title: Guided in Situ Polymerization of MEH-PPV in Mesoporous Titania Photoanodes.
abstract: Incorporation of conjugated polymers into porous metal oxide networks is a challenging task, which is being pursued via many different approaches. We have developed the guided in situ polymerization of poly(2-methoxy-5-(2'-ethylhexyloxy)-p-phenylenevinylene) (MEH-PPV) in porous titania films by means of surface functionalization. The controlled polymerization via the Gilch route was induced by an alkoxide base and by increasing the temperature. The selected and specially designed surface-functionalizing linker molecules mimic the monomer or its activated form, respectively. In this way, we drastically enhanced the amount of MEH-PPV incorporated into the porous titania phase compared to nonfunctionalized samples by a factor of 6. Additionally, photovoltaic measurements were performed. The devices show shunting or series resistance limitations, depending on the surface functionalization prior to in situ polymerization of MEH-PPV. We suggest that the reason for this behavior can be found in the orientation of the grown polymer chains with respect to the titania surface. Therefore, the geometry of the anchoring via the linker molecules is relevant for exploiting the full electronic potential of the conjugated polymer in the resulting hybrid composite. This observation will help to design future synthesis methods for new hybrid materials from conjugated polymers and n-type semiconductors to take full advantage of favorable electronic interactions between the two phases.
authors.affiliation: Department of Chemistry and Center for NanoScience (CeNS), University of Munich (LMU), Butenandtstrasse 5-13, 81377 Munich, Germany.
authors.forename: Norma K
authors.initials: NK
authors.lastname: Minar
authors.affiliation: Department of Chemistry and Center for NanoScience (CeNS), University of Munich (LMU), Butenandtstrasse 5-13, 81377 Munich, Germany.
authors.forename: Pablo
authors.initials: P
authors.lastname: Docampo
authors.affiliation: Department of Chemistry and Center for NanoScience (CeNS), University of Munich (LMU), Butenandtstrasse 5-13, 81377 Munich, Germany.
authors.forename: Dina
authors.initials: D
authors.lastname: Fattakhova-Rohlfing
authors.affiliation: Department of Chemistry and Center for NanoScience (CeNS), University of Munich (LMU), Butenandtstrasse 5-13, 81377 Munich, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Bein
keywords: MEH-PPV; hybrid materials; in situ polymerization; mesoporous titania; nanocomposite; surface functionalization