Flexibility of Poly(alkyl methacrylate)s Characterized by Their Persistence Length Determined through Pyrene Excimer Formation

A series of poly(alkyl methacrylate)s and poly(oligo(ethylene glycol) methyl ether methacrylate)s labeled with 1-pyrenebutanol were referred to as the PyC -PC MA samples with = 1, 4, 6, 8, 12, and 18 and the PyC -PEG MA samples with = 0-5, 9, 16, and 19, respectively. Pyrene excimer formation (PEF) upon the encounter between an excited and a ground-state pyrenyl labels was employed to determine their persistence length ( ) in -xylene. The fluorescence decays of the PyC -PC MA and PyC -PEG MA samples were acquired and analyzed with the fluorescence blob model to yield the number ( ) of structural units in the volume probed by an excited pyrenyl label. was found to decrease with an increasing number ( ) of non-hydrogen atoms in the side chain, reaching a plateau for the PyC -PEG MA samples with a longer side chain ( = 16 and 19). The values were used to determine . The values for the PyC -PC MA and PyC -PEG MA samples increased linearly with increasing as predicted theoretically, which agreed with the values obtained by viscometry for a series of PC MA samples. The good agreement between the values retrieved by PEF and viscometry served to validate the PEF-based methodology for determining for linear polymers.