Molecular weight determination by vapor pressure osmometry

Thomas for the molecular weight determination by vapor pressure osmometry, and A. J. Bailey for advice at various stages of the work. 

K. Kamide and M. Sanada, Molecular weight determination by vapor pressure osmometry, Kobunshi Kagaku (Chem. High Polym. Japan) 24, 751 (1967) (in Japanese). 

Bitumens are colloid systems, as are crude oils, and consist of the two colloidal components, petroleum resins and asphaltenes, dispersed in a dispersion medium. To investigate the composition of the system, a colloid precipitation according to Neumann [4-10] is carried out. The chemical nature of the bitumen and its components were determined by element analysis, where the atomic ratio H/C includes an indicator of the aromacity. Further characterization is performed by measuring the average relative particle mass (mean of the molecular weight M) by vapor pressure osmometry. 

GPC was calibrated with polystyrene standards. M was also determined by vapor pressure osmometry (VPO) on a Wescan model 233 molecular weight apparatus at a current setting of 50pamp in toluene... 

Analysis of Defined Fractions. Quantitative infrared analysis was used for those fractional groups that have definitive bands average absorptivities were estimated using model compounds (12, 16, 17). Table I lists the infrared bands and the apparent integrated absorption intensities (B) used. Quantitative IR spectra were measured in methylene chloride with 0.05 cm sodium chloride cells, using a Perkin-Elmer 521 infrared spectrophotometer. Peak area was measured by planimetry. Molecular weights were determined by vapor-pressure osmometry in benzene. 

Infrared spectra were recorded in carbon tetrachloride in 5 mm KBr liquid cells or as a thin film between NaCl plates on a Beckman IR-20 infrared spectrometer. The number-average molecular weights were determined by vapor pressure osmometry in methylene chloride solutions (3-8 g/1) (23). 

The most convincing evidence is Vofsi and Tobolsky s (24) work with 14C-labelled triethyloxonium tetrafluoroborate at 0°C. They found good agreement among the molecular weights calculated from the amounts of catalyst charged, determined by 14C end-group analysis and determined by vapor pressure osmometry. Dreyfuss et al. have also obtained NMR data on this initiation reaction (9). The spectra are entirely consistent with Reaction 4. No side reactions are indicated. 

Table 8.3.4. Number-average molecular weights of different kraft lignins determined by vapor pressure osmometry...

Molecular Weight Data. Molecular weight data for the total asphaltene and for asphaltene subfractions determined by vapor-pressure osmometry (VPO), low resolution MS, and quantitative IR spectrometry... 

Solvent 1 1 benzene-isopropanol or 1 1 benzene-ethanol or 1 1 tetrahydrofuran-isopropanol or isopropanol irradiation under nitrogen atmosphere Fischer-Black-Ray long-wavelength UV-lamp molecular weights are determined by vapor pressure osmometry in benzene. 

Of particular Interest is the fact that in the alternating oopolymerization of epoxide and phthallc anhydride with the TPPAlCl-EtPhSPBr system every aluminum atom of the catalyst carries two growing polymer molecules. As seen in Table I, the observed molecular weight of the copolymer, determined by vapor pressure osmometry (VPO), is about one-half the molecular weight calculated on the assumption that every aluminum atom carries one polymer molecule. 

Molecular Weight. The maximum number-average molecular weights obtained thus far for the poly(arylene polysulfides) are from 15,000 to 16,000. Representative examples of the reduced viscosities and molecular weights, as determined by vapor pressure osmometry (VPO) in chloroform, are given in Table I. 

As determined by vapor-pressure osmometry (VPO), the average molecular weights (MWts) of Canada s heavy oil from Norman Wells, Countess, and Cold Lake were reported to be 197, 334, and 585 g/mol, respectively (37). Relative to other feedstocks the range appears as given in Table 2. 

Poly(itaconic acid) has also been prepared in a 0.2M/liter aqueous solution using potassium persulfate at 50 C over a 5-hr period under reduced pressure. After the polymer is reprecipitated twice into methanol-ethyl acetate, a polymer is isolated with a molecular weight of 1.64 x 10, determined by vapor pressure osmometry of a methanolic solution of the methyl ester prepared from the polymer [49]. Unfortunately Tsuchida and coworkers did not report on the quantitative extent to which poly(methyl itaconate) had been formed from this polymer (presumably by reaction with diazomethane). Consequently, there is little in the literature to confirm or dispute the paper by Braun and Azis el Sayed [97], which offered evidence that during the free-radical polymerization of itaconic acid, carbon dioxide evolves to a considerable extent. During the process, it seems that hydroxyl and formyl radicals are generated and incorporated in the macromolecule. It is proposed by these authors that the homopolymer of itaconic acid contains virtually no itaconic acid repeat units but rather intramolecular lactone rings and acetal- or hemiacetal-like moieties. Since the polymer remains soluble in the reaction solvent (dioxane). 

The number average molecular weights of representative commercial terpene resins, determined by vapor pressure osmometry, are presented in Table 1. Feedstrearns for the dipentene and a-pinene resins were 95-99% pure. The feedstream for the 6-pinene was already described. 

The same catalyst was also very active for polycondensation of benzyl chloride. Thus, when 0.1 g of the catalyst was added to 5 cm of benzyl chloride at room temperature, polymerization occurred immediately with violent evolution of hydrogen chloride and completed in less than 10 s. The yield of methanol - insoluble polymer was about 70%. Elemental and NMR analyses indicated that the product is predominantly linear para-substituted polybenzyl. The molecular weight as determined by vapor pressure osmometry was 8175, the degree of polymerization being ca, 90. 

Intrinsic viscosities of polymer solutions were measured using a Cannon Ubbelohde type viscometer. Number average molecular weights of pol3nners were determined by vapor pressure osmometry (Knaner Co.). Thermal properties of polymers were studied using a DSC (Perkin Elmer, Model IB) and a TGA (Perkin Elmer, Model TGA-1) instruments. 

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