Publication: Selüloz ve dekstranın akrilatlarla kopolimerizasyonu
Abstract
SELÜLOZ VE DEKSTRANIN AKRİLATLARLA KOPOLİMERİZASYONU Selüloz ve dekstran üzerinde literatürde çok sayıda ve farklı yönlerde kopolimerizasyon çalışmaları bulunmaktadır. Bu çalışma, selüloz ve dekstranla yapılan iki bölümden oluşmaktadır selülozun etil akrilatla tek başlatıcı sistemi ile farklı monomer konsantrasyonlarında, glisidil metakrilatla ise farklı başlatıcı sistemleri ve farklı monomer konsantrasyonlarında yapılan kopolimerizasyon deneylerinden oluşmaktadır. ?-selülozun etil akrilatla graft kopolimerizasyonu, seryum(IV) başlatıcı sistemi ile gerçekleştirildi. Monomer konsantrasyonu [0.25-2.5M] aralığında değiştirildi. FTIR ile karakterize edilen kopolimerlerin graftlama parametreleri hesaplanarak, monomer konsantrasyonunun graftlama parametreleri üzerine etkisi incelendi. Kopolimerlerin termal analizleri yapılarak ?-selülozun termal özellikleri ile karşılaştırıldı. Kopolimerizasyonla ?-selülozun termal dayanıklılığının graft verimi arttıkça, arttığı gözlendi. Ayrıca kopolimerlerin taramalı elektron mikroskobu (SEM) görüntüleri alınarak kopolimerizasyonla ?-selülozun yüzeyinde meydana gelen değişiklikler tespit edildi. ?-selülozun önce glisidil metakrilatla kopolimerizasyonu farklı başlatıcı sistemlerinde sabit monomer konsantrasyonu (1M) ile yapıldı. Başlatıcı sistemi olarak azobis(siyanovalerikasit) ve seryum(IV)amonyum nitrat kullanıldı. Seryum(IV) tek başına, asitli ve bazlı ortamda olmak üzere üç değişik şekilde kullanıldı.. Elde edilen kopolimerler FTIR ile karakterize edildi. Spektrumlarda, monomerde bulunan C=C çift bağı ve epoksi grubunun farklı başlatıcı sistemlerinde nasıl değiştiği saptandı. Kopolimerlerin graftlanma parametreleri hesaplandığında en yüksek graft veriminin seryum(IV) le (tek başına) yapılan reaksiyonlarda elde edildiği belirlendi. Farklı başlatıcı sistemlerinde hazırlanan kopolimerlerin termal analizinde ise C=C çift bağı içerenlerin termal dayanıklılığının daha düşük olduğu gözlendi. Termal dayanıklılığı en yüksek kopolimer ise azobis(siyanovalerikasit)le sentezlenen kopolimer olarak tespit edildi. Ayrıca SEM görüntülerinde kopolimerizasyonla ?-selülozun yapısının tamamen değiştiği gözlendi. Tezin ikinci bölümünde, dekstranın 2-etilhekzil metakrilatla ve akrilamid ile kopolimerizasyonları yapıldı. Farklı reaksiyon şartlarında, farklı özelliklerde ürünler elde edildi. Amfifilik (zincirin bir kısmı hidrofilik, bir kısmı da hidrofobik) yapıda bir ürün elde etmek amacıyla dekstran 2-etilhekzil metakrilat kopolimerleri bazik ortamda (trietilamin) seryum(IV) başlatıcı sistemi ile çapraz bağlayıcı olarak etilen glikol dimetakrilat kullanılarak sentezlendi. Reaksiyonlarda farklı molekül ağırlıklarındaki dekstranlar kullanılarak molekül ağırlığın değişmesinin kopolimerlerin özelliklerine etkisi incelendi. Kopolimerlerin termal analizi yapıldı ve dekstranın termal özellikleri ile karşılaştırıldığında dekstranın termal dayanıklılığının kopolimerizasyonla arttığı gözlendi. Ayrıca kopolimerlerin SEM görüntüleri de alınarak dekstranın yüzeyindeki değişiklikler saptandı. Dekstran-akrilamid jelleri, başlatıcı olarak azobis(siyanovalerikasit), çapraz bağlayıcı olarak da N-metilenbisakrilamid kullanılarak sentezlendi. Elde edilen ürünlerin FTIR spektrumları alındı. Jeller, farklı monomer konsantrasyonlarında ve çapraz bağlayıcı miktarlarında sentezlenerek, bu parametrelerin şişme davranışına ve elastik özelliklerine etkisi incelendi. Monomer konsantrasyonu arttıkça çapraz bağ oranı düşmesine rağmen şişme miktarının azaldığı gözlendi. Aynı monomer konsantrasyonunda çapraz bağ miktarı düştükçe elastik modülün düştüğü ve şişme miktarının arttığı tespit edildi. Ayrıca dekstran-akrilamid ve akrilamid jellerinin SEM görüntüleri alınarak farklılıklar tespit edildi. Temmuz 2005 Suzan Abdurrahmanoğlu
COPOLYMERIZATION OF CELLULOSE AND DEXTRAN WITH ACRYLATES In the literature, there are many different studies made by cellulose and dextran. This study consists of two different parts. First part involved, graft copolymerization of ?-cellulose with ethyl acrylate, using single initiator system, and with glycidyl methacrylate using different initiator systems. Graft copolymerization of ?-cellulose with ethyl acrylate were made using cerium(IV) as initiator. Monomer concentration was varied in the range of [0.25-2.5M]. Copolymers were characterized by FTIR. Grafting parameters were calculated and effect of monomer concentration on the grafting parameters was determined. Thermal analyses of copolymers were made and results were compared with thermal properties of ?-cellulose. It was observed that after copolymerization thermal stability of ?-cellulose was increased with increasing grafting efficiency. Changes occurred on the structure of ?-cellulose were determined by SEM investigation. Graft copolymerization of ?-cellulose with glycidyl methacrylate was carried out, using different initiator systems at constant monomer concentration (1M). ACVA, and cerium(IV) (used with acid, with basis and alone) were used as initiator. Copolymers were characterized by FTIR. In spectrums of copolymers, it was observed changes of C=C double bond and epoxy group (came from monomer) after grafting. According to calculated grafting parameters, it was found that cerium(IV) (alone) is the most efficient system. Thermal investigation of copolymers were made by using TG and DSC instruments and results showed that copolymer prepared by using ACVA as initiator, is the most stable (thermally) than the others. C=C double bonds in the structure of copolymers decreased the thermal stability. SEM photographs showed that structure of ?-cellulose completely changed after copolymerization. In the second part of thesis, dextran-2-ethylhexyl methacrylate and dextran-acrylamide copolymers were prepared at different reaction conditions. Dextran-2-ethylhexyl methacrylate copolymers were prepared using cerium(IV) (in basic medium) as initiator, to obtain an amphiphilic product. EGDMA was used as crosslinking agent in the reaction. Copolymers were characterized by FTIR. Effect of molecular weight of dextran on the properties of copolymers was investigated by using different molecular weight of dextrans in reactions. Thermal properties of copolymers were determined and compared with those of dextran. It was found that thermal stability of dextran improved after copolymerization. It was observed from SEM photographs that there is a clear distinction between the structures of copolymers and dextran. Dextran-acrylamide gels were synthesized using ACVA as initiator and MBA as crosslinker. FTIR spectrums of gels were taken. Gel experiments were carried out at different monomer and crosslinker concentrations and effect of this parameter on the swelling and elastic properties of gel were investigated. Although amount of crosslinker was decreased as increasing of monomer concentration, amount of swelling were decreased. At the same monomer concentration, elastic moduli and amount of swelling were decreased while amount of crosslinker was decreased. Distinction between the structure of acrylamide and dextran -acrylamide gels were determined by SEM investigation. July 2005Suzan Abdurrahmanoğlu
COPOLYMERIZATION OF CELLULOSE AND DEXTRAN WITH ACRYLATES In the literature, there are many different studies made by cellulose and dextran. This study consists of two different parts. First part involved, graft copolymerization of ?-cellulose with ethyl acrylate, using single initiator system, and with glycidyl methacrylate using different initiator systems. Graft copolymerization of ?-cellulose with ethyl acrylate were made using cerium(IV) as initiator. Monomer concentration was varied in the range of [0.25-2.5M]. Copolymers were characterized by FTIR. Grafting parameters were calculated and effect of monomer concentration on the grafting parameters was determined. Thermal analyses of copolymers were made and results were compared with thermal properties of ?-cellulose. It was observed that after copolymerization thermal stability of ?-cellulose was increased with increasing grafting efficiency. Changes occurred on the structure of ?-cellulose were determined by SEM investigation. Graft copolymerization of ?-cellulose with glycidyl methacrylate was carried out, using different initiator systems at constant monomer concentration (1M). ACVA, and cerium(IV) (used with acid, with basis and alone) were used as initiator. Copolymers were characterized by FTIR. In spectrums of copolymers, it was observed changes of C=C double bond and epoxy group (came from monomer) after grafting. According to calculated grafting parameters, it was found that cerium(IV) (alone) is the most efficient system. Thermal investigation of copolymers were made by using TG and DSC instruments and results showed that copolymer prepared by using ACVA as initiator, is the most stable (thermally) than the others. C=C double bonds in the structure of copolymers decreased the thermal stability. SEM photographs showed that structure of ?-cellulose completely changed after copolymerization. In the second part of thesis, dextran-2-ethylhexyl methacrylate and dextran-acrylamide copolymers were prepared at different reaction conditions. Dextran-2-ethylhexyl methacrylate copolymers were prepared using cerium(IV) (in basic medium) as initiator, to obtain an amphiphilic product. EGDMA was used as crosslinking agent in the reaction. Copolymers were characterized by FTIR. Effect of molecular weight of dextran on the properties of copolymers was investigated by using different molecular weight of dextrans in reactions. Thermal properties of copolymers were determined and compared with those of dextran. It was found that thermal stability of dextran improved after copolymerization. It was observed from SEM photographs that there is a clear distinction between the structures of copolymers and dextran. Dextran-acrylamide gels were synthesized using ACVA as initiator and MBA as crosslinker. FTIR spectrums of gels were taken. Gel experiments were carried out at different monomer and crosslinker concentrations and effect of this parameter on the swelling and elastic properties of gel were investigated. Although amount of crosslinker was decreased as increasing of monomer concentration, amount of swelling were decreased. At the same monomer concentration, elastic moduli and amount of swelling were decreased while amount of crosslinker was decreased. Distinction between the structure of acrylamide and dextran -acrylamide gels were determined by SEM investigation. July 2005Suzan Abdurrahmanoğlu