Creating Supramolecular Functional Materials via Nucleobase Interaction: Investigating Molecular Recognition and the Fabrication of Surface Relief Gratings

The development of photoresponsive materials with excellent thermal properties and high formability is crucial for expanding their range of applications and addressing various challenges. In this study, we successfully synthesized and investigated the stimuli-responsive polymer P(AZO-T-MA), which contains azobenzene and thymine functionalities in its side chains along with its precursor polymer P(AZO-N3-MA). The chemical structures of the materials were corroborated through characterization methods such as Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR). Variable-temperature FTIR spectra of P(AZO-T-MA) revealed thermal-induced dissociation and association behaviors during heating and cooling processes, indicating its responsiveness to temperature changes. Isomerization degrees were calculated based on the absorption changes observed in ultraviolet–visible (UV–vis) spectra under UV irradiation. P(AZO-T-MA) exhibited efficient isomerization behavior and excellent surface relief grating (SRG) formability, achieving a modulation depth of over 800 nm at an appropriate film thickness. This value is relatively high for supramolecular materials. P(AZO-T-MA) exhibited a somewhat higher glass-transition temperature (Tg) of 121.8 °C compared to P(AZO-N3-MA) (62.7 °C). This higher Tg contributed to the better storage durability of SRG, as observed over 28 days. The fabrication of two-dimensional (2D) SRGs was also explored, and it was found that the material's Tg played a crucial role in determining the success of the 2D SRG formation. These findings suggest that the polymers hold promise for applications in long-life optical storage devices and the creation of complex architectural patterns. Their unique combination of thermal responsiveness, high formability, and storage durability makes them valuable materials for various optical applications.