Chemistry Reference
In-Depth Information
SCHEME 5.18
Functional CPs for surface activation.
protection. The second possibility is a reactive group transformation after dendrimer
synthesis in an “a posteriori” way. Both approaches have been considered.
By the “a priori” method, a decoration of the polyphenylene dendrimers with
numerous functional groups affects their solubilities, tendencies to intermolecular
interactions, their self-assembly behavior, and surface affinity or just polarity
(Scheme 5.18,
). Furthermore photonic and electronic properties can be
adjusted by dye groups as perylenmonoimide (PMI,
57-66
64
) [56] and conducting
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properties upon using terthiophenes
[69] or the hole conductor triphenylamine
as in
[70].
At this point, we will not discuss such extended surface functionalizations since
they have been reviewed earlier [14].
An example is the core-shell dendrimer using
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as endcapping reagent. The
resulting core-shell dendrimer possesses oligothiophene chains on its surface [69]. Its
chemical or electrochemical oxidative coupling yielded a 3-D network in which
dendrimer spheres were connected by sexithiophene spacers. The electrical conduc-
tivity of this 3-D structure provided insight into the mechanism of charge carrier
transport. Interestingly, the electrical conductivitywas further increasedwhen the 3-D
polyphenylene dendrimer cores were oxidatively dehydrogenated to planarized
graphitic propellers [69]. One thus obtained a unique hybrid network in which
graphene structures where embedded in an oligothiophene matrix.
The conversion of an already existing group A on the dendrimer surface according
to the “a posteriori” method into a substituent B via subsequent addition of an
electrophile is presented in Scheme 5.19 [71]. In the ideal case, this reaction should be
quantitative, but the possibility of incomplete conversions or side products must
always be considered.
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