Ac. Albertsson et R. Palmgren, CATIONIC POLYMERIZATION OF 1,5-DIOXEPAN-2-ONE WITH LEWIS-ACIDS IN BULK AND SOLUTION, Journal of macromolecular science. Pure and applied chemistry, A33(6), 1996, pp. 747-758
1,5-Dioxepane-2-one (DXO) was coordinatively ring-opening polymerized
with different Lewis acids in bulk and solution. The reactivities of a
series of initiators (SnCl4, FeCl3, AlCl3, BCl3, and BF(3)OEt(2)) at
different temperatures and reaction times were analyzed. Polymerizatio
n of DXO in bulk with SnCl4, FeCl3, AlCl3, and BCl3 gave only oligomer
s or low molecular weight polymers irrespective of temperature and/or
reaction time. Polymerization of DXO with BF(3)OEt(2) at 70 degrees C
gave yields of nearly 100% and molecular weights up to M(w) = 10,000.
The polymerization temperature was increased to 100 degrees C and the
reaction time prolonged, which resulted in nearly equal molecular weig
hts as at 70 degrees C but with lower yields, higher polydispersity, a
nd generally not full conversion. In addition, side reactions, such as
backbiting, transesterification and thermal degradation, occurred to
a larger extent at higher reaction temperatures. Solution polymerizati
on using the same initiators and THF, dioxane, or nitrobenzene as the
solvent gave polymers of low molecular weights and of low yields, exce
pt with FeCl3 and BF(3)OEt(2). The rates of polymerization were signif
icantly higher in nitrobenzene than in dioxane and THF due to polarity
and coordination of these solvents to the growing chain. Comparison o
f the initiators BF(3)OEt(2) and SnCl4 in solution polymerization show
ed equal reactivity in nitrobenzene for both of them. The BF(3)OEt(2)-
initiated systems give polymers with lower molecular weights than SnCl
4-initiated systems, but with narrower polydispersity.