ISSN:
0022-3832
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
In a radical polymerization in which initiation is solely by the addition of an initiator fragment to a monomer molecule, there must be in the polymer one combined initiator fragment for each kinetic chain; analysis of the polymer therefore can lead to a determination of the kinetic chain length. The rate of initiation is equal to the over-all rate of polymerization divided by the kinetic chain length, and so it can be calculated. This new method for calculating rates of initiation is not subject to the uncertainties associated with older methods. Analysis for initiator fragments can be performed accurately if the initiator is labeled with a radioactive isotope; in the work described here C14-α,α′-azo-bis-isobutyronitrile was used. An essential requirement is that the polymer molecules of low molecular weight must not be lost during precipitation of the polymer. Tests are described showing that loss of low molecular weight materials is negligible in most cases and that even when the average molecular weight of the polymer is low and there is an appreciable loss a correction can be made. A correction can also be made for the consumption of initiator during the reaction. The results presented in this paper refer to the copolymerization of butyl acrylate and styrene in benzene solution at 60°. It is shown that for a given monomer mixture the rate of initiation is proportional to the concentration of initiator, and that for each initiator molecule decomposed approximately one reaction chain is started.
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pol.1954.120120138
