Chemistry Reference
In-Depth Information
n
n
O
2
O
O
n
Formation of polymers by reaction of free-radical polymerizable methacryloyl groups and a
photocross-linkable pendant chalcone units was also reported [
157
]. The photocross-linking reaction
takes place in thin films and in solutions upon irradiation with high pressure mercury lamps. The
reaction can be monitored through changes in the UV absorption spectrum. The rates of photocross-
linking in solutions were reported to be faster than in films. Photocross-linking in the presence of a
triplet photosensitizer shows no significant changes in the rate of disappearance of the double bonds.
This particular polymer with a pendant chalcone unit was found to photocross-link at a high rate even
in the absence of a photosensitizer and is of interest as negative photoresist [
158
].
10.5.3 Polymers with Functional Groups Similar to Cinnamates
As stated earlier, the photocross-linking reactions of poly(vinyl cinnamate) and the reversibility of
cross-linking depends upon irradiation with light of the proper wavelength. In addition, some
intramolecular cyclizations also take place. Because the reactions found extensive commercial
applications, a number of other polymers that resemble poly(vinyl cinnamate) were developed.
Following are two examples of such functional groups [
159
]:
O
O
O
O
O
CO
