Sami Valkama

Self-Organized nanostructures of poly(4-vinylpyridine), polyaniline and polyamides due to metal complexation.

Comb-shaped supramolecules are constructed using flexible polymers and semi-rigid conjugated undoped or doped conjugated polymers upon complexing Zinc dodecyl benzene sulphonate, Zn(DBS) 2 . Self-organized nanostructures are formed in the bulk due to competing attractive interactions (coordination or water mediated hydrogen bonding) and repulsive polar/nonpolar interactions, showing characteristic long periods of ca. 30 A.

Processible conducting nanoscale cylinders due to self-organized polyaniline supramolecules

Polyaniline sulphonates contain hydrogen bonding acceptor sites, which allow construction of supramolecules and self-organized structures. Here we have characterized the phase behavior of complexes of polyaniline, camphorsulphomc acid (CSA) and 4-hexylresorcinol (tires), PANI(CSA)(x)(Hres)(y), using small-angle X-ray scattering (SAXS) and electrical conductivity. A hexagonal cylindrical structure with period around 35 Angstrom allows plastication due to the flexible side chains. The conductivity of complexes increased when CSA or tires were added to the nominal complex PANI(CSA)(0.5) indicating that CSA and Hres can be co-solvents for PANI(CSA)(0.5).

Supramolecular guest-host systems: combining high dye doping level with low aggregation tendency

We demonstrate that the aggregation tendency of dye molecules in a host polymer can be significantly reduced by exploiting non-covalent interactions between the host polymer and guest dye molecules. Such interactions occur spontaneously with no need for chemical synthesis, and could thus be utilized to combine the ease of processing of traditional guest-host systems with the high dye concentrations achievable in covalently linked systems. We studied the aggregation properties of the common azo-dye Disperse Red 1 in polymers with different functional groups. Compared to a nonpolar polymer (polystyrene), dye aggregation tendency is substantially reduced in polar polymer matrices containing hydrogen-bond donating [poly(vinylphenol)] or hydrogen-bond accepting [poly(4-vinylpyridine)] functional sites. Furthermore, by forming a polyelectrolyte-dye complex [Disperse Red 1/poly(styrenesulfonic acid)], a dye monomer can be attached to approximately each polymer unit, resulting in dye concentration of 63 wt. %. Complexation through proton transfer was further studied by using a fluorescent dye 5-phenyl-2-(4-pyridyl)oxazole. Our results indicate that polymer-dye complexes could provide a facile route for new type of optical materials, with potential applications in various fields of optics and photonics.

Polymer-dye complexes: supramolecular route toward functional optical materials

We demonstrate that the aggregation tendency of dye molecules in a host polymer can be significantly reduced by exploiting non-covalent interactions between the host polymer and guest dye molecules. Such interactions occur spontaneously with no need for chemical synthesis, and could thus be utilized to combine the ease of processing of traditional guest-host systems with the high dye concentrations achievable in covalently linked systems. We studied the aggregation properties of the common azo-dye Disperse Red 1 in polymer matrices with different functional groups. The dye aggregation tendency is substantially reduced in a polar polymer matrix and, most importantly, by forming a polyelectrolyte-dye complex, a dye monomer can be attached to approximately each polymer unit. This indicates that polymer-dye complexes provide a facile route for new type of optical materials, which could lead to applications in various fields of optics and photonics.