Chemistry Reference
In-Depth Information
SCHEME 16.8
functions.
CD
5
monomers based on the cyclotriphosphazene scaffold
were synthesized in this way. Each step of the synthesis of dendrimers with
AB
5
and
AB
5
and
CD
5
monomers needed several days to go to completion, and the synthesis
was stopped at the third generation
25-G
3
; no attempt was made to synthesize the
next generation, due to the steric hindrance of the third generation outer shell
(Scheme 16.9) [30].
In order to shortenmore the synthetic process, hyperbranched polymers appear as a
tempting alternative to dendrimers, due to their straightforward one-pot synthesis.
Thus, we designed a protected branched monomer having two types of functions in a
1:2 ratio, in which the deprotected functions react readily intermolecularly. The
Staudinger reaction is chosen, due to the absence of by-products and to its high yield.
The monomer bears one azide and two protected phosphines that are deprotected by
bases. Various hyperbranched polymers were obtained, with various molar masses
and distribution, depending on the temperature, the reaction time, the solvent, the
concentration, and the type of amine used for the deprotection. However, the degree of
branching was found very high and practically identical (0.83-0.85), irrespective of
SCHEME 16.9
