ISSN:
0022-3832
Schlagwort(e):
Chemistry
;
Polymer and Materials Science
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
,
Physik
Notizen:
In the polymerization of ally1 methacrylate in the presence of benzoyl peroxide at 75°C., gelation occurs after about 6% reaction. By carrying out the polymerization a t 1°C. to 25°C. in the presence of biacetyl or benzoyl peroxide and photoflood or ultraviolet radiation, we have been able to postpone gelation until 19 to 39% reaction. In the presence of biacetyl the extent of reaction a t the gel point is increased as the temperature is lowered and as the light intensity is raised.Biacetyl is activated by radiation in the 400-460 mμ region; benzoyl peroxide is activated by radiation in the 350-380 mμ region.Hydrolysis and bromination of the soluble polymer did not indicate any marked difference in the composition of the samples prepared at 75°C. and 15°C. The soluble polymer which is prepared at 75°C. appears to have an intrinsic viscosity which may be three to twenty times as great as that of the polymer which is prepared at 1-25°C.The polymerization of methyl methacrylate and allyl acetate under the two sets of conditions indicated that the reaction of the methacrylate was affected more than that of the allyl compound by the change in conditions. The copolymerization of methyl methacrylate and allyl chloroacetate indicated that somewhat more allyl monomer was incorporated into the copolymer at the lower temperature than a t the higher temperature.The increased extent of reaction at the gel point at the lower temperatures appears to be due almost entirely to diminished molecular weights. The decrease in molecular weight a t low temperatures is probably due to the decreased rate of chain growth, the rate of initiation remaining high because of irradiation, and the rate of termination being little dected because of its low activation energy. The effects of temperature on the composition of the copolymer, and of molecular weight on the point of gelation, are discussed briefly.
Zusätzliches Material:
3 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/pol.1948.120030212
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