Polymer conformation in mixed aqueous-polar organic solvents

The conformation of the common polysaccharide dextran has been investigated in mixed solvents at two different temperatures using viscosity measurements. In particular we considered binary mixtures of water with the polar organic solvents glycerol, formamide, dimethylsulfoxide, or ethanol. The intrinsic viscosity of dextran T500 in the different systems has been determined, and the solvent effects, as manifested in variations of the dextran intrinsic viscosity and coil radius, have been correlated to the surface tension and the fractional solubility parameters of the solvent mixture. The coil dimension changes observed in the different solvent mixtures are consistent with expectations from water-cosolvent-dextran interactions, especially as they pertain to hydrogen bonding.     

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.     

To gel or not to gel: A prior prediction of gelation in solvent mixtures

The gelation behaviours of low molecular weight gelators 1,3:2,5:4,6-tris(3,4-dichlorobenzylidene)-D-mannitol(G1)and 2,4-(3,4-dichlorobenzylidene)-N-(3-aminopropyl)-D-gluconamide(G2)in 34 solvents have been studied.We found that sample dissolved at low concentrations may become a gel or precipitate at higher concentrations.The Hansen solubility parameters(HSPs)and a Teas plot were employed to correlate the gelation behaviours with solvent properties,but with no success if the concentration of the tests was not maintained constant.Instead,on the basis of the gelation results obtained for the G1 and G2 in single solvents,we studied the gelation behaviours of G1 and G2 in 23 solvent mixtures and found that the tendency of a gelator to form a gel in mixed solvents is strongly correlated with its gelation behaviours in good solvents.If the gelation occurs in a good solvent at higher concentrations,it will take place as well in a mixed solvent(the good solvent plus a poor solvent)at a certain volume ratio.In contrast,if the gelator forms a precipitate in a good solvent at higher concentrations,no gelation is to be observed in the mixed solvents.A gelation rule for mixed solvents is thus proposed,which may facilitate decision making with regard to solvent selection for gel formation in the solvent mixtures in practical applications.     

Limits of the dilute regime for the solution viscosity of PMMA in good and in poor solvents

The concentration (c′) marking the first deviation from linearity in the Huggins plot of specific viscosity η_sp/c vs c) has been determined for PMMA in chloroform, benzene (good solvents), acetonitrile, chlorobutane (poor solvents) and acetonitrile/chlorobutane mixtures (cosolvent). The dependence of c′ on polymer chain length and on solvent quality is given. The results are analysed in terms of the influence on c′ of incipient coil overlap, peripheral entanglements and other interactions, such as polymer association.     

Solvent flux through dense polymeric nanofiltration membranes

This work examines the flux performance of organic solvents through a polydimethylsiloxane (PDMS) composite membrane. A selection of n-alkanes, i-alkanes and cyclic compounds were studied in deadend permeation experiments at pressures up to 900 kPa to give fluxes for pure solvents and mixtures between 10 and 100 l m⁻² h⁻¹. Results for the chosen alkanes and aromatics, and subsequent modelling using the Hagen–Poiseuille equation, suggest that solvent transport through PDMS can be successfully interpreted via a predominantly hydraulic mechanism. It is suggested that the mechanism has a greater influence at higher pressures and the modus operandi is supported by the non-separation of binary solvent mixtures and a dependency on viscosity and membrane thickness. The effects of swelling that follow solvent–membrane interactions show that the relative magnitudes of the Hildebrand solubility parameter for the active membrane layer and the solvent(s) are a good indicator of permeation level. Solvents constituting a group (e.g. all n-alkanes) induced similar flux behaviours when corrections were made for viscosity and affected comparable swelling properties in the PDMS membrane layer.     

Solvent effects on two-dimensional molecular self-assemblies investigated by using scanning tunneling microscopy

Self-assembly structures investigated by using scanning tunneling microscopy (STM) at liquid/solid interface have been a topic of broad interest in surface science, molecular materials, molecular electronics. The delicate balance among the adsorbate–solvent, adsorbate–adsorbate, solvent–solvent interactions would give rise to the coadsorption or competitive deposition of solvent with adsorbate. The solvents at the interface enable dynamic absorption and desorption of the adsorbates leading to the controlled assembly of the molecular architectures. The solvent-induced polymorphism, coadsorption effect, as well as solvent effects on chirality and electronic structures are discussed in this report in view of the polarity, solubility and viscosity of the solvent, the hydrogen bonding formation between solute and solvent, and the solvophobic and solvophilic effects. The systematic studies on the solvent effects would shed light on better control of assembly structures for design of new molecular materials and molecular electronics.     

A study on the physical properties of low melting mixtures and their use as catalysts/solvent in the synthesis of barbiturates

In recent years, deep eutectic solvents have become attractive due to their interesting characteristics such as, physicochemical properties, low cost of components, easiness to prepare, low toxicity, bio-renewability, and biodegradability. In order to make the deep eutectic mixture more cost-effective and renewable, carbohydrate derivatives were linked with deep eutectic mixtures, since, carbohydrates are the most important and widespread renewable compounds on the earth. In this work, we have used low melting mixtures comprised of carbohydrates to create the reaction media for organic transformations. The physical properties such as density, viscosity, acidity, refractive index, surface tension, solubility, glass transition temperature, thermal stability, solvent polarity, and toxicity of the mixture were studied. Low melting mixtures were used as reaction media and catalysts for the effective synthesis of Barbiturates. The reaction between aldehydes and barbituric acid/thiobarbituric acid, and the reaction between aldehydes, barbituric acid/thiobarbituric acid, and malononitrile/dimedone were performed effectively with good to excellent yields. The recyclability of the catalyst/solvent was also established.     

Solubility and Thermodynamic Properties of A Hexanediamine Derivative in Pure Organic Solvents and Nonaqueous Solvent Mixtures

The solubility of N,N′-Bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine in seven pure solvents (acetonitrile, acetone, methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate and isobutyl acetate) and two binary solvent mixtures (acetone?+?acetonitrile and methyl acetate?+?acetonitrile) were measured from 273.15 to 303.15 K at atmospheric pressure by a dynamic method. The solubility data in these pure solvents were correlated by the modified Apelblat model, the Wilson model and the NRTL model, and that in the binary solvents mixture were fitted to the CNIBS/R–K model and the NRTL model. Furthermore, the mixing thermodynamic properties in pure and binary solvent systems were calculated and are discussed, based on the NRTL model. Finally, the applicability of the model of Zhang et al. (Ind Eng Chem Res 51:6933–6938, 2012) in correlating solubility data versus dielectric constant was extended from organic solvent–water mixtures to pure organic solvents and nonaqueous organic solvent mixtures. It was found that the dissolution behavior of a compound in the binary solvent mixtures can be predicted to some extent from those in pure solvents.     

Solubility prediction of anthracene in mixed solvents using a minimum number of experimental data

Numerical methods to predict the solubility of anthracene in mixed solvents have been proposed. A minimum number of 3 solubility data points in sub-binary solvents has been employed to calculate the solvent-solute interaction terms of a well established colsolvency model, i.e. the combined nearly ideal binary solvent/Redlich-Kister model. The calculated interaction terms were used to predict the solubility in binary and ternary solvent systems. The predicted solubilities have been compared with experimental solubility data and the absolute percentage mean deviation (APMD) has been computed as a criterion of prediction capability. The overall APMD for 25 anthracene data sets in binary solvents is 0.40%. In order to provide a predictive method, which is based fully on theoretical calculations, the quantitative relationships between sub-binary interaction terms and physicochemical properties of the solvents have been presented. The overall APMD value for 41 binary data sets is 9.19%. The estimated binary interaction terms using a minimum number of data points and the quantitative relationships have then been used to predict anthracene solubility data in 30 ternary solvent systems. The produced APMD values are 3.72 and 15.79%, respectively. To provide an accurate correlation for solubility in ternary solvent systems, an extension to the combined nearly ideal multicomponenet solvent/Redlich-Kister (CNIMS/R-K) model was proposed and the corresponding overall AMPD is 0.38%.     

Determination of the Solubility, Dissolution Enthalpy and Entropy of Donepezil Hydrochloride Polymorphic Form III in Different Solvents

The solubilities of donepezil hydrochloride polymorphic form III in methanol, ethanol, 1-propanol and dimethyl formamide were measured at temperatures ranging from 278.15 to 333.15 K at atmosphere pressure using a gravimetrical method. The modified Apelblat model fitted the experimental data well with the root-mean-square deviations less than 6.287 × 10^?4. The dissolution enthalpy and entropy of solute were predicted from the solubility data in different solvents using the van’t Hoff equation. The relationships among solubility, temperature, the intermolecular force and hydrogen bonding between solute and solvent, and the viscosity of solvents were investigated. The viscosity and surface tension of solvents affect the dissolution enthalpy and entropy of donepezil hydrochloride polymorphic form III.     

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.     

A new theory for polymer/solvent mixtures based on hard-sphere limit

Based on hard-sphere limit of binary mixtures with different molecular size of components a theory has been developed for calculating activities of solvents in polymer/solvent mixtures. The theory considers various chain configurations for polymer molecules, varying from extended chain to the coiled chain. According to this theory the activity of solvent can be calculated from molecular weights (MWs) and densities as the only input data. The only adjustable parameter in the calculations, is the hard-sphere diameter of polymer, which provides useful criteria for the judgement on the chain configuration of polymer.The activity calculations have been performed for seven binary mixtures of polymer/solvent and compared with experimental data at various temperatures and for a varying range of MWs of polymers.The solvents in the mixtures were both of polar and nonpolar natures. The activity calculations for the same systems were performed by the well-known Flory-Huggins theory. Comparing the results of calculations with those of Flory-Huggins theory indicates that, the proposed theory is able to predict the activities of the solvent with good accuracy.The radius of gyration, excluded volume and interaction parameter for polymer chain have been calculated using the parameter obtained in the new theory. The calculated interaction parameter in the new theory, is interpreted in terms of attraction, repulsion and interchange energy of polymer and solvent in the mixture.     

New Screening Protocol for Effective Green Solvents Selection of Benzamide,Salicylamide and Ethenzamide

New protocol for screening efficient and environmentally friendly solvents was proposed and experimentally verified. The guidance for solvent selection comes from computed solubility via COSMO-RS approach. Furthermore, solute-solvent affinities computed using advanced quantum chemistry level were used as a rationale for observed solvents ranking. The screening protocol pointed out that 4-formylomorpholine (4FM) is an attractive solubilizer compared to commonly used aprotic solvents such as DMSO and DMF. This was tested experimentally by measuring the solubility of the title compounds in aqueous binary mixtures in the temperature range between 298.15 K and 313.15 K. Additional measurements were also performed for aqueous binary mixtures of DMSO and DMF. It has been found that the solubility of studied aromatic amides is very high and quite similar in all three aprotic solvents. For most aqueous binary mixtures, a significant decrease in solubility with a decrease in the organic fraction is observed, indicating that all systems can be regarded as efficient solvent-anti-solvent pairs. In the case of salicylamide dissolved in aqueous-4FM binary mixtures, a strong synergistic effect has been found leading to the highest solubility for 0.6 mole fraction of 4-FM.     

Molecular solubility and hansen solubility parameters for the analysis of phase separation in bulk heterojunctions

Although the fabrication procedures for bulk heterojunction (BHJ) solar cells are routinely optimized to accommodate new organic materials, the influence of solvent properties and cohesive forces on the film‐forming process and the self‐assembly of donor and acceptor molecules on the nanoscale are poorly understood. In this study, we measure the solubility of a variety of organic semiconductors in a range of solvents and calculate cohesive forces including dispersion forces, dipole interactions, and hydrogen bonding via Hansen Solubility Parameters (HSPs). HSPs were calculated by measuring the solubilities of various organic semiconductors in 27 solvents and the influence of solvent identity on film morphology of different BHJ mixtures was explored via atomic force microscopy (AFM). The possibility of correlations between HSPs and film morphology was considered; however, it is apparent that the HSP values alone do not play a critical role in determining the morphology of the films of conjugated polymers and molecules. This collection of solubility data constitutes the first of its type for organic semiconducting materials, and may act as a useful reference for the organic semiconductor community to aid in the understanding and selection of solvents for donor–acceptor BHJ mixtures. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Near- and supercritical fluid solvents for living anionic polymerizations

Near- and supercritical fluids are investigated as solvents for anionic polymerizations of 1,3-dienes. Solvent strength (solubility parameter) of mixtures of light hydrocarbons containing cyclohexane is shown to be adjustable using solvatochromic probe methods. The results indicate that these mixtures have solubility parameter values that are lower than conventional liquid solvents and represent a regime of solvent strength that has remained unexplored for ionic polymerizations. The anionic initiator 3-methyl-1,1-diphenyl-pentyllithium (MDPPL) was shown to be soluble in supercritical ethane and that its ultraviolet/visible absorption maximum was sensitive to systematic density changes of the supercritical fluid induced by pressure profiling. These results were extended to the anionic polymerization of isoprene in butane/cyclohexane mixtures.     

吡嗪二羧酸-三聚氰胺双组分水凝胶的制备及性能

以3,6-二甲基-2,5-吡嗪二羧酸(P)和三聚氰胺(M)为组分,采用不同的摩尔比(1∶1,1∶2,1∶3)混合配制了3个样品PM11,PM12和PM13,并对其凝胶性能进行了测试.实验结果表明,PM能在水中及部分含水有机溶剂中形成稳定的凝胶,这些凝胶对酸碱具有良好的响应性能.采用扫描电子显微镜分析了3种水凝胶的微观形貌,均为纤维状的网络结构;红外光谱及紫外光谱测试结果表明氢键是形成凝胶的关键驱动力;XRD测试结果显示凝胶为层状结构.对PM12在不同pH值的水中的凝胶性能测试结果表明,在pH=3~11的范围内PM12均能形成凝胶.测试了PM12在混合溶剂中的凝胶性能,并将测试结果与混合溶剂的Hansen溶解度参数关联,以便用于分析溶剂与凝胶因子间的相互作用,所得结果亦表明氢键在凝胶形成的过程中起重要作用.     

Hydrogen bonding and dipolar interactions between quinolines and organic solvents. Nuclear magnetic resonance and ultraviolet-visible spectroscopic studies

Solvatochromic studies on quinoline (Q), 3-cyanoquinoline (CNQ), 3-bromoquinoline (BrQ) and 8-hydroxyquinoline (OHQ) in pure solvents and alcohol-cyclohexane mixtures have been performed. The results are compared with Proton Nuclear Magnetic Resonance, 1H NMR. studies and AMI calculations. Taft and Kamlet's solvatochromic comparison method was used to disclose solvent effects in pure solvents. These studies shows that the hydrogen bond acceptor ability of the Q ring is diminished and its polarity is increased by the presence of the cyano group in CNQ and the bromo group in BrQ. In OHQ, intramolecular hydrogen bonding has been observed. This interaction is weakened by the interaction with protic solvents. The studies in binary mixtures, alcohol-cyclohexane, show solute-solvent interactions, which compete with solvent self-association in the preferential solvation phenomena. Alcohols with strong ability to self-associate have less preference toward solvation of these compounds. The association constants for solute-ethanol systems were determined by 1H NMR. The results show that the solvent hydrogen bond donor ability is the main factor involved in the interaction with these solutes at the aza aromatic site.     

Experimental phase diagram of a model colloid-polymer mixture in the protein limit

Sterically stabilized silica nanoparticles were synthesized, and turbidity measurements confirmed that they behaved as hard spheres in cyclohexane. Poly(isoprene) was added to give mixtures in the protein limit with a polymer coil/colloid radius ratio of 4.8. Their phase behavior under good solvent conditions was studied experimentally. The critical colloid volume fraction was phi = 0.13, whereas recent simulations (Bolhuis, P. G.; Meijer, E. J.; Louis, A. A. Phys. Rev. Lett. 2003, 90, 068304) predicted phi = 0.24. This difference is ascribed to the fact that many systems showing good solvent scaling behavior of the polymer still have a Flory-Huggins parameter close to 0.5, for instance, chi = 0.45 in this work.     

Photophysical Properties of 7‐(diethylamino)Coumarin‐3‐carboxylic Acid in the Nanocage of Cyclodextrins and in Different Solvents and Solvent Mixtures

The photophysical properties of 7‐(diethylamino) coumarin‐3‐carboxylic acid (7‐DCCA) were studied in cyclodextrins (α, β, γ,‐CDs), different neat solvents and solvent mixtures by using steady state absorption, emission and time‐resolved fluorescence spectroscopy. We have observed that with gradual increase in concentration of β‐CD the fluorescence quantum yield and lifetime decreased in a regular pattern whereas with gradual increase in concentration of γ‐CD the fluorescence quantum yield and lifetime gradually increased. With addition of urea, the fluorescence quantum yield and lifetime of 7‐DCCA in CDs increased. Binding constant calculation shows that 7‐DDCA forms 1:1 complex with β‐CD and with γ‐CD it forms 1:1 and 1:2 (guest:host) inclusion complex. We proposed that the dye molecule formed capping complex with β‐CD by means of hydrogen bonding and after addition of urea the hydrogen bonding network broke down and part of dye molecule entered inside the cavity of β‐CD. The photophysics of 7‐DCCA was studied in dioxane‐water mixture and ethylene glycol‐acetonitrile mixture to know the effect of polarity and viscosity of the media. The photophysics of 7‐DCCA was also studied in different neat solvents. It was found that the photophysics of 7‐DCCA depended on the structural feature of the solvents and solvent mixtures.     

Low-melting salts based on a glycolated cobalt bis(dicarbollide) anion

A new series of low-melting quaternary ammonium salts based on a glycolated cobalt bis(dicarbollide) anion structure have been synthesized and characterized, and their spectroscopic and physicochemical properties have been studied. The lowest melting point was obtained for 1-butyl-3-methylimidazolium (～50 °C) followed by 1-butyl-1-methylpiperidinium (～80 °C), 1-butyl-1-methylpyrrolidinium (～95 °C), and 1-butyl-4-methylpyridinium salts (～115 °C). The salts were thermally stable up to 180 °C [decomposition of an oligo(ethylene glycol) chain] and contained variable amounts of water. The flexible oligo(ethylene glycol) chains contributed to the waxy state of salts. The solubility of the salts was determined for 76 solvents that are commonly used in organic chemistry. Generally, the solubility increased with the dipole moment and relative polarity of the solvent. Salts exhibited good solubility in ketones and esters; moderate solubility was observed in alcohols, aromates, and chlorinated solvents, and poor solubility was obtained in ethers. The salts were practically insoluble in higher hydrocarbons and water. Salts are dissolved in the form of ion pairs or separated ions, depending on the nature of the solvent.