142 Advances in Polymer Science Editorial Board: A. Abe. A.-C ...

210 J. Roovers, B. Comanita
Scheme 13
is observed to move to higher wavelength with increased dendrimer size. In
comparison with simple poly(phenyl acetylene) the p-conjugated system in the
backbone is more extended and more uniform. This is evidence for the steric influence
of the dendritic substituents on the conformation of the poly(phenyl
acetylene) backbone.
The second method involves substitution reactions on a preformed polymer
with a stiff backbone. The advantage of this method is that it provides better
control over the MW of the starting polymer. However, the substitution may not
be 100%. The first example involved the substitution on a poly(1,1,1-propellane)
copolymer [116]. A copolymer with 80% functionalizable units has been successfully
modified with a [G-1]-Br poly(benzyl ether) dendron (see
Scheme 13a). Further studies exploring the feasibility and steric limitations of
the substitution route have been performed on poly(p-phenylene) [113, 116].
The Williamson substitution reaction on
with [G-1]-Br and [G-2]-Br poly(benzyl ether) dendrons provided 100 and 50–
60% functionalization, respectively. A [G-3]-Br substitution was therefore con-
(8)