Quantum yield and morphology control of BODIPY-based supramolecular self-assembly with a chiral polymer inhibitor

Chiral rod-coil-type organoboron polymers S-poly and R-poly were prepared from the palladium-catalyzed Sonogashira-Hagihara coupling reaction of boron dipyrromethene-based monomer 1, which has bisiodophenyl and decyl groups with S- or R-6,6'-diethynyl-2,2'-dioctyloxy-1,1'-binaphthyls (S-2 and R-2), in a solvent mixture (tetrahydrofuran (THF)/triethylamine=2/1 (v/v)) at 40 degrees C for 24h. The obtained polymers were characterized by hydrogen-1 nuclear magnetic resonance (NMR), carbon-13 NMR (C-13 NMR), boron-11 NMR (B-11 NMR) and infrared spectroscopy. The scanning electron microscopy (SEM) analysis of each chiral polymer clearly revealed micrometer-sized fiber-like structures formed by the aggregation of each particle, as we expected. Next, we examined the relationship between the ratio of photoluminescence (PL) intensity (I/I-o=R-poly/S-poly) and particle diameter, measured by dynamic light scattering analysis, versus the R-poly content of the mixed polymer of S-poly and R-poly in THF, which varied from 0 to 100%. As a result, the PL intensity and diameter showed maximum and minimum (about 32 nm) values, respectively, at 70% content, depending on the differences between both the molecular weights and absolute values of the chiral characters. These findings indicate that the PL intensity of S-poly influences morphology change by adding R-poly; that is, R-poly acts as an inhibitor toward the aggregation of S-poly. Furthermore, the SEM image of the mixed polymer (S-poly/R-poly=30/70) showed complete particle structures from nano- to micrometer sizes, which were roughly 480 nm to 1.19 mu m in diameter, and the Phi(F) of the mixed polymer was significantly high (0.98). Polymer Journal (2010) 42, 37-42; doi:10.1038/pj.2009.302