Photografting-Hydrogen Abstraction

Figure 10.4. Photografting mechanisms of HEMA or MAA on the surface of PHBHV film according to the graftingfrom technique. (I) Photolysis ofTAS and production of both thiyls and phenyl radicals. (2) Hydrogen abstraction from PHBHV film and generation of free radicals on the surface of the PHBHV film. (3) Free radicals initiate covalent attachment of HEMA or MAA on the surface, followed by polymerization of the monomer. Reproduced widt permission from The Royal Society of Chemistry [VER12]...

Poly(ethylene terephthalate) has normally been considered to be inert to photografting, but recently Lenka and Nayak have overcome this problem using potassium peroxydiphosphate as initiator. On irradiation, the initiator decomposes to yield the phosphate ion radical which will then abstract a hydrogen atom from the polymer (Scheme 13). 

Benzophenone (BP) is a very useful photosensitizer in photografting polymerization. BP was transferred to an exciting state as it absorbed in the UV range spectrum, relaxed, and abstracted the tertiary hydrogen from the polymer main chains on the PHBHV film snrface by inelastic collision. Ketyl radical (BP ) dimerized, while polymer radical P is generated at the film surface [72]. 

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