Polystyrene oligomers

Figure 9.7 shows separations under identical conditions using PSS SDV columns with 3 (Fig. 9.7a)-, 5 (Fig. 9.7b)- and 10 (Fig. 9.7c)-/i,m particle size columns. A polystyrene oligomer standard was injected and all analyses were performed in THF as the eluent. The much higher efficiencies of small particle size columns are obvious, which is important in the SEC separation of low molecular weight compounds such as additives, by-products, and resins. The reader should note that all chromatograms are area normalized and have the same Y axis to show the differences in peak width and height. 

Figure 3.14 Reversed-phase liquid chromatogram of polystyrene oligomers. Conditions. ...

Comparison 3, 2, 1 column sets illustrating effect interplay of plates and pores Probe Mix 2, polystyrene oligomer mix. 

The linearity proposed by Eq. (4) has been proven for a great variety of homologs but is no longer fulfilled by the higher members of the series. Here, the increase in log k with n declines. Recent work with polystyrene oligomers showed adherence... 

The linear increase of S with n was established experimentally with polystyrene oligomers 3 4). Of course, Eq. (6) is bound to the same decline at high degree of polymerization as Martin s rule but, at any rate, high polymers have high S values. They are in general so large that elution is restricted to an extremely narrow interval of eluent composition, vide supra. 

Gradient elution of polystyrene oligomers was performed with methanol/tetra-hydrofuran systems. In the first paper, a C 18 column (150 x 4,6 mm dP = 6 pm) was used for the separation of a PS 800 sample. The gradient rate was 2.1 % THF/ml at 1.5 ml/min flow rate (S. D. Abbott in 85>). In another investigation, the sample was PS 750, the column C 18 (300 x 3.9 mm), the gradient rate 1.67% THF/ml, and the flow rate 1 ml/min. Here, the peaks were characterized by mass spectrometry86). Interestingly, neither of these separations indicated any substructure. 

This value has been checked very recently (169), by polymerizing methyl methacrylate in the presence of varying amounts of pure polystyrene oligomers of different molecular weights (ranging from 1000 to 5000). After separating carefully the resulting polymers, it was shown... 

Figure 11.4. Example of asymptotic density programming in SFC. Polystyrene oligomer mixture with avg. MW of 2,000. Reproduced from the Journal of Chromatographic Science by permission of Preston Publications, Inc.

Figure 2. SFC chromatograms of a 2000 MW polystyrene oligomer mixture. Conditions n-pentane mobile phase at 210 C, 10 m X 100 Ji fused silica capillary column coated with a 0.25- Jm film of crosslinked 50% phenyl metbylphenylpoly-siloxane, UV-absorption at 205 nm, (A) linear pressure program from 34.6 atm (0.12 g/mL) to 60 atm at 0.15 atm/min after a 5-min isobaric period (B) asyoiptotic density program from 0.12 g/mL (34.6 atm) to 0.35 g/siL according to the...

Mass spectral data were observed on polybutadiene samples with molecular weights in the range of 1000-3000 (181), on PEG and PPG oligomers (182). and on polystyrene oligomers (183) by field desorption MS. 

Rate constant it dm of excimer formation in polystyrene oligomers as a function of the degree of polymerization N... 

Polystyrene oligomer (M. = 0.5K g mole ) was added to the block copolymer solutions to study the solubilization of homopolymers within the micelles. Separate concentration series were run for normal (PSH) and deuterated (PSD) oligomers and the isotopic difference between the oligomers should have a major effect on the scattered... 

Figure 5. dS/d n(Q) for 3,7k/16.6k polystyrene-PFOA block copolymer in supercritical CO as a function of concentration (C) of added polystyrene oligomer... 

Lattimer, R. R, Harmon, D.., and Hansen, G. E., Determination of molecular weight distributions of polystyrene oligomers by field desorption mass spectrometry, Anal. Chem., 52, 1808, 1980. 

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