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-PCMA samples with = 1, 4, 6, 8, 12, and 18 and the PyC-PEGMA 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-PCMA and PyC-PEGMA 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-PEGMA samples with a longer side chain ( = 16 and 19). The values were used to determine . The values for the PyC-PCMA and PyC-PEGMA samples increased linearly with increasing as predicted theoretically, which agreed with the values obtained by viscometry for a series of PCMA samples. The good agreement between the values retrieved by PEF and viscometry served to validate the PEF-based methodology for determining for linear polymers.