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    Cholesterol functionalized linear Poly(ε-caprolactone) polymers: Effects of chain length on mesomorphic and dielectric properties
    (Elsevier Science Sa, 2025) Doganci, Merve Dandan; Davarci, Derya; Uner, Melek; Demir, Ahmet; Musatat, Ahmad Badreddin; Akdogan, Mustafa; Doganci, Erdinc
    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.
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    Synthesis and electrical characterization of poly[(linoleic acid)-g-(styrene)-g-(?-caprolactone)] graft copolymers as gate insulator for OFET devices
    (Wiley, 2023) Gurel, Murat; Cavus, Fatma Kosovali; Demir, Ahmet; Doganci, Erdinc; Alli, Abdulkadir; Alli, Sema
    This study reports a one-pot process used to synthesize poly[(linoleic acid)-g-(styrene)-g-(epsilon-caprolactone)] (PLina-g-PSt-g-PCL) graft copolymers. The process was carried out by combining the atom transfer radical polymerization of styrene with the ring-opening polymerization of e-caprolactone from polymeric linoleic acid having hydroxyl groups and bromine groups in the main chain. The characterization of the products was achieved using proton nuclear magnetic resonance, size-exclusion chromatography, Fourier transform infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry techniques. Subsequently, an organic field effect transistor (OFET) was fabricated with PLina-g-PSt-g-PCL graft copolymers as the insulator layer. Poly(3-hexylthiophene) (P3HT) was used as the active layer and prepatterned OFET substrates were used as the welding/discharge electrodes. To measure capacitance, an ITO/P3HT/PLina-g-PSt-g-PCL/Al structure was prepared using the same method. To obtain output and transfer current-voltage characteristics, electrical characterizations of OFET devices were conducted in darkness and an atmosphere of air. From a capacitance-frequency plot, the key characteristics of the devices, including the threshold voltage (V-Th), field effect mobility, and current on/off ratio (I-on/off), were derived. The fundamental electrical parameters in the fabricated OFET devices based on styrene concentration were thoroughly examined. It was observed that the produced PLina-g-PSt-g-PCL OFETs display positive device characteristics such as low V-Th, exceptional mobility, and I-on/off values. (c) 2023 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Industrial Chemistry.