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    Investigation of the Performance of Poly(Methyl-Acrylate) as a Gate Dielectric in Organic Thin-Film Transistors
    (Springer, 2020) Yardim, Tayfun; Demir, Ahmet; Alli, Sema; Alli, Abdulkadir; Yucedag, Ibrahim
    In this study, we present two regioregular poly(3-hexylthiophene-2,5-diyl) (rr-P3HT)-based top-gate bottom-contact configured organic thin-film transistors (OTFTs) using poly(alpha-methyl acrylate) (PMA) and poly(methyl methacrylate) (PMMA) polymers separately as gate insulators for comparison. In order to compare only the performance of the dielectrics, the other parts of the devices were kept qualitatively and quantitatively identical. Unlike PMMA, PMA is flexible, and flexibility is a desirable property for an OTFT. Thus, utilizing PMA can be advantageous if it supports higher performance of the transistor. In this respect, the electronic parameters of the fabricated devices were extracted from transfer and output characteristics to determine the performance of PMA in OTFT applications. Results showed that the mobility of the OTFT with PMA (PMA-OTFT) was nearly three times greater than that of the OTFT with PMMA (PMMA-OTFT), while the PMA-OTFT threshold voltage (V-TH) was slightly less than that of the PMMA-OTFT, which was likely because of the greater effective capacitance (C-EFF) of the PMA layer compared to that of the PMMA layer. This is the main advantage of the PMA. On the other hand, the major downside is found in the reduced on-to-off current (I-ON/I-OFF) and increased subthreshold swing originating from a huge off-current (I-OFF), implying the existence of a large gate leakage current. Increasing the thickness of the PMA layer could reduce such large gate leakage current. However, this would lead to additional increase in the OTFT operating voltage. Therefore, further studies are required to improve the insulating property of the PMA polymer in order to substitute it for the PMMA.
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    Synthesis and characterization of poly(linoleic-g-epsilon-caprolactone) graft copolymers via click reaction and ring-opening polymerization
    (Indian Acad Sciences, 2021) Alli, Sema
    Linoleic acid modified with auto-oxidation, hydroxylation, bromination and azidation was used to synthesis graft copolymers using omega-alkyne-terminated poly(epsilon-caprolactone) (alk-PCLs) via click reaction. In the first step, the polymeric linoleic acid (PLina) as macroinitiator was obtained by the autoxidation of linoleic acid. Hydroxylation of the PLina was then carried out using diethanolamine to produce hydroxylated polymeric linoleic acid (PLina-OH). The PLina-OH was chemically modified with 2-bromopropionyl bromide to obtain bromo-functionalized polymeric linoleic acid (PLina-Br). This macroinitiator was then modified with sodium azide, resulting in azide polymeric linoleic acid (PLina-N-3). In a parallel process, omega-alkyne-terminated poly(epsilon-caprolactone) (alk-PCLs) were prepared via ROP of the epsilon-caprolactone monomer in the presence of propiolic acid, 3-butyn-1-ol, 5-hexynoic acid, and propargyl alcohol as the precursors and tin(II) 2-ethyl hexanoate (Sn(Oct)(2)) as the catalyst. These preliminary steps involved the synthesis of azide and alkyne compounds capable of being linked together via the alkyne-azide cycloaddition reaction catalyzed by copper (Cu(I)), which led to poly(linoleic acid)-g-poly(epsilon-caprolactone) (PLina-g-PCL). The obtained polymers were characterized by proton nuclear magnetic resonance (H-1 NMR), Fourier-transform infrared (FTIR), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA) and elemental analysis.
  • Küçük Resim Yok
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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.