Photocross-linking polymers

Photosensitized Reactions for Polymers. The economic and technical features for photocross-linking, photosolubilizafion, and photopolymerization reactions have been reviewed (55). The widely used poly(vinyl ciunamates) (PVCN) photocross-link by a photodimerization reaction. 

The subject of photocross-linking is reviewed thoroughly by Ranby, Qu and Shi in the Polymer Materials Encyclopedia.58... 

DUV exposure of poly( p-substituted styrenes), such as poly( p-chloro-styrene), poly( p-chloromethylstyrene), and poly( p-hydroxystyrene) [poly(p-vinylphenol)] (structure 3.11), in air leads to photocross-linking and photooxidation. Consequently, DUV hardening is applicable to resists based on these polymers as well as novolac-based resists (168, 169). 

Ichimura et al. [76] have described photoresists based on soluble polymers bearing methacrylated side-chain groups which are photocross-linked by a free radical mechanism using a diphenyliodonium salt as initiator, with a p-dimethylaminobenzylidine sensitizer. These investigators found spectroscopic evidence for in situ ground state charge transfer complex formation between the sensitizer and initiator, and that such complexes are involved both in the photocross-linking process as well as in the thermal instability of the photoresist films. 

The structure and cross-linked structure of the CM polymers is shown in Scheme 16. The photodimerization, i.e., 2+2 cycloaddition, of cinnamate side chains [338] is a classical method of polymer photocross-linking, e.g., used... 

A new cross-linking chroraophore has been investigated, based upon the 4-(or 4 -)substituted benzylideneacetophenone (chalcone) molecule.61 The photocross-linking of epoxyacrylates has recently been studied quantitatively.62 A novel kind of polymer containing the diazofluorene moiety (8), synthesized from... 

Fisher, J. P., Holland, T. A., Dean, D., Engel, P. S. Mikos, A. G. (2001) Synthesis and properties of photocross-linked poly(propylene fumarate) scaffolds. Journal of Biomaterials Science-Polymer Edition, 12, 673-687. 

Fig. 14 Access to shape-memory materials from photocross-linked metallo-supramolecular polymers. (a) Formation of shape-memory materials using light as a stimulus (a) UV light is absorbed by the metal-ligand complexes and is converted to localized heat, which disrupts the metal complexation (i>) the material can then be deformed (c) removal of the light while the material is deformed allows the metal-ligand complexes to re-form and to lock-in the temporary shape id) additional exposure to UV light allows a return to the permanent shape, (b) Images demonstrating the shape-memory behavior. Reprinted with permission from [274]. Copyright 2011 American Chemical Society...

Polymers That Photocross-link by Formation of Cyclobutane Rings. 736... 

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