Interactions between surfactants and {1,4-phenylene-[9,9-bis(4-phenoxy-butylsulfonate)]fluorene-2,7-diyl}

Abstract

The interaction between the water-soluble anionic conjugated copolymer poly{1,4-phenylene-[9,9-bis(4-phenoxy-butylsulfonate)]fluorene-2,7-diyl} (PBS-PFP) and various surfactants has been studied in aqueous solution by UV-vis absorption spectra, fluorescence and electrical conductivity. It is suggested from the linear dependence of absorbance, fluorescence and electrical conductivity on concentration that in the absence of surfactant, moderately stable dispersions are formed. These are affected in different ways on adding cationic, anionic or neutral surfactants. With the cationic cetyltrimethylammonium bromide, quenching of fluorescence intensity and lifetime, and formation of a new emission occurs at concentrations well below the critical micelle concentration (cmc). Electrical conductivity measurements indicate a discontinuity at surfactant/polymer ratio corresponding to electroneutrality, due to complexation. With the anionic sodium dodecyl sulfate, fluorescence quenching is also observed, but is attributed to formation of some mixed polymer/surfactant aggregate. The most striking changes are observed with the non-ionic pentaethyleneglycol monododecyl ether (C 12 E 5 ), where a blue shift in fluorescence emission, dramatic increases in lifetime and quantum yield, and changes in electrical around the cmc are interpreted in terms of incorporation of single polymer chains in elongated cylindrical micelles. This is supported by 1 H NMR spectroscopic measurements.

What conjugated polyelectrolytes tell us about aggregation in polyelectrolyte/surfactant systems

“…We have observed similar spectroscopic changes with the anionic conjugated polymer poly(1,4-phenylene- [9,9-bis(4-phenoxybutylsulfonate)]fluorene-2,7-diyl) (PBS-PFP, average molecular weight 6500 g mol − 1 ,~9 monomers per chain) upon interaction with the non-ionic surfactant n-dodecyl pentaoxyethylene glycol ether (C 12 E 5 ) [22,29] and with several cationic surfactants: the amino acid glyceride conjugate, 1-O-(L-arginyl) 2,3-O-di-lauroyl-sn-glycerol dichlorhydrate (1212R, a mimic for the phospholipid lecithin) [30] and cationic gemini surfactants: α,ω-(C m H 2m + 1 N + (CH 3 ) 2 ) 2 (CH 2 ) s (Br − ) 2 (m-s-m; m = 12, s = 2, 3, 5, 6 and 12) [31], Scheme 2.…”

“…Three different types of changes of the fluorescence properties of conjugated polymers have been observed upon addition of surfactants: a) enhancement of the emission quantum yield, b) quenching, sometimes accompanied by the appearance of new, red-shifted, bands in the emission spectrum [22] and c) a combination of these behaviours in which the surfactant can both, quench and increase, the conjugated polymer emission intensity, depending on its concentration [23]. From the point of view of applications, particularly in biosensory processes, an enhancement of the emission intensity of the conjugated material upon addition of surfactant is always desirable.…”

Interplay of Electrostatic and Hydrophobic Effects with Binding of Cationic Gemini Surfactants and a Conjugated Polyanion: Experimental and Molecular Modeling Studies

“…This has been interpreted in terms of the breakup of PBS-PFP aggregates and the incorporation of one or more isolated chains of the polymer into long wormlike micelles. This is supported by small-angle neutron scattering (SANS) measurements 17 and 1 H NMR 23 spectroscopy.…”

Interactions between hairy rod anionic conjugated polyelectrolytes and nonionic alkyloxyethylene surfactants in aqueous solution: Observations from cloud point behaviour

“…However, the structures of these aggregates of surfactants with the rigid rod conjugated polyelectrolytes are very different from those of more flexible polyelectrolytes or water soluble polymers, where a "pearl necklace" structure is normally thought to be formed at surfactant concentrations (critical aggregation concentrations) considerably below the surfactant cmc [16]. Small angle neutron scattering (SANS) studies [13], coupled with NMR measurements [17], suggest that this results from incorporation of PBS-PFP as isolated chains into long, wormlike micelles.…”