Excited photocrosslinkable polymers

Electronic Structures in the Excited States of the Photosensitive Groups of Photocrosslinkable Polymers. (I) Polyvinyl dnnamate... 

Natural polymers such as albumin, gelatin, fish glue, shellac, and gum arabic received attention up to the early 1900 s, after which time other materials such as bichromate, diazo compounds, iron salts, and silver halides were added to resins in order to hasten or accomplish their crosslinking. These systems were neither photopolymerization nor photocrosslinkable polymers. Instead, the added second component, when excited by light, produced a species which itself caused the formation of radical sites on a prepolymer or polymer chain which then led to cross-linking. 

A large number of examples of polymers containing tertiary amines are reported to photocrosslink in the presence of alkyl halides. One combination would be poIy(p-dimethyI ami nostyrene) and ethyl iodide (2 ). The mechanism is not reported, but may involve charge-transfer excitation to form radicals. 

According to the previously reported results of very familiar hydrogen abstraction of triplet excited state benzophenone (BP) [156] and photocrosslinking observed in BP-connecting vinyl polymers... 

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