Comb-shaped Polymer Research Articles

Accelerating rate calorimetry study on the thermal stability of interpenetrating network type poly(siloxane- g-ethylene oxide) polymer electrolyte

Safety study regarding an exothermic reaction at elevated temperature of comb-shaped siloxane polymer and its interpenetrating network type solid polymer electrolyte (SPE) are investigated. Accelerating rate calorimetry (ARC) is used to examine exothermic reactions. The thermal stability of the polymer electrolyte in the presence of charged electrodes is also monitored. Resulting data were compared with those of 1.0 M LiPF 6 in ethylene carbonate:ethyl methyl carbonate (3:7 by wt.) electrolyte. The self-heating exothermic reaction of mono comb-shaped siloxane polymer electrolyte starts at approximately 300 °C. Comparison of the heat generation profiles from ARC tests indicates that SPE reduces the intensity of exothermic reactions resulting from charged electrodes and electrolyte.

Binding Behavior of Crystalline and Noncrystalline Phases: Evaluation of the Enthalpic and Entropic Contributions to the Separation Selectivity of Nonpolar Solutes with a Novel Chromatographic Sorbent

In this paper, we describe studies of the retention characteristics of nonpolar molecules with a novel liquid-crystalline, silica-supported, comb-shaped polymer chromatographic phase, Sil-ODA18. These results extend and amplify previous reports of the roles of enthalpic- and entropic-driven processes in the modulation of the selectivity of nonpolar and polar compounds in reversed-phase high-performance liquid chromatography (RP-HPLC). The investigations reveal that phase reorganization is the most important factor controlling selectivity enhancement with silica-supported, comb-shaped polymer phases as the temperature, T, of the system is varied. Moreover, these studies demonstrate that contributions from the stationary and the mobile phases can be independently fine-tuned to achieve enhanced selectivity via partition and/or adsorption binding processes. The relevant thermodynamic parameters, namely, the changes in enthalpy, entropy, and heat capacity for various nonpolar solutes with this comb-shaped polymeric sorbent, have also been determined using recently developed analytical procedures for the evaluation of nonlinear van't Hoff plots. These investigations into the thermodynamic properties of the comb-shaped polymeric sorbent in its ordered crystalline and noncrystalline states clearly delineate the differences in binding behavior compared to conventional types of monolayer n-alkylsilica sorbents and thus should facilitate wider application of this new class of reversed-phase sorbents in the separation sciences.

Electrochemical properties of amorphous comb-shaped composite PEO polymer electrolyte

The electrochemical behaviour of a polyethylene oxide (PEO)-based composite polymer electrolyte are studied. The crystallinity of the PEO is suppressed by using a comb-shaped polymer to improve polymer chain mobility. An amorphous comb-shaped polymer, ‘TEC-24’, with a side-chain content of 24 mol%, is designed and fine silica powder is dispersed within it to enhance the mechanical properties above the melting point. The composite polymer electrolyte has an ionic conductivity of 1.6×10 −4 and 1.6×10 −3 S cm −1 at 30 and 90 °C, respectively, with an electrochemical stability window close to 5.0 V, even at 80 °C (versus Li/Li +). The polymer electrolyte is evaluated using CuS as a cathode material and shows better cycle performance than that obtained with a liquid electrolyte.

The structure of liquid heptane at wax surfaces

The properties of the molecules in a liquid heptane film on an octacosane crystal surface have been studied using molecular dynamics techniques. Molecule energies, conformational properties and dynamic properties were calculated and correlated with height above the crystal surface. This analysis indicated that the liquid heptane is strongly ordered in the vicinity of the wax surface, showing at least four layers in which the heptane tended to align parallel to the surface. Substantially more structure was found in the interfacial heptane layer, with the heptane also being aligned parallel to the paraffin molecules in the wax surface, and showing a strongly anisotropic diffusive behaviour that reflected the underlying topology of the wax surface. Simulations were also performed to study the effect of an adsorbed comb-shaped polymer (poly(octadecyl acrylate)) on the liquid properties. The polymer was found to mix with the heptane to produce an additional, strongly ordered layer that would provide a kinetic barrier to any subsequent wax deposition.

RETENTION BEHAVIORS OF POLYCYCLIC AROMATIC HYDROCARBONS ON COMB-SHAPED POLYMER IMMOBILIZED-SILICA IN RPLC

The comb-shaped polymer (ODA18) was prepared by telomerization of octadecyl acrylate with 3-mercapto-propyltrimethoxysilane and immobilized onto porous silica gels. The DSC thermograms of both ODA18 and Sil-ODA18 showed a crystalline-to-isotropic phase transition. The polymer-immobilized silica (Sil-ODA18) showed a selective retention towards polycyclic aromatic hydrocarbons (PAHs). The enhanced selectivity was observed in the crystalline region. The relatively bulky solute molecules were retained preferentially in the non-crystalline region and exhibited a k'-jump at around the phase transition temperature in the temperature dependent plot. The increase in retention factor with increasing temperature arises from the gradual increase in solute-stationary phase contact volume. We assume that the enhancement of retention factor in the crystalline region towards slender and planar PAHs arises from the incorporation with the ordered side chains or the alignment with the ordered carbonyl groups for π-π interaction. The selectivity of ODS and of Sil-ODA18 at the isotropic state towards PAHs was found to be similar.

Recognition of critical pairs of polycyclic aromatics on crystalline, liquid-crystalline and isotropic regions of silica-supported polymer in HPLC

The silica-supported comb-shaped polymer (Sil-ODA18) with a “crystalline-to-isotropic” phase transition showed the characteristic behaviors of both polymeric and monomeric ODS phases. This was examined using a SRM 869 test mixture. Furthermore, Sil-ODA18 exhibited a specific selectivity towards the critical pairs of polycyclic aromatic hydrocarbons (PAHs), such as acenaphthene and fluorene, or benz(a)anthracene and chrysene, or benzo(ghi)perylene, indeno(1,2,3-cd)pyrene and dibenz(a,h)anthracene. The separation of these solutes was controlled by selecting temperature and solvent systems. The selectivity on Sil-ODA18 was also compared with a conventional ODS (octadecylsilyl silica gel) column. The selectivity on a Sil-ODA18 matrix is attributable to an orientation change of the long-chain alkyl substituents on the surface of the silica base material on transition from crystalline to isotropic state.

Retention versatility of silica-supported comb-shaped crystalline and non-crystalline phases in high-performance liquid chromatography

Silica-supported comb-shaped polymer (Sil-ODA 18) provided a specific selectivity towards aromatic and non-aromatic solutes. Selectivity of Sil-ODA 18 and ODS (polymeric and monomeric) columns towards polycyclic aromatic hydrocarbons and geometric isomers have been discussed in respect of molecular shapes and sizes. The retention versatility of this phase arises from the orientation change on transition from the ordered crystalline to the less ordered non-crystalline state. Selectivity in the crystalline and non-crystalline regions of Sil-ODA 18 is similar to that of polymeric and monomeric ODS phases, respectively. Sil-ODA 18 column also exhibited the characteristic temperature dependency of liquid–crystalline phases, i.e., an increase in retention with increasing temperature on transition from crystalline to isotropic state.

Phase Diagram of Poly(4-vinylphenol)−N,N-Dimethyloctadecylamine Mixture

The phase diagram of poly(4-vinylphenol)−N,N-dimethyloctadecylamine (PVPh−NDOA) mixture is investigated by X-ray diffraction measurements and optical microscopy. In the low-temperature region PVPh−NDOA mixtures take the mesoscopically ordered phase like a comb-shaped polymer above the melting temperature of the crystal of PVPh−NDOA aggregates. With elevating temperature PVPh−NDOA mixtures undergo an order−disorder phase transition that is a characteristic phase transition in block- or comb-shaped polymers and take homogeneous single phase. Furthermore, at higher temperatures PVPh−NDOA mixtures show the LCST-type phase transition and macroscopically separate into two homogeneous phases. These complex phase behavior in the PVPh−NDOA mixture is explained in relation to the balances of association between the hydroxyphenyl group of PVPh and the dimethylamino group of NDOA, repulsion between PVPh and the octadecyl group of NDOA, and the variation of the entropy contribution with varying temperature.

Rotation relaxation in a side chain liquid crystal polymer in the vicinity of the nematic-isotropic transition temperature

Abstract The electric birefringence of three fractions of a comb-shaped nematic polymer with different molecular masses, and having cyanobiphenyl mesogenic groups, in the vicinity of the nematic-isotropic transition temperature has been studied. It was established that two types of relaxation process exist in the vicinity of the nematic-isotropic transition temperature. The Landau-de Gennes model is adequate for a description of the pretransitional electro-optic properties of all the polymer fractions. At the same time, a comparison of some kinetic electro-optical parameters of low molar mass and polymer liquid crystals of similar molecular structure has revealed essential differences in their values that probably are explained by the hindered rotation of mesogenic groups in the polymer samples.

Lipid Membrane Analogue-Immobilized Silica Gels for Separation with Molecular Recognition

Abstract The comb-shaped polymer (ODAn) composed of a reactive terminal group and highly-orienting side-chain groups was prepared by telomerization using 3-mercaptopropyl trimethoxysilane and octadecylacrylate. The polymer was readily immobilized onto porous silica gels through a terminal reactive group. DSC indicated that the silica-supported polymer (Sil-ODAn) underwent crystal-to-isotropic phase transition on silica gels at a temperature range of 28–47°C (in the case of n = 27) in methanol. Polarity microscopic observation of the polymer showed the phase transition included a nematic liquid crystalline state. The packed column showed a remarkably higher separation factor for mixtures of planar aromatics (e.g. triphenylene and trans-stilbene) and non-planar aromatics (e.g. o-terphenyl or cis-stilbene) at room temperatures than did the conventional hydrophobic stationary phases, i.e. octadecylated silica gels. In addition, the Sil-ODAn column showed remarkable temperature dependence on both retention cap...

Rheological material functions for associating comb-shaped or H-shaped polymers A fractional calculus approach

Abstract A rheological constitutive equation for associating comb-shaped or H-shaped polymer solutions is derived, which shows a unique power-law zone characterized by two time parameters and one power-law exponent in the terminal relaxation region. The constitutive equation is of fractional integral or fractional differential type and contains two additional parameters. A comparison with experimental data demonstrates very good agreement with the theoretical predictions. The material functions in the frequency domain represent a generalization of the well known Cole-Cole behaviour.

The chiral smectic H liquid crystalline structure of a comb-shaped side-chain polymer

The polymer investigated is a comb-shaped polymer with long oligomeric side chains containing a chiral center. The chiral center contains the strongly dipolar nitrile group bound to the aliphatic spacer between aryl units in a stereo-ordered fashion. The chemical structure of the comb polymer is shown below:

A new type of liquid crystalline structure- The chiral smectic E phase of a comb-shaped polymer

The polymer investigated here is a comb-shaped macromolecule containing long chiral teeth. The highly dipolar -CN group is part of the stereogenic center located in an aliphatic spacer between aryl units. This center occurs with a high degree of configurational order, thus yielding a chiral molecule of high enantiomeric purity. The chemical structure of the polymer is shown below, Thin films of this polymer were prepared using a solution casting technique and examined in a Philips 420 electron microscope.Fig. 1 shows a selected area electron diffraction pattern of the film, indicating that reflections are distributed with hexagonal symmetry. However this pattern cannot be indexed by hexagonal unit cell parameters but only orthorhombic ones having the values, a=8.24Å, b=5.34Å, γ=90° . The observed d-spacings and their indices are listed in Table 1. Based on Table 1 it is obvious that the lattice of the polymer is orthorhombic and the c axis (the side-chain axis ) is perpendicular to the film.

Optical and hydrodynamic properties of a comb-shaped mesogenic polymer and its copolymer

The hydrodynamic (translational diffusion, sedimentation, and intrinsic viscosity) and optical (flow birefringence) properties of a comb-like mesogenic homopolymer and its copolymer are studied. Equations are obtained connecting the diffusion and viscosity with the MM. The equilibrium rigidity of the homopolymer and copolymer in different solvents is determined: the value of the Kuhn segment of the whole polymer is A=45 A ̊ in tetrachloromethane and A=55 A ̊ in dioxane as against A=40 A ̊ in tetrachloromethane and A=58 A ̊ in benzene for the copolymer respectively. The optical anisotropy of the copolymer molecule reflects the high (intra-molecular) orientational order and the fact that it is essentially dependent on the concentration of the mesogenic groups and their location relative to the molecule backbone.

Ionic conductivity in mixtures of salts with comb‐shaped polymers based on ethylene oxide macromers

AbstractA comb‐shaped polymer was prepared from a vinyl ether monomer comprising three oxyethylene units with a terminal methoxy group. The polymer could dissolve LiClO4, NaClO4, and LiSO3CF3 salts to form homogeneous amorphous mixtures, and the glass transition temperatures in each system were observed to increase with added salt. A.c. conductivity studies on the mixtures of polymer‐LiClO4 showed a dependence on both salt concentration and temperature. Room temperature conductivities were around 10−5Scm−1 rising to about 10−3Scm−1 at ∼ 380K. A maximum in the conductivity was detected which altered with temperature. Conductivities which displayed non‐Arrhenius behaviour were analysed using the Vogel‐Tammann‐Fulcher equation and interpreted on the basis of the configurational entropy model derived by Gibbs and coworkers.