Cansel Tuncer

pH-Responsive polymers

In this review, we provide an analysis of some of the recent literature reports on the synthesis and applications of pH-responsive polymers. Depending on the solution pH, such copolymers can self-assemble and form various nanosized structures including core–shell micellar structures, micelles/reverse micelles, hollow spheres, vesicle structures, adsorbed species at the water–air interface, and more complex architectures. Their self-assembly behaviors open the door for the production of various novel nanostructures including shell/core cross-linked micelles, hollow spheres, hydrogels, microgels, layer-by-layer (LbL) nanofilms, controlled releasing systems, drug carrier systems, etc. The review consists of various major parts including types of pH-responsive polymers, synthetic methods for their synthesis and their solution behaviors, their nanostructures in aqueous media, applications as LbL nanofilms, delivery devices, controlled release systems, sensors, stabilizers, solubilizers, etc. In the last two decades, there have been great developments in synthetic methods and strategies for the preparation of novel pH-responsive polymers or polymeric materials providing possible materials for various applications including biotechnology, nanotechnology, colloid and surface science, materials science, etc.

Novel Multiresponsive Microgels: Synthesis and Characterization Studies

The dispersion polymerization of 2-(N-morpholino)ethyl methacrylate (MEMA) in the presence of ethylene glycol dimethylacrylate (EGDMA) cross-linker and diblock copolymer stabilizer in n-hexane afforded sterically stabilized multiresponsive PMEMA microgels. By changing the reaction parameters, a wide range of particle sizes (120-720 nm) was obtained. Both dynamic light scattering and electron microscopy studies confirmed monodisperse spherical morphologies. These microgels had a response to the solution pH, temperature, and ionic strength. As expected, PMEMA microgels acquired cationic character at low pH because of the protonation of all morpholino groups. Although PMEMA microgels are in a swollen state in both acidic media and at low temperatures, they are in a deswollen state in basic media at high temperatures and in the presence of electrolytes above pH 6. In addition to these multiresponsive behaviors, PMEMA microgels have the ability to swell in various organic solvents. They also interact very well with magnetic particles and gain responsiveness to the magnetic field. Multiresponsive behaviors of PMEMA microgels were investigated by using DLS, UV-vis spectrophotometry, and zeta potentiometry.

Characterization of PDPA-b-PDMA-b-PDPA triblock copolymer Langmuir-Blodgett films for organic vapor sensing application

ABSTRACT This study reports the synthesis, characterization, and gas sensing applications of the PDPA-b-PDMA-b-PDPA triblock copolymer material using NMR, UV-visible spectroscopy, atomic force microscopy (AFM), quartz crystal microbalance (QCM), and Langmuir-Blodgett (LB) thin film deposition techniques. The thin film deposition conditions of the copolymer material, which are prepared by LB film technique, are characterized by UV-visible spectroscopy, AFM, and QCM system. In this study, the swelling behaviors of the PDPA-b-PDMA-b-PDPA triblock copolymer Langmuir-Blodgett (LB) films were investigated with respect to volatile organic compounds (VOCs) at room temperature. The sensing responses of the films against VOCs were measured by QCM method. The swelling processes could be investigated using the early-time Ficks law of diffusion.

Synthesis and characterization of water-insoluble statistical copolymer and its application in the development of electrochemical DNA sensor

Water-insoluble statistical copolymer was synthesized by copolymerization of methyl methacrylate (MMA) with 2-(dimethylamino)ethyl methacrylate (DMA) via group transfer polymerization (GTP). The DMA residues of the precursor P(MMA-co-DMA) statistical copolymer were then quaternized by reacting with methyl iodide under mild conditions to get well-defined P(MMA-co-QDMA) cationic copolymer. Then, P(MMA-co-QDMA) copolymer was successfully used for surface modification of pencil graphite electrode (PGE) to develop a disposable DNA sensor. This P(MMA-co-QDMA) copolymer modified electrode (q-PGE) was examined for electrochemical monitoring of DNA by using differential pulse voltammetry (DPV) in contrast to unmodified one. The effect of both DNA concentration and sonication time was also examined based on the response of q-PGE. The detection limit was calculated to be 8.06 μg/mL at q-PGE. Electrochemical impedance spectroscopy (EIS) was used for the characterization of the surface modification of q-PGE and consequently, the results were found to be in good agreement with the voltammetric measurements.

Use of Sulfobetaine-Based Block Copolymer as Stabilizer in Silver Nanoparticle Production and Catalytic Activity Studies

A zwitterionic sulfobetaine-based diblock copolymer was successfully synthesized and used in the preparation and stabilization of Ag nanoparticles (AgNPs). For the related block copolymer, a precursor AB type diblock copolymer was synthesized via atom transfer radical polymerization by using a MPEG-based ATRP macroinitiator and 2-(N-dimethylamino)ethyl methacrylate (DMA) comonomer. Tertiary amine residues of PDMA blocks in poly(ethylene glycol) methyl ether-b-poly[2-(N-diethylamino)ethyl methacrylate] (MPEG-b-PDMA) precursor was then converted to polybetaine structures by reacting with 1,3-propanesultone to obtain poly(ethylene glycol) methyl ether-b-poly[3-dimethyl(methacryloyloxyethyl) ammonium propane sulfonate] (MPEG-b-PβDMA) derivative. The resulting block copolymer was successfully used as stabilizer in the chemical and sonochemical synthesis of spherical AgNPs with a diameter in the range of 7.9-9.3 nm. The average diameter of AgNPs synthesized by sonochemical method was smaller than those synthesized by chemical method. The MPEG-b-PβDMA diblock copolymer was determined to be a good stabilizer for AgNPs. The AgNPs dispersion was stable for more than 5 months without any flocculation at room temperature. The catalytic activity of polymer-AgNP dispersion was also investigated in the reduction of p-nitrophenol to p-aminophenol and was found to be quite effective.

Optimization of a biosurfactant production from bacteria isolated from soil and characterization of the surfactant / Topraktan izole edilen bakterilerden biyosurfaktan üretiminin optimizasyonu ve surfaktanın karakterizasyonu

Abstract Objective: Biosurfactants are surface-active substances produced by microorganisms. The growth of microorganism supports biosurfactant production on hydrocarbon polluted environments. In this study, the capacity of biosurfactant production of Georgenia daeguensis (accession number, KP798810) isolated from hydrocarbon- contaminated soil was studied. Methods: The components of biosurfactant production medium were investigated through Plackett-Burman methodology. By using Placket-Burman based on statistical screening, six of the eleven factors of production medium were found to be critically effective on the biosurfactant production. Results: The significant factors were KCl, ZnSO4.7H2O, CaCl2.2H2O, KH2PO4, MgSO4.7H2O and glucose. Among of these, KCl had the highest effect contribution with 55.22%. After the optimization by such design, critical micelle concentration value was reached to 2.2 g L-1. When antibacterial activity of biosurfactant was screened, it showed antibacterial effect against to Klebsiella pneumoniae. Besides, the biosurfactant was characterized by FT-IR, critic micelle concentration and zeta analysis. Conclusion: This study reported that Georgenia daeguensis is able to produce effective biosurfactant exhibiting antibacterial activity against K. pneumoniae. Özet Amaç: Biyosurfaktanlar, mikroorganizmalar tarafından üretilen yüzey aktif bileşiklerdir. Hidrokarbonla kirlenmiş çevrelerde mikroorganizmanın gelişmesi biyosurfaktan üretimini destekler. Bu calışmada hidrokarbonca kirlenmiş topraktan izole edilen Georgenia daeguensis (giriş numarası, KP798810)’nin biyosurfaktan üretme kapasitesi calışılmıştır. Metod: Biyosurfaktan üretim ortamının bileşenleri Plackett- Burman metodolojisi kullanılarak değerlendirilmiştir. Istatistiksel taramaya bağlı Plackett-Burmankullanılarak, üretim ortamının 11 faktorden 6’sının biyosurfaktan üretiminde önemli ölcüde etkili olduğunu ortaya çıkarılmıştır. Bulgular: Önemli faktörler; KCl, ZnSO4.7H2O, CaCl2.2H2O, KH2PO4, MgSO4.7H2O ve glukoz olarak belirlenmiştir. Bunlarına arasından KCl, %55,2 ile en yüksek katkıya sahip olmuştur. Bu şekilde gerçekleştirilen optimizasyon sonrası, kritik misel konsantrasyonu 2,2 g L-1’ye ulaşmıştır. Biyosurfaktanın antibakteriyel aktivitesi değerlendirildiğinde Klebsiella pneumoniae’ye karşı antibakteriyel etkiye sahip olduğu gösterilmiştir. Bunun yanısıra, biyosurfaktan FTIR, kritik misel konsantrasyonu ve zeta analizi açısından da karakterize edilmiştir. Sonuç: Bu çalışma Georgenia daeguensis’in, K. pneumoniae’ye karşı antibakteriyel etki sergileyen etkili bir şekilde biyosurfaktan üretebildiğini bildirmektedir.

Production of CdS nanoparticles with different methods and their usage in waste-water treatment

I recent years, special attention has been given to the benefits of polymer nanocomposite technology to improve the inherent properties of biodegradable polymers. These materials are called “bionanocomposites”, and they provide a fascinating interdisciplinary research field that combines materials science, nanotechnology and biological science. The composites based on biodegradable polymers and different nanofillers with varying functionalities can lead to bionanocomposites with applications ranging from environmentally friendly packaging to automotive uses. Along with many interesting nanofillers, inorganic Transition Metal Dichalcogenide Materials (TMDCs), such as tungsten and Molybdenum Disulfides (WS2 and MoS2), are of interest to the scientific community because of their unique layered structure and functional properties, with nano-sized particles tending to exhibit a different set of properties compared to the bulk forms. TMDCs nanostructures can be zero-dimensional (0-D) (nanoparticles), one-dimensional (1-D) (nanotubes) or two-dimensional (2-D) (nanosheets). In particular, the use of environmentally friendly and biocompatible Inorganic Fullerene-like nanoparticles (IF-WS2) and nanotubes (INT-WS2) have been shown to offer design, processing, performance and cost advantages when compared to carbon nanotubes, nanoclays or other inorganic nanoparticles, for manufacturing advanced polymer nanocomposites. Incorporating of INT-WS2 into biopolymer can modify the crystallization behavior. The present research continues work in this field and focuses on the use of well-dispersed INT-WS2 for enhancing the processability and crystallization behaviour of poly(hydroxybutyrate-cohydroxyvalerate) (PHBV) (Figure 1). In particular, the effects of different INT-WS2 loadings on the isothermal and non-isothermal crystallization behavior of PHBV were studied in detail, using neat PHBV for comparisons.