Polystyrenes high-molecular-weight

Fig. 38. LS plots31) for high molecular weight polystyrene (M = 2.8 x 106) at a fixed angle (90°) and variable wavelength...

The limitation of Dole s experiments was that the ions of the electrosprayed high-molecular weight polystyrene used in his group could not be detected by mass spectrometry. [42-44] It took years of work and lasted until the ending 1980s for the Fenn group to fully realize that analytes of 100-2000 u molecular weight can be readily analyzed with a quadrupole analyzer attached to a properly constructed ESI ion source. [2,6,45]... 

Calibration of Gel Permeation Chromatograph Polystyrene Calibration. A plot of molecular size in (S) versus elution volume for polysty-rene standards in dichloromethane showed deviation from linearity at about 2,200 which may be attributed to Imperfect column resolution, peak broadening, axial dispersion and skewing. The extensive tailing of the chromatograms of high molecular weight polystyrene standards observed in dichloromethane has also been reported in the literature (23-26). 

The overall procedure was similar for each sample (high molecular weight polystyrene, low molecular weight epoxy resin) and is outlined in Table I. 

Dead Volume. The dead volume difference between the viscometer and DRI must be accounted for. Otherwise systematic errors in Mark-Houwink parameters K and u can occur. In the previous paper (16), a method developed by Lesec and co-workers (38) based on injecting a known amount of a very high molecular weight polystyrene standard onto low porosity columns was used. From the viscometer and DRI chromatograms, the apparent intrinsic viscosity [h] was plotted against retention volume V. A series of [n] vs. V plots are then constructed assuming a range of dead volume, AV. 

Styrene-butadiene block polymers also find applications in blends with polystyrene and ABS plastics. When minor amounts of rubbery SBS or (SB)n- X block polymers are blended with high molecular weight polystyrene such that the polystyrene forms the... 

The following intrinsic viscosity values of some high molecular weight polystyrene fractions have been reportedf ... 

The culmination of this trend is illustrated in Fig. 5.2 by dynamic data on undiluted polystyrene of low molecular weight (124). Agreement with the Rouse model here is by no means as good as that seen in Fig. 5.1 with the Zimm model for a high molecular weight polystyrene at infinite dilution. Indeed, the value of Je° deduced from G (to) for the sample in Fig. 5.2 exceeds the value from... 

Bueche-Ferry theory describes a very special second order fluid, the above statement means that a validity of this theory can only be expected at shear rates much lower than those, at which the measurements shown in Fig. 4.6 were possible. In fact, the course of the given experimental curves at low shear rates and frequencies is not known precisely enough. It is imaginable that the initial slope of these curves is, at extremely low shear rates or frequencies, still a factor two higher than the one estimated from the present measurements. This would be sufficient to explain the shift factor of Fig. 4.5, where has been calculated with the aid of the measured non-Newtonian viscosity of the melt. A similar argumentation may perhaps be valid with respect to the "too low /efi-values of the high molecular weight polystyrenes (Fig. 4.4). 

Figure 3. Comparison of GPC and TLC molecular weight distribution for a high polydispersity, high molecular weight polystyrene. ttw = 2.22 X 10f, Mn = 8.16 X 104 from GPC ttw = 2.14 X I05,...

The polymerisation of styrene, which is an exceptionally versatile monomer, in the presence of various Ziegler-Natta and related coordination catalysts produces high molecular weight polystyrenes, both highly isotactic polymers [1-4] and highly syndiotactic polymers [5-10]. 

It is unfortunate that research in the area of polymer solutions has been deserted during the past ten years in favor of blend work. With the advent of shear cells, it is expected that research in polymer solutions will become fashionable again. For instance, the phenomenon of shear-induced apparent demixing of high molecular weight polystyrene in semidilute solutions (in DOP for example) is not understood. Kinetics measurements will hopefully permit a close monitoring of the remixing effect after shear cessation as well. 

Figure 1. Pure, high-molecular-weight polystyrene. 1150 X.

Fig. 16.9 shows the low frequency slopes of 2 and 1, respectively, as expected for viscoelastic liquids and the high frequency slopes Vi and 2/3 for Rouse s and Zimm s models, respectively. Experimentally it appears that in general Zimm s model is in agreement with very dilute polymer solutions, and Rouse s model at moderately concentrated polymer solutions to polymer melts. An example is presented in Fig. 16.10. The solution of the high molecular weight polystyrene (III) behaves Rouse-like (free-draining), whereas the low molecular weight polystyrene with approximately the same concentration behaves Zimm-like (non-draining). The higher concentrated solution of this polymer illustrates a transition from Zimm-like to Rouse-like behaviour (non-draining nor free-draining, hence with intermediate hydrodynamic interaction).

The minimization of the formation of a bulk phase during polymerization constitutes an important factor in the success of this method, since the rate of the process as well as the molecular weight is much lower in bulk polymerization. A relatively low temperature, a small amount of electrolyte, a suitable amount of water, and an optimum amount of surfactant minimize the occurrence of a bulk phase. The preparation of high molecular weight polystyrene latexes with low size dispersity by concentrated emulsion polymerization was examined in some detail in [19]. 

SbCls also chlorinates alkenes and is reduced to the much less reactive SbCl3. This reaction probably prevents formation of high molecular weight polystyrenes [145]. 

C. A 50 50 (by weight) immiscible blend of high molecular weight polystyrene and polybutadiene. 

Figure 29 Average relaxation time of a high molecular weight polystyrene (M = 900 000) in the presence of short chains (M = 8 500). The dotted line represents pure reptation and the full line stands for the contribution of tube renewal according to relation (6-8).[from ref. 28]...

---