Polystyrene In Toluene Research Articles

Heparinization of gas plasma-modified polystyrene surfaces and the interactions of these surfaces with proteins studied with surface plasmon resonance

Polystyrene surfaces obtained by spin-coating a solution of polystyrene in toluene on a gold layer were functionalized with carboxylic acid groups by preadsorption of the sodium salt of undecylenic acid, followed by an argon plasma treatment. A conjugate of albumin and heparin (alb-hep) was covalently immobilized onto the functionalized surface via preactivation of carboxylic acid groups with a water-soluble carbodiimide. The immobilization of alb-hep conjugate and the subsequent interactions of the heparinized surface with antithrombin III (ATIII, a heparin cofactor) and thrombin were monitored with surface plasmon resonance (SPR). The surface concentration of conjugate as determined with SPR deviated quantitatively from the results obtained with radiolabelled conjugate. The difference in surface concentrations of conjugate obtained with the two methods probably originates from the uncertainty of the refractive index of the alb-hep conjugate in the SPR technique. ATIII could be bound to the surface modified with alb-hep conjugate but not to a polystyrene surface modified with albumin. Rabbit anti-human ATIII did bind to the alb-hep surface previously exposed to ATIII, confirming the presence of surface bound ATIII. The alb-hep immobilized surface was able to bind much more thrombin than ATIII, which is probably due to the less specific heparin-thrombin interaction as compared to the heparin-ATIII interaction. This study shows that SPR is a technique that can be used to study, in real time, both the modification of polymer surfaces and the subsequent interactions of the modified surfaces with proteins.

Micellization of Polystyrene-block-poly(ethylene/propylene) in Toluene Solutions of Polystyrene

The thermodynamics of the micellization process of polystyrene-block-poly(ethylene/propylene) in solutions of polystyrene in toluene was studied. Toluene is a good solvent for both copolymer blocks, whereas polystyrene and poly(ethylene/propylene) are not compatible polymers. The influence of the polystyrene concentration on the standard Gibbs energy, ΔG°, enthalpy, ΔH°, and entropy, ΔS°, of micellization was investigated. The thermodynamic magnitudes were calculated from critical micelle temperature and concentration data. The critical micelle temperatures of the different micellar solutions were determined by light scattering measurements. All of the standard magnitudes of micellization become more negative as the polystyrene concentration increases, suggesting an increment of medium selectivity.

Polymer Polydispersity Analysis by Thermal Diffusion Forced Rayleigh Scattering

Polydispersity effects in thermal diffusion forced Rayleigh scattering (TDFRS) on dilute polymer solutions are investigated both theoretically and experimentally and are compared to photon correlation spectroscopy (PCS). Contrary to PCS the statistical weights of the individual molar masses in the TDFRS signal can be changed by variation of the excitation pattern. With short excitation pulses the statistical weights are proportional to the concentration and independent of molar mass. The thermal diffusion coefficient DT, the weight average Soret and diffusion coefficient, 〈ST〉c and 〈D〉c, and 〈D〉c/D, from which the weight average hydrodynamic radius 〈Rh〉c is derived, are directly obtained from the experiment. From a deconvolution of the multiexponential decay function the molar mass distribution can be determined. Experiments are reported for solutions of polystyrene in toluene and ethyl acetate and for polystyrene microgels in toluene. The thermal diffusion coefficient of polystyrene in ethyl acetate is o...

Association of Amino-Terminated Polystyrenes. 2. Dynamic Light Scattering of Associating Linear Chains

Dynamic light scattering was used to study the associating coupling process of amino-terminated polystyrene chains with monofunctional and bifunctional dinitrophenol reagents. The tertiary amino end group and the end group which results from association with monofunctional dinitrophenol were found to have no effect on the solution behavior in good solvents. The interaction with the coupling reagent caused a decrease in the mutual diffusion coefficients Dc with increasing polymer concentration. Translational diffusion coefficients Dz°(c) of the associating polymers at each concentration c with a corresponding molecular weight Mw(c) were determined from Dc and its concentration dependence which is expressed by the kD parameter. The molecular weight dependence of the kD parameter was obtained from experimental values of linear polystyrenes in toluene. On the time scale of these experiments, the associates were found to show a diffusion behavior that corresponds to covalently linked chains. Apparently the lifetime of a complex is longer than the measurement time in typical experiments.

Polymer Solutions and Melts: Viscosity, Diffusion, and Elasticity

In an empirical attempt to extend the rubberlike liquid temporary-junction network theory to polymeric liquids whose viscosity η depends on shear rate γ, it is assumed that, in steady shear flow, the sample-average strand lifetime may depend on γ, and that, for linear polymers of a given molecular weight M, is inversely proportional to the self-diffusion coefficient D in a liquid at rest. It is assumed that the plateau modulus G 0 may be used to determine the strand concentration ν. Literature data for molten polystyrene and for a 15% solution of polystyrene in toluene give approximate superposition of the curves for σ/G 0 vs γ/D, where σ denotes the shear stress ; curves for σ vs γ differ by a factor of about 10 000. Curves for G 0 (N 1 - N 2 )/σ 2 vs σ/G 0 are about 100 times closer together than the corresponding curves for (N 1 - N 2 )/σ 2 vs σ, but do not superpose ; this suggests that 2 / 2 depends on the polymer concentration. N 1 and N 2 denote the first and second normal stress differences.

Adsorption Behavior of Polymers with Ionic End Groups: Mono- and Difunctional Polystyrenes in Toluene

The adsorption behavior of mono- and difunctional telechelic polymers, ω- and α,ω-sulfonato polystyrenes, from dilute toluene solution on the surface of a silicon wafer is investigated by ellipsometry. Polystyrene without ionic end groups does not adsorb, and the attachment of molecules to the silicon dioxide surface proceeds via the functional ionic ends. Already a single ionic group promotes adsorption, and adsorption kinetics at small times is found to be diffusion limited. The approach of an equilibrium adsorbed amount at later times is controlled by the hindered diffusion of chains through the already existing layer. With monofunctional chains a thin stable monolayer at the surface is formed. With difunctional chains there is strong indication for coupling of ionic ends and the formation of additional layers. It is caused by the interaction of dangling ends, when only one end of the chains is adsorbed at the surface. The molecular weight dependence of the grafting density is consistent with scaling predictions, and differences in the adsorbed amount of telechelics with different counterions are explained on the basis of different valencies.

Solvent concentration measurement for spin coating

AbstractPlanarization of spin‐coated polymer films is of great importance for the lithographic process in the microelectronic industry. Solvent retention is an important factor for determining the coating profile during spinning. In this research, solutions of polystyrene in toluene are spin‐coated. The coating concentration during spinning is measured on‐line using a laser interferometry technique. The optical measurement is evaluated by an off‐line gel permeation chromatograph technique. The experiments indicate that a smooth coating surface is required to use the optical method for concentration measurement. The optical technique also provides information regarding the coating surface structure during spinning. © 1995 John Wiley & Sons, Inc.

Formation of block copolymer micelles in solutions of a linear homopolymer in a good solvent

AbstractThe existence of micelles of polystyrene‐block‐poly(ethylene/propene) in solutions of polystyrene in toluene was investigated. Toluene is a good solvent of both copolymer blocks whereas polystyrene and poly(ethylene/propene) are immiscible polymers. The presence of homopolystyrene at high enough concentration can induce the micellization of polystyrene‐block‐poly(ethylene/propene) in solution of a good solvent such as toluene. The thermodynamics of this new micelle system at a given polystyrene concentration was studied. Light scattering measurements were carried out in order to determine the critical micelle temperature (CMT) of different micellar solutions. Standard Gibbs energy, enthalpy and entropy of micellization were estimated from CMT and concentration data. The numerical values found were less negative than those found for micelle systems consisting in a block copolymer dissolved in a single selective solvent.

Measurements of mutual diffusivities in concentrated solutions of membrane‐forming polyamides and cellulose acetate

AbstractMutual diffusivities at 25°C were measured in the range of the polymer weight fraction of 0.15–0.5, using differential interference microscopy. Diffusivities of atactic polystyrene in toluene at 25°C for 0.35‐0.5 polymer weight fractions showed good agreement with the prediction of Vrentas and Duda. Polyamides (nylon‐6, nylon‐66, and a nylon‐6, ‐66, and ‐610 amorphous terpolymer) in formic acid all exhibited very similar diffusivities. Although slightly higher in magnitude, the mutual diffusivities of cellulose acetate (39.8 wt% acetyl) in acetone had a compositional dependence that was parallel to the data for the polyamides. In the range of composition studied, there was an unanticipated very weak dependence of mutual diffusivity on the polymer weight fraction. © 1995 John Wiley & Sons, Inc.

Aggregation Behavior of .omega.- and .alpha.,.omega.-Metal Sulfonato Polystyrene in Toluene

The aggregation behavior of ω- and α,ω-metal sulfonato polystyrene in toluene has been investigated by static and dynamic light scattering. Monofunctional chains reversibly associate into small reverse micelles. Lithium-based ionic aggregates contain an average of 12 ion pairs, which corresponds to a preferential structure for the ionic cores. When the molecular weight of the chains is increased, polymer-solvent interactions progressively distort the ionic aggregates, and above a critical molecular weight, estimated to be 50 000 in toluene, the multiplets collapse into smaller aggregates of an average of 3 ion pairs. Traces of polar solvents do not strongly affect the aggregation number, but do weaken the dipole-dipole interactions. Structure of the ionic cores strongly depends on the nature of the ion pairs, which suggests that this structural feature is a key parameter in the control of the structure-property relationships in ionomers. The aggregation behavior of the difunctional chains is complex, due to the occurrence of a closed association mechanism for the individual multiplets and an open association of reverse micelles into larger aggregates.

Microdynamics of Reverse Micelles of .omega.- and .alpha.,.omega.-Metal Sulfonato Polystyrene in Toluene

Reverse micelles of ω- and α,ω-metal sulfonato polystyrenes in toluene have been investigated by 6 Li, 7 Li, and pulsed field gradient NMR. Micelles are found to be of a narrow size distribution and to consist of roughly spherical ionic cores shielded from the solvent by a polystyrene shell. The nature of the ion pair is found to influence significantly the micellar size. The correlation time characteristic of lithium relaxation is faster than the reorientational correlation time of the aggregates, which means that lithium relaxation essentially takes place within the ionic cores. The effective relaxation mechanism is consistent with a fast exchange of lithium ions between different coordination sites within the aggregates. In concentrated solutions, the equilibrium between aggregated polymer chains and unassociated chains is essentially shifted toward the aggregated species. This tendency is reversed upon dilution. Below a critical micellar concentration of ca. 0.01 g/dL, only «free» chains persist in solution. Temperature has no significant effect on the position of the aggregation equilibrium. The aggregates are dissociated by the addition of a polar cosolvent, such as methanol, which solvates the ion pairs. The MeOH/Li + molar ratio must, however, be higher than 100 to perturb significantly the ion pair aggregation. Up to a MeOH/Li + ratio of 10 000, part of the chains remain aggregated, and the lithium spin-lattice relaxation is dominated by the aggregates. Above a MeOH/Li + ratio of 10 000, the aggregates are almost completely disrupted. Self-diffusion coefficients of the difunctional chains are not dramatically smaller compared to the monofunctional counterparts, even when solutions of difunctional compounds form a gel. This behavior might be explained by the percolation model applied to the aggregation process, with the pulsed field NMR experiment probing only the self-diffusion of the clusters in the sol phase of the gel

A New Holographic Grating Technique for the Measurement of Diffusion and Thermal Diffusion of Polymers in Solution

Abstract Despite being a fundamental transport property, thermal diffusion in polymer solutions is still poorly understood, and reliable experimental data are scarce. After a brief review of previous experimental techniques and results, the application of forced Rayleigh scattering to the study of diffusion and thermal diffusion in polymer solutions is discussed. Due to the μm diffusion lengths, equilibration times are reduced to typically 100 ms, and signal averaging allows noise reduction. From a single experiment three different diffusion coefficients are obtained without the need for chain labeling: the thermal diffusivity, the translational diffusion coefficient, and the thermal diffusion coefficient. An improved setup, allowing convection-free heterodyne detection, is discussed. Results for polystyrene in toluene and ethyl acetate are reported, and the measured translational diffusion coefficients are compared with data obtained from photon correlation spectroscopy.

Holographic grating study of mass and thermal diffusion of polystyrene/toluene solutions

The transient grating technique of thermal diffusion forced Rayleigh scattering (TDFRS) has been employed to study translational and thermal diffusion of polystyrene in toluene. Different molar masses and concentrations below or slightly above (lie overlap concentrationc* have been investigated. The translational diffusion coefficients agree well with results obtained from photon correlation spectroscopy. Small remaining diferences can be attributed to sample polydispersity. The molar mass independence of the thermal diffusion coefficient is confirmed, and thermal diffusion and Soret coefficients are compared with data obtained from thermal field flow fractionation and diffusion cell experiments.

SAXS study of .omega.- and .alpha.,.omega.-metal sulfonato polystyrenes in toluene solution

Solutions of ω- and α,ω-barium sulfonato polystyrenes in toluene have been investigated by SAXS as a function of concentration. A chacteristic ionic peak is displayed over the whole investigated concentration range. The experimental data are in favor of the ion pair aggregation into small stable multiplets homogeneously distributed throughout the material. The characteristic ditance is related to the average intermultiplet distance d. A general law has been derived for the dependence of d on molecular weight, functionality, and concentration of the polymer. The size of the multiplets does not depend significantly on polymer concentration and molecular weight

New use of size exclusion chromatography in kinetics of mechanical degradation of polymers in solution

AbstractA new method to investigate the mechanical degradation of polymers in solution is described that uses size exclusion chromatograms of the initial polymer and of the degraded sample. The incipient parts of these chromatograms are analyzed to obtain kinetic data about degradation at the level of infinitesimal fractions. The procedure is based on the fact that mechanical degradation of the polymers is a first‐order reaction and macromolecules are cleaved mostly in their central region. The rate constant and the variation in the rate constant with molecular weight are determined in a single experiment, avoiding additional fractionation steps. Moreover, the slope of the size exclusion chromatographic calibration curve is derived, opening new ways to determine polydispersities or even to make rapid calibration for unknown polymers. To verify the method, the rate constant and the molecular weight dependence of the rate constant were determined for the sonic degradation of polystyrene in toluene. The rate constant is found to vary with the square of the molecular weight, and its value is in good agreement with results reported using much more laborious methods. © 1993 John Wiley & Sons, Inc.

SAXS study of solutions of telechelic polymers in nonpolar solvents

Influence of both polymer molecular weight and concentration, and solution preparation on the SAXS profile of ω- and α,ω-metal sulfonato and carboxylato polystyrenes in toluene has been investigated. For sulfonated polymers, position of the ionic peak obeys a general law which allows the phase morphology to be predicted. Ionic end-groups are phase-separated into small multiplets which act as physical crosslinks. Size of the multiplets does not depend on polymer molecular weight and concentration. Multiplets are homogeneously distributed throughout the polymer matrix, and organized in a liquid-like manner. Difunctional samples obey the same general behavior but only above a critical concentration which depends on the chain molecular weight. Although the position of the ionic peak is independent of the sample preparation, shape and intensity are clearly related to the large-scale heterogeneity of solutions

A fast membrane osmometer based on a porous glass membrane: first results

AbstractThe prototype of a fast and versatile membrane osmometer based on a capillary shaped porous glass membrane has been developed and successfully tested with solutions of polystyrene in toluene. The coaxial design of the cell is ideally suited both for batch and continuous flow operation. Time constants on the order of several seconds are observed with membranes of 10 nm and 20 nm nominal pore size. Important design criteria are discussed and first results for the cut‐off molar mass are reported.

Determination of absolute polydispersity and molecular weight distribution of high molecular weight polymers from dynamic light scattering

Intensity correlation function obtained from dynamic light scattering (DLS) experiments has been theoretically analyzed within the framework of the Schulz molecular weight distribution. The correlation function has been expanded about the mean molecular weight instead of the average linewidth as is normally done in cumulant analysis. This allows the explicit determination of polydispersity (Z). In addition to this, it has been shown that the molecular weight exponent of diffusion coefficient ν, occurring in the Mark–Houwink equation DM−ν and the average molecular weight M̄, can in principle be determined from DLS data. Finally, from the knowledge of Z and M̄ it is possible to construct the Schulz molecular weight distribution function. Experiments performed on three model systems, polystyrene in cyclohexane at 35 °C (θ system), polystyrene in toluene at 20 °C (good system), and latex beads in a deionized aqueous medium (hard spheres system), provide excellent matching between the experimental data and results obtained using our proposed method of analysis of DLS studies.

Coupling of density to concentration fluctuations in concentrated solutions of polystyrene in toluene

In concentrated polystyrene (PS) solutions in toluene, close to the glass transition temperature (Tg), both concentration (q2 dependent) and density fluctuations (q independent) are simultaneously observable in the time window of the polarized (VV) dynamic light scattering experiment. At Φp=0.89, both modes (Γc and Γd) are well separated on the time scale. Close to Tg, the diffusion relaxation is ‘‘frozen-in,’’ a phenomenon anticipated from free-volume theory but not previously observed in polymer solutions. At Φp=0.78, a q2-dependent mode is found above about 40 °C, whereas it is q independent at 17 °C. At intermediate temperatures, the two modes are coupled when Γc≊Γd. The coupling of density to concentration fluctuations is analyzed here in terms of a recent theory of Jäckle and Frisch [J. Polym. Sci. Polym. Phys. Ed. 23, 675 (1985)]. The latter is found to provide a good semiquantitative description of the complex dynamic behavior in this system close to the glass transition.

Measurement of Viscoelastic Properties of Polymer Solutions by Torsional Crystals

The network analyzer was used for measurement of the viscoelastic properties of dilute polymer solutions. It is a sensitive instrument to measure resonance resistance and resonant frequency of crystals by the admittance circle diagrams shown on the digital oscilloscope. Measurements can be conducted more correctly and rapidly compared to the previous measuring system. Its validity was verified by measuring the complex shear modulus of dilute polymer solutions and comparing the results with the Rouse theory. The complex shear modulus was determined by measuring changes in the properties of a torsionally vibrating crystal. Frequency dependence of complex shear modulus is investigated in the frequency range from 3 to 252 kHz and temperature range from −60 to 23°C. The samples are several kinds of dilute solutions of polystyrene in toluene. The use of polystyrene is limited in narrow molecular weight fractions ranging in number-average molecular weight from 2.1×103 to 1.60×105. The results agreed with the theory by Rouse.