Chemistry Reference
In-Depth Information
irradiation. Also an absorption band was observed at 1,500/cm in the infra-red region of the irradiated
and cross-linked polymer. This band is due to N
group. Based on that,
Tsuda concluded the cross-linking reaction takes place by dimerization, as expected [
179
].
There are reports in the literature that photosensitive azide polymers formed from polymers
substituted with isocianate groups [
176
,
177
]. The preparation and properties of many other polymers
containing pendant aryl azide groups were described by Delzenne and Laridon [
178
]. The polymers
were prepared by interfacial polycondensation of azido-substituted acid chlorides with diols and
diamines. Also, in one experiment, a cinnamate moiety was combined with an azide group, together
in one pendant functional structure [
178
]. It was found, however, that addition of the azide groups to
the cinnamate side chain does not increase reactivity. A marked wavelength dependence was
observed on
ΒΌ
N stretching vibration of the
azo
p ! p
* and n
! p
* transitions that occurs in both functional groups [
179
].
10.5.9 Polymers Designed to Cross-link Upon Irradiation with Laser Beams
To accommodate the needs of photolithography, some polymers were developed that cross-link upon
irradiation with an Ar-F excimer laser source at 193 nm [
180
]. To this end were synthesized
cycloolefin-maleic anhydride-alternating copolymers. This material was formed by free-radical
copolymerization of norbornene and maleic anhydride:
THF ABIN
(A)
+
n
O
63
o
C
O
O
O
O
O
+
(B)
+
O
O
O
O
OH
m
n
O
HO
O
O
O
To render the polymers soluble in aqueous base, acrylic acid terpolymerization was also carried
out as shown in (B) above.
10.6 Photo-Responsive Polymers
Photo-responsive polymers are materials that are able to respond to light irradiation by undergoing
reversible changes in their chemical structures and/or their physical properties. Also, photochromism
refers to the photo-induced reversible transformations in chemical compounds between two
