Water-Soluble Conjugated Polyelectrolytes with Branched Polyionic Side Chains

Abstract

A new series of conjugated polyelectrolytes (CPE) consisting of an arylene–ethynylene backbone featuring phenyl (Ph), 2,1,3-benzothiadiazole (BTD), or 4,7-bis(2′-thienyl)-2,1,3-benzothiadiazole (TBT) units have been synthesized and characterized. On each polymer repeat unit the CPEs contain two branched ionic side groups each featuring a “triad” of carboxylate (R-CO2 –Na+) or ammonium (R-NH3 +Cl–) units, giving the polymers six ionic charges per repeat. The photophysical properties of the series of CPEs were investigated in CH3OH and H2O solution by absorption, steady-state fluorescence, and fluorescence lifetime spectroscopy. The different arylene units in the backbone lead to the variation of the HOMO–LUMO gap across the series. The branched, polyionic side chains suppress aggregation of the polymer chains, even in aqueous solution, leading to higher fluorescence quantum yields relative to similar CPEs with linear side chains. UV–vis absorption spectra show that CPEs with anionic branched side chains (R-bCO2 –Na) aggregate at low pH, while retaining the photophysical properties of their organic-soluble precursors at high pH. CPEs having branched cationic side chains (R-bNH3 +Cl–) exhibit the opposite response to pH change.

Fluorescence Array-Based Sensing of Metal Ions Using Conjugated Polyelectrolytes

“…The synthesis of PPE1 and PPE2 were referred to the method previously reported. 38,39 Poly ( 4 NOH in methanol and stirred at room temperature for 24 h. During the course of the hydrolysis, 2 mL of water was systematically added to keep the solution clear. Then a solution of 0.2 g of NaIO 4 in 3 mL of water was added to the hydrolyzed polymer solution, and the resulting mixture was poured into 400 mL of cold acetone, resulting in the precipitation of PPE−IDA as yellow powders (92.5 mg, yield 76%).…”

Bright Quantum‐Dot‐Sized Single‐Chain Conjugated Polyelectrolyte Nanoparticles: Synthesis, Characterization and Application for Specific Extracellular Labeling and Imaging

“…The optical properties of CPEs are generally determined by the chemical and electronic structure of conjugated backbones . However, due to their inherent amphiphilic structures, CPEs are prone to aggregate in aqueous media.…”

Nanohybrid conjugated polyelectrolytes: highly photostable and ultrabright nanoparticles

“…New strategies to disaggregate the polymer have emerged by deliberately engineering the polymer side chains and its backbone. 34 PPEbased conjugated polyelectrolytes were modified with dendritic poly(benzyl ether) terminated with carboxylic acid groups as side chains. 35 With each dendrimer generation, the backbone charge density increased, resulting in its disaggregation and subsequent increase in its fluorescence quantum yield.…”