Chemistry Reference
In-Depth Information
from an excited n
* state to a high vibrational level of the ground state [
170
,
171
]. Introductions
of pendant azide and sufonyl azide groups into polymeric structures are possible in a variety of ways
and many publications describe different approaches. Thus, Tsuda and Yamaoka [
81
] introduced
azide groups into a phenolic novolac resin by the following scheme:
! p
OH
NO
2
OH
N
3
1. H2NNH2
PdC
2. HNO
3
OH
OH
portion of a novolac
Tsunoda and Yamaoka [
173
,
174
] also condensed formyl-1-naphthyl azide with poly(vinyl
alcohol). All steps in the synthesis were not disclosed. The preparation was illustrated as follows:
NH
2
N
3
OH
O
O
H
H
CH
2
O
O
N
3
Preparations of azide derivatives from styrene-maleic anhydride copolymers, cellulose, and
gelatin by attaching aromatic azide compounds are described in the literature [
175
]. Most of the
resultant polymers cross-link rapidly when exposed to light of 260
m wavelength. Also, as much as
90% of the hydroxy groups of poly(vinyl alcohol) can be esterified with
m
-azido-benzoyl chloride.
These reactions must be carried out in mixtures of chloroform and aqueous sodium hydroxide [
175
].
Earlier, Merrill and Unruh [
175
] described formation of derivatives from poly(vinyl alcohol) and
attachment of aromatic azide groups.
Most of these azide polymers photocross-link at a faster rate than does poly(vinyl cinnamate), when
exposed to light of 260
p
m
m. In addition, they responded well to photosensitization. Also, it was
observed [
50
] that the 4-isomer of azidophthalate shows greater speed increase than does the 3-isomer.
In general, the poly(vinyl alcohol) derivatives were reported to exhibit higher cross-linking speeds
than do other azide functionalized polymers [
176
].
The reaction product of
-azidobenzoyl chloride with polyvinyl alcohol was investigated by Tsuda
and coworkers [
179
]. In the polymer studied by them, over 90% of the hydroxy groups were esterified.
The photocross-linking reaction was followed by observing changes in the ultraviolet and infra-red
absorption spectra. It was shown that the simple photochemical reaction occurs stochiometrically upon
p
