Photocrosslinking of Polymers with Light-Sensitive Groups

Photocrosslinking of Polymers with Light-Sensitive Groups 

The photocrosslinking reactions of poly(vinyl cinnamate), shown earlier, are reversible when irradiated with light of proper wavelength. Some intramolecular cyclizations take place as well. Nevertheless, these reactions found many commercial applications and led to the development of other materials with similar photosensitive groups. All of them photocrosslink in a similar manner. Some of these groups are shown below  

The dimerizations take place upon irradiation with light of a wavelength longer than 300 nm. 

The dimers, however, dissociate back to the monomeric forms upon irradiation with light of 254 

The rates of the crosslinking reactions can be greatly accelerated by addition of photosensitizers. They are molecules that, after absorption of light and attaining the triplet state, transfer the energy to other molecules. The effectiveness of sensitizers in accelerating the reactions of poly(vinyl cinnamate) is illustrated in Table 8.1. 

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