Rigid cross-shaped multipodes: molecules designed for molecular reinforcement

Cross-like rigid multipodes consisting of a spyro center unit and arms containing one or two phenyl units designed for molecular reinforcement effects are considered. The expectation based on theoretical considerations was that such multipodes would display an enhanced solubility both in low molar mass solvents and in polymer matrices. The shape, structure formation in the condensed state, dynamic properties, solubility and the effect of the multipodes on the dynamics of the polymer matrix were investigated. The main results are that the peculiar shape of such multipodes does not prevent a dense packing and crystallization, that the solubility is enhanced by two orders of magnitude compared with linear rigid molecules and that the presence of such multipodes in a polymer matrix composed of flexible chain molecules affects the matrix dynamics.     

Rigid stars: properties and functions

The properties of star-shaped adamantane multipodes with different types of rigid branches with various lengths are discussed. The expectation based on theoretical considerations was that such multipodes would display an enhanced solubility both in low molar mass solvents and in polymer matrices. These multipodes have a three-dimensional star-like shape, are able to crystallize but can also be obtained in the glassy state, and they show a relaxational behavior typical for polyarylates. They are soluble in various low molar mass organic solvents much better than linear rigid molecules of the same chemical constitution and of similar length and they are miscible in polymer matrices up to concentrations of 30 wt%. The multipodes were found to influence the dielectric and mechanical properties of the matrix polymers significantly. © 1998 John Wiley & Sons, Ltd.     

λ-Shaped mesogens. Structure, phase formation and properties

This contribution is concerned with molecules composed of rigid linear segments which are connected in such a way that a λ-shape results. Such types of shape have been predicted to lead to an enhanced solubility in low molar mass solvents and in the melt state of flexible chain molecules. The theoretical treatment predicted additionally that such molecules should be able to form lyotropic and thermotropic liquid crystalline phases. Experimental data on the thermodynamic properties, the structure formation in the solid and fluid condensed state, the solubility in low molar mass solvents and selected optical and electro-optical properties are reported; these are in good agreement with the predictions.     

Liquid crystal/liquid-crystalline network composite systems Structure formation and electro-optic properties

The supermolecular structure and the electro-optic properties of a composite system consisting of a dense liquid-crystalline network and a low molar mass liquid crystal embedded in the network have been characterized. The composite systems were obtained by a photopolymerization of mixtures of a rigid mesogenic spacerless diacrylate and a low molar mass liquid crystal. They are characterized by a homogeneous distribution of the low molar mass liquid crystal in the network. The network has a cocontinuous periodic spinodal-type structure having a characteristic length scale of the order of 10 nm, if the low molar mass liquid crystal is removed or replaced by other solvents. The electro-optic switching properties are characterized by the fact that the active switching time and the width of the Frederiks transition are shifted to larger values as compared to those of the pure liquid-crystalline state. The decay times, on the other hand, are strongly reduced in the network.     

Liquid crystal/liquid-crystalline network composite systems Structure formation and electro-optic properties

Abstract

The supermolecular structure and the electro-optic properties of a composite system consisting of a dense liquid-crystalline network and a low molar mass liquid crystal embedded in the network have been characterized. The composite systems were obtained by a photopolymerization of mixtures of a rigid mesogenic spacerless diacrylate and a low molar mass liquid crystal. They are characterized by a homogeneous distribution of the low molar mass liquid crystal in the network. The network has a cocontinuous periodic spinodal-type structure having a characteristic length scale of the order of 10 nm, if the low molar mass liquid crystal is removed or replaced by other solvents. The electro-optic switching properties are characterized by the fact that the active switching time and the width of the Frederiks transition are shifted to larger values as compared to those of the pure liquid-crystalline state. The decay times, on the other hand, are strongly reduced in the network.     

Synthesis and characterization of a new benzofulvene polymer showing a thermoreversible polymerization behavior

A new polymer based on a functionalized benzofulvene moiety has been synthesized by spontaneous polymerization of the monomer in the solid state. This polymer shows a very high molar mass, high solubility in the most common organic solvents, and thermoreversible polymerization properties. An interesting application in synthesis is reported.     

Investigation of thermodynamic properties of poly(methyl methacrylate-co-n-butylacrylate-co-cyclopentyl styryl-polyhedral oligomeric silsesquioxane) by inverse gas chromatography

The thermodynamic properties of poly(methyl methacrylate-co-butyl acrylate-co-cyclo -pentylstyryl polyhedral oligomeric silsesquioxane) (poly(MMA-co-BA-co-styryl-POSS)) were investigated by means of inverse gas chromatography (IGC) using 20 different kinds of solvents as the probes. Some thermodynamic parameters, such as molar heats of sorption, weight fraction activity coefficient, Flory-Huggins interaction parameter, partial molar heats of mixing and solubility parameter were obtained to judge the interactions between POSS-contained polymers and solvents and the solubility of the polymers in these solvents. It was found that acetates, aromatic hydrocarbons and hydrocarbon halides were good solvents, n-hexane, ethanol, n-propanol, n-butanol and n-pentanol were moderate solvents, while n-heptane, n-octane, n-nonane, n-decane and methanol were poor solvents for all POSS-contained polymers within the experimental temperature range. Incorporation of POSS in polymer increased the solubility of polymers in solvents, and the more the POSS in polymer was, the better the solubility was and stronger the hydrogen bonding interaction was, but the POSS content in polymers seemed to have no obvious influence on the solubility parameter of polymers.     

空气在二甲基硅油和液压油中的溶解度

对于诸多工程运用场合, 获得空气在硅油以及液压油中溶解度可靠的数据至关重要. 针对已有测量装置及方法的不足, 建立了一种基于理想气体状态方程来确定气体溶解量的新型精密活塞式装置. 获得了温度为293.2及353.2 K, 压力在0-350 kPa范围内, 空气在500cSt 二甲基硅油中的本生溶解度表达式. 测量了298.2 K时20cSt二甲基硅油及国产32#抗磨液压油在多种气相压力下的本生溶解度. 精度及可靠性分析表明实验数据的误差范围为6%. 本生溶解度与气相压力呈较好的线性关系, 以摩尔分数表示的溶解度与压力呈非线性关系, 但可用Krichevsky-Ilinskaya方程拟合. 发现空气在相对分子质量差异很大的两种二甲基硅油中的本生溶解度很接近, 由此提出, 对于小分子的非极性溶质在聚合物溶剂中的溶解度, 用聚合物单体的摩尔数而不是聚合物分子摩尔数来表示摩尔浓度更有利于实验数据的外推和工程应用. 对于相对分子质量差别较大或无法确定相对分子质量的溶剂, 工程应用中适宜采用本生溶解度.     

Solution properties of cellulose triacetate. II. Solubility and viscosity studies

The solubility of cellulose triacetate in a range of solvents was measured, and the results for tetrachloroethane, chloroform, and acetic acid were compared with those from initial phase separation in solvent–nonsolvent mixtures and viscosity–concentration studies. The correlation found between solubilities, precipitation values, and values of the Huggins viscosity constant is discussed with reference to the type of polymer–solvent interaction proposed previously to explain fractionation behavior. A qualitative comparison of solubility–swelling behaviour was also made for a very low molecular weight cellulose triacetate sample in a wide range of solvents. Results are compared with those for higher molecular weight samples and discussed with regard to the cohesiveenergy densities of solvent and polymer. Some attempt has been made to predict suitable solvents for cellulose triacetate, based on consideration of their molecular structures.     

Physicochemical Characterization of Transport in Nanosized Membrane Structures

The understanding of polymer–solvent interactions is highly important for the development of tailored membrane manufacturing procedures and for the prediction of membrane performance from transport mechanisms. This study examines the permeation performance of organic solvents through state‐of‐the‐art polyimide membranes (STARMEM, Membrane Extraction Technology Ltd.). Solvents are systematically selected to allow investigation of the effects of key physicochemical transport parameters by keeping constant all other parameters thought to be relevant. The effect of the solubility parameter, polarity (dielectric constant), surface tension, and viscosity are studied in detail. Dead‐end permeation experiments are carried out at 20 bar with STARMEM 122 and STARMEM 240 membranes. Results for the selected solvents show higher permeation rates for ketones over alcohols and aromatics as well as for acids. It is suggested that the viscosity and polarity have a greater influence than the other parameters. The effect of solvent molar volume is also investigated. Transport of solvents with high molar volume, independent of their polarity and compatibility with the membrane material, is slower in all cases than for solvents with smaller molar volume. The solubility parameter does not show any significant effect on transport phenomena.     

Effect and Mechanism of Solvent Properties on Solution Behavior and Films Condensed State Structure for the Semi-rigid Conjugated Polymers

Solvents have an essential association with polymer solution behavior. However, few researches have been deeply done on this respect. In recent years, our research group focus on the study on effect of solvent properties on solution behavior and film condensed state structure for semi-rigid conjugated polymer up till to apply for optoelectronic device. Herein, influence of solvent properties including solubility of solvent, aromaticity, polarity and hydrogen bonds on semi-rigid polymer chain sol...     

The tenth anniversary of Suzuki polycondensation (SPC)

This article describes the successful transfer of the Suzuki cross-coupling (SCC) reaction to polymer synthesis, one of the major developments within the last decade of polymer synthesis. The polymers prepared by Suzuki polycondensation (SPC) and its Ni-catalyzed reductive counterpart are soluble and processable poly(arylene)s that, because of their rigid and conjugated backbones, are of interest for the materials sciences. Achievable molar masses easily compete with those of traditional polyesters and polyamides. This article also provides insight into some synthetic problems associated with the transfer of SCC from low molar mass organic chemistry to high molar mass polymer chemistry by addressing issues such as monomer purity, stoichiometric balance, achievable molar masses, and defects in the polymer structure. Although the emphasis of this article is synthetic and structural issues, some potential applications of the polyarylenes obtained are briefly mentioned. Together with the enormous developments in the areas of metallocene, ring-opening metathesis, and acyclic diene metathesis polymerization, the success of SPC impressingly underlines the increasing importance of transition-metal-catalyzed CC-bond-forming reactions in polymer synthesis. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1533–1556, 2001     

Spectrochemical Properties of Noncubical Transition Metal Complexes in Solutions. XIV. Angular Overlap Studies of bis(Salicylidene-2-aminothiazole)Copper(II) in Various Solvents

The copper(II) complex [Cu(sat)], where Hsat is salicylidene-2-aminothiazole (bidentate Schiff - base), was studied in variety of solvents. In the solid state, the complex is black. It has been characterized by elemental analysis, solubility in common solvents, molar conductivity, and ultraviolet (UV) and visible (Vis) spectroscopy. The complex is easily soluble in common solvents such as chloroform, dimethylformamide, dimethyl sulfoxide, and 1,4-dioxane. The known crystal structure of similar compounds shows planar coordination geometry for the copper center. Combined multitechnique experiments have been applied to confirm the structure of the complex in solutions. The molar conductivities indicate their nonelectrolyte properties in all these solvents. The spectroscopic measurements were used to study the coordination properties of donoratoms and their bonding abilities.     

Using MESIMS to analyze polymer MALDI matrix solubility

The development of reliable sample preparation methods has been critical to the success of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry experiments. Good MALDI sample preparation for polymers involves choosing the solvent system, the matrix, and the ionization agent correctly, and combining them in a manner that will lead to a sample that will produce the desired ions. The vast diversity of chemistry available in industrial polymers has challenged our ability to design reliable sample preparation methods. In the experiments reported here, we show that matrix-enhanced secondary ion mass spectrometry (MESIMS) is an effective analytical technique to explore sample segregation in solid phase MALDI samples. Qualitative comparison of MESIMS and MALDI results for polymer samples prepared with multiple matrices aids our investigation of the solid-phase solubility of a variety of low molecular weight polymer materials. Including the solid-phase solubility with the liquid-phase solubility of the polymer samples and the matrices enables the construction of a relative solubility chart, which shows the best solubility matches between the polymer and matrix materials for MALDI experiments.     

Shear induced mixing/demixing: blends of homopolymers,of homopolymers plus copolymers,and blends in solution

Shear may shift the phase boundary towards the homogeneous state (shear induced mixing, SIM), or in the opposite direction (shear induced demixing, SID). SIM is the typical behavior of mixtures of components of low molar mass and polymer solutions, SID can be observed with solutions of high molar mass polymers and polymer blends at higher shear rates. The typical sequence with increasing shear rate is SIM, then occurrence of an isolated additional immiscible area (SID), melting of this island into the main miscibility gap, and finally SIM again. A three phase line originates and ends in two critical end points. Raising pressure increases the shear effects. For copolymer containing systems SID is sometimes observed at very low shear rates, preceding the just mentioned sequence of shear influences.     

Synthesis and characterization of negative‐type photosensitive hyperbranched polyimides with excellent organosolubility from an A2 + B3 monomer system

A series of photosensitive hyperbranched polyimides (HB‐PIs) were prepared through facile end‐group modifications of the fully imidized polymer. A triamine, 1,3,5‐tris(4‐aminophenoxy)benzene, and a dianhydride, 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride, were condensed with a dropwise addition method in a molar ratio of 1/2 to afford an anhydride‐terminated poly(amic acid) precursor, which was then end‐capped by 4‐aminophenol and chemically imidized to yield a phenol‐terminated HB‐PI. The modifications of the terminal phenol groups of the polyimide by acyl chloride compounds (acryloyl chloride, methylacryloyl chloride, and cinnamoyl chloride) gave the target polymers. The photosensitive HB‐PIs showed good thermal properties and excellent solubility even in low‐boiling‐point solvents at room temperature, such as acetone, 1,1,2‐trichloroethane, tetrahydrofuran, and chloroform. Photosensitive property studies revealed good photolithographic properties with a resolution greater than 3 μm and a sensitivity of 650–680 mJ/cm². © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1735–1744, 2004     

Phenoxyhydroxypropylhydroxyethylcellulose—new amphiphilic cellulose derivative

A new amphiphilic cellulose derivative phenoxyhydroxypropylhydroxyethylcellulose of substitution degree up to 0.67 was synthesized by reaction of water-soluble hydroxyethylcellulose with 2,3-epoxypropylphenylether in the presence of sodium hydroxide as a catalyst. The chemical composition of the derivative was confirmed by means of UV, IR- and ¹³C-NMR-spectroscopy. The derivatives with substitution degree up to 0.12 are soluble in water and water–alcohol mixtures. With increasing substitution degree, the polymers lose their water solubility, but still dissolve in water–alcohol mixtures. All products are soluble in aprotic solvents. The effect of the reaction conditions, such as temperature and molar ratios of reaction components, on both the reaction rate and degree of substitution was investigated.     

Lowering the molecular mass limit of thermal field-flow fractionation for polymer separations

Thermal field-flow fractionation (ThFFF) is capable of separating a wide molecular mass range of polymers by their molecular mass (Mr) and chemical composition. However, retention and resolution decrease significantly for polymers with Mr<20 kDa. Various approaches for increasing the retention of low Mr (<15 kDa) polymers were investigated. Our results showed that temperature conditions and single-component solvents had a limited effect on polymer retention and that certain binary solvent mixtures caused a dramatic increase in retention. The binary solvents approach has enabled the use of a ThFFF system and temperature conditions to separate 2.6 kDa PS from 4.4 kDa PS, thereby extending the applicability of ThFFF to lower molecular masses. The effect of binary solvent mixtures on polymer retention is correlated with the mixture viscosity.     

Solubility profiles of poly(ethylene glycol)/solvent systems, I: Qualitative comparison of solubility parameter approaches

Solubility of systems involving four different molecular weights of poly(ethylene glycol) (PEG) in tetrahydrofuran (THF), chloroform, dimethylsulfoxide (DMSO), methanol and water have been investigated by different algorithmic approaches as the mathematical application of the “like dissolves like” principle. In this study, the solubility parameters and their components for PEG and solvents have been evaluated by using of atomic group contribution methods; Small, van Krevelen-Hoftyzer (VKH), Hoy and Breitkreutz methods, respectively. Then their 2-dimensional graphs (Bagley, Henry and Hoernschemeyer diagrams) and 3-dimensional graph (Hansen diagram) have been drawn by creating the solubility profiles of the polymer in selected solvents. The dissolving capability of these solvents has been discussed. In addition the solubility parameters have been calculated by use of the van der Waals volume in the selected molecule or repeating unit of the polymer instead of the molar volume which is used in atomic group contribution methods (Askadskii approach). Surface tensions of the polymer and solvent systems have been calculated with this method and solubility criteria of PEG have been explained after a serial calculation steps. In addition, influence of molecular weight of PEG on solubility has been also analyzed. As a consequence of algorithmic calculations, THF has been determined as the best solvent whereas water is found to be the weakest solvent for polymer/solvent systems.     

Inverse gas chromatographic characterization of triblock copolymer of polystyrene–poly(ethylene oxide)–polystyrene

The thermodynamic properties of triblock copolymer of polystyrene–poly (ethylene oxide)–polystyrene (PS‐b‐PEO‐b‐PS) were investigated by means of inverse gas chromatography (IGC) using 15 different kinds of solvents as the probes. Some thermodynamic parameters, such as specific retention volume, molar heats of sorption, weight fraction activity coefficient, Flory‐Huggins interaction parameter, partial molar heats of mixing and solubility parameter were obtained to judge the interactions between PS‐b‐PEO‐b‐PS polymers and solvents and the solubility of the polymers in these solvents. It was found that increasing PEO content in PS‐b‐PEO‐b‐PS resulted in the increase in the solubility of PS‐b‐PEO‐b‐PS in alkanes and acetates solvents, but the solubility in alcohols had no change, and more PEO content in polymer caused a small decrease in the solubility parameter of PS‐b‐PEO‐b‐PS polymer, © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2015–2022, 2007