POLYMERIZATION OF STYRENE BY PERCHLORIC ACID
Final technical rept. Sep 1967-Aug 1968
TRINITY COLL DUBLIN (IRELAND) CHEMICAL LAB
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The report presents extensive measurements of number-average molecular weights Mn, yields and rates obtained in the polymerization of styrene by perchloric acid in solution in methylene chloride over the temperature range of 25C to -97C. The measurements show that the polymerization changes its kinetic pattern as the temperature is reduced and that the following well-defined characteristics can be recognized in different regions. At -97C a flash polymerization produces only a definitely limited yield of polymer, with Mn corresponding to one chain per initiator, i.e. no transfer reactions are involved. At intermediate temperatures, e.g. -78C to -30C, a two-stage reaction occurs in which Stage I is similar to the above. Stage I is followed by Stage II, a stationary polymerization. Above -30C a conventional transfer dominated stationary polymerization is obtained in which Mn decreases with conversion and is virtually independent of initiator concentration. An inert perchlorate salt, nBu4NC104, causes severe reduction of the Stage I yields and partial reduction of the Stage II rates, indicating that free carbonium ions are the main propagating species in Stage I and two species act in Stage II.
- Organic Chemistry