Structure and "surfactochromic" properties of conjugated polyelectrolyte (CPE): surfactant complexes between a cationic polythiophene and SDS in water.
We report on the phase transitions, solution structure, and consequent effect on the photophysical properties of poly[3-(6-trimethylammoniumhexyl)thiophene] bromide (P3TMAHT) in aqueous sodium dodecylsulfate (SDS). Polythiophene was mixed with SDS or deuterated SDS to form P3TMAHT(SDS)(x) complex (x = the molar ratio of surfactant over monomer units) in D(2)O and studied by small-angle neutron and X-ray scattering (SANS/SAXS) and optical spectroscopy. At room temperature, P3TMAHT forms charged aggregates with interparticle order. The addition of SDS eliminates the interparticle order and leads to rod-like (x = 1/5) or sheet-like polymer-SDS aggregates (x = 1/2 to 1) containing rod-like (x = 1/5 to 1/2) or sheet-like (x = 1/2 to 1) polymer associations. Partial precipitation occurs at the charge compensation point (x = 1). Ellipsoidal particles without interparticle order, reminiscent of SDS micelles modified by separated polymer chains, occur for x = 2 to 5. Free SDS micelles dominate for x = 20. Structural transitions lead to a concomitant variation in the solution color from red (P3TMAHT) to violet (x = 1/5 to 1) to yellow (x > 2). The photoluminescence fingerprint changes progressively from a broad featureless band (x = 0) through the band narrowing and appearance of vibronic structure (x = 1/5 to 1) to the return to a blue-shifted broad emission band (x = 5). The polymer stiffness reaches a maximum for x = 1, which leads to minimization of the Stokes shift (0.08 eV). This work gives fundamental information upon how surfactant complexation can influence both the solution structure and photophysical properties of a water-soluble polythiophene.
Knaapila
Matti
M
Physics Department, Institute for Energy Technology, NO-2027 Kjeller, Norway. matti.knaapila@ife.no
Evans
Rachel C
RC
Garamus
Vasil M
VM
Almásy
László
L
Székely
Noémi K
NK
Gutacker
Andrea
A
Scherf
Ullrich
U
Burrows
Hugh D
HD
D002412:Cations; D004573:Electrolytes / Q000737:chemistry*; D015394:Molecular Structure; D011108:Polymers / Q000737:chemistry*; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry*; D013501:Surface-Active Agents / Q000737:chemistry*; D013876:Thiophenes / Q000737:chemistry*; D014867:Water
D002412:Cations; D004573:Electrolytes; D011108:Polymers; D013501:Surface-Active Agents; D013876:Thiophenes; D014867:Water; C066730:polythiophene; D012967:Sodium Dodecyl Sulfate