Copolymers of isoprenyl alkyl ethers with fluorinated acrylates and fluoroacrylates: influence of fluorine on their thermal, photochemical and hydrolytic stability

The homopolymer of butyl isopropenyl ether (pBPE) and a series of homo- and copolymers of BPE and decyl isopropenyl ether (DPE) with acrylates and methacrylates fluorinated on the vinyl and/or the alkoxy group were synthesized by cationic (pBPE) or free-radical process. The three structurally analogous 1,1,1,3,3,3-hexafluoroisopropyl methacrylate (HFIMA), 1,1,1,3,3,3-hexafluoroisopropyl 2-fluoroacrylate (HFIFA), and isopropyl 2-fluoroacrylate (IFA) as well as ethyl 3,3-difluoro-2-methylpropenoate (EFMA) were used as the fluorinated comonomers. The thermal properties and aging behavior of the copolymers were correlated to their structure and particularly to the protective action of the fluorinated moieties against photooxidative and acidcatalyzed hydrolytic degradation triggered by the labile side chains of the BPE units. Depending on their distance from the primary center of photooxidation, the fluorinated groups can either slow down or largely modify the degradation pathway, as shown by the dominant cross-linking in the strictly alternating HFIFA/BPE which outweighs the prevailing chain fragmentation of the other copolymers.