4, 3″, 4″- p-terphenyltetracarboxdiimide ring and aliphatic chains were prepared by melt polycondensation of a dihexanol derivative of 3, 4, 3″, 4″- p-terphenyltetracarboxdiimide and/or a dioxydihexanol of biphenyl taken in a definite molar ratio with hexamethylene diphenyl dicarbonate in the presence of zinc acetate, and their thermal and mesogenic properties were evaluated. The assigned structures of polymers were characterized by FT-IR and 13C NMR spectroscopy, and elemental analyses. DSC and TG-DTA measurements, polarizing microscope observations of textures and temperature-dependent x-ray analyses demonstrated that the polymers have wider LC temperature ranges (nematic phase) than analogous semirigid poly(ester-imide)s and are thermally stable up to 300 °C in air.

Liquid Crystalline Phase Transition in Organophosphazenes with 4-Octyloxybiphenyl Mesogenic Groups

Abstract Cyclotriphosphazenes with the same 4-octyloxybiphenyl mesogenic side groups have been synthesized and were studied their phase transition and liquid crystallinity using DSC measurements and polarizing microscope observations. We found an enantiotropic smectic C phase in hexakis(4-(4′-octyloxy)biphenoxy)cyclotriphosphazene but no liquid crystalline phase was observed in octakis(4-(4′-octyloxy)biphenoxy)cyclotetraphosphazene. These may originate from each of the three side chains of the cyclotriphosphazene molecules pointed upwards and downwards perpendicularly from the cyclotriphosphazene ring, which helps the formation of the liquid crystalline layer structure. However, in the cyclotetraphosphazene, the eight side chains orient relatively at random and this prevents the formation of the mesogenic layer structure.

Preparation of new poly(ester‐imide)s with cyanoazobenzene side chains generating optical phase‐conjugate signals

AbstractNew semi‐rigid poly(ester‐imide)s with cyanoazobenzene side chains were prepared by melt polycondensation of a diethyl isophthalate derivative of cyanoazobenzene with N, N′‐dihexanols of five aromatic diimides in the presence of zinc acetate. Differential scanning calorimetry (DSC) measurements and polarizing microscope observations demonstrated that the polymers have glass transitions (Tg) between 46 and 93°C and show no liquid crystalline (LC) properties. All poly(ester‐imide)s generated optical phase‐conjugate (PC) signals at high reflectivity by degenerate four‐wave mixing (DFWM) at low pump‐beam power.

Thermal and Structural Study on Liquid-Crystalline Phase Transition in Hexakis(4-(4‘-alkyloxy)biphenoxy)cyclotriphosphazene

A series of hexakis(4-(4‘-alkyloxy)biphenoxy)cyclotriphosphazene [PN(OC6H4C6H4OC)nH2n+1)2]3 (HACP, n = 6−12) compounds was synthesized from sodium salts of 4-alkyloxy-4‘-hydroxybiphenyl and hexachlorocyclotriphosphazene. The phase transition and mesogenicity of these substances were studied by FT-IR, X-ray diffraction, and DSC measurements and polarizing microscope observations. In the crystalline-to-smectic C phase transition of HACP with n = 8, the infrared bands of PN and P−O−(C) stretching vibrations were found to shift to the lower frequency, indicating the weakening of the cyclotriphosphazene ring in the liquid-crystalline phase. The X-ray analyzed interlayer spacing 36 Å is smaller than the value expected for the fully extended molecular model, indicating that the tilt angle of the molecules is about 35° from the normal to the layer plane. For HACP with n = 6, monotropic nematic and smectic C phases were found to appear only in the cooling process. Enantiotropic N and Sc phases were found for the n = 7 member. For the HACP with the n = 8−12, only an enantiotropic Sc phase was detected. In the series of HACP, the temperature range of the mesomorphic phase increased with an increase in n. The odd−even effect was not clear, originating from the peculiar shape of the hexakis(4-(4‘-alkyloxy)biphenoxy)cyclotriphosphazene with three side chains pointing three upward and three downward in both sides of the cyclotriphosphazene ring.

Synthesis and properties of a new poly(acrylamide) containing phosphatidylcholine analogues and cholesterol groups in side chains

Amphiphilic acrylamide monomer containing a cholesterol moiety as a hydrophobic group and a phosphatidylcholine analogue as a hydrophilic group was synthesized in high yield. Radical polymerization was carried out in the presence of α,α′-azobisisobutyronitrile (AIBN) as initiator. The obtained monomer and homopolymer were characterized by 1H-NMR, IR and melting point, respectively. The packing structure and thermal properties of the obtained polymer were investigated by X-ray diffraction analysis, DSC measurement and polarizing microscopy observation. It has been proposed that the homopolymer consists of a stacked bilayer structure in a smectic liquid crystalline phase over a wide temperature range. In addition, the monolayers of monomer and homopolymer on the surface of water were investigated at different temperatures and different subphase pH. The optimum condition for preparing stable and order monolayer has been determined as 10 °C and pH 4.0 for a monomer, and over a wide range of temperature (10–30 °C) and pH (pH 4.0–10.0) for a homopolymer.