| Autor: |
Luthjens, L. H., Frahn, M. S., Abellon, R. D., Hom, M. L., Warman, J. M. |
| Předmět: |
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| Zdroj: |
Research on Chemical Intermediates; 2001, Vol. 27 Issue 7/8, p765-773, 9p |
| Abstrakt: |
In order to quantify our fluorogenic molecular probe studies on the radiation-induced polymerization of methyl methacrylate (MMA), measurements have been made of the monomer conversion, C[sub M], and polymer molecular weight distribution as a function of dose for bulk MMA polymerized by steady-state ([sup 60]Co γ-rays) and nanosecond-pulsed (3 MeV electrons) radiation. In all cases, C[sub M] was found to increase close to linearly with dose up to ca. 30%. Above this conversion, autoacceleration of polymerization (the gel or Trommsdorff effect) occurs in the γ-irradiated samples. From the low-conversion steady-state data, using dose-rates of 0.21 and 2.7 Gy/s, the parameter 〈k[sub p]〉 [sup 2]G(R[sup .])/2〈k[sub t]> = 0.011 and 0.015 lmol[sup -1] s[sup -1] (100 eV)[sup -1] respectively have been determined (with 〈k[sub p]〉 and 〈k[sub t]> the average rate coefficients for bimolecular propagation and termination respectively, and G(R[sup .]) the yield of the chain-initiating free radicals per 100 eV (G = 1 (100 eV)[sup -1] 0.1036 μmol J[sup -1])). From the 5 Hz repetitive pulse data the value of 〈k[sub p]〉 G(R[sup .]) = 1700 lmol[sup -1] s[sup -1] (100 eV)[sup -1] has been determined. Taking 〈k[sub p]〉 = 342 lmol[sup -1] s[sup -1] from the literature results in G(R[sup .]) = 5.0 (100 eV)[sup -1] and 〈k[sub t]> = 2.7 × 10[sup 7] lmol[sup -1] s[sup -1]. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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