Unveiling mechanical, optical and conductivity properties in naphthalenediimide bridged polysilsesquioxane gels

Abstract

Organo-bridged polysilsesquioxanes (PSQ) incorporating photo-and electroactive motifs are promising candidates for optoelectronic and ion-conductive materials. We report the synthesis of PSQ gels incorporating redox-and photo-sensitive naphthalene diimide (NDI) units capable of self-assembly via π-π interactions. Two distinct synthetic routes were explored: the first offering simplicity and quick access to the targeted materials, the second being longer but bringing better control of their composition. The NDI-PSQ gels obtained by these two different routes were exhaustively characterized using rheology, XRD, fluorescence, spectroelectrochemistry, electrochemistry, impedance, NMR, and IR spectroscopy measurements. Both routes yield gels with similar morphological characteristics but exhibit notable differences in the aggregation modes of the NDI motifs. The NDI-PSQ gels exhibit dual emission states (λₑ = 450 and 550 nm) attributed to the coexistence of at least two distinct aggregate domains. The remarkable ionic conductivity of NDI-PSQ gels is also particularly interesting for considering applications in optoelectronics. Overall, this study provides new insights into the design and applications of redox/photo-responsive PSQ-based gels.