Polystyrene distributions from

Figure 17 Molar mass distributions of polystyrene in ethyl acetate obtained by dynamic light scattering (photon correlation spectroscopy, PCS) and TDFRS with short and long exposure time tp. The dashed curves represent the distribution as determined by SEC. Reproduced with permission from Rossmanith and Kohler [107]. Copyright 1996 American Chemical Society.

The same authors then discuss the determination of the entire molar mass distribution from sedimentation velocity runs via scaling laws for the polymer polystyrene in cyclohexane, where the scaling law is also known [78] ... 

Novolac molecular weights were measured in THF at 35°C by high pressure size exclusion chromatography using a Waters Model 510 pump (flow rate=1.0 ml/min), 401 differential viscometer detector and a set of Dupont PSM 60 silanized columns. A universal calibration curve was obtained with a kit of 10 narrow molecular weight distribution, linear polystyrene standards from Toya Soda Company. Data acquisition and analysis were performed on an AT T 6312 computer using ASYST Unical 3.02 software supplied with the Viscotek instrument. 

Table I. Yields and Molecular Weights (Relative to Polystyrene) for Both Fractions of the Bimodal Distribution from Gel Permeation Chromatography in THF of Organosilane Polymers.

FJg. 2. Cumulative and differential molecular weight distribution for polystyrene from mutual radiation... 

In the Introduction it has been mentioned that the immediate reason for the development of phase distribution chromatography was the search for a fast and exact method to determine very narrow molecular weight distributions of polystyrenes obtained from anionic polymerization. The long way to reach this goal became evident only in the course of the investigations shown in the previous sections and representing a basis for the computation of such MWDs. In fact, not only exact measurements are necessary, but also mathematical expressions for the measured calibration curves and for the spreading of the injected concentration profile in the column must be stated, which cannot be done empirically. 

FIG. 16.16 Shear rate dependence of viscosity as a function of concentration. Data were obtained on a single narrow molecular weight distribution of polystyrene (Mw = 411 kg/mol) in n-butyl benzene at 30 °C. From Graessley, Hazleton and Lindeman (1967). Courtesy Society of Rheology. 

Figure 9.8 Double logarithmic plot of the retardation spectrum versus the retardation time for a polystyrene fraction of molecular weight 3400 with a narrow molecular weight distribution. (From Ref. 8.)...

Figure 2. Frequency-conductivity phase diagram for 1 pm polystyrene particles left). Steady state distribution of polystyrene particles suspended in distilled water (2.6 x 10 S/m) after applying 10 V peak-to-peak AC electric field for 5 min at specified frequencies right). For image , concentrated particles on the center of electrode surface driven by AC-EO mechanism are also shown. Due to the nature of negative DEP that repels particles away from the electrode surface, the particles for case were sedimented for 3 h to capture their lateral motion at the image focal plane.

Styrene (2-5vol% in CH2C12) was polymerized with HC104 (0.01 mole l-1) and the system was kept at —78 °C a few minutes. Then, the second monomer 1 -/-butyl aziridine (TBA) or l(2-phenylethyl)-2-methyl aziridine (PEMA) was added to the solution 104). The mixture was stored at —78 °C for several hours and then warmed up to room temperature. A sample of polystyrene solution was taken before the addition of aziridine and its Mn was determined. A block copolymer was isolated and its Mn was determined separately. GPC traces of both products showed unimodal molecular weight distributions. The GPC trace of the copolymer indicated a considerable molecular weight increase, as compared to the homopolymer. Two block copolymers were obtained with Mn = 4,100 (starting from polystyrene of Mn = 800) and Mn = 7,100 (from polystyrene of Mn = 1,800). 

Polystyrene - Thermal degradation is the simplest of the current techniques used to recover feedstock chemicals from styrene-based polymers and has therefore been studied extensively. Investigations of the product distributions from thermal degradation of polystyrene have mainly focused on liquid products. It has been observed that the yield and the composition of liquid products vary strongly with temperature and the reactor configuration,... 

Figure 10 Product distributions from coal and polystyrene coprocessing reactions in the absence of catalyst and donor solvent ...

Considering aU the above-discussed data, we conclude that the linear dependence in the coordinates of the BET equation does not yet imply that the general conclusions of the polymolecular adsorption theory can be applied to the description of sorption on hypercrosslinked polystyrenes. These cannot be regarded as rigid sorbents with a constant heterophase structure. Accordingly, calculation of the pore size distribution from the desorption branch of the isotherms for carbon dioxide using the Kelvin equation (Eq. [3.4], Chapter 3) results in the unrealistic pore dimensions of about 0.1 A. The isotherms for water produce more sensible data for pore diameters, 20—40 A, but one should not assume that the plots presented in Fig. 10.4 correspond correcdy to the real pore size distribution of the material. 

Figure 7 Particle size distribution for polystyrene microlatices at different conversions with 0.27 mM KPS at 70"C (From Ref. 75.)...

Raman microscopy has been used to probe photo-oxidation of imstabilized PP (90). It was concluded that the catalyst residues, for the type of PP studied, tend to stabilize the polymer in the immediate vicinity, but also form reactive species that diffuse away from the catalyst to initiate oxidation. Localized oxidation was also confirmed by examining the distribution of polystyrene grafl ed onto the hydroperoxide sites in photo-oxidized PP (91). 

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