Polystyrenes narrow

In this stage of the investigation, poly(methyl methacrylates) (PMMAs) were selected as the polymeric probes of intermediate polarity. Polymers of medium broad molar mass distribution and of low tacticity (14) were a gift of Dr. W. Wunderlich of Rohm Co., Darmstadt, Germany. Their molar masses ranged from 1.6 X 10" to 6.13 X 10 g-mol. For some comparative tests, narrow polystyrene standards from Pressure Co. (Pittsburgh, PA) were used. 

This simply relates to how linear the relationship between the peak molecular weight of narrow polystyrene standards versus elution volume fits a straight line. This is typically measured with the linear correlation coefficient, r. ... 

Figure 3. Calibration relationship between [r/]mpos CLnd SEC retention ((O) measured [r/] of narrow polystyrene standards in THF)...

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 molecular-weight distributions were measured using a Waters GPC in the dual-detector mode (DRI and UV). The UV detector was operated at 254 nm. The samples were prepared by dissolving 2 mg of polymer in 10 ml of THE The injection volume was 200 pi. Separations were effected using two Polymer Labs 10-gm PL mixed-B columns. THF was used as the mobile phase. The molecular-weight distributions were calculated relative to narrow polystyrene standards ranging from 102 to 4 x 106 M ,... 

Fig. 2. Effect of the uv detector noise on the estimation of the molecular weight as function of elution volume for a narrow polystyrene standard. The symbols represent molecular weights obtained using the universal calibration and viscosity measurements on collected fractions...

Figure 1. Determination of molecular weight distribution for narrow polystyrene standard. Curve I, calibration of Rf vs. M curve II, densitogram of two dimensionally developed sample curve III, molecular weight distribution Mw/Mn = 1.02 (12).

Table II. Basis-Generating Chromatograms of Narrow Polystyrene Fractions Peak Position,6 ...

FIG. 15.37 Extrudate swell ratio vs. shear stress at the wall, for melts of polystyrenes of broad and narrow molecular-weight distributions. Filled symbols the broad polystyrene mentioned in Fig. 15.34-15.36 Mw = 2.2 x 105 and Mw/Mn = 3.1. Open symbols narrow polystyrene Mw = 1.6 x 105 and M /Mn < 1.1. From Greassley et al. (1970). Courtesy Society of Rheology. 

Venema et al. studied SEEC with porous silica particles [14,15]. They separated narrow polystyrene standards on columns packed with particles of different pore size, and observed a significant improvement of the efficiency in SEEC over that in pressure-driven size-exclusion chromatography. Also, they observed that the efficiency improvement was more significant for large-pore particles and related this to a higher pore flow. 

The experimental evidence of the importance of the tube renewal mechanism when short molecules are added to a high polymer is provided by blends of narrow polystyrene (Mg = 8 500 and Ml = 900 OOO) [28]. 

Firstly, it has been shown that there may be many experimental problems in a direct determination of the experimental fimction. In shear, damping functions obtained from step strain and from step strain rate experiments do not match each other. This poses an important question on the validity of the separability assumption in the short time rai e. Significant departures from this factorization have already been observed in the case of narrow polystyrene fractions by Takahashi et al. [54]. These authors found that time-strain superposition of the linear and nonlinear relaxation moduli was only possible above a cert2un characteristic time. It is interesting to note that this is predicted by the Doi-Edwards theory [10] and according to this theory, this phenomena is attributed to an additional decrease of the modulus connected to a tube contraction process and time-strain separability may hold after this equilibration process has been completed. Other examples of non-separability were also reported by Einaga et al. [55] and more recently by Venerus et al. [56] for solutions. 

Light-scattering chromatograms of a narrow polystyrene standard with a peak molecular weight reported by the vendor of 1,030,000 are shown in Figure 1. Now, greater scattering intensity is clearly observed... 

Figure 4. Log M-retention volume data for narrow polystyrene standards (m) and a broad molecular weight distribution polysyrene.--------, the extrap-...

Figure 5. Log y -retention volume data for narrow polystyrene standards...

Figure 6. Log M versus local root-mean-square radius for a broad polystyrene standard (-----) and narrow polystyrene standards (m).

Figure 8.17 Isotherms showing the recoverable creep compliance for a narrow polystyrene distribution with molecular weight 3400. (From Ref. 16.)...

If the values of A, 6, and Dj are available, the molecular weight of a polymer can be directly determined from its retention time using Eq. (3). If Dj is not available, one may use a calibration curve [log DlDj) versus log M] constructed with a series of narrow polystyrene standards of known molecular weights. For the molecular-weight analysis of an unknown, the DlDj value of the sample is first calculated from its measured retention time, and then the molecular weight is determined from the calibration curve. 

A number of narrow polystyrene standards (Waters Scientific) were examined in order to quantify the dependence of the specific refractive index increments in THF on the molecular weight of the polymer. The results shown in Figure 4 agree quite well with those reported by Schulz and Baumann (18). The values of v increase slightly with molecular weight up to approximately 20,000 and then remain constant within the experimental error. Partial specific volumes v, were estimated using the equation... 

When a narrow polystyrene sample, as described above, is injected... 

Table 1. Emulsion polymerization recipes for the synthesis of narrow polystyrene submicron size beads...

With the exception of the work reported on polyolefins, the applications described above have involved polystyrene samples. The reason for this restricted initial scope is that thermal FFF has evolved primarily in an academic setting where the availability of a wide range of narrow polystyrene standards was considered indispensable to the evolution and refinement of the mechanism and behaviour of thermal FFF systems. However, as thermal FFF increasingly enters the industrial laboratory, its applicability to other polymers becomes crucially important. Fortunately, we have done enough work with other polymer systems to understand the general behaviour of various polymer classes in thermal FFF systems. 

Parth, M. Aust, N. Lederer, K. SEC of ultra-high molar mass polymers Optimization of experimental conditions to avoid molecular degradation in the case of narrow polystyrene standards. Int. J. Polym. Anal. Character. 

Samples of narrow polystyrene (PS) latex, steam-stripped to remove excess, unreacted monomer, were purchased from a supplier in order to test the calculation of extinction efficiencies for use in correcting data from a disc centrifuge photosedimentometer.l It was crucial that the sizes were known with an accuracy of 1%, independent of the DCP measurement. TEM values were given by the manufacturer. In addition PCS and DCP measurements were made. Table 1 shows the results. 

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