Synthesis and comparison of the structure-property relationships of symmetric and asymmetric water-soluble Poly(p-phenylene)s

Abstract

Sodium salts of water-soluble polymers poly{[2,5-bis(3-sulfonatopropoxy)-1, 4-phenylene]-alt-[2,5-bis(hexyloxy)-1,4-phenylene]} (P1), poly{[2,5-bis(3- sulfonatopropoxy)-1,4-phenylene]-alt-[2,5-bis(dodecyloxy)-1,4-phenylene]J (P2), poly{[2,5-bis(3-sulfonatopropoxy)-1,4-phenylene]-alt-[2,5-bis(dibenzyloxy)-1, 4-phenylene]} (P3), poly[2-hexyloxy-5-(3-sulfonatopropoxy)-1,4-phenylene] (P4), and poly[2-dodecyloxy-5-(3-sulfonatopropoxy)-1, 4-phenylene] (P5)] were synthesized with Suzuki coupling reactions and fully characterized. The first group of polymers (P1-P3) with symmetric structures gave lower absorption maxima [maximum absorption wavelength (λmax) = 296-305 nm] and emission maxima [maximum emission wavelength (λem) = 361-398 nm] than asymmetric polymers P4 (λmax = 329 nm, λem = 399 nm) and P5 (λmax = 335 nm, λem = 401 nm). The aggregation properties of polymers P1-P5 in different solvent mixtures were investigated, and their influence on the optical properties was examined in detail. Dynamic light scattering studies of the aggregation behavior of polymer P1 in solvents indicated the presence of aggregated species of various sizes ranging from 80 to 800 nm. The presence of alkoxy groups and 3-sulfonatopropoxy groups on adjacent phenylene rings along the polymer backbone of the first set hindered the optimization of nonpolar interactions. The alkyl chain crystallization on one side of the polymer chain and the polar interactions on the other side allowed the polymers (P4 and P5) to form a lamellar structure in the polymer lattice. Significant quenching of the polymer fluorescence upon the addition of positively charged viologen derivatives or cytochrome-C was also observed. The quenching effect on the polymer fluorescence confirmed that the newly synthesized polymers could be used in the fabrication of biological and chemical sensors. © 2006 Wiley Periodicals, Inc.