Standard Polystyrene Samples Research Articles

Metal-Catalyzed, Photo-Assisted Selective Transformation of Tertiary Alkylbenzenes and Polystyrenes into Carbonyl Compounds.

Every year, thousands of tons of polystyrene are produced and discarded, filling landfills and polluting the marine environment. Although several degradation alternatives have been proposed, the need for an effective procedure for the chemical recycling of polystyrene still remains. Here, a vanadium‐catalyzed reaction, assisted by visible light, promoted the direct, selective conversion of tertiary alkylbenzenes into acetophenone and other ketone derivatives. Likewise, standard polystyrene samples as well as polystyrenes from insulation and packaging waste could be chemically recycled into acetophenone in a scalable way regardless of their molecular weight, polydispersity, or form. Preliminary mechanistic investigations revealed the participation of singlet oxygen, superoxide, and hydroxyl radical species in this homogenously catalyzed process. Acetophenone could be used as an additive to accelerate the reaction and to increase the yields in some cases.

Determination of polymeric functional additives in diesel fuel by gel penetration chromatography

Current article is devoted to the development of a method for determining polymer functional additives and their molecular weight characteristics in diesel fuel by gel penetration chromatography. The objects of the study were solutions of “C5A”, “Maxoil D”, “Detersol”, polymethymethacrylate “D” (PMAD), “Keropur D ”, Antigel “Difron 3319” and “Superantigel” individual additives as well as the diesel fuel produced by the “Kuban Oil and Gas Company - Ilskiy Oil Refinery”, LLC. The conditions for chromatographic separation and determination of polymeric functional additives were determined considering the analyzed fuel matrix, the working range of the separated masses and molecular weights of analytes, and the composition of the eluent applicable for wide range of analytes. The chromatographic system was calibrated using the narrowly dispersed analytical standard polystyrene samples with molecular weights of 1000, 2000, 4000, 10000, 30,000, 50,000, and 70,000 Da respectively. The molecular weight characteristics were calculated for each functional additive from the analytical standard samples of polystyrene. The method of GPC determination of polymeric functional additives in diesel fuel, along with the concentration characteristics, also makes it possible to determine the molecular weight parameters of wide range of polymeric functional additives; therefore, it is promising for monitoring the quality of the diesel fuel. The proposed analytical scheme was tested in the analysis of real sample of diesel fuel. The GPC scheme for the determination of the “Keroflux 3699” depressant-dispersant additive in diesel fuel included sample preparation using the solid-phase extraction, calibration of the chromatographic system using the standard polystyrene samples, GPC determination of additive components, and the calculation of molecular weight characteristics. The molecular weight characteristics of the “Keroflux 3699” depressant dispersant additive in diesel fuel have been established - the number average and weight average molecular weights equivalent to polystyrene were 10,300 and 8800 Da respectively, and the polydispersity index of the additive was 1.17.

A hybrid artificial bee colony algorithm and pattern search method for inversion of particle size distribution from spectral extinction data

In this paper, a hybrid artificial bee colony (ABC) algorithm and pattern search (PS) method is proposed and applied for recovery of particle size distribution (PSD) from spectral extinction data. To be more useful and practical, size distribution function is modelled as the general Johnson’s function that can overcome the difficulty of not knowing the exact type beforehand encountered in many real circumstances. The proposed hybrid algorithm is evaluated through simulated examples involving unimodal, bimodal and trimodal PSDs with different widths and mean particle diameters. For comparison, all examples are additionally validated by the single ABC algorithm. In addition, the performance of the proposed algorithm is further tested by actual extinction measurements with real standard polystyrene samples immersed in water. Simulation and experimental results illustrate that the hybrid algorithm can be used as an effective technique to retrieve the PSDs with high reliability and accuracy. Compared with the single ABC algorithm, our proposed algorithm can produce more accurate and robust inversion results while taking almost comparative CPU time over ABC algorithm alone. The superiority of ABC and PS hybridization strategy in terms of reaching a better balance of estimation accuracy and computation effort increases its potentials as an excellent inversion technique for reliable and efficient actual measurement of PSD.

Evaluation of gel permeation chromatography to Fourier transform infrared spectrometric detection using a modified thermospray for analysis of polystyrene samples

A heated gas flow modified thermospray was used to couple gel permeation chromatography (GPC) to Fourier transform infrared spectrometry (FTIR) for the analysis of the standard polystyrene samples. Effluents from the GPC column were evaporated and the solutes were deposited as a series of spots on the surface of a moving stainless steel belt (0.025 mm thickness × 13 mm width). The belt continuously transferred the spots into the diffuse reflectance (DRIFT) accessory of the FTIR spectrometer, enabling identification of the deposited solutes by measurement of the diffuse reflectance IR spectrum. The IR spectra of the separated components showed excellent agreement of the spectral features to those of standard FTIR spectra and no thermal degradation was observed.

Hydrodynamic constants and frictional properties of polystyrene in dilute solution

AbstractExperimental data from hydrodynamic measurements on eleven standard polystyrene samples in a poor and a good solvent (cyclohexane at theta‐temperature 34,5°C, toluene at 25°C) are analyzed in terms of the two‐parameter theory of the hydrodynamic properties of random coils. The discussion is focussed on the expansion factors of hydrodynamic radii αf and αμ, evaluated from the translation friction coefficients and the intrinsic viscosity, and on the hydrodynamic‐interaction parameters P and Φ. The expansion factors αf and αη are shown to assume nearly equal values (at 1,15 ≤αη ≤ 1,5). That implies that the dependences on coil expansion must be very similar for P and Φ1/3. The value of the P parameter in the unperturbed state (i.e. P0) is shown to be close to that recently calculated by Zimm and to be significantly higher than the results of previous theoretical calculations.

Determination of Molecular Weight Distribution of Polymers by Thermal Field-Flow Fractionation

Abstract The Thermal Field-Flow Fractionation method was used to determine average molecular weights for standard polystyrene samples with narrow distribution whose molecular weight ranged from 3600 to 867000. An effective calibration method was proposed and verified, and through the use of this method experimental fractograms could be interpreted in terms of sample molecular weight. Results were obtained by measuring at three temperature differentials (ΔT = 10°, 15°, and 40°C). The average molecular weights calculated from the fractograms were in very good agreement with the data given for these polystyrene standards by the supplier, and with the results calculated from size exclusion chromatography data. Polydispersity indices were calculated from the fractograms without corrections for longitudinal zone broadening. In view of the potential experimental errors associated with any measurement of polydispersity such corrections do not appear necessary for proper evaluation of data collected even in channe...

Aspects of vapor pressure osmometry

AbstractThree aspects of vapor pressure osmometry were examined: drop size, solute volatility, and the constancy of the calibration factor. It was shown that there is a drop size effect which is dependent on the solute concentration. Solutes having vapor pressures as low as 0.3 mm Hg under the operating conditions were found to give unsatisfactory results. The calibration factor was determined using eight compounds in the molecular weight range of 128 to 883 in chloroform, toluene, and methyl ethyl ketone at several temperatures; a small but significant dependence of the calibration factor on molecular weight was demonstrated. The results fitted, with a high degree of accuracy, the relation log M̄n = a + b log (ΔV/C)C = 0, where a and b are constants for a given solvent/temperature combination. However, measurements with standard polystyrene samples, using extrapolations of this relationship to higher molecular weights, revealed considerable discrepancies in results for the one compound under different solvent/temperature combinations.

On‐line viscometry combined with gel permeation chromatography. I. Instrumental calibration and testing with linear polymers

AbstractGel permeation chromatography (GPC) was combined with flow time measurements on the eluent to provide both the distribution of hydrodynamic volumes and the distribution of intrinsic viscosities in linear polymers. Standard polystyrene samples were used to establish a universal hydrodynamic volume calibration as well as the zone spreading and viscometer transfer line tailing parameters. Viscometry data are particularly helpful in establishing the zone spreading parameters and the calibration curve at very high molecular weights. The results were applied to measurements on samples of linear polybutadiene and polyvinyl acetate. Agreement between values of Mw from GPC with those obtained by light scattering confirmed the universal calibration principle.

Computer analysis of light scattering data. II. Critical assessment of molecular parameters

AbstractThree different Fortran computer programs based upon different regression models have been applied to the computer analysis of light scattering data by variously weighted linear and nonlinear least‐squares methods to calculate the molecular parameters, viz., (MW)w,<S2>z. etc. for standard polystyrene samples in good solvents (benzene and toluene). Comparison of the results from the computer programs provides greater insight into the theoretical validity of these parameters, and leads to the conclusion that standardization of the data processing is an essential part of any “Round Robin” experiment to evaluate the molecular weight of standard polymer samples in different laboratories.

Determination of radii of gyration of particles in the 200 to 70 Å interval by the light scattering method. Polystyrene in toluene and poly(methyl methacrylate) in acetonitrile

AbstractFirst results obtained with an apparatus constructed in our laboratory for precision determination of radii of gyration of particles in solution by the light scattering method are described. The utilized principle of measuring the scattering curves yields a much more exact dependence of the scattering intensity on the angle which permits to solve the problem of applying the light scattering technique for determining the radii of gyration rg for particles of 200 to 70Å. For the example of low molecular weight standard polystyrene samples in toluene (molecular weights 51 000 and 200 000) it is shown that the radii of gyration of such molecules can be determined with an error of no worse than ±2% (rg = 77 Å and 167 Å at 22°C resp.). These values are in exact quantitative accordance with the viscosity data of these samples and also fall on the gradual curve of the rg dependence on the molecular weight, obtained in the range of low molecular weights by Kirste et al., and in the range of high molecular weights by Baumann with standard light scattering methods.

High‐resolution gel‐permeation chromatography

AbstractThe resolution attainable in gel‐permeation chromatography (GPC) was investigated by using columns packed with polystyrene gel particles of about 5 μ diameter and mixtures of two monodisperse poly‐α‐methylstyrene samples studied previously. The resolution of GPC was found comparable to that of the sedimentation velocity method and slightly better than that of precipitation chromatography. Standard polystyrene samples obtained from Pressure Chemical Co. also were measured with the same columns. It was found that weight‐average to number‐average molecular weight ratios (M̄w/M̄n) of these samples with molecular weight in the range 97,000–411,000 are smaller than 1.006. For samples with molecular weight of 10,000–51,000 and 498,000–860,000, M̄w/M̄n is larger than 1.006, and the width of molecular weight distributions of these samples differed. In particular, molecular weight distributions of samples with molecular weights 19,800 and 51,000 were shown to be bimodal. It is therefore concluded that GPC is useful for samples of very narrow molecular weight distribution if high‐resolution columns are used.

Molecular weight distributions of standard polystyrene samples by GPC and by sedimentation velocity analysis

AbstractIn precision gel permeation chromatographic (GPC) work, the spreading (zone spreading) characteristics of the instrument must be calibrated. Standard samples of anionic polystyrene have been used for this purpose. The molecular weight distributions of these standard samples, nevertheless, have not been determined carefully. In this work, several standard polystyrene samples obtained from Pressure Chemical Company were examined by GPC and by sedimentation velocity analysis. The results show that (1) the high molecular weight polystyrene samples have skewed molecular weight distributions as has been suspected and that (2) the present data treatment technique for GPC is effective for these very narrow‐distribution samples.

Brillouin spectroscopy of macromolecular solutions

AbstractBrillouin spectroscopy was evaluated as an experimental method for measuring the molecular weights of macromolecules. This evaluation included an examination of instrumental parameters, sample preparation, and spectral analysis. The Brillouin peaks were found to be independant of solute concentration for dilute solutions, in accordance with the assumptions of Miller's approximate theory. This theory was used to calculate molecular weights of five standard polystyrene samples. These values compared well with molecular weights derived from regular photometric light scattering and viscosity measurements.

Calibration of instrumental spreading for GPC

AbstractThe proper use of the method for correcting instrumental spreading in GPC requires a precise calibration of the spreading characteristics of the instrument. Heretofore, such a calibration could be obtained only through the tedious reverse‐flow experiments. A more rapid method of calibrating instrumental spreading is presented in this work. This method uses the leading halves of the chromatograms of several standard polystyrene samples. These chromatograms are normally used in the calibration of molecular weight; additional experimental steps are therefore not required. The calculation of the instrumental spreading characteristics from these chromatograms is also relatively simple. The instrumental spreading characteristics were found to depend on the elution volume but not on the nature of the polymer. Thus, calibration results from using polystyrene standards can be used to treat chromatograms for other polymers. For the present GPC instrument, the spreading was found to reach a maximum at an elution volume near 400,000 in polystyrene molecular weight. The existence of this maximum is in agreement with observations made by other investigators and is and indication that diffusion in the mobile phase is not an important contribution to instrumental spreading. The problem of skewing or tailing is discussed. Indication of skewing was observed for one of the higher molecular weight polystyrene samples but the extent of skewing was not severe at the present flow rate of 2 ml/min.

Report on molecular‐weight measurements of standard polystyrene samples. II. International union of pure and applied chemistry

AbstractAs an extension of our original program, one more polystyrene fraction was investigated in numerous laboratories by means of viscosimetry, osmometry, light scattering, and ultracentrifuge. The various results are compared and critically discussed. Possible explanations and suggestions for improvement are offered in those cases in which considerable discrepancies occur. The viscosity results show satisfactory agreement. The discrepancies among osmotic results are believed to be due largely to unsatisfactory performance of the so‐called semipermeable membranes. Discrepancies among light‐scattering results can mostly be traced back to the unsatisfactory state of the various calibration techniques. The results obtained with the ultracentrifuge agree quite satisfactorily.

Report on molecular‐weight measurements of standard polystyrene samples

AbstractFour polystyrene samples were investigated in numerous laboratories by means of viscosimetry, osmometry, light scattering, and ultracentrifuge. The various results are compared and critically discussed. Possible explanations and suggestions for improvement are offered in those cases where considerable discrepancies occur. The results of viscosimetry and osmometry in general do not give satisfactory agreement whereas the light‐scattering data, particularly in the high‐molecular‐weight range, and the few available ultracentrifugal results agree quite satisfactorily.