Design of photocrosslinkable polyesters with specific absorptions^†

2,5-Bis(4-hydroxy-3-methoxybenzylidene)cyclopentanone (DVCP), when condensed to form polyesters, polysulfonates, polycarbonates, and polyphosphonates, provides photocrosslinkable polymers useful in photoresist and photolithographic applications. With the use of 26 distyryl ketones related to DVCP, a series of polyesters have been prepared which reflect in their photoresponse the structural variations of the monomeric bisphenols. Those prepared from cyclopentanone are more light sensitive than those from acetone, cyclohexanone, etc. Methoxyl groups on the bisphenol enhance sensitivity and solubility and cause a bathochromic shift. Nitro- and ortho-hydroxyl substituents cause desensitization. Halogens on the bisphenol do not significantly change the polymer sensitivity or absorption. The polymers prepared from DVCP-type bisphenols usually show a hypsochromic shift of 30–40 nm from the monomer's absorption maximum. By selecting the proper bisphenol, one can “tailor” the absorption, sensitivity, and solubility of the resulting polyester. Most of the polyesters of this work were prepared from azelaoyl chloride or sebacyl chloride and had up to 50 mole-% of a nonlight-sensitive bisphenol such as tetrachlorobisphenol A present to improve their solubility in dichloroethane.