Biomedical Engineering Reference
In-Depth Information
Fig. 4
DSC thermograms of
hb
-PYs measured at a scan rate of 10
◦
C
/
min under nitrogen
tures in comparison to their copolyyne congeners, which is probably because
the former have more reactive terminal acetylene peripheries [119] and ster-
ically less crowded aryl cores. When the terminal acetylene groups of
hb
-P
20
were end-capped by phenyl groups, the resultant
hb
-P(
20
-II) contained only
internal acetylene groups, which needed higher temperatures to initiate and
complete its thermal curing reactions. This further manifests the effect of the
acetylene reactivity on the thermal curability of the
hb
-PYs.
Many of the hyperbranched polymers contain aromatic chromophores in
their
-conjugated structures and should show interesting optical proper-
ties [31]. This is indeed the case. For example,
hb
-P
20
carries the TPA chro-
mophore, which is often used as hole-transport materials in the fabrication of
light-emitting diodes [120]. The
π
λ
ab
of triyne
20
appeared at 342 nm (Fig. 5),
Fig. 5
Absorption spectra of THF solutions of triyne
20
and its polymer
hb
-P
20
(
c
= 12
µ
g
/
mL) and emission spectrum of the
hb
-P
20
solution (
λ
ex
= 368 nm)
