Current conduction in Schottky barrier diodes with poly(propylene glycol)-b-polystyrene block copolymer interfacial layer

Polymeric materials have gained great importance in electron devices. There has been considerable number of studies on block copolymers due to enhanced features that appear after co-polymerization. In this study, poly (propylene glycol)-b-polystyrene block copolymer has been synthesized and Schottky barrier diodes (SBDs) have been fabricated with this block copolymer. Current-voltage (I-V) measurements have been conducted at room temperature in order to investigate electrical characteristics and current conductions governing in these SBDs. Series resistance and shunt resistance of the SBDs have been calculated using Ohm’s law. Ideality factor, reverse saturation current and zero-bias barrier height of the SBDs have been extracted from the forward-bias I-V data. Fabricated SBDs exhibited high rectifying ratio of the order 104. Also, current conduction mechanisms and the density of interface states in the SBDs have been investigated. Calculated values of density of interface states in the SBDs are on the order of 1013 which is acceptable for this kind of SBDs having polymeric interfacial layer

Synthesis and characterization of cryogels of p(HEMA-N-vinylformamide) and p(HEMA-N-Vinylpyrrolidone) for chemical release behaviour

Macroporous polymeric gels has received great attention in many fields focused on biotechnological applications. In this study, two new HEMA-based cryogel columns were synthesized. To this end, poly(HEMA-VF) and poly(HEMA-NVP) cryogels were prepared by copolymerization of 2-Hydroxyethyl methacrylate (HEMA) with N-vinylformamide (VF) and N-vinylpyrrolidone (VP) in the presence of N,N-methylenebisacrylamide (as cross-linker), then polymerization initiated by ammonium persulfate (APS) and N,N,N ',N '-tetramethylenediamine (TEMED) with free-radical polymerizations method in cryogelation conditions, respectively. p(HEMA-VF) and p(HEMA-VP) cryogels contain a continuous polymeric matrix with interconnected pores of size 2-100 mu m. Swelling behavior for these cryogels in various solvents was investigated, wherein the characterization of the cryogels is conducted via by surface area measurement (BET), Fourier transforms infrared spectroscopy (FT-IR), elemental analysis, scanning electron microscopy (SEM), Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). As drug model compounds, Methyl Red (MR), methylene blue (MB) and methylene green (MG) were loaded into prepared cryogels and the controlled release properties of cryogel columns were examined comparatively each other. It has been shown that approximately 90% of its release from the cryogels occurred within about 2 h. In addition, MB release from p(HEMA-VF) and p(HEMA-VP) cryogels was found to be around 80% over a similar period. The proposed cryogels can be regarded as controlled release system on future biomedical applications.Duzce University Research FundDuzce University [2019.05.03.1024]This work was supported financially by the Duzce University Research Fund (Grant Number 2019.05.03.1024).WOS:0006143196000012-s2.0-8510029336

Synthesis and characterization of star-shaped block copolymers composed of poly(3-hydroxy octanoate) and styrene via RAFT polymerization

This study investigated a macro reversible addition fraction chain transfer (RAFT) agent based on three-arm hydroxylated star-shaped poly(3-hydroxy octanoate). The utilization of this star-shaped poly(3-hydroxy octanoate) macro-RAFT agent in the RAFT process resulted in efficient control in the preparation of star-shaped block styrene copolymers. Poly(3-hydroxy octanoate) (PHO) was reacted with diethanol amine (DEA) in order to obtain three-arm hydroxylated poly(3-hydroxy octanoate) (PHO-DEA). A carboxylic acid-functionalized RAFT agent (2-(dodecylthiocarbonothioylthio)-2-methylpropionic acid) was reacted with the PHO-DEA in order to obtain a star-shaped PHO macro-RAFT agent (PHO-R2). A series of AB3 type PHO-polystyrene (PHO-PS) star-shaped block copolymers were obtained via the polymerization of styrene (S) using the PHO-R2 in toluene at 80 °C. The RAFT polymerization was seen to obey the polymerization kinetics of controlled free radical polymerization. The plasticizing effect of the PHO soft segments was influenced by the glass transition temperature (Tg) of polystyrene. This was clearly observed in the block copolymers. Moreover, it was clear that this plasticizing effect disappeared in the block copolymers as a result of the increase in polymerization time. The molar masses of the obtained copolymers increased in parallel with increases in the polymerization time. Structural, physiochemical, and thermal characterization of the obtained products was carried out using size-exclusion chromatography (SEC), proton nuclear magnetic resonance (1H NMR), differential scanning calorimetry (DSC), and thermal gravimetric analysis (TGA) techniques. The polymerization kinetics of the star-shaped block copolymers were also investigated in detail

One-pot PolimerleşmeYöntemiyle Poli(linoleik asit)-g-Poli(N-isopropilakrilamit)-g-Poli(D,L-laktid) Graft Kopolimerlerin Sentezi ve Karakterizasyonu

Bu çalışmada, Otookside polimerik linoleik asit peroksit (PLina)’nın halka açılma polimerizasyonu ve serbest radikal polimerizasyonu bir arada kullanılarak tek adımda (one-pot) üç bloklu graft kopolimerler sentezlendi. Poli(linoleik asit)-g-poli(N-isopropilakrilamit)-g-poli(D,L-laktid) yapısına sahip graft kopolimerler; PLina’nın ana zincirinde bulunan peroksit grupları ile N-isopropilakrilamit (NIPAM) monomeriyle serbest radikal polimerizasyonu ve PLina’nın karboksilik asit grupları ile D,L-laktid (LA) monomeri arasındaki halka açılma polimerizasyonunun bir arada (one-pot) kullanılmasıyla sentezlendiler. One-pot polimerizasyon reaksiyonuna etki eden polimerizasyon süresi, başlatıcı konsantrasyonu ve monomer konsantrasyonu gibi temel parametreler incelendi. Elde edilen graft kopolimerlerin karakterizasyonları 1H NMR ve GPC teknikleri kullanılarak yapıldı

Halka Açılma Polimerizasyonuyla Poli(linoleik asit)-g-Poli(ε-kaprolakton) ve Poli(linolenik asit)-g-Poli(ε-kaprolakton) Graft Kopolimerlerin Sentezi ve Karakterizasyonu

Bu çalışmada, linoleik asit (Lina) ve linolenik asit (Linl)’ler otooksidasyona uğratılarak polimerik linoleik asit peroksit (PLina) ve polimerik linolenik asit peroksit (PLinl) elde edildi. Lina ve Linl’lerin otooksidasyonu hava ortamında oda sıcaklığında gerçekleştirilerek % 1.10-1.20 peroksit içeren, % 98 çözünür kısımlarına sahip yapıları elde edildi. Biyobozunur poli(linoleik asit)-g-poli(ε-kaprolakton) ve poli(linolenik asit)-g-poli(ε-kaprolakton) graft kopolimerler, otookside olmuş linoleik asit ve linolenik asit’lerin karboksilik asit grupları ile  ε-kaprolakton monomeri arasındaki halka açılma polimerizasyonuyla elde edildiler. Poli(linoleik asit)-g-poli(ε-kaprolakton) ve poli(linolenik asit)-g-poli(ε-kaprolakton) graft kopolimerlerin instristik viskozite değerleri belirlendi. Elde edilen graft kopolimerlerin karakterizasyonları 1H NMR, FT-IR,  TGA, DSC ve GPC teknikleri kullanılarak yapıldı

Biodegradable Poly(epsilon-Caprolactone)-Based Graft Copolymers Via Poly(Linoleic Acid): In Vitro Enzymatic Evaluation

WOS: 000350563400016Well-defined graft copolymers based on poly(epsilon-caprolactone) (PCL) via poly(linoleic acid) (PLina), are derived from soybean oil. Poly(linoleic acid)-g-poly(epsilon-caprolactone) (PLina-g-PCL) and poly(linoleic acid)-g-poly(styrene)-g-poly(epsilon-caprolactone) (PLina-g-PSt-g-PCL) were synthesized by ring-opening polymerization of epsilon-caprolactone initiated by PLina and one-pot synthesis of graft copolymers, and by ring-opening polymerization and free radical polymerization by using PLina, respectively. PLina-g-PCL, PLina-g-PSt-g-PCL3, and PLina-g-PSt-g-PCL4 copolymers containing 96.97, 75.04 and 80.34 mol% CL, respectively, have been investigated regarding their enzymatic degradation properties in the presence of Pseudomonas lipase. In terms of weight loss, after 1 month, 51.5 % of PLina-g-PCL, 18.8 % of PLina-g-PSt-g-PCL3, and 38.4 % of PLina-g-PSt-g-PCL4 were degraded, leaving remaining copolymers with molecular weights of 16,140, 83,220 and 70,600 Da, respectively. Introducing the PLina unit into the copolymers greatly decreased the degradation rate. The molar ratio of [CL]/[Lina] dramatically decreased, from 21.3 to 8.4, after 30 days of incubation. Moreover, reduced PCL content in PLina-g-PSt-g-PCL copolymers decreased the degradation rate, probably due to the PSt enrichment within the structure, which blocks lipase contact with PCL units. Thus, copolymerization of PCL with PLina and PSt units leads to a controllable degradation profile, which encourages the use of these polymers as promising biomaterials for tissue engineering applications.Turkish Scientific Research CouncilTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [110T884, 211T016]; Bulent Ecevit University Research FundBulent Ecevit University [2012-17-21-03]This work was supported financially by the Turkish Scientific Research Council (Grants Numbers: 110T884, 211T016) and Bulent Ecevit University Research Fund (Grant Number: 2012-17-21-03)

One-step preparation of poly(NIPAM-pyrrole) electroconductive composite hydrogel and its dielectric properties

Conductive polymers and hydrogels are two of the hot prospect polymer types that are used for new stimuli responsive materials. In this study, one-step preparation of electroconductive composite hydrogels containing polypyrrole (PPy) and N-isopropylacrylamide (NIPAM) using free radical polymerization technique was achieved with N,N-methylenebisacrylamide as a crosslinker and ammonium peroxy disulphate (APS) as initiator, in mixture of water/isopropyl alcohol. The equilibrium swelling degree of the poly(NIPAM)-pyrrole) electroconductive composite hydrogel was 9.88 g of H2O/g dry polymer. According to TGA results, the thermal stability of the prepared composite poly(NIPAM-PPy) conductive hydrogel (700 degrees C) hydrogel is higher than that of pure poly(NIPAM) hydrogel (600 degrees C). Furthermore, prepared samples were characterized by FTIR, and SEM analyzes. Later, the samples were pressured into pellets so that electrical impedance spectroscopy (EIS) measurements were taken between 10 and 10 MHz at room temperature. The dielectric constant value of composite poly(NIPAM-PPy) hydrogel at 10 Hz is almost 10 times higher than that of poly(NIPAM) hydrogel. Both samples' real and imaginary parts of dielectric constant decreased with increased frequency. Samples exhibited non-Debye relaxation since experimental data fit into dielectric model of Havriliak-Negami. Moreover, low frequency data yielded d.c. conductivity of the pure and composite samples as 3.74 x 10(-11) and 1.02 x 10(-8) S/cm, respectively. Real part of impedance at low frequencies also points out similar to 10(3) times lower resistance values at 10 Hz for composite poly(NIPAM-PPy) hydrogel. Therefore, EIS results support that electroconductive composite hydrogel fabrication was achieved using free radical polymerization technique.Duzce Universitesi [2019.05.03.1024]Duzce Universitesi, Grant/Award Number: 2019.05.03.1024WOS:0006146009000012-s2.0-8510033935

Dielectric properties of CdSe quantum dots-loaded cryogel for potential future electronic applications

Cryogels are an outstanding class of materials with special and functionalized physical properties in various fields and privileges for different industrial applications. Due to unique properties of quantum dots, properties of cryogels can be engineered by adding quantum dots in. In this study, both p(HEMA)-based cryogel and CdSe QDs synthesized and characterized, separately. Then, CdSe QDs were loaded into p(HEMA) cryogels by immersing cryogel into QDs solutions. FTIR-ATR, SEM and TGA characterizations were performed to ensure that CdSe QDs penetrate p(HEMA) cryogels effectively. Dielectric properties of CdSe QDs-loaded cryogel were investigated using Electrical Impedance Spectroscopy (EIS). Real and imaginary parts of dielectric constants were decreased significantly at low frequencies in QD-loaded cryogels. While real part of impedance was increased in CdSe QDs-loaded cryogel at low frequencies. In addition, at high frequencies, those parameters were observed to be same in both cases.Duzce University Scientific Research Project (DUBAP)Duzce University [2017.06.03.592]Authors kindly would like to thank Duzce University Scientific Research Project (DUBAP) Coordination for the support with the project number of 2017.06.03.592.WOS:0005626794000072-s2.0-8508750832

Comparison of Electronic Parameters of Low Voltage Organic Field-Effect Transistors with Novel Gel Gate Insulators

WOS: 000469369800012In this paper, regioregular poly(3-hexylthiophene-2,5-diyl) (rr-P3HT)-based low voltage organic field-effect transistors (OFETs) with three kinds of non-ionic gel gate insulators (NIGIs) were fabricated and compared in terms of their electronic properties. One of the NIGI was prepared by mixing solution-processed poly(methyl acrylate) (PMA) with propylene carbonate (PC) until it becoming a gel state and same procedure was applied to the solution-processed copolymers of PMA called as P18 and P28. As a result, it was seen that fabricated OFETs could be operated at low voltages which is very significant property in order to manipulate the devices in low power electronic applications. On the other hand, it was noted that mobilities of the transistors were enhanced by reducing the effective capacitance (EC) of the NIGIs. This could be attributed to less charge carrier self-localization formation between the insulator-semiconductor interface when the EC was decreased. Furthermore, devices showed similar on-to-off current (I-ON/I-OFF) ratio which was good for using them in inverter applications. Besides, subthreshold swing (SS) for the P18 non-ionic gel OFET (NIGOFET) was the highest probably due to the less water-repellent chemical structure of the P18 NIGI.Duzce University Scientific Research Projects unitDuzce University [2017.07.02.621, 2015.05.03.381]This study was presented in the 5th International Conference on Materials Science and Nanotechnology For Next Generation (MSNG2018) which held between 4-6 October 2018 in Cappadocia Turkey. Furthermore, we appreciate the Duzce University Scientific Research Projects unit for providing us financial support under the Grant [2017.07.02.621] and [2015.05.03.381]

ULTRAVIOLET ILLUMINATION RESPONSIVITY OF THE Au/n-Si DIODES WITH AND WITHOUT POLY (LINOLENIC ACID)-G-POLY (CAPROLACTONE)-G-POLY (T-BUTYL ACRYLATE) INTERFACIAL LAYER

Au/n-Si (MS) and Au/Poly (linolenic acid)-g-poly (caprolactone)-g-poly (t-butyl acrylate) (PLilPCLPtBA)/n-Si (MPS) diodes were fabricated to investigate the electrical and responsivity effects of interfacial layer on the diodes under ultra violet (UV) illumination. Electrospinning method was used for coating of the PLilPCLPtBA polymer layer on n-Si single crystal as nanofibers. Surface formation and nanofiber characteristics of the polymer layer were investigated by an electron microscope. The current-voltage (I-V) measurements of the MS and MPS diodes were carried out in dark and under UV (365 nm) illumination conditions at room temperature. Basic electrical parameters of the diodes; such as reverse bias saturation current (I-0), zero bias barrier height (Phi(B0)), ideality factor (n), series resistance (R-s) and interface state density (N-ss) were extracted from the experimental I-V measurements by thermionic emission and Norde equations. Also, power law of the photocurrents (I-pc) and responsivity (R) behavior were obtained and given comparatively.Duzce University Research FundDuzce University [2014.05.02.260, 2015.05.03.381, 2018.05.03.681]This work is supported by Duzce University Research Fund Project Number: 2014.05.02.260, 2015.05.03.381, 2018.05.03.681.WOS:0005691284000082-s2.0-8509007047