title: Photodegradation of polyfluorene and fluorene oligomers with alkyl and aromatic disubstitutions.
abstract: The stability of fluorene-based compounds and polymers, especially at the bridged C-9 position under photoirradiation and thermal treatment, has claimed wide attention. We report the electronic, vibrational, and MALDI-TOF mass spectral combined studies for the fluorene oligomers with alkyl and aromatic substitutions under UV-light irradiation. The low-energy emission and the formation of ketonic defects after degradation highly depend on the proportion of alkyl substitution. The oligomer with fully aromatic substitution shows good stability, but when the proportion of alkyl substitution increases, their photostability rapidly decreases. The mass spectra show not only the mass of the fluorenone-fluorene trimer but also another new degradation product with a large mass (pristine oligomer plus 14) from alkyl oxidation, which testify to the assistance of alkyl side chain during degradation. We propose that the degradation of fluorene is a radical chain process propagated by alkyl side chains, and then the different stability between alkyl and aromatic substitution can be well explained.
authors.affiliation: Key Lab for Supramolecular Structure and Materials of Ministry of Education, Jilin University, Changchun 130012, P R China.
authors.forename: Linlin
authors.initials: L
authors.lastname: Liu
authors.forename: Shi
authors.initials: S
authors.lastname: Tang
authors.forename: Meirong
authors.initials: M
authors.lastname: Liu
authors.forename: Zengqi
authors.initials: Z
authors.lastname: Xie
authors.forename: Wu
authors.initials: W
authors.lastname: Zhang
authors.forename: Ping
authors.initials: P
authors.lastname: Lu
authors.forename: Muddasir
authors.initials: M
authors.lastname: Hanif
authors.forename: Yuguang
authors.initials: Y
authors.lastname: Ma
mesh_terms: D005449:Fluorenes / Q000737:chemistry / Q000528:radiation effects*; D006838:Hydrocarbons / Q000737:chemistry / Q000528:radiation effects*; D015394:Molecular Structure; D010777:Photochemistry; D010782:Photolysis; D011108:Polymers / Q000737:chemistry / Q000528:radiation effects*; D014466:Ultraviolet Rays
chemical_list: D005449:Fluorenes; D006838:Hydrocarbons; D011108:Polymers