Molecular Weight Distribution Of Poly Research Articles

Ultrasonic degradation of poly(methyl methacrylate

Ultrasonic degradation studies on a variety of molecular weights and molecular weight distributions of poly(methyl methacrylate) are reported. The extent of degradation was measured using gel permeation chromatography. Polydispersity decreased as a function of irradiation time for polymers with initial broad distributions. In contrast, polymers with an initial narrow distribution increased in polydispersity, passed through a maximum and then gradually decreased in polydispersity. Results appear to show no limiting degree of polymerization for poly(methyl methacrylate).

Radiation chemistry of polymer degradation processes: Molecular weight distribution effects

The molecular weight distributions of poly(methyl methacrylate) irradiated at 15 and 25 MeV with electron beams were investigated. The experimental values for the effect of chain scissions on the dispersivity agreed well with theoretical predictions. (JSR)

Gel electrophoretic analysis of poly(riboadenylic acid)

It is shown that molecular weights and molecular-weight distributions of poly(rA), and by implication other single-stranded polynucleotides, and synthetic and natural polyelectrolytes in general, can be determined by electrophoresis in polyacrylamide gels. It is shown that fractions of very narrow molecular-weight distribution can be obtained by preparative electrophoresis of polydisperse samples. Molecular-weight calibrations based on sedimentation coefficients of such fractions are given, and in aqueous systems do not coincide with calibrations for partially base-paired RNA species. Poly(rU) fractions fall on the same calibration as poly(rA). Relations between mobilities, relative to standard markers, and molecular weight for poly(rA) over a wide range of molecular weights are given, which allow rapid molecular-weight determination on poly(rA) samples, such as the segments found in many types of messenger RNA.

Bimodal molecular weight distribution of poly(vinyl acetate) produced in n‐hexane by radiation

Bimodal molecular weight distribution of poly(vinyl acetate) produced in n‐hexane by radiation

Effect of various factors on the molecular weight distribution of poly-( m-phenylene)isophthalamide in emulsion polymerization

Effect of various factors on the molecular weight distribution of poly-( m-phenylene)isophthalamide in emulsion polymerization

Polymerisation of vinyl monomers by transition‐metal allyl compounds. IV. Molecular weight distribution of poly(methyl methacrylate)

AbstractMolecular weights and molecular weight distributions of poly(methyl methacrylate) initiated by Cr(2‐methallyl)3 have been determined by gel permeation chromatography. The distribution is shown to broaden with polymerisation conversion, and it is suggested that this results from the formation of long chains having a high isotactic triad content. Number average molecular weights extrapolated to zero conversion are shown to depend largely on transfer processes. The experimental molecular weight distribution at zero conversion is shown to correspond to that expected from the polymerisation mechanism.

Molecular weight distribution of poly(vinyl chloride)

AbstractUnder the assumption that poly (vinyl chloride) (PVC) contains a negligible amount of long branches, simple kinetic considerations lead to the result that the molecular weight distribution (MWD) function resulting from a heterogeneous polymerization will be in accordance with the functional expression for the most probable distribution (mpd). A comparison between the experimental MWD curves determined by gel permeation chromatography (GPC) and the mpd supports this hypothesis and it is shown that the form of the MWD of PVC is very close to or identical with the mpd. Furthermore, it is found that PVC samples prepared by heterogeneous polymerization in the temperature interval 25–55°C have approximately identical distributions when normalized molecular weights are used. The degree of long chain branching is estimated to be equal to or less than 2 × 10−4 long branches per repetition unit.

Molecular weight distribution of poly‐N‐vinylcarbazole obtained in catalytic solid‐state polymerization

AbstractThe molecular weight distribution of poly‐N‐vinylcarbazole (PVCar) obtained in solid‐state polymerization with various catalysts or γ‐rays was measured by gel‐permeation chromatography, in order to determine the mechanism of the solid‐state polymerization. In addition, the molecular weight distribution of PVCar obtained in the solution polymerization by the cationic catalyst was also measured. The molecular weight distribution of PVCar obtained in the catalytic solid‐state polymerization was broad and had three peaks, independent of the nature of catalysts, radical and cationic. A large amount of low molecular weight oligomer (probably dimer or trimer) was formed in the catalytic solid‐state polymerization of VCar. The molecular weight distribution of PVCar obtained in the cationic solution polymerization showed only one sharp peak. On the other hand, the molecular weight of PVCar obtained in the radiation‐induced solid‐state polymerization was larger than that obtained in the catalytic solid‐state polymerization, and dimer or trimer was not formed. The molecular weight distribution of PVCar obtained was composed of one sharp peak in the high molecular weight region, and a broad peak in the low molecular weight region, and was extremely different from that of PVCar obtained in the catalytic solid‐state polymerization.

442. The kinetics of catalytic polymerizations. Part V. The molecular-weight distribution of poly-(α-methylstyrene) prepared by the aluminium chloride-catalyzed polymerization

442. The kinetics of catalytic polymerizations. Part V. The molecular-weight distribution of poly-(α-methylstyrene) prepared by the aluminium chloride-catalyzed polymerization