Structure Dependence of Photophysical Behavior for the Pyrene Derivatives with Branched Side Chain in PDMS Films

Pyrene-based oxygen sensor films were composed of poly(dimethylsiloxane, PDMS) and the pyrene derivatives with branched side chains synthesized by silanization of 1-pyrenylbutanol or 1-pyrenylmethanol with R₃SiCl, where R is alkyl chain of certain length. The photophysical characteristics of the pyrene derivatives embedded in PDMS matrix were studied in order to explore the relationship between the structure of the pyrene derivatives and their oxygen sensor performance. The results reveal that the photophysical behavior of the pyrene derivatives depends on the branched structure bound to the pyrene ring. When the alkyl length of R are within certain length, the pyrene derivatives substituted with branched structures render good storage stability because of the suppressed molecular mobility. Especially, such derivatives show not only longer fluorescence lifetime, higher oxygen quenching sensitivity, but also excellent linearity of Stern-Volmer plot due to the relative homogeneous dispersion of the derivatives in the polymer matrix. However, the response times for oxygen quenching of the sensing films containing the derivatives with varying side-chain structures are independent of whether the substituent chains are branched or linear.