Biomedical Engineering Reference
In-Depth Information
2.1
Polycoupling
Homo- and cross-couplings of alkyne promoted by metallic catalysts are ver-
satile reactions for carbon-carbon bond formation and have been utilized to
synthesize functional hyperbranched polymers.
2.1.1
Palladium-Catalyzed Polycoupling
Repetitive coupling of acetylenes with aryl halides is an effective way to
directly build hyperbranched architecture in a stepwise manner. This type
of polycoupling is often catalyzed by palladium complexes in the presence
of amines and has been widely used for the preparation of well-defined
oligomers, linear polymers, and perfectly branched dendrimers [19, 20].
Employing this reaction protocol,
hb
-PAEs, particularly
hb
-PPEs, have
been prepared. Diiodophenylacetylene (
1
)representsatypicalAB
2
-type
building block in this approach (Scheme 1). Palladium-catalyzed polycou-
pling of
1
furnished an
hb
-PPE with a bimodal SEC elution profile, charac-
Scheme 1
Synthesis of
hb
-PPEs on a solid support (S), in the presence of core (C)
molecules, and/or by the addition of a non-halogenated arylethyne terminator (T)
