SYNTHESIS AND MESOMORPHIC PROPERTIES OF PALLADIUM CHELATES OF LIQUID CRYSTAL POLYSILOXANE WITH β-DIKETONE-BASED SIDE CHAINS

A new type of palladium chelate of β-diketone-based side chain liquid crystal polysiloxane (Pd-DKLCP) has been synthesized by chelation reaction of palladium dichloride with polymeric ligand, β-diketone polysiloxane (DKLCP), using THF as solvent at R.T.. The Pd-chelation results in greatly increasing the phase transition temperature T_K and the enthalpy change △H_K from crystal to liquid crystal state and making the temperature range of LC state △T(△T=T_(Cl)-T_K) widened. All these chelates Pd-DKLCP's do not show T_(Cl) until decomposition at 205℃. It is noteworthy that the Pd-chelation can exert more positive effect on the mesomorphic behaviour of the polymer ligand than the counterpart Cu-DKLCP does. It is probable due to the bigger size of disc-like mesogen formed from β-diketone and Pd~(+2) ion with 4d orbital.     

STUDY ON THE BLENDS OF NYLON 66 AND LIQUID CRYSTALLINE POLYESTERS

Blends of polyamide (Nylon 66) with two different kinds of liquid crystalline polyesters were studied in all the composition range. Homogeneous samples were obtained by coprccipitation from 2 wt%. solution of blends. The thermal properties, crystallinity and morphology of these blends were studied by using DSC, polarizing microscopy, and scanning electron microscopy. The phase transition and morphology of the blends are markedly-influenced by the composition of liquid crystalline polyesters. The mechanical behaviour of PHB/HNA-Nylon 66 blend was improved. although polyamidc (Nylon 66)with the liquid crystalline polyesters were incompatible, but a rather strong interaction between the polymers did exist.     

A RAMAN-SPECTROSCOPIC STUDY OF PHASE STRUCTURE OF DRAWN POLYETHYLENE

A drawn high density polyethylene(HDPE)has been measured by Raman spectroscopy and differential scanning calorimetry (DSC). The crystalline structure of drawn HDPE is analysed by the Raman internal modes in terms of mass fractions of the crystalline orthorhombic phase, the liquid- like amorphous phase and the disordered anisotropic phase. The mass fractions depend on draw temperature T_d and draw ratio R_d . The fraction of disordered anisotropic amorphous phase changes very little with, the T_d and increases with increasing R_d. Sum of the mass fractions of crystalline orthorhombic phase and the disordered anisotropic phase increases linearly as the same slope as the crystallinity W_c determined from DSC measurements with increasing T_d or R_d and it is higher than the W_c for all the samples. The results show that the mass fraction of disordered anisotropic phase is partially devoted by the taut tie molecules (TTM s) in the amorphous state. The dependence of the disordered anisotropic phase on T_d and R_d supports the mechanism of plastic deformation of fibre structure.     

STUDY ON LIQUID CRYSTALLINITY OF POLY(N-VINYLCARBAZOLE)

The liquid crystallinity of poly(N-vinylcarbazole) was studied by using powder X-ray diffraction, polarized opticalmicroscopy, and differential scanning calorimetry. The results show that the lower molecular weight fractions of this polymerdo not form a liquid crystalline phase, while the samples of sufficiently high molecular weight do form a mesophase attemperatures above the glass transition. The lowest value of the degree of polymerization for PVK to form a stable liquidcrystalline phase was found to be in the range of 150 to 200, significantly higher than the value of 50 for most conventionalside chain liquid crystaline polymers.     

INFRARED SPECTROSCOPIC STUDY OF STRUCTURE TRANSITION IN THE PEROVSKITE-TYPE LAYER COMPOUND: (n-C_9H_(19_NH_3)_2CuCl_4

Infrared spectra of (n-C_9H_(19)NH_3)_2CuCl_4 in three solid phases were investigated. It was found that the phase transition at T_(cl)(25℃) arises from the change of the interaction and packing structure of the chain. The phase transition at T_(c2)(34℃)is related to the change of a partial conformational order-disorder. The GTC or GTG' and small concentration of TG structure near CH_3 group exist in phase Ⅲ (above 38℃).     

SYNTHESIS AND MESOMORPHIC PROPERTIES OF FISHBONE-LIKE LIQUID CRYSTALLINE POLYSILSESQUIOXANES——Ⅰ. FISHBONE-LIKE, β-DIKETONE-BASED LIQUID CRYSTALLINE POLYSILSESQUIOXANES AND THEIR COPPER COMPLEXES*

Two kinds of fishbone-like, β-diketone-based liquid crystalline polysilsesquioxanes(FBDKLCP'S), homopolymeric (H-FBDKLCP) and copolymeric (C-FBDKaLCP) have been first synthesized via the hydrosilylation reaction of a vinyl-terminated β-diketone with the homopolymeric ladderlike polyhydrosilsesquioxane (LPHSQ) and random copolymethylhydrosilsesquioxane (LRPMHSQ) respectively. These new kinds of FBDKLCP with M of 10~4 is thermotroic liquid crystalline polymer and its clearing temperatures T_i's and mesophase range △T's are much higher than those of the corresponding comb-like β-diketone liquid crystalline polysiloxane (DKLCP) by about 200℃. Similar results have been observed with the comparison of the two different structure Cu-coordinating compounds The significant increases in T_((?))'s and △T's of the FBDKLCP and Cu-FBDKLCP are mainly attributed to the great rigidity of the ladderlike polysilsesquioxane backbone.     

Liquid crystal character controlled by complementary discotic molecules mixtures: Columnar stacking type and mesophase temperature range

In this work, the mesophase properties were tuned via mixing two discotic molecules with structural complementarity. Compared with the liquid crystalline hexakis(n-hexyloxy)triphenylene(H6TP)materials(columnar hexagonal phase from 53 8C to 91 8C), mesophase types as well as phase transition temperatures varied with the introduction of crystalline hexaazatriphenylene derivative(PBH)molecules. The introduction of less than 33% amount of PBH disrupted the columnar hexagonal phase formed by H6 TP remarkably, followed by the decreased clearing temperatures of liquid crystals. As the PBH amount was further increased, the destroyed columnar hexagonal phase was turned into the columnar rectangular phase, in which H6 TP and PBH molecules together formed the columnar mesophase. The formation of new mesophase contributed to the enlarged mesophase temperature(from44 8C to 144 8C). We speculated that the alkyl chains interaction induced by the PBH component competed with the strong p–p stacking between H6 TP molecules, thus altering the liquid crystalline properties including mesophase types and phase transition temperatures.     

STUDIES ON CRITICAL CONCENTRATION OF LIQUID CRYSTALLINE ETHYLCELLULOSE

Critical concentrations of lyotropic liquid crystalline ethylcellulose in more than tensolvents were determined using both Abbe refractometer and polarized microscopy. Criti-cal concentration C_(crit) of forming liquid crystal phase decreased with increasing solubilityparameter δ of solvent until approaching the δ of polymer. Although the alcohols usedas solvents had the same variation rule, the critical concentration values of their solutionswere much higher, due to their excessive large hydrogen bond component of δ. The experi-ments of using mixed solvents which showed good linear relation between C_(crit) and δ alsoproved this rule. A technique of Transmission Optical Analysis was first used to estimatethe concentration dependence of critical phase transition temperature T_(crit) of EC, and aT-C phase diagram could be drawn.     

FT-Raman Spectroscopic Studies on the Interaction of Metal Ions With Sphingomyelin Bilayer

The interaction of trivalent lanthanide ions and divalent calcium ions with sph-'ngomyelm bilayer has been studied by FT-Raman spectroscopy.The results showed that the bonding of metal ions to the phosphate group of sphingomyelin bi-iayer,either La3 or Ca2 did not change the conformation of the choline group,that is,O-C-C-N is still in its gauche conformation.The presence of metal ions changed the states of the interfacial region from liquid-like to amorphous state and even to crystalline.They increased the fluidity of acyl chains of sphingomyelin bilaver and made them packed disorderly.     

CALORIMETRIC AND RAMAN SPECTROSCOPIC STUDIES ON THE INTERACTION OF LANTHANOID IONS WITH DIPALMITOYLPHOSPHATIDYLCHOLINE BILAYER

The interactions of lanthanoid ions with dipalmitoylphosphatidylcholine bilayer werestudied by DSC and Raman spectroscopy.The results show that the addition of lanthanoid ionscauses a considerable increase of the gel to liquid crystalline transition temperature ofphospholipid and a reduction of order of lateral packing and conformation of acyl chains in SUVs.     

STUDY ON THE PHASE TRANSITION KINETICS OF THERMOTROPIC LIQUID CRYSTALLINE AROMATIC-ALIPHATIC COPOLYESTER

The phase transition kinetics of thennotropic liquid crystalline aromatic-aliphatic regular copolyester: were studied by DSC. By means of Kissinger's method the kinetic equation and parameters including activation energy, rate order and preexponential factor for phase transition from nematic to isotropic were obtained. The activation energy from crystal to nematic was also presented.     

MORPHOLOGICAL STUDIES OF A THERMOTROPIC SIDE-CHAIN LIQUID CRYSTALLINE POLYMER DURING MESOPHASE TRANSITIONS*

The morphological features of a side-chain liquid crystalline polymer during the mesophasetransitions were investigated by using the DSC technique. The polymer used was polyacrylate with mesogensof three benzene rings attached to the main chain through a flexible spacer. A special two-phase texture wasobserved in the transition temperature range. Similar to main-chain liquid crystalline polymers the transitionprocess of the side-chain liquid crystalline polymer was composed of an initiation of the new phase at localplaces of the old phase matrix and a growth process of the new phase domains.     

SYNTHESIS AND CHARACTERIZATION OF β-DIKETONE BASED SIDE CHAIN LIQUID CRYSTALLINE POLYSILOXANES

A new type of β-diketone based side chain liquid crystalline polysiloxanes (DKLCP) with different length of flexible spacers and end groups have been synthesized by hydrosilation reaction. This is liquid crystal polymers (LCP) using coordinating β-diketone ligand as mesogens. The phase behaviour of DKLCP polymers was studied by differential scanning calorimetry and polarizing microscopy. X-ray diffraction investigations demonstrated that the polysiloxanes with sufficiently long flexible spacers were smectic liquid crystal polymers, while those with much shorter spacers were nematic ones.     

过渡金属离子识别的1，8-萘二甲酰亚氨衍生物作为荧光传感器的研究

Two fluorosensor systems have been designed and synthesized with their photophysical properties and fluorescence responses toward the transition metal ions studied. The fluorosensor was composed of 1,8-naphthalimide and 4-chloro-1,8-naphthalimide as fluorophore respectively, an amino moiety as the receptor and a hydrocarbon chain as the spacer to link the fluorophore and receptor. Fluorescence intensity of these systems is very weak due to the process of the efficient intramolecular photoinduced electron transfer （PET） in the absence of metal ions. Titration of the transition metal ions can switch on the fluorescence immediately. The intensity of released fluorescence is even higher than the expected from the consideration of the PET in these systems. It may be rationalized that the receptor bound to transition metal ions and the solvation of the fluorophore by the water molecules from the hydrated transition metal salts, may significantly cause fluorescence enhancement.     

Fluorescence microscopy observation of self-organized microstructure formed by a rare earth compound

The morphologies of monolayers containing Eu(TTA)3Phen (TTA=thenoyltrifluoroace-tone, Phen = 1, 10-phenanthroline) were studied at the air/liquid interface on different subphases by fluorescence microscopy (FM). The composite subphase was the basic premise for the stable existence of the rare earth compound at air/liquid interface. The process that rare earth compound phase changes from liquid expanded state to liquid condensed state corresponded to a plateau in the π-A isotherm. In the pure Eu(TTA)3Phen monolayer, rod domains of Eu(TTA)3Phen formed and packed with no order. In the mixed monolayers with stearic acid (SA), phase transition of SA occurred first and formed domains with an electric gradient field, which induced the rare earth compound to form luminescent ring domains. Influence of intermolecular interaction on the self-organized microstructure was revealed.     

Deformation temperature and lamellar thickness dependency of Form I to Form III phase transition in syndiotactic polypropylene during tensile stretching

Phase transition from form Ⅰ to form Ⅲ in syndiotactic polypropylene crystallized at different conditions during tensile deformation at different temperatures was investigated by using in situ synchrotron wide angle X-ray diffraction technique. In all cases, the occurrence of this phase transition was observed. The onset strain of this transition was found to be crystalline thickness decided by crystallization temperature and drawing temperature dependent. The effect of drawing temperature on this phase transition is understood by the changes in mechanical properties with temperature. Moreover, crystalline thickness dependency of the phase transition reveals that this form Ⅰ to from Ⅲ phase transition occurs first in those lamellae with their normal along the stretching direction which have not experienced stress induced melting and recrystallization.     

STATISTICS OF A NOVEL CLASS OF LIQUID CRYSTAL POLYMERS

A novel class of the liquid crystal polymers with mesogens laterally attached to flexible main chain backbones has been synthesized recently by us. While the flexible backbones tend to take configuration of maximum entropy the mesogenic side groups tend to orientate because of the anisotropie soft dispersion forces. A mean field theory is presented to describe the competition between these two trends which makes it possible for this class of polymers to show anisotropic (liquid crystal) phase within certain temperature range where the polymer main chains and the side chain mesogens will take approximately parallel arrangement, which is different from the normal side chain liquid crystal polymers. The temperature range of the liquid crystal phase, its ordering and phase transition all depend on the flexibility of the backbone, the strengthof the anisotropic forces of the side groups and the hinge elasticity. The results show that the liquid crystalisotropic phase transition is of the first order. The phase diagram, i. e. the dependence of the transition temperature on the structure of the polymers is also given.     

Deformation Temperature and Lamellar Thickness Dependency of FormⅠto Form Ⅲ Phase Transition in Syndiotactic Polypropylene during Tensile Stretching

Phase transition from form Ⅰto form Ⅲ in syndiotactic polypropylene crystallized at different conditions during tensile deformation at different temperatures was investigated by using in situ synchrotron wide angle X-ray diffraction technique. In all cases, the occurrence of this phase transition was observed. The onset strain of this transition was found to be crystalline thickness decided by crystallization temperature and drawing temperature dependent. The effect of drawing temperature on this phase transition is understood by the changes in mechanical properties with temperature. Moreover, crystalline thickness dependency of the phase transition reveals that this form I to from III phase transition occurs first in those lamellae with their normal along the stretching direction which have not experienced stress induced melting and recrystallization.     

FOURIER TRANSFORM INFRARED SPECTROSCOPIC STUDY OF EFFECT OF LANTHANIDE IONS ON PHOSPHOLIPID MULTIBILAYERS

The molecular interactions between Nd~(3+), Gd~(3+)and Yb~(3+) and DPPC in multibilayer have been studied by Fourier transform infrared spectroscopy. The results show that incorporations of the lanthanide ions considerably shift the gel to liquid-crystal phase transition to higher temperatures. The incorporations of Gd~(3+) and Yb~(3+) obviously reduce the cooperations of the transition. The phosphate region of the spectra indicates that the Ln~(3+) binding to DPPC forms DPPC-Ln~(3+)complex and the Lna~(3+)binding is not dependent on the phase state of DPPC. The C-H stretching region of the spectra suggests that the incorporation of Ln~(3+)increases the conformational order of DPPC both in gel and in liquid-crystal phase as a result of the reduction of gauche rotamers.     

Investigation on the gelation behavior of biodegradable poly(butylene succinate) during isothermal crystallization process

The early stage of polymer crystallization may be viewed as physical gelation process,i.e.,the phase transition of polymer from liquid to solid.Determination of the gel point is of significance in polymer processing.In this work,the gelation behavior of poly(butylene succinate)(PBS) at different temperatures has been investigated by rheological method.It was found that during the isothermal crystallization process of PBS,both the storage modulus(G′) and the loss modulus(G″) increase with time,and the rheological response of the system varies from viscous-dominated(G′G″),meaning the phase transition from liquid to solid.The physical gel point was determined by the intersection point of loss tangent curves measured under different frequencies.The gel time(t_c) for PBS was found to increase with increasing crystallization temperature.The relative crystallinity of PBS at the gel point is very low(2.5%-8.5%) and increases with increasing the crystallization temperature.The low crystallinity of PBS at the gel point suggests that only a few junctions are necessary to form a spanning network,indicating that the network is"loosely"connected,in another word,the critical gel is soft.Due to the elevated crystallinity at gel point under higher crystallization temperature,the gel strength S_g increases, while the relaxation exponent n decreases with increasing the crystallization temperature.These experimental results suggest that rheological method is an effective tool for verifying the gel point of biodegradable semi-crystalline polymers.