Poly(L-lactide) initiated by silver N-heterocyclic carbene complexes: synthesis, characterization and properties

WOS: 000325774400016Poly(l-lactide) (PLLA) was successfully synthesized by ring-opening polymerization (ROP) in bulk using silver N-heterocyclic carbene (Ag-NHC) complex. The effect of reaction time, temperature and monomer/initiator ratio on polymerization process were determined. The optimum conditions were found as 130 A degrees C, 4 h and M/I molar ratio of about 100. The polymers were characterized by FTIR, H-1-NMR, GPC and TG. High-molecular-weight PLLA (M (w) = 3.78 x 10(4), M (n) = 1.91 x 10(4), PDI = 1.97) was synthesized by the ROP of l-lactide (LLA) with bis-(N-methyl N'-dodecylimidazole) silver(I) di-bromo argentate (1a) in bulk. The effect of different N-substituted ligand groups on the polymerization was studied. The antimicrobial activity of the synthesized polymers were investigated by using minimum inhibitory concentration test against gram positive (Staphylococcus aureus) and gram negative (Escherichia coli and Pseudomonas aeruginosa). It was observed that the synthesized polymers displayed moderate antimicrobial activity.research foundation of Ege University-TurkeyEge University [2009 FEN035]This work was supported by the research foundation of Ege University-Turkey (No: 2009 FEN035). We thank Prof. Dr. Ates for determining antimicrobial activity of materials in microbiology laboratory. We also thank Dr. Kunduracioglu, Ege University-Turkey, for providing Ag-NHC samples

Computational determination of ring opening polymerization reaction mechanism of alpha-angelica lactone

WOS: 000447572000001In the present study, we investigated the ring opening polymerization of alpha-angelica lactone (AL) catalyzed by the tin (II) 2-ethylhexanoate, Sn(Oct)(2) through the coordination insertion mechanism by employing the semi empirical PM6, PM6-D3H4, PM7, and the DFT-B3LYP, B3LYP-D2 and omega B97X-D methods in both gas and solvent (toluene, THE, DMF and DMSO) media. The DFT calculations revealed that the initiation stage consists of three steps; a stable complex formation, a low energy conformational transformation and the ring opening. NBO analysis was conducted to explain the interactions between the electrophilic and nucleophilic centers. The omega B97X-D method gives the closest result (30.2 kcal/mol) to the experimentally found activation barrier (26.3 kcal/mol) for this system. Therefore, omega B97X-D has the best performance among all the methods studied here. The mechanism of the addition of a new monomer to the active chain, which constitutes the propagation stage of the polymerization, was further investigated and, as expected, a lower barrier compared to that of the initiation stage was obtained (14.5 kcal/mol). The PCM calculations revealed that the solvent did not affect the activation barrier. In addition, the enthalpy of ring opening polymerization of alpha-angelica lactone was calculated based on the initiation and propagation stages and the thermodynamics of the system was discussed.research foundation of Ege University-TurkeyEge University [2016 FEN 041]This work was supported by the research foundation of Ege University-Turkey (No: 2016 FEN 041). The DFT calculations reported in this study were performed at TUBITAK ULAKBIM, High Performance and Grid Computing Center (TRUBA resources)

Polyglycolide-montmorillonite as a novel nanocomposite platform for biosensing applications

WOS: 000411762600081In catalytic biosensors, the immobilization of biomolecules in a suitable matrix is one of the vital parameters for obtaining improved systems. Clays, which are intercalated with various organic compounds, have a great tendency to develop biosensors with high stability, sensitivity and reproducibility. Herein, a polymer/clay nanocomposite based on natural silicate montmorilonite (Mt) and a biodegradable polymer polyglycolide (PGA) was prepared and characterized by FT-IR, thermogravimetric analysis, differential thermogravimetric analysis and X-ray diffraction. Then, the resulting matrix was used as a fixation matrix for pyranose oxidase (POx), which was selected as a model enzyme. The bioactive layer was fabricated by immobilization of POx on glassy carbon electrodes by means of PGA-Mt and bovine serum albumin. The POx biosensor revealed a good linear range from 0.01 to 0.5 mM glucose with a LOD of 1.2 mM. After the optimization of the working and preparation conditions, characterization studies were performed for glucose detection. Finally, the PGA-Mt/POx biosensor was confirmed to have detected glucose in beverages without needing any sample pre-treatment.TUBITAK (Program for the University Students at undergraduate level Program) [TUBITAK-2209, 215Z194]; Ege University Research FundsEge University [2013FEN066]The authors also would like to thank TUBITAK (Program for the University Students at undergraduate level Program Number TUBITAK-2209 and Project number: 215Z194) and Ege University Research Funds (Project number: 2013FEN066). Dr D. O. Demirkol acknowledges The Turkish Academy of Sciences-Outstanding Young Scientists Award Program-2015 (TUBA-GEBIP). Authors thank to Assoc. of Prof. Dr Mustafa Can for his helps to take AFM images, Dr Murat Yavuz and Technician Sureyya Kacar (Dicle University Science and Technology Research and Application Center (DUBTAM)) for TEM images