Biomedical Engineering Reference
In-Depth Information
Chart 1
Structures of dendrtic (
D
), linear (
L
)andterminal(
T
)unitsin
hb
-P
21
and their
31
P NMR chemical shifts
the peripheries of the polymers by end-capping reactions. This is demon-
strated by the coupling of
hb
-P
20
with aryl iodides II and III (Scheme 10).
The polymer capped by phenyl iodide (
hb
-P
20
-II) became partially soluble
after purification, possibly due to the
stacking-induced supramolecular
aggregation during the precipitation and drying processes. Product
hb
-P
20
-
III was soluble, thanks to the long dodecyloxy group of the end-capping
agent. No signal of terminal acetylene resonance was observed in its
1
HNMR
spectrum, unambiguously confirming the completion of the end-capping re-
action.
π
-
π
Scheme 10
End-capping reactions of
hb
-P
20
2.2
Polyhydrosilylation
Similar to olefins, acetylenes undergo facile addition reactions. Transition
metal-catalyzed hydrosilylation is such a reaction that has been utilized for
the synthesis of silicon-containing hyperbranched polymers.
