10.1021/la060519u.s001
Antti Viinikanoja
Antti
Viinikanoja
Sami Areva
Sami
Areva
Natalia Kocharova
Natalia
Kocharova
Timo Ääritalo
Timo
Ääritalo
Maarit Vuorinen
Maarit
Vuorinen
Arto Savunen
Arto
Savunen
Jouko Kankare
Jouko
Kankare
Jukka Lukkari
Jukka
Lukkari
Structure of Self-Assembled Multilayers Prepared from Water-Soluble
Polythiophenes
American Chemical Society
2006
3TOHIM
3TOPIM
side chain
surface number density
P 4Me
thiophene
AFM
PSS
poly
multilayer
film
2006-07-04 00:00:00
Journal contribution
https://acs.figshare.com/articles/journal_contribution/Structure_of_Self_Assembled_Multilayers_Prepared_from_Water_Soluble_Polythiophenes/3073147
We have studied the structure and morphology of self-assembled polyelectrolyte multilayers prepared using poly(styrenesulfonate) (PSS) and four different cationic poly(alkoxythiophene) derivatives bearing methylimidazolium-terminated ionic side chain at the 3-position of the thiophene ring: poly(1-methyl-3-[3-[3-thienyloxy]-propyl]-1<i>H</i>-imidazolium) (P3TOPIM), poly(1-methyl-3-[6-[3-thienyloxy]-hexyl]-1<i>H</i>-imidazolium) (P3TOHIM), poly(1-methyl-3-[2-[(4-methyl-3-thienyl)oxy]-ethyl]-1<i>H</i>-imidazolium ) (P4Me-3TOEIM), and poly(1-methyl-3-[6-[(4-methyl-3-thienyl)oxy]-hexyl]-1<i>H</i>-imidazolium ) (P4Me-3TOHIM). All the multilayers exhibited regular growth. The thickness
of the multilayers was measured with ellipsometry, their layer-by-layer growth was followed by polarization modulation
infrared reflection−absorption spectroscopy (PM-IRRAS) and ellipsometry, and the morphology of the films was
studied by atomic force microscopy (AFM). The length of the methylimidazolium-terminated side chain (C<i><sub>n</sub></i>, <i>n</i> = 2,
3, 6) and the substituent (H or Me) at the 4-position of the thiophene ring were varied. All multilayers were inhomogeneous
in the sub-micrometer scale and contained aggregates of two kinds. The large ones with a low and constant surface
number density were attributed to PSS, whereas the small aggregates were polythiophene-based. The surface density
of these organic semiconducting nanoparticles greatly depended on the structure of polythiophene, being favored by
polymer regioregularity and the length of the side chain. The side chains remained disordered in all the multilayers,
but with polythiophenes having hexyl chains both the imidazolium and thiophene rings tended to orient themselves
more perpendicular to the surface than in films containing shorter chains (C<sub>2</sub> or C<sub>3</sub>). The relative water content of
the multilayers (at 7.1% relative humidity) did not depend on the film thickness and was the lowest for P4Me-3TOHIM.
As the number of bilayers increased the methylimidazolium−sulfonate ion pairs gradually weakened and became more
individually hydrated.