Polystyrene particle size distributions

This paper will be limited to a discussion of our packed column studies in which we have addressed attention to questions regarding, (a) the role of ionic strength and surfactant effects on both HDC and porous packed column behavior, (b) the effects of pore size and pore size distribution on resolution, and (c) the effects of the light scattering characteristics of polystyrene on signal resolution and particle size distribution determination. 

In order to calculate particle size distributions in the adsorption regime and also to determine the relative effects of wavelength on the extinction cross section and imaginary refractive index of the particles, a series of turbidity meas irements were made on the polystyrene standards using a variable wavelength UV detector. More detailed discussions are presented elsewhere (23) > shown here is a brief summary of some of the major results and conclusions. 

Figure 14 Particle size distribution of a ten-component mixture of narrow polystyrene dispersions. Left intensity measured as function of t with a turbidity detector. Right integral and differential particle size distribution. Reproduced from Machtle [84] by permission of The Royal Society of Chemistry. 

The first attempt to radiolabel drug particles (instead of polymers like polystyrene or Teflon particles) for pharmaceutical aerosols was carried out on fenoterol and salbutamol by Kohler et al. [12] Scheme 3). However, it was later found that their method would change the particle size distribution of the labelled aerosol, resulting in a coarser aerosol than the imlabelled product. After subsequent improvement by Summers et al. [18] Scheme 4), this method has become widely used for radiolabelling MDIs. It is preferred over other methods as it does not involve extraction with tetraphenylarsonium chloride and chloroform. 

Although a majority of these composite thermistors are based upon carbon black as the conductive filler, it is difficult to control in terms of particle size, distribution, and morphology. One alternative is to use transition metal oxides such as TiO, VO2, and V2O3 as the filler. An advantage of using a ceramic material is that it is possible to easily control critical parameters such as particle size and shape. Typical polymer matrix materials include poly(methyl methacrylate) PMMA, epoxy, silicone elastomer, polyurethane, polycarbonate, and polystyrene. 

Use these data to determine either rj or the yield value for these dispersions depending on whether or not the system is Newtonian. Are these results consistent with the fact that the axial ratio was nearer unity and the particle size distribution narrower for the polystyrene than the silica Explain. 

A wide variety of polymers have been analyzed by gel-permeation, or size-exclusion, chromatography (sec) to determine molecular weight distribution of the polymer and additives (86—92). Some work has been completed on expanding this technique to determine branching in certain polymers (93). Combinations of sec with pyrolysis—gc systems have been used to show that the relative composition of polystyrene or acrylonitrile—polystyrene copolymer is independent of molecule size (94). Improvements in gpc include smaller cross-linked polystyrene beads having narrow particle size distributions, which allow higher column efficiency and new families of porous hydrophilic gels to be used for aqueous gpc (95). 

The analysis of the autocorrelation function data by the Coulter Model N4 is carried out by the Size Distribution Program (SDP), which gives the particle size distribution in the form of various output displays (see Section 10.4). The SDP analysis utilizes the computer program CONTIN developed by S.W. Provencher (ref. 467-470 see also Section 10.2). (This program has been tested on computer-generated data, monomodal polystyrene samples, and a vesicle system (ref. 466-468,471).) Since the SDP does not fit to any specific distribution type, it offers the ability to detect multimodal and very broad distributions. 

Figure 5. Particle size distribution of a mixture of polystyrene latexes with nominal diameters of 0.804 and 1.09 pm obtained by disk centrifugation at 4000 rpm in a 1/4% sucrose gradient.

Calibration Samples. Monodisperse polystyrene latices are available with known, narrow particle size distributions. Coefficients of variance about the mean diameter are typically less than 6% of diameter measured using electron microscopy (25). HDC typically cannot resolve differences in diameter of only 6%. Therefore, these polystyrenes are sufficiently narrow to be used as HDC calibration reference samples. However, doing so may result in incorporation of a systematic error in the particle size versus elution volume calibration, arising from known electron microscopy errors of as much as 5% for particles below 1 um (26). Therefore, accuracy can only be stated as relative to electron microscopy results for the calibration samples. FlowSizer performance specifications have been reported elsewhere (27) with diameter and mass percent results within 5% of those determined by electron microscopy for a series of these monodisperse polystyrene latices. 

This investigation will show that reproducible particle size distributions are possible using hydrodynamic chromatography, even though a portion of the injected sample may be trapped within the column matrix. In addition, it will illustrate the effects of using fixed factors for different types of latex whose scattering and absorbing characteristics different from those of polystyrene. 

Figure 8.6. Separation of polystyrene latex beads of four different diameters (indicated in the figure) by a disc centrifuge operated at 3586 rpm. (From ref. 44. Reprinted with permission from R. M. Holsworth, T. Provder, and J. J. Stansbrey, in T. Provder, Ed., Particle Size Distribution, ACS Symposium Series No. 332, American Chemical Society, Washington, DC, 1987, Chapter 13. Copyright 1987 American Chemical Society.)...

It was also found that the polystyrene-b-PDMS block copolymers were not only effective at stabilizing styrene polymerizations in C02, but also in stabilizing MMA polymerizations. When using a polystyrene-b-PDMS block copolymer as the stabilizer the resulting PMMA was recovered in 94.1% yield with a Mn = 1.8 x 10 g/mol and a PDI = 2.8. The particles obtained are much smaller and more polydisperse than the particles obtained when using poly(FOA) homopolymer as the stabilizer (particle size = 1.55 - 2.86 pm vs. 0.23 pm and particle size distribution = 1.05 vs. 1.46). 

Fig. 34.A Correction for zone broadening of a model fractogram. a represents the original curve and the corrected one whereas b is the uncorrected fractogram. Reproduced from [460] with kind permission of the American Chemical Society. B Comparison of differential particle size distributions of narrowly distributed polystyrene latex standards derived by MALLS and Fl-FFF without correction for zone broadening. Reproduced from [461] with kind permission of Academic Press...

Polystyrene can be easily prepared by emulsion or suspension techniques. Harkins (1 ), Smith and Ewart(2) and Garden ( ) have described the mechanisms of emulsTon polymerization in batch reactors, and the results have been extended to a series of continuous stirred tank reactors (CSTR)( o Much information on continuous emulsion reactors Ts documented in the patent literature, with such innovations as use of a seed latex (5), use of pulsatile flow to reduce plugging of the tube ( ), and turbulent flow to reduce plugging (7 ). Feldon (8) discusses the tubular polymerization of SBR rubber wTth laminar flow (at Reynolds numbers of 660). There have been recent studies on continuous stirred tank reactors utilizing Smith-Ewart kinetics in a single CSTR ( ) as well as predictions of particle size distribution (10). Continuous tubular reactors have been examined for non-polymeric reactions (1 1 ) and polymeric reactions (12.1 31 The objective of this study was to develop a model for the continuous emulsion polymerization of styrene in a tubular reactor, and to verify the model with experimental data. 

Polystyrene Latex (PSL) Bead Solution Filtration Experiments were conducted to obtain filter retention, flow rate, and Ap data for a DI water based PSL bead mix solution prepared using particles ranging from bead diameters of 0.772 to 20 pm. It is a common practice to use PSL bead challenge solutions (created by mixing different size PSL bead standards in specific volumetric ratio to simulate slurry-like particle size distribution for the bead mix solution) to obtain relative quantitative retention data for various filters. These solutions are expected to retain stable PSD and provide more consistent information compared to real CMP slurries, which may change particle characteristics over time. 

Another example of an alternative rubber system is the asymmetric radial polymer (ARPS). ARPS has four equal arms of polybutadiene, with a polystyrene segment attached to one of the polybutadiene arms. A HIPS product made with ARPS blends polybutadiene produces two separate rubber phases with different morphologies and particle size distributions. The ARPS produces a capsular morphology and the polybutadiene produces a normal cellular morphology surrounded by a lamellar structure that provides a reactor product with both high gloss and high impact. 

A method for on-line monitoring of particle size distribution and volume fraction in real time using frequency domain photon migration measurements (FDPM) has been described. In FDPM the time dependence of the propagation of multiply scattered light provides measurement of particle size distribution and volume fraction. The technique has been applied to a polystyrene latex and a titanium dioxide sluny at volume concentrations in the range 0.3 to 1% [341]. 

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