A combinatorial approach to studying the effects of N-alkyl groups on poly(N-alkyl and N,N-dialkylacrylamide) solubility

Soluble polymers including poly(N-alkylacrylamide)s with low mole percent loadings of pendant groups are of interest in applications in catalysis, synthesis, sequestration, and soluble affinity chromatography where their thermal and phase-dependent solubility facilitates purification and separation. This work describes a library synthesis and study of the effects of polymer composition on the phase-selective solubility of dye-labeled poly(N-n-octadecylacrylamide-co-N-n-butylacrylamide) copolymers. To study the relative importance of n-octadecyl versus n-butyl groups, copolymers with different ratios of n-octadecylacrylamide and n-butylacrylamide but with similar degrees of polymerization and polydispersity were prepared by a split-pool synthesis using a highly soluble poly(N-acryloxy-2-dodecylsuccinimide) as the precursor. Polymer sequestrants were used to remove excess amines and the byproduct N-hydroxyl-2-dodecylsuccinimide without fractionation of the polyacrylamides. Other studies of dye-labeled poly(N,N-dialkylacrylamide)s prepared by the polymerization of N,N-dialkylacrylamides with methyl, ethyl, propyl, butyl, pentyl, and hexyl N-alkyl groups in a variety of thermomorphic or latent biphasic polar/nonpolar solvent mixtures showed that poly(N,N-dialkylacrylamide)s like poly(N-alkylacrylamide)s have phase-selective solubility that is highly dependent on the size of the N-alkyl group.     

Correlations for the solubility of normal alkanoic acids ando-toluic acid in binary solvent mixtures

Reasonable estimates of ternary solid-liquid equilibrium can be obtained by application of the Wilson and UNIFAC models. The solubilities of octadecanoic, eicosanoic, docosanoic, and o-toluic acids in binary solvents consisting of a common component (cyclohexane) and a varying second component (heptane, ethanol, methanol, 2-propanol, and 1-butanol) have been measured by a dynamic method from 290 to 340 K. The systems containing cyclohexane-alcohols mixed solvents were found to exhibit a synergistic effect of solubility. The best prediction was obtained for the Wilson equation utilizing temperature dependent _ij parameters. For solubilities in nonpolar solvents, the standard deviations for predicted solubilities are comparable to the experimental errors.Presentation to First International Symposium on Solubility Phenomena, University of Western Ontario, London, Ontario, August 21–23, 1984.     

Two-dimensional surface chirality control by solvent-induced helicity inversion of a helical polyacetylene on graphite

We report the direct evidence for the macromolecular helicity inversion of a helical poly(phenylacetylene) bearing l- or d-alanine pendants with a long alkyl chain in different solvents by atomic force microscopy observations of the diastereomeric helical structures. The diastereomeric helical poly(phenylacetylene)s induced in polar and nonpolar solvents self-assembled into ordered, two-dimensional helix bundles with controlled molecular packing, helical pitch, and handedness on graphite upon exposure of each solvent. The macromolecular helicity deposited on graphite from a polar solvent further inverted to the opposite handedness by exposure to a specific nonpolar solvent, and these changes in the surface chirality based on the inversion of helicity could be visualized by atomic force microscopy with molecular resolution, and the results were quantified by X-ray diffraction of the oriented liquid crystalline, diastereomeric helical polymer films.     

不同极性的临界介质对孔道中甲醇的脱附和萃取作用

针对临界溶剂对多孔介质中甲醇的脱附和萃取作用，利用Monte Carlo (MC)方法考察了溶剂的分子结构与外在因素（孔道尺寸）对甲醇合成过程的影响。研究表明，极性溶剂丙酮能够促进甲醇脱附，而非极性溶剂正庚烷对孔道中甲醇有更强的萃取能力。在一定范围内，随孔道尺寸的增加，溶剂对甲醇的脱附能力增加，但对孔道中甲醇的萃取能力却减弱。     

Estimation of Solubility of Carbon Dioxide in Polar Solvents

The solubility of CO₂ in polar solvents is poorly predicted by all estimation methods that use only properties of the pure components. It is thought that this is because CO₂ molecules, although they do not have a permanent dipole moment, behave like electrical multipoles as a consequence of their strongly polar bonds. An equation, proposed in a previous paper, for estimating the activity coefficient of a nonpolar gas dissolved in a polar liquid is modified by adding a term containing the quadrupole moment of the gas molecule. Errors in estimating gas solubilities on that basis are less than 20%, except for the solvents in which specific interactions (e.g., acid–base interactions) are present.     

Safer solvents for reactive organometallic reagents

This paper describes the use of poly(α -olefin)s (PAOs) as safer alternatives to cyclohexane, hexanes, and heptane as solvents for alkyllithium reagents. While PAOs like any alkane are flammable, PAOs do not readily catch on fire because they contain 20 or more carbon atoms, a low volatility, and have a high flash point vis-à-vis alkanes like hexane. Also unlike conventional alkanes, PAOs can be quantitatively separated from polar organic solvents and polar organic products either by a simple gravity separation or by an extraction after a reaction. Any leaching of the PAO solvent into a polar phase during such a separation can be minimized by addition of small amounts of water to the polar phase. However, while these PAO solvents have some physical differences from conventional low molecular weight volatile alkanes, they otherwise behave like alkanes and alkyllithium reagents in these PAO solvents can used in their conventional reactions in these PAO solvents.     

Improvement to the lattice-fluid prediction of gas solubilities in polymer liquids

Previously we have shown that the Lattice Fluid (LF) model can quantitatively predict, without adjustable parameters, gas solubilities for hydrocarbon and chlorinated hydrocarbon vapors in nonpolar polymers. For polar polymers, the model can also predict, with reasonable success, the solubilities of polar and aromatic vapors. However, the solubilities in polar/nonpolar combinations of gas and polymer are systematically overestimated. These are cases in which the geometric mean approximation for the interaction parameter is not expected to be valid. This paper demonstrates that with the addition of a simple empirical correlation for the interaction parameter based on Hansen's three-dimensional solubility parameters, the LF model is then able to quantitatively predict solubilities in all types of gas/polymer systems (excluding strongly self-associating systems, such as alcohols). No adjustable parameters are used; only the pure component equation-of-state and solubility parameters are required. © 1993 John Wiley & Sons, Inc.     

Control of various morphological changes of poly(meth)acrylate microspheres and their swelling degrees by SPG emulsification

Crosslinked poly(meth)acrylate polymers with a variety of morphologies were synthesized with two steps. In the first step, a microporous glass membrane (Shirasu Porous Glass, SPG) was employed to prepare uniform emulsion droplets by applying an adequate pressure to the monomer phase, which was composed of the ADVN initiator, solvent of toluene or heptane or their mixture, and a mixture of (meth)acrylate monomers. The droplets were formed continuously through the membrane and suspended in the aqueous solution, which contained a PVA‐127 suspending agent, SLS emulsifier, and NaNO₂ inhibitor to suppress the nucleation of secondary particles. SPG pore sizes of 0.90, 5.25, and 9.25 μm were used. Then the emulsion droplets were polymerized at 343 K with a rotation rate 160 rpm for 24 h. The (meth)acrylate monomers 2‐ethylhexyl acrylate (2‐EHA), 2‐ethylhexyl methacrylate (2‐EHMA), cyclohexyl acrylate (CHA), methyl methacrylate (MMA), lauryl acrylate (LA), and lauryl methacrylate (LMA) were used in this research. The influences of the ratios of the monomer and crosslinking agent EGDMA, the amount of diluents, the monomer type on the polymer particle morphology, the swelling degree, and the polymer particle size were investigated. It was found that an increase in the concentrations of EGDMA and heptane resulted in higher coarse porous spheres and smaller polymer particle sizes. A coefficient with a variation close to 10%, or a standard deviation of about 4, was obtained. The capacity of these spheres as solvent absorption materials was examined. The highest swelling degrees of heptane and toluene were obtained when LA was employed as the monomer with 30% (by weight) of EGDMA and 70% (by weight) of heptane as an inert solvent. The highest capacity of the solvent absorption was obtained when using a polymer particle size of 4.81 μm, as prepared by SPG pore size 0.9 μm. The polymer particles were able to absorb aliphatic hydrocarbon solvents, aromatic hydrocarbon solvents, and a mix of aliphatic hydrocarbon solvents and aromatic hydrocarbon solvents, such as toluene and heptane. The capacity of solvent absorption for the aromatic hydrocarbon solvents was higher than for the aliphatic hydrocarbon solvents. In addition, the particles did not rupture or collapse after absorption in solvents. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4038–4056, 2000     

Sol-gel immobilized cyano-polydimethylsiloxane coating for capillary microextraction of aqueous trace analytes ranging from polycyclic aromatic hydrocarbons to free fatty acids

Sol-gel coating containing highly polar cyanopropyl and nonpolar poly(dimethylsiloxane) components (sol-gel CN-PDMS coating) was developed for capillary microextraction (CME). The sol-gel chemistry provided an efficient means to immobilize the CN-PDMS coating by establishing chemical anchorage between the coating and the fused silica capillary inner surface. This chemical bond provided excellent thermal and solvent stability to the created sol-gel coating. For the extraction of polar and nonpolar analytes, the upper allowable conditioning temperatures were 330 degrees C and 350 degrees C, respectively. To our knowledge, this is the first time when a CN-PDMS thick coating survived such a high operation temperature. The prepared sol-gel CN-PDMS coating provided effective extraction of polar and nonpolar analytes simultaneously from aqueous samples. The cyanopropyl moiety in sol-gel CN-PDMS coatings provided effective extraction of highly polar analytes such as free fatty acids, alcohols, and phenols without requiring derivatization, pH adjustment or salting out procedures. The PDMS moiety, on the other hand, provided efficient extraction of nonpolar analytes. The extraction properties of the sol-gel CN-PDMS coatings can be fine tuned via manipulation of relative proportions of 3-cyanopropyltriethoxysilane and hydroxy-terminated PDMS in the sol solution used to create the coatings. Detection limits of nanogram/liter (ng/L) were achieved for both highly polar and nonpolar analytes directly extracted from aqueous media using sol-gel CN-PDMS coated microextraction capillaries followed by GC analysis.     

Degradation of parathion methyl by reactive sorption on the cerium oxide surface: The effect of solvent on the degradation efficiency

A simple and easily scalable “wet” procedure was used to prepare nanocrystalline cerium oxide capable of destroying the toxic organophosphate pesticide parathion methyl. The synthetic procedure consists of the direct precipitation of cerous salt with aqueous ammonia in the absence of CO₂. The prepared cerium oxide was able to decompose the organophosphate compounds both in nonpolar (e.g., heptane) and polar aprotic (e.g., acetonitrile) solvents. However, in solvents with hydrogen-bond donating ability, the –OH groups on the cerium oxide surface were solvated and inactivated. The preferential solvation model was used to express the experimental dependencies of the cerium oxide degradation efficiency on the composition of the water-acetonitrile mixture. In certain solvent systems, some empirical polarity scales, such as the alpha-scale or the Dimrodth-Richardt parameter ET(30), may be correlated with the degradation efficiency of cerium oxide.     

Organic solid photochromism by photoreduction mechanism: Viologen embedded in solid polar aprotic polymer matrix

Reversible photocolor developments of viologens embedded in poly(N-vinyl-2-pyrrolidone) films, a typical polar aprotic solid matrix, were found to be affected by the kinds of viologen cation as well as the paired anion. The color developments in the corresponding low-molecular-weight solvents are connected closely to the solubility of viologens in these solvents; viologens are highly sensitive in the polar aprotic solvents in which they have poor solubilities, such as N-methyl-2-pyrrolidone and hexamethyl phosphoric triamide. These facts confirm the color-development mechanism consistings of electron transfer to the photoexcited viologen cation from the paired anion in polar aprotic solid matrices such as poly(N-vinyl-2-pyrrolidone).     

A liquid-phase peptide synthesis in cyclohexane-based biphasic thermomorphic systems

Combinations of typical organic solvents composed of cyclohexane and qualified aprotic polar organic solvents were found to realize an effective, biphasic thermomorphic system in arbitrary ratios of upper and lower phases that enable a practical application of a liquid-phase peptide synthesis.     

Improved preparation and use of room-temperature ionic liquids in lipase-catalyzed enantio- and regioselective acylations.

Polar organic solvents such as methanol or N-methylformamide inactivate lipases. Although ionic liquids such as 3-alkyl-1-methylimidazolium tetrafluoroborates have polarities similar to these polar organic solvents, they do not inactivate lipases. To get reliable lipase-catalyzed reactions in ionic liquids, we modified their preparation by adding a wash with aqueous sodium carbonate. Lipase-catalyzed reactions that previously did not occur in untreated ionic liquids now occur at rates comparable to those in nonpolar organic solvents such as toluene. Acetylation of 1-phenylethanol catalyzed by lipase from Pseudomonas cepacia (PCL) was as fast and as enantioselective in ionic liquids as in toluene. Ionic liquids permit reactions in a more polar solvent than previously possible. Acetylation of glucose catalyzed by lipase B from Candida antarctica (CAL-B) was more regioselective in ionic liquids because glucose is up to one hundred times more soluble in ionic liquids. Acetylation of insoluble glucose in organic solvents yielded the more soluble 6-O-acetyl glucose, which underwent further acetylation to give 3,6-O-diacetyl glucose (2-3:1 mixture). However, acetylation of glucose in ionic liquids yielded only 6-O-acetyl glucose (>13:1 and up to >50:1).     

Contact mechanics of nanometer-scale molecular contacts: correlation between adhesion, friction, and hydrogen bond thermodynamics

Using a scanning force microscope, adhesion forces have been measured between carboxylic acid terminated self-assembled monolayers in different nonpolar solvents or in two-component liquid mixtures consisting of a polar solvent (ethyl acetate or acetone) in heptane. The adhesion forces measured in pure acetone and ethyl acetate were small (0.24 nN) but increased logarithmically as the concentration of the polar solvent decreased to reach a maximum value (2.77 nN), equal to that measured in pure heptane, and for lower concentrations of polar solvent, the adhesion force remained constant. This behavior is identical to that observed for association constants measured for the formation of 1:1 H-bonded complexes between dilute solutes in solvent mixtures. The transition between the solvent-dependent and -independent regimes occurs at a polar solvent concentration corresponding to 1/K(S), where K(S) is the equilibrium constant for solvation of a carboxylic acid by the polar solvent in heptane. A simple model, in which the solvation of the carboxylic acid groups may be estimated by considering the concentration and polarity of functional groups in the liquid, accurately predicts values of K(S) that were found to correlate very well with the observed solvent-dependence of the adhesion force. Friction-load relationships were measured using friction-force microscopy. In pure acetone and ethyl acetate, a linear friction-load relationship was observed, in agreement with Amontons' law. However, as the concentration of polar solvent was reduced, a nonlinear relationship was observed and the friction-load relationship was found to fit the Derjaguin-Müller-Toporov (DMT) model for single asperity contacts. For pure heptane and a range of other nonpolar liquids with identical dielectric constants, the friction-load relationship was described by DMT mechanics. Exceptionally, for perfluorodecalin, Johnson-Kendall-Roberts mechanics was observed. These observations may be rationalized by treating the friction force as the sum of load-dependent and shear contributions. Under conditions of low adhesion, where the carboxylic acid surface is solvated by polar solvent molecules, the shear term is negligible and the sliding interaction is dominated by load-dependent friction. As the degree of solvation of the carboxylic acid groups decreases and the adhesion force increases, the shear friction contribution increases, dominating the interaction for media in which the adhesion force is greater than ca. 0.6 nN.     

Solvent effect on the self-assembled structure of an amphiphilic perylene diimide derivative

An amphiphilic electron-deficient (n-type) perylene diimide has been synthesized and characterized. The diimide contains a hydrophobic long chain on one end and a hydrophilic ethoxy chain on the other. The self-assembly of this molecule in polar and nonpolar solvents has been demonstrated by concentration- and temperature-dependent absorption and fluorescence spectroscopies. Analysis of the spectral change for the aggregates shows typical J-aggregates for structures precipitated from polar solvents and H-aggregates for structures precipitated from nonpolar solvents. SEM and TEM micrographs and a suggested packing scheme, compatible with the formation of nanostrips in nonpolar solvents and nanofibers in polar solvents, are presented.     

Investigation of the interfacial properties of water-in-diluted-bitumen emulsions using micropipette techniques

The interfacial properties of water-in-diluted bitumen emulsions were studied using micropipette techniques. It was observed that, as bitumen concentration in the bulk phase (C0) increased, the interfacial tension on the water droplet surfaces decreased. In addition, there was a small effect on the interfacial tension when different solvent mixtures were used. Mixtures of toluene and heptane in different ratios were used as solvents for bitumen dilution. Crumpling of the interface was influenced by bitumen concentration and type of solvent. No crumpling was found for bitumen content less than 0.01% for all solvents used. Crumpling was observed at higher bitumen concentrations when deionized water (pH 5.4-5.6) was used. Setting "heptol[A]" to be the mixture of toluene and heptane, with the volume percent of toluene being A, the following were concluded. Crumpling disappeared at C0 > 1% and when heptol[100] was used, and also at C0 > 10% and when heptol[30] was used. Crumpling was strongly affected by the water pH. In the case of heptol[50], at a higher pH, the crumpling region that normally occurred at C0 > 0.01% disappeared. The micropipette technique proved to be useful in studying the interfacial properties of micrometer-sized emulsion drops.     

Phenazasiline-containing polyamides and polyesters

A Phenazasiline ring was incorporated into a polymer backbone by polycondensation of 2,8-dichloroformyl-5,10-dihydro-5-methyl-10,10-diphenylphenazasiline (V) with aromatic diamines or bisphenols, and phenazasiline-containing polyamides and polyesters were obtained. The polyamides were prepared by low-temperature solution polycondensation in N-methyl-2-pyrrolidone (NMP) in the presence of lithium chloride. The polyesters were synthesized by interfacial polycondensation in a mixture of 1,2-dichloroethane and aqueous alkali in the presence of tetrabutylammonium chloride as an accelerator. These reaction conditions gave the corresponding polymers with high viscosities. The phenazasiline-containing polyamides exhibited good solubilities in polar aprotic solvents such as dimethylformamide, dimethylacetamide, and NMP, and also in m-cresol, although the polyesters showed limited solubilities in organic solvents. Under nitrogen, the phenazasiline-containing polyamides and polyesters showed little degradation below 400°C and had good heat resistance.     

Beta-alanine-based dendritic beta-peptides: dendrimers possessing unusually strong binding ability towards protic solvents and their self-assembly into nanoscale aggregates through hydrogen-bond interactions

A series of poly(beta-alanine) dendrimers 1-4 with Boc-carbamate as the surface functionality, beta-alanine as the dendritic branch, 3,5-diaminobenzoic acid as the branching agent, and 1,2diaminoethane as the interior core has been synthesized by a solution-phase peptide-coupling method. The structural identities and purities of the products have been fully characterized by spectroscopic and chromatographic methods. 1H NMR studies on the dendrimers indicated that the Boc-carbamate surface groups exist as a mixture of syn and anti rotamers in solution, and that the dendrimers adopt an open structure in polar solvents; this allows the free interaction of the interior core functionality with solvent molecules. Due to the cooperative effect of a large number of carbamate and amide groups, the dendrimers exhibit an unusually strong binding ability towards protic solvents and behave as H-bond sponges. As a result, the H/D exchange rates of the N-H protons are significantly enhanced in such dendritic structures, as compared to those of nondendritic carbamates and amides. These dendritic peptide dendrimers also exhibit a strong tendency to form nanoscopic aggregates in nonpolar or polar aprotic solvents through intermolecular H-bond interactions.     

Radical polymerization of methyl methacrylate in the presence of stereoregular poly(methyl methacrylate). IV. Influence of solvent type

Methyl methacrylate (MMA) was polymerized by radical initiation at 25°C or 35°C in various solvents in the presence of stereoregular poly(methyl methacrylate) (PMMA). The occurrence of stereospecific replica polymerization appeared to be related to the capability of stereoassociation of isotactic and syndiotactic PMMA. The solvents can be roughly divided into three types. Type A solvents are polar solvents, which promote stereoassociation resulting in gelation and precipitation. Examples are dimethylformamide, dimethyl sulfoxide, and acetone. Type B solvents are nonpolar aromatic solvents like benzene and toluene, wherein stereoassociation is weaker but still leads to gelation. Type C solvents are very good solvents, in which stereoassociation does not occur. Chloroform and dichloromethane belong to this class. In solvents of type A as well as type B, polymerization in the presence of i-PMMA as a polymer matrix was syndiospecific. However, in the presence of s-PMMA as a polymer matrix the polymerization was isospecific only in type A solvents. The syndiotactic or isotactic triad contents of the polymer formed could be as high as ca. 90% at low conversions. In solvents of type C, polymerization in the presence of stereoregular PMMA proceeds according to a normal radical mechanism. Syndiotacticity was always less than 70%. Stereocomplexes formed in situ during replica polymerization were partly crystalline as detected by x-ray diffraction. The highest crystallinity was detected in those formed in type A solvents.     

On the temperature dependence of amide I frequencies of peptides in solution

The temperature dependence of the amide I vibrational frequencies of peptides in solution was investigated. In D2O, the amide I' bands of both an alpha-helical oligopeptide, the random-coil poly(L-lysine), and the simplest amide, N-methyl acetamide (NMA), exhibit linear frequency shifts of approximately 0.07 cm(-1)/degrees C with increasing temperature. Similar amide I frequency shifts are also observed for NMA in both polar (acetonitrile and DMSO) and nonpolar (1,4-dioxane) organic solvents, thus ruling out hydrogen-bonding strength as the cause of these effects. The experimental NMA amide I frequencies in the organic solvents can be accurately described by a simple theory based on the Onsager reaction field with temperature-dependent solvent dielectric properties and a solute molecular cavity. DFT-level calculations (BPW91/cc-pVDZ) for NMA with an Onsager reaction field confirm the significant contribution of the molecular cavity to the predicted amide I frequencies. Comparison of the computations to experimental data shows that the frequency-dependent response of the reaction field, taken into account by the index of refraction, is crucial for describing the amide I frequencies in polar solvents. The poor predictions of the model for the NMA amide I band in D2O might be due, in part, to the unknown temperature dependence of the refractive index of D2O in the mid-IR range, which was approximated by the available values in the visible region.