Pendent functionalization chemistry

Acid-C t lyzed Chemistry. Acid-catalyzed reactions form the basis for essentially all chemically amplified resist systems for microlithography appHcations (61). These reactions can be generally classified as either cross-linking (photopolymerization) or deprotection reactions. The latter are used to unmask acidic functionality such as phenohc or pendent carboxyhc acid groups, and thus lend themselves to positive tone resist apphcations. Acid-catalyzed polymer cross-linking and photopolymerization reactions, on the other hand, find appHcation in negative tone resist systems. Representative examples of each type of chemistry are Hsted below. 

The capped radical-generating centers of living polymerization, located on the surface of monolith pores, can be further used for functionalization, by grafting various monomers, for example, vinylbenzyl chloride, tert-butyl methacrylate, or vinylpyridine [393], as well as 2-hydroxyethyl methacrylate and 3-sulfopropyl methacrylate [394]. Another possibiHty for changing the surface chemistry is the involvement of pendent double bonds that remain on the pore surface of highly crossUnked styrene-DVB rods, in a variety of chemical reactions these have been reviewed by Hubbard et al. [395]. 

Use of the pendent acetylene functionality and click chemistry carries a number of benefits relative to other methods discussed thus far, including the relatively easy one step monomer synthesis, the ability to homopolymerize or copolymerize the acetylene-functionalized lactone, and the single postpolymerization step that enables coupling of a very diverse range of azide-... 

In summary, aliphatic polyesters, already an important class of synthetic degradable polymeric biomaterials, have been taken to unprecedented levels of synthetic diversity and tailoring through the efforts of many research groups in the U.S. and abroad. Some of these have been described in this brief review, with a focus on pendent or graft functionality by polymerization of functionalized lactones, and post-polymerization modification. Future efforts in this area must attempt to connect these synthetic advances to specific applications, through the collaborative efforts of experts in the chemistry, biology, and clinical use of synthetic polymer materials. 

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