Faruk Yilmaz

Highly Fluorescent Pyrene-Functional Polystyrene Copolymer Nanofibers for Enhanced Sensing Performance of TNT.

A pyrene-functional polystyrene copolymer was prepared via 1,3-dipolar cycloaddition reaction (Sharpless-type click recation) between azide-functional styrene copolymer and 1-ethynylpyrene. Subsequently, nanofibers of pyrene-functional polystyrene copolymer were obtained by using electrospinning technique. The nanofibers thus obtained, found to preserve their parent fluorescence nature, confirmed the avoidance of aggregation during fiber formation. The trace detection of trinitrotoluene (TNT) in water with a detection limit of 5 nM was demonstrated, which is much lower than the maximum allowable limit set by the U.S. Environmental Protection Agency. Interestingly, the sensing performance was found to be selective toward TNT in water, even in the presence of higher concentrations of toxic metal pollutants such as Cd(2+), Co(2+), Cu(2+), and Hg(2+). The enhanced sensing performance was found to be due to the enlarged contact area and intrinsic nanoporous fiber morphology. Effortlessly, the visual colorimetric sensing performance can be seen by naked eye with a color change in a response time of few seconds. Furthermore, vapor-phase detection of TNT was studied, and the results are discussed herein. In terms of practical application, electrospun nanofibrous web of pyrene-functional polystyrene copolymer has various salient features including flexibility, reproducibility, and ease of use, and visual outputs increase their value and add to their advantage.

Thiophene Ended ϵ‐Caprolactone Conducting Copolymers and their Electrochromic Properties

ϵ‐Caprolactone was polymerized by ring‐opening polymerization (ROP), using thiophene methanol as the initiator and stannous octoate as the catalyst to yield poly(ϵ‐caprolactone) with a thiophene end group. Homopolymerization of thiophene functionalized poly (ϵ‐caprolactone) (PCL) was achieved by a constant current electrolysis method. Copolymerizations of PCL with thiophene and pyrrole were achieved in acetonitrile (ACN)‐tetrabutylammonium tetrafluoroborate (TBAFB) solvent‐electrolyte couple via constant potential electrolysis. Characterization of the samples were performed by nuclear magnetic resonance spectroscopy (NMR), cyclic voltammetry (CV), fourier transform infrared spectroscopy (FT‐IR) and scanning electron microscopy (SEM). Electrical conductivities were measured by the four‐probe technique. Spectroelectrochemical behavior of PCL/PTh film, which was deposited on ITO‐glass, was investigated by UV‐Vis Spectrophotometer. Furthermore, it is found to be an anodically coloring copolymer that electrochemically switches between gray‐blue oxidized state and pale red reduced state, exhibiting electrochromic behavior.

Controlled Synthesis of Block Copolymers Containing Side Chain Thiophene Units and Their Use in Electrocopolymerization with Thiophene and Pyrrole

Abstract This paper reports on the synthesis of conducting polypyrrole and polythiophene grafted block copolymers of methylmethacrylate (MMA) and 3‐methylthienylmethacrylate (MTM) by a multi‐step process. For this purpose, block copolymers of MMA and MTM were prepared by controlled radical polymerization using 1,1‐diphenylethene (DPE). Subsequently, polypyrrole and polythiophene sequences were grafted onto these block copolymers by constant potential electrolysis.

Synthesis and mesophase properties of block and random co-polymers of electroactive and liquid crystalline monomers

Homo-polymers and random co-polymers of electroactive and liquid crystalline monomers, namely 3-thienylmethyl methacrylate (MTM) and 6-(4-cyanobiphenyl-4′-oxy)hexyl acrylate (LC6), were prepared by conventional free radical polymerization. Block co-polymers of MTM and LC6 were also synthesized by using the 1,1-diphenylethene (DPE) method. The obtained random and block co-polymers exhibited liquid crystal behavior depending on the content of the LC6 units. It was found that microphase separation of the polymer blocks is an effective means to stabilize the mesophase in the block co-polymers relative to compositionally similar random co-polymers

Newly synthesized poly(glycidyl methacrylate-co-3-thienylmethylmethacrylate)-based electrode designs for phenol biosensors

A newly synthesized poly(glycidyl methacrylate-co-3-thienylmethylmethacrylate) [poly(GMA-co-MTM)] was designed to fabricate various HRP electrodes for detection of phenol derivatives. The results showed that the poly(GMA-co-MTM)/polypyrrole composite film microarchitecture provided a good electroactivity as a result of pyrrole and thiophene interaction, and provided chemical bonds for enzyme immobilization via the epoxy groups of poly(GMA-co-MTM). The glassy carbon-based working electrode displayed significantly higher performance for the same composite film configuration comparing to the gold-based working electrode. Poly(GMA-co-MTM)/polypyrrole/HRP coated glassy carbon electrode exhibited a fast response less than 3s, a high sensitivity (200 nA microM(-1)for hydroquinone), a good operational stability (%RSD values ranged between 2 and 5.1 for all phenolics), a long-term stability (retained about 80% of initial activity at the end of 40th day) and a low detection limit ranging between 0.13 and 1.87 microM for the tested.

Influences of Injection Conditions on Strength Properties of Recycled and Virgin PBT/PC/ABS

Effect of conditions on the rheological and mechanical properties of virgin and recycled poly(butylene terephthalate)/polycarbonate/acrylonitrile-butadiene-styrene (PBT/PC/ABS) blends was investigated in injection molding by using Taguchis experimental design. PBT, PC, and ABS polymers were compounded in an extruder to obtain ternary blends. Blend was recycled five times. Injection pressure, holding pressure, and injection temperature were taken into consideration as the input. Ratio of signal-to-noise (S/N) was employed to determine whether optimum conditions of control inputs could be used to achieve the highest properties. Analysis of variance was used to determine how inputs affect outputs.

Recyclability of Polyethylene/Polypropylene Binary Blends and Enhancement of Their Mechanical Properties by Reinforcement with Glass Fiber

In this work, glass-fiber-reinforced and unreinforced polypropylene-polyethylene blends were obtained to examine the effects of recycling process on the mechanical and chemical properties. Tensile strength, flexural strength, izod impact strength, and melt flow index tests were applied to test specimens. After recycling process, the mechanical properties of both glass-fiber-reinforced and unreinforced polypropylene-polyethylene blends declined. Decrease of the mechanical properties of the recycled blends was supported by scanning electron microscopy morphologies revealed separation and degradation in matrix phase. It was observed that adding glass fiber in polypropylene-polyethylene led to the improvement in mechanical properties except impact strength.

Conducting Copolymers of Random and Block Copolymers of Electroactive and Liquid Crystalline Monomers with Pyrrole and Thiophene

Block and random copolymers having 3‐methyl thienylmethacrylate and 6‐(4‐cyanobiphenyl‐4′‐oxy)hexyl acrylate moieties were utilized as precursor polymers in this study. Electrochemical copolymerizations were performed in the presence of thiophene or pyrrole in acetonitrile‐tetrabutylammonium tetrafluoroborate (TBAFB) at constant potential. The characterizations were performed by cyclic voltammetry (CV), fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermal gravimetry analysis (TGA), scanning electron microscopy (SEM), conductivity measurements. Electrochromic properties of the resultant conducting copolymers were investigated by spectroelectrochemistry and colorimetry studies. It was observed that, variation in the copolymer type or composition of the precursor polymer resulted in stern effects on surface morphology, spectroelectrochemistry, color and conductivity of the resultant graft copolymer.

The effects of recycling process on thermal, chemical, rheological, and mechanical properties of PC/ABS binary and PA6/PC/ABS ternary blends

In this study, polycarbonate/acrylonitrile–butadiene–styrene (PC/ABS) and polyamide 6/PC/ABS (PA6/PC/ABS) blends were reprocessed (recycled) five times and the influences of multiple molding processes on the thermal, chemical, morphological, rheological, and mechanical properties of the recycled and virgin specimens were investigated. The impact strength, tensile properties (elastic modulus, strength, and strain at break), and flexural properties (modulus and strength) were measured to determine the mechanical properties of the blends. The rheology of the samples was evaluated via measuring the melt flow index (MFI). It was concluded that the chemical structures, melting temperatures, and thermal properties of both blends did not significantly change with recycling. From the mechanical tests, in general, it was found that increasing the number of recycling processes did not considerably alter the flexural properties and tensile strength of PC/ABS blends, but decreased their MFI and impact strength. On the other hand, the elastic modulus and tensile strength of PA6/PC/ABS decreased with the number of recycling processes, whereas MFI, flexural properties, and impact strength of the ternary blends improved.

Enzyme based phenol biosensors

Phenol and its derivatives is one of the most important parameters which should be monitored in environmental engineering. They are present in many wastewater streams of the oil, paint, paper, polymer and pharmaceutical industries. Phenolic compounds reach into the food chain by wastewaters then lead to dangerous and toxic effect on aquatic organisms. Principal standard methods for quantitative phenol measurement are high performance liquid chromatography (HPLC), electrochemical capillary electrophoresis (CE), gas chromatography (GC) and colorimetric spectrophotometry. Although, these methods are analytically capable, generally they require pretreatment processes such as extraction, cleaning, dilution of the samples as well as additional chemicals. Owing to those disadvantages, researchers have focused on enzyme based amperometric biosensors for measuring phenolic compounds due to their advantages such as good selectivity, working possibility in aqueous medium, fast responding, relatively low cost of realization and storage and the potential for miniaturization and automation. Amperometric biosensors, have been developing for phenol and its derivatives, are usually prepared with working electrodes which include polyphenol oxidases (PPO) (tyrosinase and laccase) and enzyme horseradish peroxidase (HRP). HRP reaction with phenols is faster than PPO enzyme reactions, and HRP-based working electrodes show higher sensitivity in comparison to PPO-based electrodes. Thus, the usage of HRP on working electrodes can be advised for fast and effective phenol measurements. The design of a support matrix that binds the enzyme and bare electrode can be target specific providing efficient electron transport via added functional groups or nanoparticles into the composite structure of the electrode. Conducting polymers as supporting matrix are usually used as copolymers or composite films in biosensor systems since mechanical and processing properties of their homopolymers are weak (Tsai & Chui, 2007; Heras et al., 2005; Carvalho et al., 2007; Serra et al., 2001; Mailley et al., 2003). Copolymerization does not require rigorous experimental conditions, and can be employed for the polymerization of a large variety of monomers leading to the formation of new advantageous materials (Boyukbayram et al., 2006; Kuwahara et al., 2005; Yilmaz et al., 2004; Yilmaz et al., 2005). Nanomaterials have also been used to improve the operational characteristics of biosensors (Yang et al., 2006; Zhou et al., 2007; Rajesh et al, 2005; Shan et al., 2007). This improvement