ISSN:
0022-3832
Schlagwort(e):
Chemistry
;
Polymer and Materials Science
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
,
Physik
Notizen:
Acrylamide was polymerized in aqueous solution with chlorate-sulfite initiator under the following conditions: temperature, 15-75°C.; pH, 1.5-3.9; monomer concentration, 0.3-1.1 mole/liter; NaClO3 concentration, 0.26-2.1 × 10-4 mole/liter; and Na2-SO3 concentration, 0.79-6.3 × 10-4 mole/liter. The weight-average molecular weight of the polymers formed under these conditions is in the range of 1-3 × 106. It was found that up to 40-50% conversion, the following rate equation holds: \documentclass{article}\pagestyle{empty}\begin{document}$ R_p = - \frac{{d[{\rm M}]}}{{dt}} = K\frac{{\left( {\left[ {\rm C} \right]{\rm O}_3^ - \left[ {{\rm H}_2 {\rm SO}_3 } \right]} \right)^{1/2} }}{{[{\rm M}]_0^{3/2} }}[{\rm M}]^{3/2} $\end{document} where Rp is the overall rate of polymerization, [M] the instantaneous monomer concentration at time t, and [M]0 the initial monomer concentration. At 50°C., K = 6.9 ± 0.9 l. mole-1 sec.-1 Activation energy within the temperature range studied was found to be 7.3 kcal./mole. The value of k2p/kt at 50°C. was estimated to be about 30 l. mole-1 sec.-1 The rate dependence on [M]5/2[M]-3/20 is explained by assuming that the polymer formed binds part of the remaining monomer. The presence of ferrous ions in the polymerization system increases the rate but decreases the molecular weight of the polymer formed. Up to 3.6 × 10-3 mole/l. of [Fe++], the rate is affected in such a manner that \documentclass{article}\pagestyle{empty}\begin{document}$ K = 6.9 + 29{\rm }[{\rm Fe}^{ + + } ]^{0.3} $\end{document} Chromic ions tend to retard and nickel ions tend to accelerate the rate of polymerization. It was found that HSO3- is an effective chain transfer agent. Its chain transfer constant was estimated to be about 0.17.
Zusätzliches Material:
11 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/pol.1958.1203112325
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