Interactions of short-chain surfactants with a nonionic polymer

Aqueous solutions containing poly(vinylpyrrolidone) (PVP) and sodium caprylate (SCAP) or tetraethylammonium perfluorooctanesulfonate have been investigated as a function of the surfactant content, the added polymer, temperature and ionic strength. According to experimental evidence, significant interactions have been observed in both systems, with the occurrence of both critical association and micelle formation thresholds. Volumetric, viscometric, ionic conductivity and surface tension methods have been used to quantify the interactions between surfactants and the polymer in ternary systems containing PVP and SCAP or the polymer and the fluorinated surfactant. In both cases, the width of the interaction region is proportional to the PVP content in the mixture. Temperature and ionic strength have a relevant effect on the width of the interaction region, which decreases on increasing the temperature. Binding onto PVP and micelle formation were analyzed in terms of a mass-action model. In this way, the observed behavior was rationalized and information on the thermodynamics of such mixtures was given. Received: 28 February 2001 Accepted: 5 June 2001     

Reduction of polymer surface tension by crystallized polymer nanoparticles

Self-consistent field theory is applied to investigate the effects of crystallized polymer nanoparticles on polymer surface tension. It is predicted that the nanoparticles locate preferentially at the polymer surface and significantly reduce the surface tension, in agreement with experiment. In addition to the reduction of surface tension, the width of the polymer surface is found to narrow. The reduced width and surface tension are due to the smaller spatial extent of the nanoparticles compared to the polymer. This allows the interface to become less diffuse and so reduces the energies of interaction at the surface, which lowers the surface tension. The solubility of the surrounding solvent phase into the polymer melt is mostly unchanged, a very slight decrease being detectable. The solubility is constant because away from the interface, the system is homogeneous and the replacement of polymer with nanoparticles has little effect.     

Interaction of cationic surfactant and anionic polyelectrolytes in mixed aqueous solutions

Surfactant–polymer interactions in aqueous solutions have been studied using dynamic surface tension, polyelectrolyte titration, nephelometric turbidity, and dynamic light scattering. For the preparation of complexes, a technical cationic surfactant was used in combination with two poly(maleic acid-co-polymers) of similar structure but different hydrophobicity. The dynamic surface tensions of mixed solutions as functions of surfactant concentration at constant polyelectrolyte content, as well as changes in the surface activity due to the influence of polyanion at constant surfactant concentration are discussed in terms of a complex or aggregate formation in the bulk phase. The interaction of the surfactant with poly(maleic acid-alt-propene) (P-MS-P) and poly(maleic acid-alt--methylstyrene) (P-MS-MeSty), respectively, is strong in both cases and results in the formation of nanoparticles with properties depending on the composition of the corresponding mixture.     

Phase equilibrium of poly(n-butyl acrylate) and E7

The experimental equilibrium phase diagram of mixtures of linear poly(n-butyl acrylate) of molecular mass M_w = 112000 g mol^-1 and the low molecular mass LC mixture E7 has been established using polarized optical microscopy and light scattering techniques. The diagram is found to be reminiscent of an upper critical solution temperature system. Two independent series of samples with the same composition were studied, yielding consistent results. A region of nematic and isotropic coexisting phases and a region of a single isotropic phase were identified in the composition-temperature phase diagram. The results were analysed within a theoretical model combining the Flory-Huggins lattice theory for isotropic mixing and the Maier-Saupe theory for nematic ordering. Interestingly, no region of isotropic coexisting phases was observed in our experiments. This is probably due to the fact that the nematic interaction overwhelms the isotropic interaction in the region where (I + I) coexisting phases could appear. A preferential solubility of certain constituents of the LC mixture in the polymer could possibly be a reason for this behaviour.     

Poly(ethylene oxide) thin films produced by electrospray deposition: morphology control and additive effects of alcohols on nanostructure

Nanostructured thin films were prepared by electrospray deposition (ESD) from poly(ethylene oxide) (PEO) aqueous solution. The surface morphologies of the deposited films were observed using scanning electron microscopy (SEM). The SEM images revealed the correlations between the morphologies and the ESD conditions. By changing the applied voltage and solution properties such as viscosity, surface tension, conductivity, and molecular weight, PEO thin films with diverse nanostructures--from nanospheres to nanofibers--were fabricated. It was also revealed that the addition of alcohols to polymer solution, which enables simultaneously changing the viscosity, the surface tension, and the conductivity, enhanced the formation of the fibrous structure. These results indicate that the ESD method is potentially a useful option for producing nanoengineered polymer surface.     

Interaction between poly(ethylene oxide) and sodium dodecyl sulfonate as studied by surface tension, conductivity, viscosity, electron spin resonance and nuclear magnetic resonance

The aggregation of sodium dodecyl sulfonate (AS) in aqueous solution containing various amounts of poly(ethylene oxide) (PEO) has been investigated by different experimental techniques. The experimental techniques include surface tension, conductivity, viscosity, electron spin resonance (ESR) and nuclear magnetic resonance (NMR). The critical aggregate concentration of AS on polymer strands as well as the concentration where the polymer becomes saturated with surfactant has been determined. Both ESR and NMR results indicate that the AS–PEO complex forms a more “open” structure and that PEO may penetrate into the interior of the micelles. Received: 22 October 1998 Accepted in revised form: 1 April 1999     

Competitive adsorption of neutral comb polymers and sodium dodecyl sulfate at the air/water interface

The interfacial behavior of aqueous solutions of four different neutral polymers in the presence of sodium dodecyl sulfate (SDS) has been investigated by surface tension measurements and ellipsometry. The polymers comprised linear poly(ethylene oxide) with low and high molecular masses (10(3) and 10(6) Dalton (Da), respectively), and two high molecular mass methacrylate-based comb polymers containing poly(ethylene oxide) side chains. The adsorption isotherms of SDS, determined by Gibbs analysis of surface tension data, are nearly the same in the presence of the high molecular mass linear polymer and the comb polymers. Analysis of the ellipsometric data reveals that while a single surface layer model is appropriate for films of polymer alone, a more sophisticated interfacial layer model is necessary for films of SDS alone. For the polymer/surfactant mixtures, a novel semiempirical approach is proposed to determine the surface excess of polymer, and hence quantify the interfacial composition, through analysis of data from the two techniques. The replacement of the polymer due to surfactant adsorption is much less pronounced for the high molecular mass linear polymer and for the comb polymers than for the low molecular mass linear polymer. This finding is rationalized by the significantly higher adsorption driving force of the larger polymer molecules as well as by their more amphiphilic structure in the case of the comb polymers.     

Binding studies of sodium dodecyl benzene sulphonate with poly(N-vinyl-2-pyrrolidone)

The binding of sodium dodecyl benzene sulphonate (SDBS) with poly(N-vinyl-2-pyrrolidone) (PVP) has been investigated at 303.15 and 313.15 K using equilibrium dialysis, surface tension, viscosity, ultrasound velocity and ultrasound absorption techniques. From each of these studies four distinct regions of SDBS-PVP interactions were observed. Interaction of SDBS with PVP was found to involve the binding of surfactant dimers with the polymer molecule followed by usual micellization. The binding data has been analyzed in terms of various models of polymer-surfactant interaction.     

Effect of Polymer Concentration on the Surface Properties of Polyacid–Poly(N-vinylpyrrolidone) Complexes

The effect of polymer concentration on the surface properties of equimolar interpolymer complexes of polyacrylic and polymethacrylic acids with poly(N-vinylpyrrolidone) is studied at 298 K by measuring surface tension, conductivity, and viscosity, as well as by the potentiometric titration of mixed polymer solutions. The surface activity and the standard free energy of the adsorption of the individual polyelectrolytes and interpolymer complexes are calculated from the surface tension isotherms. Complexation is shown to increase the surface activity and decrease the standard free energy of the adsorption of macromolecules.     

Phase equilibrium of poly(n-butyl acrylate) and E7

The experimental equilibrium phase diagram of mixtures of linear poly(n-butyl acrylate) of molecular mass M_w = 112000 g mol^-1 and the low molecular mass LC mixture E7 has been established using polarized optical microscopy and light scattering techniques. The diagram is found to be reminiscent of an upper critical solution temperature system. Two independent series of samples with the same composition were studied, yielding consistent results. A region of nematic and isotropic coexisting phases and a region of a single isotropic phase were identified in the composition-temperature phase diagram. The results were analysed within a theoretical model combining the Flory-Huggins lattice theory for isotropic mixing and the Maier-Saupe theory for nematic ordering. Interestingly, no region of isotropic coexisting phases was observed in our experiments. This is probably due to the fact that the nematic interaction overwhelms the isotropic interaction in the region where (I + I) coexisting phases could appear. A preferential solubility of certain constituents of the LC mixture in the polymer could possibly be a reason for this behaviour.     

Preparation of electrospun chitosan/poly(vinyl alcohol) membranes

Electrospinning of chitosan from its solutions in 2% aqueous acetic acid was studied by adding poly(vinyl alcohol) (PVA) as a “guest” polymer. Properties of the chitosan/PVA solutions including viscosity, conductivity, and surface tension were measured, and effects of the polymer concentration, chitosan/PVA mass ratio and processing parameters (applied voltage, flow rate, capillary-to-collector distance) on the electrospinnability of chitosan/PVA were investigated. Analyses of scanning electron micrographs and transmission electron micrographs suggested that the chitosan/PVA ultrafine fibers were often obtained along with beads, and chitosan was located in the elctrospun fibers as well as in the beads. Uniform chitosan/PVA fibers with an average diameter of 99 ± 21 nm could be prepared from a 7% chitosan/PVA solution in 40:60 mass ratio. Results of Fourier transform infrared spectroscopy and X-ray diffraction demonstrated that there were possible hydrogen bonds between chitosan and PVA molecules, which could weaken the strong interaction in chitosan itself and facilitate chitosan/PVA electrospinnability. The electrospun chitosan/PVA membranes showed higher water uptake and would have potential applications in wound dressings.     

疏水缔合聚丙烯酰胺与阳离子双子表面活性剂的相互作用

通过表面张力法和电导率法分别考察了阳离子双子表面活性剂(12-2-12)与非离子疏水缔合聚丙烯酰胺(HMPAM)和普通聚丙烯酰胺(PAM),传统表面活性剂十二烷基三甲基溴化铵(DTAB)与HMPAM和PAM之间的相互作用。结果表明,12-2-12 HMPAM复合体系与12-2-12水溶液体系相比,在w(聚合物含量)CMC时,复合体系的电导率(κ)具有下降的趋势,且κ随着w的增大下降的趋势越明显,说明12-2-12与HMPAM之间存在相互作用。     

Study of some properties of poly(N-vinyl imidazole) partially quaternized with n-butyl bromide aqueous solutions

This paper presents a study of the properties of aqueous solutions of poly(N-vinyl imidazole) quaternized with n-butyl bromide (PVIQ3). The influence of the temperature and polymer concentration on refractive index, electrical conductivity and surface tension was studied. The critical micelar concentration of PVIQ3 in aqueous solution was determined and correlated with the polymer solubility in water.All the PVIQ3 aqueous solutions properties were compared with those of poly(N-vinyl imidazole) (PNVI) and the influence of the quaternization process on the polymer properties was evidenced.     

NMR investigations of self-aggregation characteristics of SDS in a model assembled tri-block copolymer solution

The present work was undertaken with a view to understand the influence of a model non-ionic tri-block copolymer PEO-PPO-PEO (poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide)) with molecular weight 5800 i.e., P123 [(EO)(20)-(PO)(70)-(EO)(20)] on the self-aggregation characteristics of the anionic surfactant sodium dodecylsulfate (SDS) in aqueous solution (D(2)O) using NMR chemical shift, self-diffusion and nuclear spin-relaxation as suitable experimental probes. In addition, polymer diffusion has been monitored as a function of SDS concentration. The concentration-dependent chemical shift, diffusion data and relaxation data indicated the significant interaction of polymeric micelles with SDS monomers and micelles at lower and intermediate concentrations of SDS, whereas the weak interaction of the polymer with SDS micelles at higher concentrations of SDS. It has been observed that SDS starts aggregating on the polymer at a lower concentration i.e., critical aggregation concentration (cac=1.94 mM) compared to polymer-free situation, and the onset of secondary micelle concentration (C(2)=27.16 mM) points out the saturation of the 0.2 wt% polymer or free SDS monomers/micelles at higher concentrations of SDS. It has also been observed that the parameter cac is almost independent in the polymer concentrations of study. The TMS (tetramethylsilane) has been used as a solubilizate to measure the bound diffusion coefficient of SDS-polymer mixed system. The self-diffusion data were analyzed using two-site exchange model and the obtained information on aggregation dynamics was commensurate with that inferred from chemical shift and relaxation data. The information on slow motions of polymer-SDS system was also extracted using spin-spin and spin-lattice relaxation rate measurements. The relaxation data points out the disintegration of polymer network at higher concentrations of SDS. The present NMR investigations have been well corroborated by surface tension and conductivity measurements.     

An improvement in the flory corresponding-states theory of polymer solutions

The original Flory corresponding-states theory of polymer solutions requires an entropic correction parameter Q₁₂, the sign and value of which seem to be arbitrary, and the physical meaning of which is obscure. Moreover, calculated excess volumes of mixing for many polymer solutions are often in significant disagreement with experimental data. In order to eliminate these problems, we have modified the kinetic part of the partition function, introduced an effective mass for the mixture segment, and adopted the nonlinearity of the number of degrees of freedom with respect to the composition for the mixture segment. In addition, the effect of nonrandom configurations of the segments in the mixture has been included. In the improved equations, derived in this work, the Flory interaction parameter χ can be considered to comprise three parts: (a) a kinetic part due to the contribution of the average number of degrees of freedom and the effective mass of the mixture; (b) a free volume part; and (c) an interaction part including the contributions due to the contact interaction and the nonrandom configuration of the segments in the mixture, caused by the interaction. The improved theory is in good agreement with literature data on polystyrene solutions and poly (dimethyl siloxane) solutions.     

Phase behavior of charge stablized colloid dispersion with added water soluble polymers

Demixing and colloidal crystallization in the mixture of charge stabilized colloidal poly(methyl methacrylate) particles and soluble poly(ethylene oxide) were investigated by means of synchrotron small-angle X-ray scattering (SAXS) technique. Phase diagram of the mixture was obtained based on visual inspection and SAXS results. The phase behavior is determined as a function of the concentration of the polymer as well as the volume fraction of the colloidal particles. The system shows a one phase region when the concentration of the polymer is low, whereas a two-phase region is present when the concentration of the polymer is larger than a critical concentration at certain volume fraction of the colloids. Interestingly, a face centered cubic colloidal crystalline structure was formed under certain conditions, which has been rarely observed in experiments of colloid-polymer mixtures with competing interactions.     

Melting point depression in poly (ethylene oxide)-poly (methyl methacrylate) blends

Thermo-optical analysis of solution cast mixtures of poly (ethylene oxide) (POE) and poly (methyl methacrylate) (PMMA) has been carried out. Melting point depression was observed for increasing proportion of PMMA in the mixture. An analytical expression appropriate to the crystallineamorphous polymer pair has been applied to explain the melting point depression in terms of thermodynamic quantities. From this expression, the interaction parameter for the mixture has been evaluated. The influence of $\text{M}$_w of POE on the binary interaction parameter has been studied.     

Studies on Substituted Derivatives of Polyaniline: Effect of Polymerization Conditions on Electrical Conductivity

Abstract

Polyaniline, poly(o-methoxyaniline)and poly(N-phenylaniline) were synthesized chemically under different polymerization conditions by peroxodisulphate oxidation in HCl and in a mixture of HCl and CH₃CN. The polymer prepared at 0°C, monomer-oxidant ratio 1:1.15 and a strong acidic medium, has the least bandgap and maximum electrical conductivity. The electrical conductivity depends on degree of oxidation and protonation. The bulky substituents increase the torsion angle and hence disorder causes the decrease in the electrical conductivity of polymer.     

A note on the selectivity of γ-radiation polymerised molecularly imprinted poly (HEMA)

γ-radiation was used to synthesise molecularly imprinted poly (2-hydroxy ethyl methacrylate) containing memory sites for testosterone. The high degree of selectivity of the polymer towards testosterone has been demonstrated by studying the interaction of the polymer with a mixture of testosterone and cholesterol, a molecule with a similar ring structure and shape as testosterone.     

Core-corona polymer composite particles by self-assembled heterocoagulation based on a hydrogen-bonding interaction

Poly(ethylene glycol dimethacrylate-co-acrylic acid) (poly(EGDMA-co-AA)) small microspheres were effectively self-assembled on poly(ethylene glycol dimethacrylate-co-4-vinylpyridine) (poly(EGDMA-co-VPy)) surfaces to form a core-corona structure with a raspberry-like polymer composite by a hydrogen interaction mechanism through an affinity complex between the carboxylic acid group and pyridine group. The control of coverage of the poly(EGDMA-co-AA) corona on the surface of poly(EGDMA-co-VPy) was studied in detail via adjustment of the nature of the mass ratio between the core and corona. The effects of the pH and solvent used on the morphology of the self-assembled core-corona polymer composites were investigated. The nature of the interaction between the core and corona polymer particles was identified as hydrogen bonding with FT-IR spectroscopy.