Cholesterol functionalized linear Poly(?-caprolactone) polymers: Effects of chain length on mesomorphic and dielectric properties

Abstract

Cholesterol-functionalized linear poly (epsilon-caprolactone) (Chol-PCL) polymers with different chain lengths (n = 10, 20, 30, and 70) were successfully synthesized via a ring-opening polymerization reaction using cholesterol as initiator. Their structures were confirmed by 1H NMR and FT-IR spectroscopy, and their various dielectric properties were extensively investigated in a frequency range from 100 Hz to 1 MHz under different voltage conditions (0-20 V). The results revealed that all the obtained polymers have focal conic fan shape textures of the smectic phase, encouraging the mesomorphism. In particular, Chol-PCL30 showed superior dielectric performance and exhibited the highest capacitance values and optimal dielectric stability over the measured frequency spectrum. The study showed a non-linear relationship between the chain length of PCL and dielectric properties, with the medium chain length (n = 30) providing the most favorable molecular architecture for enhanced charge capability and dielectric response. Complex impedance analysis revealed a pronounced relaxation behavior as a function of chain length, with Chol-PCL30 showing the most pronounced impedance response. These results provide valuable insights into the structure-property relationships in cholesterol-modified PCL systems and their potential applications in dielectric materials. To address the limitations of existing dielectric materials and explore novel polymeric systems with enhanced electrical properties, cholesterol-functionalized linear poly (epsilon-caprolactone) (Chol-PCL) polymers were successfully synthesized with precisely controlled chain lengths (n = 10, 20, 30, and 70) via ring-opening polymerization using cholesterol as an initiator. Structural confirmation was achieved through 1H NMR and FT-IR spectroscopy. A comprehensive investigation into their dielectric properties, including capacitance, conductance, dielectric constant, dissipation factor, electrical modulus, and impedance, was conducted across a broad frequency range (100 Hz-1 MHz) under varying voltage conditions (0-20 V). All synthesized polymers exhibited focal conic fan shape textures characteristic of the smectic phase, indicating their mesomorphic nature. Notably, Chol-PCL30 demonstrated exceptional dielectric performance, exhibiting the highest capacitance values and notable dielectric stability across the measured frequency spectrum. This study revealed a significant non-linear correlation between the PCL chain length and the observed dielectric properties, with the medium chain length (n = 30) providing an optimal molecular architecture for enhanced charge storage capability and dielectric response. Furthermore, complex impedance analysis elucidated a pronounced relaxation behavior that was highly dependent on chain length, with Chol-PCL30 exhibiting the most significant impedance response. These findings offer crucial insights into the intricate structure-property relationships within cholesterol-modified PCL systems, paving the way for their potential application in advanced dielectric materials.