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

Abstract

Chiral rod-coil-type organoboron polymers S-poly and R-poly were prepared from the palladium-catalyzed SonogashiraHagihara 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 4°C for 24 h. The obtained polymers were characterized by hydrogen-1 nuclear magnetic resonance (NMR), carbon-13 NMR (13C NMR), boron-11 NMR (11B 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/I0=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 μm in diameter, and the ΦF of the mixed polymer was significantly high (0.98). © The Society of Polymer Science, Japan (SPSJ) All rights reserved.