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Chain Transfer to Monomer and Polymer in the Radical Polymerization of Vinyl Neo-decanoate
Balic, Robert,Fellows, Christopher M.,Van Herk, Alex M. The Polymer Society of Korea 2004 Macromolecular Research Vol.12 No.4
Molecular weight distributions of poly(vinyl neo-decanoate) produced by the bulk polymerization of the monomer to low conversions were investigated to obtain values of the rate constants for the chain transfer to monomer ( $C_{M}$). The value of $C_{M}$ of 7.5($\pm$0.6)${\times}$10$^{-4}$ was obtained from a logarithmic plot of the number distribution at 5,25, and 5$0^{\circ}C$, which suggests that the activation energy for chain transfer is on the order of 20-25 kJ ㏖$^{-1}$ . These plots were linear between the number and weight-average degrees of polymerization, but not over the whole molecular weight range for which a significant signal was observed in the gel permeation chromatography (GPC) trace. Modeling suggests that the deviations observed at high molecular weights can be explained by branching of the chains through chain transfer to the polymer, with a branching density as low as 10$^{-5}$ , without affecting the slope at low values of the number of monomer unit, N. This deviation from the expected distribution of linear chains was used to estimate the branching densities at low conversion.ion.
Chain Transfer to Monomer and Polymer in Radical Polymerization of Vinyl Neo-decanoate
Robert Balic,Christopher M. Fellows,Alex M. van Herk 한국고분자학회 2004 Macromolecular Research Vol.12 No.4
Molecular weight distributions of poly(vinyl neo-decanoate) produced by the bulk polymerization of the monomer to low conversions were investigated to obtain values of the rate constants for the chain transfer to monomer (CM). The value of CM of 7.5 ( ± 0.6) × 10- 4 was obtained from a logarithmic plot of the number distribution at 5, 25, and 50 oC, which suggests that the activation energy for chain transfer is on the order of 20-25 kJ mol- 1. These plots were linear between the number and weight-average degrees of polymerization, but not over the whole molecular weight range for which a significant signal was observed in the gel permeation chromatography (GPC) trace. Modeling suggests that the by branching of the chains through chain transfer to the polymer, with a branching density as low as 10- 5, without affecting the slope at low values of the number of monomer unit, N. This deviation from the expected distribution of linear chains was used to estimate the branching densities at low conversion.
Nath Dilip Chandra Deb,Fellows Christopher M.,Shiono Takeshi The Polymer Society of Korea 2006 Macromolecular Research Vol.14 No.3
The kinetic features of polymerization with an active site comprising cobalt dihalides ($CoX_2$, where X=Cl, Br, I) activated by methylaluminoxane (MAO) were investigated in 1,3-butadiene polymerization. The catalytic system exhibited the characteristic features of living polymerization. The initiation ($k_i$) and propagation ($k_p$) rate coefficients were estimated using the kinetic model for slow initiation previously reported by Shiono et al. The energy of activation fur the propagation reaction was calculated to be 27-30 $kJmol^{-1}$. The marked changes in reaction rate observed with different halides could be adequately described in terms of variations in the initiation process, with the same Arrhenius curve fitting propagation rate coeffcients estimated from all three halides, suggesting that the halide does not participate in the growing chain end.