Differential insights into structural dynamics and photophysical behavior of two phosphorus-containing diesters

Understanding the phase transitions and structural dynamics of monomers is essential for designing advanced materials. In this study, the phase transitions of two phosphorus-containing monomers with methoxycarbonyl functional end groups were investigated. Polarized light optical microscopy, differential scanning calorimetry, and UV-vis absorption and fluorescence spectroscopy were used to examine microstructural changes and molecular conformational rearrangements during temperature variations. Additionally, attenuated total reflectance Fourier-transform infrared spectroscopy was used to explore these changes with high sensitivity. The specific sensitive absorption bands offered significant information regarding the phase transition, even within a narrow transition temperature range, demonstrating the efficiency of such a method in the investigation of polymorphic and liquid crystalline materials. Interestingly, although both molecules absorb light at similar wavelengths regardless of the solvent, their emission properties are different, suggesting that the presence of an extra oxygen atom linked to the central phosphorus atom influences the movement of electrons in the excited state.