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

Abstract

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-N 3 -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 (T g ) of 121.8 °C compared to P(AZO-N 3 -MA) (62.7 °C). This higher T g 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 T g played a crucial role in determining the success of the 2D SRG formation. These findings suggest that the polymers hold promise for applications in longlife 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.

Hydrogen Bonding-Mediated Supramolecular Blend for the Fabrication of Amplitude-Controllable Surface Relief Gratings

“…On the contrary, P­(iBMA- co -MA-T) presents the highest decomposition temperature and char yield among the polymethacrylates. These results may be attributed to the incorporation of thymine moieties, which can provide a physical cross-linked environment and substantially increase the difficulty to decompose . The multiple hydrogen bonding groups thus improve the thermal stability of the polymer, making it possible to operate under high-temperature conditions.…”

“…The most significant difference is that the T g of P­(iBMA- co -MA-T) became 132.1 °C, which was much higher than those of PiBMA and P­(iBMA- co -MA-N 3 ). We have reported before that T g may increase when the polymer is incorporated with thymine . However, the increased temperatures of P­(iBMA- co -MA-T) are still higher than those found in the past, indicating that the physical cross-linking effect provided by the multiple hydrogen bonding network should be more effective and thus restrict the motion of the polymer.…”

“…This study significantly improved the issue of low grating amplitudes formed by materials connected via supramolecular linkages, compared to the 7 nm grating amplitude reported in our previous study utilizing similar supramolecular materials design . This blended material also achieved a higher modulation depth than our recent findings with an azo-containing copolymer …”

“…SRGs were fabricated through the polarization holographic recording process outlined in our prior publication . The laser beam, with a power of 30 mW and a Gaussian distribution profile, was divided into two equal parts by using a beam splitter.…”

“…Polymer bearing hydrogen bonding motifs in side chains have been proven to become an efficient SRG material with high stability, as shown in our previous report . The key reason for the stability may be attributed to the high T g value after introducing multiple hydrogen bonding motifs with the enhancement of the interaction between polymer networks.…”