Toluene, solvent weight fraction

Figure 5. Plot of solvent weight fraction versus partial pressure of solvent for toluene at 70°C.

When 3(4)-substituted thiophenes (e.g., 3-hexylthiophene) are used as monomers, the polymers are partly or completely soluble in low polar organic solvents like toluene, chloroform, dichloromethane, THF. Therefore, after washing with ethanol, the polymer is dried, then dissolved in chloroform and reprecipitated into methanol or acetone to remove low-molecular-weight fractions. The solid is collected by filtration, washed with methanol, and dried in vacuo. 

Off-Line Mw Measurements in Several Solvents. Table 1 shows results oT din/dc (column 3T and off-line Mw measurements (column 6) which were carried out in THF, toluene, and chloroform. The dn/dc also was calculated via Equation lb using the weight fraction of each monomer (from proton NMR, "Experimental") and the dn/dc for the corresponding homo polymers. Values of the homopolymers in THF styrene (0.190), isoprene (0.127), butadiene (0.132) toluene styrene (0.108), isoprene (O.O3I), butadiene (0.032) chloroform styrene (0.155), isoprene (0.093), butadiene (0.094). Values of dn/dc derived in this manner are presented in column 4. 

The classical solvent precipitation fractionation technique provides reproducible fractionations for determining molecular weight distributions of CTPB and almost 100% recovery of the sample from the column. A solvent-nonsolvent combination which has been used effectively is the toluene—acetone-methanol system, where acetone and methanol are used as the nonsolvents. The precipitating fractions are required to stand approximately 24 hours to ensure complete separation. Each fraction is vacuum stripped of solvent at approximately 30 °C., and the molecular weight of each fraction is then determined by either VPO or intrinsic viscosity. 

Blends, e.g. 80 20, of poly (methyl methacrylate) (PMMA, weight average molar mass, Mw, of 15,000 g/mol) and polybutadiene (PB, with Mw 420,000 g/mol) (e.g. from Aldrich) are prepared by mixing solutions of a mass fraction of PMMA of 0.02 in toluene and mass fraction of PB of 0.02 in toluene in a ratio of 8 2 followed by spin-coating onto pre-cleaned silicon wafers. Following the spinning, the samples are treated for 24 h at ambient temperatures under vacuum to remove residual solvent. Pieces of the blend-covered silicon wafer are glued to the sample holder disc and inserted into the AFM. 

Problem 3.5 Measurements were made of the vapor pressure of polystyrene (mol. wt. 290,000) solutions in toluene and methyl ethyl ketone (MEK) [3]. The table below shows the ratios of the vapor pressure of the solvent over the solution, Pi, to the vapor pressure of the pure solvent, p°, against the corresponding weight fraction w of the solvent at 25°C. 

Fig. 8.1 Weight fraction of the oligomers CH2[=CHCH2CH2CH=] ,CH2 produced by the metathesis of hexa-1,5-diene (M), as a function of time. Catalyst WCVEt3Al2Cl3/ MeCCl(OH)CH2Cl/PPh3 (1/2/1/0.5) W/M= 1/375. Solvent toluene, 25°C (Dall Asta...

SEC analyses of the same samples as in Figure 1 with a toluene carrier solvent (500 A 60 cm PL gel, toluene, 1 ml/minute, 100 pi, RI detector). The whole asphalt is analyzed using a 7 wt% solution the Corbett fractions are adjusted according to their weight fraction. 

Mixtures of rhodium eicosanoate or copper dodecanoate with solvents such as toluene, decahydronaphthalene, and (-i-) cam-phene have been studied. The mesophases found at high temperature turns from columnar to nematic when the weight fraction of the solvent is increased beyond a value of about 50% [50]. 

Polymer concentration and temperature effects on solvent self-diffusion were examined by Pickup and Blum(25), who made pulsed-field-gradient NMR measurements on toluene 270 kDa polystyrene. Figure 5.2 shows representative measurements. At each temperature, D (c) of the solvent is a simple exponential for c < 0.4 (weight fraction) and a stretched exponential at larger c. The slopes of the exponentials as seen in the figixre are very nearly the same at all T, but v of the larger-c form increases with increasing T. 

Fig. 143.—The intrinsic viscosity of a polyisobutylene fraction of high molecular weight plotted against temperature in four solvents cyclohexane, diisobutylene (DIB), toluene and benzene. The lines shown have been calculated according to theory. (Fox and Flory. )...

Soxhlet extraction, with toluene as solvent, of the soluble fraction from the cross-linked gels produced by irradiation, was used as a method to determine the radiation cross-linking efficiency, G(X), for the homopolymers and blends under investigation. Samples were extracted to constant weight and two or three replicate extractions were carried out. 

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