Predicting solubilities of vinyl polymers

Accurate solubility limits of polymers are best expressed by molecular weight fractionation curves. Individual curves may be obtained for each polymer–solvent (–nonsolvent) system. A method for predicting solubility behavior, based on solubility parameter δ and hydrogen bonding index γ, is proposed here. The correlation is of the form where [η] = intrinsic viscosity of precipitated polymer; T = absolute temperature; (v.f.) = volume fraction of solvent; R = (δ_s ? δ_n) ? 0.3(γ_s ? γ_n); Q = (γ_p ? γ_e)^2.2/(δ_p ? δ_e); p refers to polymer; s refers to solvent; n refers to nonsolvent; e refers to solvent system at theta temperature; and a,b,c, and k are fitted constants. The correlation was derived from data for poly(vinylpyrrolidone) and polyacrylamide. It probably is limited to systems in which the precipitate occurs as a liquid.     

Compatibility of polymer blends. I. Copolymers with organic solvents

In this work, we present a theoretical discussion regarding the Flory–Huggins χ interaction parameter for 11 random copolymer‐solvent systems along with their corresponding polymer pairs. Copolymers studied are poly(acrylonitrile‐co‐butadiene) in acetonitrile, poly(styrene‐co‐acrylonitrile) in 1,2‐dichloroethane, poly(acrylonitrile‐co‐butadiene) in hexane, and poly(acrylonitrile‐co‐butadiene) in pentane. For ternary systems, the results are expressed in terms of χ_1,23, which is reduced to the classical Flory–Huggins χ₁₂ interaction parameter in case of binary mixtures. The data on χ_1,23 may be used for an approximate estimation of the χ′₂₃ interaction parameter for the limiting case of zero solvent concentration. For this purpose, at the end of each subsection of tables, the limiting value of is given. The limiting values of , , and χ′₂₃ also appear at the end of each table. It should be noted that these values are obtained by the graphical extrapolation of data to zero concentration of solvent. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 492–498, 2006     

Influence of solvent on measurement of cohesive energy density of polystyrene

The solubility parameter (δ₂) of polystyrene was measured by the maximum [δ] method in four series of solvents which were structurally different. In each case δ₂ varied with the solvent series used, from 8·75 to 9·25 (cal/ml)^1/2 The enthalpy parameter (X_H), which was calculated for polystyrene dissolved in at least one member of each series, was then used to derive δ₂, and little or no variation in δ₂, with solvent was observed. The average value was δ₂ = 9·16 ± 0·1 (cal/ml)^1/2 It has been shown that determination of δ₂, from [η]_max can be solvent-dependent because of the influence of the entropy term Xs. It was concluded that if reliable values of δ₂ are to be obtained, they should be estimated from X_H.     

Polypentadecalactone prepared by lipase catalysis: crystallization kinetics and morphology

BACKGROUND: This work addresses the need to better understand the crystallization kinetics and morphology of poly (ω‐pentadecalactone) (PPDL). This polyester has promising mechanical properties and a unique structure that resembles that of polyethylene. PPDL is a member of the poly(ω‐hydroxy fatty acid) family, which can be derived from biobased feedstocks. RESULTS: PPDL (M_n = 34 000 g mol^?1 and dispersity D = M_w/M_n = 2.7) was synthesized using enzyme catalysis. Equilibrium melting enthalpy and equilibrium melting point were determined using extrapolation techniques, being 227 J g^?1 and 101 °C, respectively. In addition, the equilibrium melting point ( ) was found to be 109.3 °C by the nonlinear Hoffman‐Weeks plot. For , the lateral surface free energy (σ), fold surface free energy (σ_e) and fold work (q) are 10.4 erg cm^?2, 47.5 erg cm^?2 and 2.6 kcal mol^?1, respectively; while for , they are 25.1 erg cm^?2, 46.6 erg cm^?2 and 2.6 kcal mol^?1, respectively. The results indicated the existence of a regime I to regime II transition during crystallization at about 80 °C. Polarized optical microscopy and AFM provided further evidence for the regime I–II transition. In regime I, coarse spherulites were formed through splaying out and occasional branching of lamellae, as well as stacking of lamellae through screw dislocation. In contrast, in regime II, banded spherulites were formed through crystal twisting. CONCLUSION: Morphological changes in PPDL at spherulitic and lamellar levels in regimes I and II were confirmed by differential scanning calorimetry, POM and AFM. Copyright © 2009 Society of Chemical Industry     

Synthesis and Physicochemical Properties of Alanine-Based Surfactants

The synthesis of a homologous series of alanine-based surfactants, namely sodium salts of n-alkanesulfonamido-2-propanoic acids in which n-alkane is n-dodecane, n-tetradecane, n–hexadecane, and n-octadecane having the formula RSO₂NHCH (CH₃)COO^?Na⁺, is described. The starting materials used were a mixture of secondary positional isomers of n-alkanesulfonyl chlorides obtained by photosulfochlorination reaction using sulfuryl chloride and a catalyst. Surface properties of the aqueous solutions of the synthesized surfactants, including the critical micelle concentration and minimal surface tension δ_min, were determined using surface tension measurements at 25 °C. The surface excess Γ and minimum area per molecule (A _min) where calculated using the Gibbs equation. The foaming power was also determined by the Bartsh method, and the R ₅ parameter was calculated to estimate the stability of the foam formed. The results obtained were compared to those of a commercial surfactant, sodium dodecylsulfate, and a series of synthesized glycine-based surfactants. The results obtained clearly show that the alanine-based surfactants possess good surface properties. The investigations highlight the influence on the surface properties of the addition of a methyl group in the hydrophilic part.     

Solubility properties of poly(1,1-difluoroethylene) in dipolar aprotic solvents

A screening study of the solubility of poly(1,1-difluoroethylene) (PVF₂, M?_w = 2 × 10⁵) at room temperature in a wide variety of dipolar aprotic species has facilitated the discovery of a series of new solvents (N-methyloxazolidone, cyclic-substituted ureas) and rationalization of the data in a two-dimensional solubility map involving their dipole moment, μ, and their hydrogenx-bond-accepting (HBA) power β (Taft solvatochromic parameter). This map may be used as a predictive tool for the research of new functional classes of solvents, such as N-substituted mixed amideester of phosphoric acid or N-substituted sulfurous diamides. The variations of the intrinsic viscosity of the polymer with solvent polarity may be quantitatively analyzed using a linear multiparametric correlation which emphasizes the two opposite contributions of cavitation effects (Hildebrand solubility parameter δ) and of polymer–solvent interactions (β) on the coil expansion: [η] (dL.g^?1) = 0.792 - 1.2 × 10^?3δ2(J.cm^?3) + 1.59 β. Finally, 1,3-dimethyl-2-oxo-hexahydropyrimidine (N,N′-dimethylpropylene urea) leads to the highest value of the refractive index increment (dn/dc = ?0.065 mL.g^?1 at λ = 632 nm), and thus appears as the best solvent for light-scattering measurements.     

Differential scanning calorimetry analysis of thermoset cure kinetics: Phenolic resole resin

The Differential Scanning Calorimetry (DSC) trace for a commercial phenolic resole resin shows two distinct peaks. Assuming that these represent two independent cure reactions results in a kinetic model of the form: with κ_i = κ_io exp(-B_i/T). The Arrhenius parameters were estimated from a plot of ln(β/T) versus 1/T_p. The parameters, p, n₁, and n₂ were obtained by writing the DSC response predicted by the equation above in terms of a function which contains temperature as the only variable. with $ \theta _i = \left({1/\beta} \right)\int_{T_0}^T {\kappa _i dT \le r_i} $ dT ? r_i and r_i = 1/(1-n_i). Fitting this equation to the DSC response measured at a scan rate of 4°C/min obtains p ≈ 0.66; n₁ ≈ 0.55; n₂ ≈ 2.2; B₁ ≈ 8285; B₂ ≈ 7480; κ₁ ≈ 1. 12 × 10⁸ s^?1; κ₂ ≈ 0.99 × 10⁶ S^?1.     

Elongational flow studies of hinged rodlike molecules

Poly(amino acid) in an intermediate state of its helix-coil transition is known to be in a hinged rodlike conformation. In this work, the responses of poly(amino acids) in the hinged rodlike conformation against an elongational flow field were investigated by monitoring their flow-induced birefringence. Poly(L-glutamic acids) (PGA) and poly(γ-benzyl-L-glutamate) (PBLG) were examined as polyelectrolyte and noncharged poly(amino acids), respectively, and the results were compared. In the plots of flow-induced birefringence, Δn, against strain rate, $ {\dot \varepsilon } $, for hinged rodlike PBLG, there was a critical strain rate, $ \dot \varepsilon_0 $, below which Δn was not observed. Over $ \dot \varepsilon_0 $, the birefringence pattern observed was identical with that of rodlike molecules. The Δn vs. $ {\dot \varepsilon } $ plot for hinged rodlike PGA had characteristics of a rigid rod at any strain rate and there was no $ \dot \varepsilon_0$ observed. The rotational diffusion coefficient, D_r, of PBLG in the hinged rodlike conformation was larger than that for its helical conformation, while D_r, for the hinged-rodlike PGA was smaller than that for its helical conformation. It is concluded that the hinged-rodlike PGA molecule is in an extended form and that the hinged-rodlike PBLG is hydrodynamically more compact and rigid than that in its quiescent state. It is deduced that at $\dot \varepsilon_0$ hinged rodlike PBLG molecules collapse to a conformation optically anisotropic and mechanically rigid. © 1996 John Wiley & Sons, Inc.     

Yield stress and flow measurements in ABA block copolymer melts

A parallel-plate constant-stress rheometer is used to measure the yield stress τ_y, and the post-yield flow curve T(\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document}), where τ is shear stress and \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document} is shear rate, for microphase-separated triblock copolymer melts. Five polymer samples, all styrene-butadiene-styrene but with differing composition ratios and molecular weights, are tested at 125°C. Specimens are prepared by casting sheets from solutions made with different solvents. The τ(\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document}) is found usually to be sigmoidal, for the range 10^?5 < \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document} < 10^?3 s^?1, representing different stages of microstructural degradation in flow. Measurements indicate that a true τ_y exists, with values in the range 100 < τ_y < 500 Pa for these melts. A general trend is detected for τ_y to decrease as the casting solvent solubility parameter increases. A scheme for correlating the dependence of τ_y, on composition and molecular weight is proposed for the various polymers. For selected samples, the effect of mechanical history (sequence of stress application) and a temperature variation that crosses T_s (110 to 150°C) are also explored.     

Deformation of λ-phage DNA molecules in an elongational flow field

The response of λ-phage DNA molecules to a well-defined elongational flow field generated by a Taylor four-roller mill was investigated by observing the flow birefringence, Δn. Δn in the center of the four rollers, near the stagnation point, was localized at the mill exit symmetry plane. The intensity gradually increased from the off-symmetrical plane to the center of the mill, and at the exit symmetrical plane, the intensity was maximum. Δn also gradually increases with the strain rate, $\dot \varepsilon$. These observations indicate that DNA molecules in the solution would be free draining in nature. From the decay of λn at each point in the mill after a sudden stop of the mill operation at 24 s⁻¹, the rotational diffusion coefficient of molecules, D_r, at each point in the mill space was estimated, where the relaxation time of the decay of λn was considered to be related to the molecular disorienting process. It is concluded that at 24 s⁻¹ λ-phage DNA molecular coils near the stagnation point, which was assumed to be a prolate spheroid as a whole, was so deformed that the aspect ratio p (=b/a ≦ 1, where a and b are, respectively, the longer and shorter axes) would be ${\textstyle{1 \over {12}}}$ of that of the DNA molecule which has just entered the mill space. This result suggests that there is a possibility for the DNA molecule to be in a stretched conformation at a higher strain rate. © 1996 John Wiley & Sons, Inc.     

Investigation of Some Physicochemical Properties of Mixtures of Morama Seed Oil with (C6–C9) n-Alkanes at 298.15 and Atmospheric Pressure

Densities ρ, ultrasonic speeds u and dynamic viscosities η, of mixtures of morama, Tylosema esculentum, seed oil with n‐hexane, n‐heptane, n‐octane and n‐nonane were determined over the entire composition range at 298.15 K and atmospheric pressure. Excess molar volumes, , excess molar free volumes , deviations in isentropic compressibility, Δκ_s, deviations in ultrasonic speed, Δu, deviations in viscosity, Δη, and the excess free energy of activation of viscous flow, ΔG*^E, were calculated therefrom and correlated by the Redlich–Kister equation for each of the [morama seed oil + (n‐hexane or n‐heptane or n‐octane or n‐nonane)] mixtures. The results have been discussed in terms of possible intermolecular interactions and structural effects.     

Thermodynamics of polymer systems

Summary Gas chromatography has been employed to determine partial molar free energies of sorption, C₁ ^s, as well as partial molar free energies of mixing, C₁ , of atactic poly(styrene) with linear and branched alkanes (C₆-C₉), alkenes (C₈), cyclohexane and alkylbenzenes (Ph-H to PhC₆H₁₃) within the temperature range from 403 to 463 K. The influence of nature and constitution of the solute molecule on sorption and mixing properties in poly(styrene) are discussed in terms of the competing group contributions of the components. Knowledge of this influence may be transduced to understand polymer-polymer compatibility. The cohesive energy density concept has been used to calculate the infinite dilution solubility parameter for the polymer, with the aid of G ₁ . From the high temperature range the HILDEBRAND parameter ₂ was extrapolated to 298 K. The value obtained, 9.14, indicates that gas chromatography is an promising alternative to the conventional methods for determination of the solubility parameter for polymers.Herrn Prof. Dr. R. C. Schulz zu seinem 65. Geburtstag herzlichst gewidmet     

Sillimanite‐mullite transformation observed in synchrotron X‐ray diffraction experiments

High‐resolution synchrotron powder X‐ray diffraction (XRD) experiments were conducted to clarify the transformation of sillimanite to mullite (mullitization) and determine the mullitization temperature (T_c). We were able to distinguish sillimanite and mullite in the XRD patterns, despite their very similar crystallographic parameters, and to detect the appearance of small mullite peaks among sillimanite peaks. Analysis of the Johnson‐Mehl‐Avrami (JMA) equation for mullitization ratio (ζ) revealed that at temperatures T≥1240°C the mullitization had the same kinetics. The activation energy E at T≥1240°C obtained from the Arrhenius plot was 679.8 kJ mol^?1. In analysis using a time‐temperature‐transformation diagram for mullitization, a mullitization curve of ζ=1% can be described as where t is time, n is a reaction‐mechanism‐dependent parameter determined as 0.324 by JMA‐analysis, k₀ is the frequency factor, E_A is the activation energy for atomic diffusion, and represents the activation energy for nucleation. The results of fitting the data to this equation were T_c=1199°C, A=3.9×10⁶ kJ mol^?1 K^?2, E_A=605 kJ mol^?1, and k₀=3.65×10¹⁵. We conclude that the boundary between sillimanite and mullite+SiO₂ in the phase diagram is ~1200°C.     

Densities of hydrocarbons in their saturated vapor and liquid states

The Sum and differences of the saturated vapor and liquid densities of 23 hydrocarbons were used to develop the following reduced density relationships for these saturated states The hydrocarbons considered included n-parafins, olefins, diolefins, naphthenes, and aromatics. Constants β, γ, and δ, and exponent n were found to be dependent on,. Equation (a) can reproduce liquid densities with an overall average deviation of 1.1 % over the entire temperature range, while Equation (b) was found to apply only in the interval 0.900 ≤ T_R ≤ 1.00 with an average deviation of 2.2%. For temperatures of T_k < 0.90, the saturated vapor density was found to depend on temperature as follows where k and m were also found to be Z_c dependent. Values calculated using Equation (c), when compared with 81 available experimental densities for 12 hydrocarbons, produced an average deviation of 3.0%.     

Polymer solubility parameters determined from measurements in a single solvent

The solubility parameter of polyisobutylene has been determined from intrinsic viscosity measurements in a single solvent as a function of temperature. The change in solubility parameter of the solvent as a function of temperature was calculated form the equation \documentclass{article}\pagestyle{empty}\begin{document}$ \frac{{d{\rm}ln \delta s}}{{d{\rm}ln Vs}} = - \frac{{n + 1}}{2} $\end{document} where Vs, the molal volume, changes with temperature. The vlaue for the solubility parameter thus obtained compares well with values reported in the literature for intrinsic viscosity measurements in a series of solvents. Similar measurements were made with an ethylenepropylene copolymer. The solubility parameter of 87 mole % C₂ ethylene-propylene copolymer was determined to be 8.1-8.6 in either toluene or methylcyclohexane.     

Solubility parameters of hydrocarbons

Information available in the literature on vapor pressures, saturated vapor and liquid densities, and critical constants, for different hydrocarbons, has permitted the calculation of δ, the solubility parameter advanced by Hildebrand, at temperatures up to and including the critical point. For these hydrocarbons, the residual quantity, δ-δ_c was found to depend on 1-T_R according to the relationship, where k appears to be a constant within different classes of hydrocarbons. Values of δ calculated with this equation were compared with the corresponding values used to develop it, and produced an average deviation of 0.85% for 153 values considered which represented 17 hydrocarbons.     

Inverse gas chromatography of poly(vinylisobutyl ethers) and polymer-solute thermodynamic interactions

Gas chromatography (GC) retention behavior of atactic and isotactic poly(vinylisobutyl ether) stationary phases has been studied in the temperature range 30–90°C using 16 solutes which include various alkanes, alkylbenzenes, and chlorinated aliphatic hydrocarbons. The bulk sorption equilibrium retention data have been employed to derive various thermodynamic quantities at infinite dilution of solutes in the polymers, viz., χ, χ^*, χ_H, χ_S, X₁₂, δH_S, h . Their dependence on temperature, polymer structure, and chemical nature of solutes has been discussed.     

Polymeric composite systems with two continuous phases

A general mixture rule, which has the correct type of phase symmetry, is proposed for estimating the properties of composites having two continuous phases. The form of this equation is different from the equations used to predict the properties of composites with one continuous phase and one dispersed phase. The proposed equation for property P is where the volume fractions of components A and B are ø_A and ø_B, respectively, and n is a constant. A simple model is used to correlate the morphology of systems having two continuous phase with the parameter n of the mixture rule. The connectivity of the phase varies with concentration. The properties, such as elastic modulus, depend primarily upon the modulus of the material with the higher modulus. In general, the properties depend very little on the morphology of the system.     

Determination of carboxyl endgroups and comonomers in poly(ethylene terephthalate) with hydrazine

On complete hydrazinolysis of poly(ethylene terephthalate), terephthalomonohydrazide is formed from carboxyl-end terephthaloyl residues in a quantity equivalent to the content of carboxyl endgroups in the polymer. The compound is separated from the reaction mixture by ion exchange and determined photometrically [epsiv;₂₄₀ in 0.1 N HCl = 16,700 (1000 cm²/mole)]. A COOH determination carried out in this way is endgroup specific and, unlike titration, is not subject to interference by ionogenic fiber additives. Aromatic comonomers with acidic substituents (e.g., 5-sulfoisophthalic acid) in chemically modified, cationically dyeable poly(ethylene terephthalate) are determined simultaneously with the carboxyl endgroups by the same analytical method. In this case, the terephthalamonohydrazide and 5-sulfoisophthalodihydrazide are separated by ion exchange, and the difference in their spectral behavior is used for quantitative determination with the aid of a two-component analysis: where c₁c₂ = concentration of terephthalomonohydrazide and 5-sulfoisophthalodihydrazide, respectively; and D₂₄₀ D₂₁₂ = optical density at 240 and 212 nm, respectively. The content of carboxyl endgroups in polyether esters poly(p-(2-ethyleneoxy)-benzoate), is determined on the basis of the p-(β-hydroxyethoxy)benzoic acid [epsiv;₂₅₈ in 0.1 N HCl = 16,100 (1000 cm²/mole)] liberated from carboxyl-end monomer units by hydrazinolysis. For copolyether esters with p-(β-hydroxyethoxy)benzoic acid as a comonomer, the contents of carboxyl-end terephthalic acid and p-(β-hydroxyethoxy)benzoic acid are determined simultaneously with the acid of a spectrophotometric twocomponent analysis: where c₂, c₂ = concentration of terephthalomonohydrazide and p-(β-hydroxyethoxy)-benzoic acid, respectively; and D₂₄₀, D₂₅₈ = optical density at 240 and 258 nm, respectively.     

Study on conformational transition phenomena of poly(methyl methacrylate) in acetonitrile near theta conditions

The coil–globule transition for poly(methyl methacrylate) (PMMA) has been studied in a theta solvent, acetonitrile (Θ = 45 °C). The viscosity of PMMA was measured as a function of temperature in the range 26–55 °C. The contraction and expansion of the molecular chains are determined using the measured viscosity values. The temperature dependence of the intrinsic viscosity can be represented by a master curve in a versus |τ|M _w^1/2 (g^1/2 mol^−1/2) plot, where τ = |T − Θ|/T is the reduced temperature and M_w‐is the weight‐average molecular weight. A universal plot of reduced viscosity versus reduced blob parameter (N/N_c) shows the attainment of the collapsed state below the theta temperature. The dimensions of PMMA in acetonitrile (M_w = 3.15 × 10⁶ g mol⁻¹) decrease to 63 % at 26 °C of those in the unperturbed state. The results in this work are compared with those previously published. © 2000 Society of Chemical Industry