Effects of molecular structures and solvent properties on the self-assembly of carbazole-based conjugated dendrimers by solvent vapor annealing

Abstract

The effects of molecular structures and solvent properties on the self-assembly behavior of carbazole-based conjugated dendrimers by solvent vapor annealing (SVA) were systematically studied. Different film morphology changes from three different carbazole dendrimers through annealing in tetrahydrofuran (THF) and hexane vapor, two solvents with approximately the same vapor pressure but different polarity, were observed. For the first generation dendrimer H1–BCz, the film morphology was changed from random single fibers to spherulites with a decrease of vapor pressure in THF vapor, while only curled fibers and dendrites formed in hexane vapor. For the second generation dendrimer H2–BCz, the film morphology was not changed at low vapor pressure conditions, only fibers formed in THF vapor and nano-sized needle-like aggregates formed at high vapor pressure in hexane vapor. For the second generation dendrimer H28 with n-octyl instead of tert-butyl as the surface groups, only dewetting took place. Through a comparative study of the morphologies and the spectra of the annealed films, we speculated that the molecule–solvent and molecule interactions dominate for H1–BCz films, the molecule–molecule interaction is predominant for H2–BCz films and the solvent–molecule interaction controls the dewetting process of H28 films.