A new monomer
1,1-bis[(1-adamantyloxy)carbonyl]-2-vinylcyclopropane
(3) was readily
synthesized and polymerized by radical initiators. Monomer
3 afforded a 1,5-addition polymer selectively
and in good conversion, even at high temperatures or low monomer
concentrations. Poly(3) is soluble in
common organic solvents, but insoluble in ether and methanol.
Poly(3) (M
n = 51 000
estimated by GPC
based on polystyrene standard) exhibited a grass transition at 34 °C
and 10% weight loss at 377 °C
under nitrogen. Monomer 3 showed a positive volume
change (+4.5 ± 1.1%) upon polymerization. This
phenomenon can be rationalized by several reasons, such as the
depression of recyclization during
propagation by bulky ester groups, conversion of the crystalline
monomer to the amorphous polymer,
and the fact that 3 contains a pair of large spreadable
ester groups that may increase the free volume of
the polymer matrix. The kinetics of the homopolymerization of
3 with AIBN was investigated in benzene.
The rate of polymerization (R
p) can be
expressed by R
p =
k[AIBN]0.52[3]1.2,
and the overall activation
energy E
a has been calculated to be 20.8
kcal/mol.
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