Imaging Processes Based on Side-Chain Modification of Polymers

The first use of ether protecting groups in the design of imaging systems based on substituted poly(hydroxystyrenes) is reported. Polymers containing 4-(2-cyclohexenyloxy) or 4-(1-phenylethyloxy) derivatives of 4-vinylphenol or 3,5-dimethyl-4-vinylphenol have been prepared from the corresponding monomers. Due to their design, which allows for facile elimination or rearrangement reactions, the ether protecting groups can be removed easily by acidolysis, or thermolysis, or a combination thereof. In some instances, the protecting groups can be split quantitatively from the polymers, while in others a thermal Claisen rearrangement or an acid-catalyzed alkylation occur with the formation of some alkylated phenolic moieties. Application of the design to imaging systems is achieved through the use of triarylsulfonium salts as photochemical triggers. Exposure of films of poly[4-(2-cyclohexenyloxy)-3,5-dimethyl-styrene] containing some of the onium salt to irradiation at 254 nm results in the formation of acid in the exposed areas which catalyzes the polymer deprotection and allows for the development of images in either positive or negative mode through a differential dissolution process.