Viscosity-Average Molecular Weight Mv

Viscosity average molecular weights Mv were determined using a Ubbelohde viscometer and diisobutylene solutions at 20 °C with at least three dilutions for every solution. The Mv was calculated from intrinsic viscosity28. Averages of two determinations are reported. Reproducibility was 10%. 

Equation (32) has been compared with phase boundary concentration data in the following way. For each solution, N of the polymer sample is estimated from Mw or the viscosity-average molecular weight Mv along with the molecular parameters ML and q listed in Table 1, and d is calculated with d from II or 0II/0c data. For systems which lack these data, the values of d from the (partial) specific volume vsp may be substituted. Table 2 lists the resulting values of d from II, 0II/0c, or vsp for various systems. The phase boundary volume fractions vc v ( = vc v v = I and A) are calculated from experimental phase boundary weight fractions (or mass concentrations) with d, Mw (or Mv), and Ml. Finally, with these numerical results, [vc v/dav(d)] — AV(N, d) is computed... 

The equilibrium value of a in the nematic phase can be determined by minimizing AF. With Eq. (19) for AF from the scaled particle theory, S has been computed as a function of c, and the results are shown by the curves in Fig. 12. Here, the molecular parameters Lc and N were estimated from the viscosity average molecular weight Mv along with ML and q listed in Table 1, and d was chosen to be 1.40 nm (PBLG), 1.15 nm (PHIC), and 1.08 nm (PYPt), as in the comparison of the experimental phase boundary concentrations with the scaled particle theory (cf. Table 2). 

Polyisobutylene. The solution viscosity of an irradiated polyisobutylene block was measured in CC14 at 30 °C. to determine the degree of degradation (5). The variation of viscosity-average molecular weight, Mv, with the dose, r, is shown in Figure 3. Nitrous oxide reduced the... 

Gamma radiation can be used with macroscopic amounts of polymer. This is particularly welcome when polymers are not compatible with the GPC technique. Larger samples can be characterized by viscosity changes, usually measured in dilute solutions. All that is needed is a suitable solvent. If the Mark-Houwink parameters are known, it is possible to calculate viscosity-average molecular weight, Mv, from dilute solution viscosities. However, even the raw viscosity-concentration data in terms of the reduced viscosity may be enough to indicate the sensitivity of a given polymer in qualitative terms. The reduced viscosity at concentrations c is isp/c where t]sp — (solution viscosity — solvent viscosity)/solvent viscosity. 

Fig. 92. K-value of as a function of its viscosity average molecular weight, Mv [212]...

We first consider below the commonly used nomenclature for solution viscosity and then describe in later sections the definition and significance of viscosity average molecular weight (Mv) and the method of its determination from solution viscosity. 

Figure 12.1. Predicted trends for the intrinsic viscosity [p] of a polymer with M=100 g/mole, K=30 g°-25,cm1-5/mole0-75 and Mcr=10000 g/mole, as a function of the viscosity-average molecular weight Mv of the polymer (for Mv>Mcr) and the quality of the solvent (and hence the value of the exponent a in Equation 12.14).

The mechanical behaviour of UHWMPE is related to the average molecular weight, which is routinely inferred from intrinsic viscosity measurements. There are commonly used methods for calculating the viscosity average molecular weight (Mv) for UHMWPE based on the intrinsic... 

The microwave-assisted ring-opening polymerization of poly(p-dioxanone) (PPDO) from the monomer p-dioxanone (PDO) was observed by Li et al. (2006), with constant microwave power (90, 180, 270 and 360 W) and temperature maintained at 158 to 198°C. The polymerization at 270 W for 25 min using Sn(Oct)j as a catalyst gave 63% yield of PPDO with a viscosity-average molecular weight (Mv) of 156,000 g/mol. It was observed that time for polymerization was 14 h in conventional polymerization method. 

The Mark-Houwink parameters allow to relate the intrinsic viscosity [q] with the viscometric average molecular weight Mv through the relation ... 

Fig. 4. Correlation of the ratio of viscosity average molecular weight M, obtained without and with hydrogen Mv/M , H to the ratio pH/pM of hydrogen and mohomer (ethene) pressure in the feed. [Al] = 1.72 x 10" 2 mol/1 line a-[Cp2ZrCl2] = 2x 10 s at 60°C line b-[Cp2ZrCl2] = 7.5 x 10 6 mol/1 at 70 °C...

Mv viscosity-average molecular weight MDE maleic acid diester... 

---