Styrenation of triglyceride oil through controlled / living free radical polymerization

Bu çalışmada, kontrollü/yaşayan radikal polimerizasyon tekniklerinden biri olan tersinir katılma –bölüşme zincir transfer polimerizasyon (reversible addition – fragmentation chain transfer polymerization - RAFT) tekniği kullanılarak hava üflenmiş keten yağının stirenlenmesi gerçekleştirilmiştir. RAFT ajanı (Zincir transfer ajanı) olarak Fenasil Morfolin Ditiokarbamat (PMDC) kullanılmıştır ve polimerizasyonda uygun miktarı belirlenmiştir. RAFT ajanı miktarı, peroksit gruplarının oluşturacağı serbest radikaller esas alınarak hesaplanmıştır. Polimerizasyonda, değişen miktarlarda PMDC kullanılarak, miktarın ürün özellikleri üzerine etkisi incelenmiştir. Elde edilen sonuçlara göre, ortamda oluşan serbest radikallere ekivalent miktarda PMDC kullanıldığında polimerizasyonun kontrol edilebildiği ve dar molekül ağırlığı dağılımının sağlandığı görülmüştür. Ekivalent miktardan daha fazla PMDC kullanıldığında ise polidispersitenin daha da düştüğü gözlenmiştir. Elde edilen stirenlenmiş yağ örnekleri GPC ve FT-IR analizleri ile karakterize edilmiştir. Sonuç olarak RAFT polimerizasyon tekniği kullanılarak, polidispersitesi düşük (<1.5) ürünler elde edilmiştir. Bu yöntem ile elde edilen ürünlerin, klasik yöntemin tersine, homopolimer içermedikleri çapraz bağlı filmler üzerinden yapılan test ile anlaşılmıştır. Ayrıca elde edilen ürünlerin film özellikleri, ilgili standartlara göre incelenmiş ve klasik yöntem ile elde edilen ürünün film özellikleri ile karşılaştırılmıştır. Karşılaştırma sonucunda, RAFT tekniği kullanılarak elde edilen ürünlerin, klasik yöntem ile üretilene göre suya ve baza karşı daha dayanıklı oldukları ve kuruma süresinin daha kısa olduğu görülmüştür. Filmin daha kısa sürede kuruması yüzey kaplama endüstrisinde istenilen bir özelliktir. Ayrıca bu ürünlerin yapışma özelliği de klasik yöntem örneğine göre daha iyi çıkmıştır.  Anahtar Kelimeler: Stirenlenmiş yağ, kontrollü/yaşayan polimerizasyon, RAFT.Triglyceride oils owe their value as raw materials for decorative and protective coatings to their ability to polymerize and cross-link or dry after they have been applied to a surface, to form tough, adherent films. In order to obtain coating material having better performance in industry, oils are modified with various methods. Among these modified methods, copolymerization of oils with vinyl monomers such as styrene occupies an important place. In the classical styrenation process, homopolystyrene formation is likely to occur. The formation of homopolystyrene is not favor in product since the presence of homopolymer leads to weak film properties. By taking this fact into account, the methods by which homopolymerization was minimized and polymer structure was controlled, were previously developed in our laboratory. As a continuation of these studies, in this study, in order to obtain styrenated oil, air blowing linseed oil was copolymerized with styrene by the controlled / living radical polymerization technique (CLRP). CLRP is particularly appealing as it not only delivers polymers having a narrow molecular weight distribution with predetermined average molecular weight but also can be performed using normal radical procedures without the stringent experimental conditions required in living ionic polymerization. The most widely used controlled radical polymerization techniques are reversible addition fragmentation chain transfer polymerization (RAFT), nitroxide mediated polymerization (NMRP) and atom transfer radical polymerization (ATRP). Among of these techniques,  the RAFT polymerization has been considered a the most versatile and robust method, since it can be compatible with almost all monomers and reactions conditions that are applicable to conventional free radical polymerization. The RAFT process and its benefits are achieved simply by the addition of a suitable RAFT agent to the reaction medium. In this work, styrenated oil was obtained in three step. In the first step, the air was passed out through preheated linseed oil for 18 hours at 80 0C, thus, the peroxide groups on the oil triglyceride molecules created. Polymerization of oils is provided due to free radicals resulting in their decomposition. Peroxide value of oil was determined as 485 meq peroxide - oxygen/kg oil. In the second step, phenacyl morpholine dithiocarbamate (PMDC) was prepared in laboratory and used as RAFT agent, R and Z being phenacyl and morpholine, respectively. The structures of R and Z of the RAFT agent would exist in the chain ends of the final polymers. Thus, the end group of the polymer can be predesigned by choosing the RAFT agent with the desired structures. In the third step, air blown linseed oil was styrenated in the presence of PMDC under nitrogen atmosphere at 90 0 C. Temperature was kept constant with controlled heating. In order to investigate the effect of the RAFT agent amount on the copolymer, different amounts of the RAFT agent were used in the reaction. The characteristic properties of the samples such as molecular weight, polydispersity and molecular structure were determined by Gel Permeation Chromatography (GPC). The results show that, in the RAFT polymerization technique, when RAFT agent was used in the equivalent amount to the free radicals, products with low polydispersity were obtained while without homopolystyrene formation. Also when the amount of RAFT agent was excess than that of the equivalent to the free radicals, polydispersity became lower. In addition to these, polymer with higher molecular weight and higher conversion were obtained with increasing reaction time and polydispersity was still at low level.  For all that, three peaks were observed in GPC chromatograms. This is the expected result since the hydroperoxides decompose to give free radicals under blowing conditions. As a result this fact, chain propagation by coupling and abstraction reactions cause different molecular weight and ultimately leads to deviation from the unimodel shape. Besides, the oil-styrene copolymer structure was assigned by means of FT - IR measurements. The FT - IR spectrum of styrenated oil showed the characteristic bands of both styrene and initial oil segment. The film properties of the resulting sample was determined according to related standards as well. Copolymer of the oil with styrene was also prepared by conventional method and this sample were used as a comparative sample. The sample obtained with RAFT polymerization technique showed better alkali and water resistance and better adhesion and the shorter drying time than the classical sample which obtained in the absence of the RAFT agent..  Keywords: Styrenated oil, controlled/living polymerization, RAFT

Fabrication of a novel bone ash-reinforced gelatin/alginate/hyaluronic acid composite film for controlled drug delivery

In this study, a novel pH-sensitive composite film with enhanced thermal and mechanical properties was prepared by the incorporation of bone ash at varying concentrations from 0 to 10 v.% into gelatin/sodium alginate/hyaluronic acid (Gel/SA/HyA) polymeric structure for colon-specific drug delivery system. Films were characterized by FT-IR, SEM, and XRD analyses. Thermal and mechanical performances of films were determined by DSC, TGA and universal mechanical tester, respectively. Results proved that thermal stability and mechanical properties of bone ash-reinforced composite films improved significantly with respect to that of neat Gel/SA/HyA film. Cytotoxicity assay for composite films was carried out by using L929 cells. Water uptake capacity of films was determined by swelling test. Herein, release experiments of 5-Fluorouracil (5-FU) were performed in two different solutions (pH 2.1 and 7.4). The results assured that Gel/SA/HyA film containing BA could be considered as a potential biomaterial for controlled drug delivery systems. (C) 2016 Elsevier Ltd. All rights reserved

Oxygen-Generating Photocrosslinkable Hydrogel

Providing sufficient amount of oxygen to the cells is a critical issue since the lack of adequate oxygen leads to cell death and tissue necrosis. Therefore, there is a vital need to design and fabricate oxygen-generating biomaterials to mitigate hypoxia-induced cell death in engineered tissues. Here, we report the fabrication of an oxygen-generating hydrogel by incorporating calcium peroxide (CPO) into the methacrylated gelatin (GelMA) structure using photocrosslinking process. A sustainable release of oxygen could be provided from CPO-GelMA hydrogel over a period of 5 days under hypoxic conditions (1% O-2)

Bipolar membrane electrodialysis for mixed salt water treatment: Evaluation of parameters on process performance

In the present study, bipolar membrane electrodialysis (BMED) process was employed as an alternative separation method to the distillation unit in the Solvay process for the synthetic soda ash production. The applicability of BMED was investigated by evaluating the effects of system parameters on process performance. Desalination ratio, salt based acid and base conversion ratio, flux, product purity, and energy consumption were defined as the process performance criteria for the BMED systems. Initial salt concentration, applied current and voltage, and initial acid and base concentrations were chosen as system parameters. The results of the study revealed that current/voltage and initial salt concentration are the most effective factors affecting all performance criteria. When all system parameters were considered, BMED provides the desalination ratio in between 90% and 98%, the acid and base conversion ratio of salt in between 60% and 80%, and the energy consumption in the range of 1.54-2.33 kWh/kg acid. Furthermore, the desalinated water can be reused as process water and the distillation unit waste problem can be resolved by the utilization of BMED system

Electroconductive hyaluronic acid/gelatin/poly(ethylene oxide) polymeric film reinforced by reduced graphene oxide

Novel electroconductive polymeric films with enhanced mechanical performance were fabricated by encapsulating reduced graphene oxide (RGO) at different concentrations (0-50 vol %) into a hyaluronic acid/gelatin/poly(ethylene oxide) (HyA/Gel/PEO) polymeric structure. The obtained RGO-reinforced polymeric films were characterized by Fourier transform infrared and scanning electron microscopy analyses. Mechanical performances were measured with a universal mechanical testing machine. The results verified that the RGO reinforcement significantly enhanced the mechanical performances of the films. To determine the biocompatibility of the polymeric films, L929 (murine fibroblast) cell lines were used. The water uptake capacities were measured using swelling tests. A four-probe method was used to measure conductivity characteristics. The conductivity results indicated that HyA/Gel/PEO film containing 20 vol % RGO has the highest average electrical conductivity (1.832 x 10(-6) S/cm). All of the results demonstrated that the obtained electroconductive films could be used in biomedical fields in the future, especially in controlled drug release systems and tissue engineering. (c) 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 46905

Electrically controlled release of 5-fluorouracil from conductive gelatin methacryloyl-based hydrogels

Herein, electro-responsive hydrogels were obtained by incorporation of poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS) into the gelatin methacryloyl (GelMA) by using photopolymerization technique. Hydrogels were characterized by FTIR and scanning electron microscopy analyses. Cytotoxicity tests were performed by L929 cell lines to determine cell compatibility. Swelling tests were conducted to investigate the water uptake capacity of hydrogels. 5-fluorouracil (5-FU) was selected as a model drug as it is known as a topical drug for some skin cancer type treatment. The release of 5-FU from the hydrogel was provided in efficient and controlled manner at simulated skin cancer (pH = 5.5) and under 0 and 1.5 V. The simulated drug delivery experiments conducted in vitro revealed that the drug releasing amount was higher when voltage is applied to the hydrogels. All results visualized that the obtained GelMA-based PEDOT/PSS hydrogels with enhanced electrical properties could be a potential candidate as an electrically sensitive drug carrier for treatment of skin cancer in the future applications. (c) 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 46914

Production of reduced graphene oxide-based electrically conductive hydrogel by using modified chitosan

Herein, a new approach was applied to produce reduced graphene oxide (RGO)-based conductive hydrogel by using modified chitosan (CTS) as a primary constituent. A variety amounts of RGO (from 0 to 15%) were incorporated into the polymeric network generated by photopolymerization of CTS-graft-glycidyl methacrylate (CTS-g-GMA) and poly(ethylene glycol)diacrylate (PEGDA). The structures of hydrogels were confirmed by FT-IR, XRD, and SEM analyses. Water uptake capacity of hydrogels determined gravimetrically. L929 fibroblast cells were used for cytotoxicity test. According to conductivity measurements carried out by four-point probe technique, the highest conductivity (1.716 x 10(-3) S/cm) was obtained when 10% RGO was encapsulated into the polymeric structure. From the results, it could be envisaged that electroconductive hydrogel (ECH) fabricated in this study could have a potential usage for biosensor applications in the future projects. (c) 2019 Wiley Periodicals, Inc

Styrenated urethane oil synthesis via CuAAC click chemistry approach

In this study, a novel route for the modification of sunflower oil-based partial triglycerides with styrene (St) was described. For this purpose, in the first step, copolymers of St and 4-chloromethyl styrene (P(St-co-CMS)) were synthesized by free radical polymerization (FRP) and controlled/living radical polymerization (nitroxide mediated radical polymerization (NMRP)) methods. In the second step, chloro groups of these samples were transformed into azido groups by using NaN3/DMF and then azido groups were coupled with propargyl alcohol to achieve hydroxyl functional polystyrene chain (PSt-OH) via Cu(I)-catalyzed 1,3-dipolar azide-alkyne cycloaddition (CuAAC) click chemistry approach. Finally, alcohol groups of PSt-OH and the partial glyceride (PG) were combined by the reaction with toluene 2,4-diisocyanate (TDI). As a result, styrenated urethane oil (PG-TDI-PSt) was obtained as an oil-based binder. The structures were determined by FT-IR, H-1 NMR and GPC analyses, and film properties of the products were examined according to the related standards. (PG-TDI-PSt) gave good film properties, and therefore could be considered as an applicable oil-based binder. (C) 2015 Elsevier B.V. All rights reserved

Oxygen-Generating Photocrosslinkable Hydrogel

Providing sufficient amount of oxygen to the cells is a critical issue since the lack of adequate oxygen leads to cell death and tissue necrosis. Therefore, there is a vital need to design and fabricate oxygen-generating biomaterials to mitigate hypoxia-induced cell death in engineered tissues. Here, we report the fabrication of an oxygen-generating hydrogel by incorporating calcium peroxide (CPO) into the methacrylated gelatin (GelMA) structure using photocrosslinking process. A sustainable release of oxygen could be provided from CPO-GelMA hydrogel over a period of 5 days under hypoxic conditions (1% O-2)