Polipirolün tiyenil uç gruplu poli (dimetilsiloksan) ile FeCl3 varlığında kopolimerizasyonu
Copolymerization of pyrrole and thienyl end capped poly(dimethylsiloxane) by iron (III) chloride
Yazar: DUYGU BADEMCİ
Danışman: PROF. NİLGÜN KIZILCAN
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Kimya Ana Bilim Dalı / Kimya Bilim Dalı
Derece: Yüksek Lisans, 2018
Konu: Kimya = Chemistry ; Kimya Mühendisliği = Chemical Engineering ; Polimer Bilim ve Teknolojisi = Polymer Science and Technology
Dizin: Blok kopolimerler = Block copolymers ; Kopolimerleşme = Copolymerization ; İletken kopolimerler = Conducting copolymers

Özet:
İletken polimerlerin elektriği neredeyse metaller kadar iyi iletmeleri, benzer elektronik ve optik özellikleri göstermeleri, korozyona karşı dayanıklı olmaları ve kolay yöntemlerle elde edilebilmeleri gibi başlıca avantajları bilim ve teknoloji alanındaki ilgiyi üzerlerine çekmelerini sağlamıştır. İlerleyen zaman içinde proses edilmelerindeki güçlükler uygulamada zorluklara sebep olmuş ve ticarileşmelerine engel oluşturmuştur. Dolayısıyla iletken polimer alanındaki yeni çalışmalar konjuge polimerlerin elektriksel özelliklerinden kaybetmeden aynı zamanda işlenebilir bir malzeme elde etmek üzere modifiye edilerek yeni kopolimerlerin dizaynı ve sentezi üzerine yoğunlaştı. 
Polipirol, iyi bir iletkenlik gösteren ve korozyona dayanıklı, kullanışlı bir iletken polimerdir. İkincil piller, elektrokromik görüntü cihazları, ışık yayan diyotlar (LEDs), kapasitörler, sensörler, membranlar ve enzim elektrotlar gibi geniş kullanım alanlarına yayıldıkça, polimerin özellikleri ile ilgili gelişmeler gözlenmeye başlandı. 
Polipirol, pirol monomerinin kimyasal redoks polimerizasyonu ile sentezlenebilir. Kimyasal oksidatif polimerizasyon için oksidant ve çözücü seçimi çok önemlidir. Potasyum persülfat (K2S208), hidrojen peroksit (H202), demir (III) ve seryum (IV) tuzları en çok kullanılan oksidantlardır. DMF (dimetil formamide) ve DMSO (dimetilsülfoksit) gibi yüksek donör numaralı solventler dışında protik ve aprotik birçok solvent bu reaksiyonda kullanılabilir. Machida ve diğ. (1989) tarafından yapılan çalışmada en yüksek iletkenlik değeri, solvent olarak metanol seçildiğinde ve oksidant olarak demir (III) klorür seçildiğinde 220 S/cm olarak bulunmuştur. Polidimetilsiloksan polisiloksanlar arasında en yaygın kullanılan polimerdir. PDMS gibi iyi özelliklere sahip polimerik malzemeleri hazırlamak için silikon atomunda sübstitüe edilmiş reaktif gruba sahip polisiloksanlar başlangıç bileşikleri olarak kullanılır. Esnek siloksan kısım iletken polimerlerin fiziksel özelliklerini arttırır. Yumuşak kontakt lensler ve suni ciltler gibi biyomedikal metaryaller, yapıştırıcılar, yüksek performanslı elastomerler ve sıvılar ile yüzey modifikasyonları uygulamalarında yaygın olarak kullanılır.
Bu çalışmanın amacı, büyük tanecik boyutları ve birçok çözücüde çözünememesinden dolayı işlenemeyen polipirolün kopolimerini yaparak daha küçük tanecik boyutunda, işlenebilir ve çözünebilir bir polimer elde etmektir. Bu gaye ile, tiyenil sonlu Poli (dimetilsiloksan) ile polipirol'ün demir (III) klorür varlığında kopolimerizasyonu incelenmiştir. Mono hidroksi poli (dimetilsiloksan) 2-tiyofenkarbonil klorür ile reaksiyona girerek tiyenil sonlu bir makromonomer haline gelmiştir. Tiyenil grubunun amacı ileride yapılacak blok kopolimer yapısında iletken polipirol kısmı ve iletken olmayan poli (dimetilsiloksan) kısmı arası köprü görevi görmek ve malzemenin kimyasal yükseltgenme potansiyelini arttırarak demir (III) klorür oksidantı için uygun hale getirmektir. 24 saat süren reaksiyon sonucu tiyenil uçlu Poli (dimetilsiloksan) (PDMS-ThC) elde edilmiş ve reaksiyonun başarıyla sonuçlandığı FTIR sonuçlarıyla kanıtlanmıştır. 
Tiyenil sonlu poli (dimetilsiloksan) ile pirol monomerinin kopolimerizasyonu demir (III) klorür varlığında, oda sıcaklığında gerçekleşmiştir. Reaksiyon ortamı olarak saf THF kullanıldı. Elde edilen ürünler FTIR spektroskopik yöntemi ile karakterize edildi ve SEM görüntüleri ile morfolojik olarak incelendi. 
Yapılan deney sonuçlarına göre tiyenilleme reaksiyonunun FTIR verilerine göre başarıyla gerçekleştirildiği ve tiyenil uçlu Poli(dimetilsiloksan) grubunun etkisiyle polipirol ortalama tanecik boyutlarında azalma olduğu gözlemlendi. Kopolimerizasyon işlemleri sırasında mol oranları optimum hesaplanarak da beklenen iletkenlik kaybı minimum düzeyde tutuldu, böylece işlenebilir ve yüksek iletkenlikte bir polipirol kopolimeri elde edildi.

Abstract:
Conductive polymers have attracted interest in the field of science and technology because of their main advantages such as electrical conductivity almost as good as metals, similar electronic and optical properties, corrosion resistance and easy handling. But over the years, the difficulties of being processed have caused difficulties in implementation and hindered their commercialization. Thus, new studies in the field of conducting polymers have concentrated on the design and synthesis of new copolymers by modifying them to obtain a processable material at the same time without losing the electrical properties of the conjugated polymers. 
Polypyrrole is by far the most extensively studied conducting polymer, since monomer pyrrole is easily oxidized, water soluble, commercially available, and possesses environmental stability, good redox properties, and high electrical conductivity, and is promising for application in batteries, supercapacitors, electrochemical (bio)sensors, conductive textiles and fabrics, mechanical actuators, electromagnetic interference shielding, antistatic coating, and drug delivery systems.
Polypyrrole is also a useful conductive polymer with good conductivity and corrosion resistance. As the polypyrrole spreads to a wide range of uses such as secondary batteries, electrochromic display devices, light emitting diodes (LEDs), capacitors, sensors, membranes and enzyme electrodes, improvements have been observed in the properties of this polymer.
Studies of the thesis mainly contains synthesis of various of pyrrolebased polymers in order to improve electrical conductivity, yield and processability of polypyrrole. Polymers were synthesized via chemical oxidative polymerization and electrochemical polymerization methods leading to products as powders and films, respectively.
There are few reports about PPy block copolymers. Generally, two different methods have been employed to produce block copolymers. In the first method, nonconductive block containing pyrrole or thiophene chain ends is produced and oxidatively copolymerised with Py by an oxidant such as Fe3+. This method consists of a number of steps (Luebben et al., 2007). In the second method, nonconductive blocks contain ketonic resin containing methyl groups or polydimethylsiloxane (PDMS) containing either methylol group or amine group chain ends. These compounds were added into the Py and polymerised with oxidants such as Fe3+ or Ce4+. This method is much easier and consists of one step.
The polypyrrole can be synthesized by chemical redox polymerization of the pyrrole monomer. The choice of oxidant and solvent for chemical oxidative polymerization are very important. Polymerization was performed in the presence of inorganic oxidants such as potassium persulfate (K2S208), hydrogen peroxide (H202), iron (III) and cerium (IV) salts are the most commonly used oxidants. The influence of synthesis parameters such as solvent, reaction temperature and time, type of oxidant, oxidant/monomer ratio and effect of a dopant on properties of the products were investigated. Optimum conditions were used for synthesis of pyrrole containing copolymers. To improve polymerization of pyrrole in non–aqueous medium, cerium(IV) oxidic dibenzoate (CODB) and phenyl iodine(III) bis(trifluoroacetate) (PIFA) were used as organic oxidants. These oxidants provided opportunity to obtain polypyrrole in aprotic solvents such as toluene and dichloromethane. Polypyrroles with conductivities of 5–10-3 S.cm-1 and 1–10-2 S.cm-1 were synthesized without additional dopants in the presence of PIFA and CODB, respectively. As a result, polypyrroles with conductivities in the range of 10-4–102 S.cm-1 were prepared with various types of oxidants. More generally, polypyrroles with high conductivities were obtained by decreasing reaction time and temperature. By the way many protic and aprotic solvents can be used in this reaction except for high donor number solvents such as DMF (dimethyl formamide) and DMSO (dimethyl sulfoxide). Machida et al. (1989) found that the highest conductivity value was 220 S / cm when methanol was selected as the solvent and iron (III) chloride was selected as the oxidant.
Polysiloxanes are materials that find many applications in a variety of industrial areas. The high flexibility and hydrophobicity, high thermal and chemical resistance, good resistance against radiation and solubility in nonpolar and/or low polarity solvents are some of their main properties. The most widely used member of this class is polydimethylsiloxanes. To prepare polymeric materials that have good properties, polysiloxanes having reactive group substituted at the silicon atom (organofunctional substituents) were used as starting compounds. The flexible siloxane moiety may also improve the physical properties of conducting polymers.
Poly (dimethylsiloxane) is the most widely used polymer among polysiloxanes. The polysiloxanes having a reactive group substituted on the silicon atom are used as starting compounds to prepare polymeric materials having good properties such as PDMS. The flexible siloxane part enhances the physical properties of the conductive polymers. Poly (dimethylsiloxane) is commonly used in biomedical materials such as soft contact lenses and artificial binders, adhesives, surface modifications with high performance elastomers and liquids.
There are several ways to prepare organofunctional polysiloxanes. Mostly, the preparation methods start from the synthesis of silicofunctional polydimethysiloxanes containing Si-H bonds followed by the hydrosilation of unsaturated compounds. Another method is to provide cationic or anionic equilibration of cyclic siloxanes together with disiloxanes as an end-blocking agent. In addition to that, reactions of functional siloxanes with some reagents provide desired functionality. All these methods are used to prepare organofunctional polysiloxanes containing hydroxyalklyl, hydroxyaryl, carboxyl, aminoalkyl, epoxy, methacryloxyalkyl and mercaptoalkyl groups.
The aim of this study is to obtain a copolymer of polypyrrole which is processable, soluble with a smaller particle size because pyyrole is unproccessed due to its large particle size and inability to dissolve. For this purpose, the copolymerization of thienyl-terminated poly (dimethylsiloxane) and polypyrrole in the presence of iron (III) chloride has been investigated. 
Mono hydroxy poly (dimethylsiloxane) was converted to a thienyl end capped macromonomer by reacting with 2-thiophenecarbonyl chloride. The purpose of the thienyl group is to bridge between in the conductive (polypyrrole part) and the non-conductive (poly (dimethylsiloxane) part) in the future block copolymer structure and to make the material suitable for iron (III) chloride oxidant by increasing the chemical oxidation potential of the material. After 24 h, according to FTIR results, the thienyl terminated poly (dimethylsiloxane) (PDMS-ThC) was obtained successfully. Copolymerization of the thienyl terminated poly (dimethylsiloxane) with the pyrrole monomer occurred in the presence of iron (III) chloride at room temperature. Pure THF was used as the reaction medium. 
Summarize this study presents synthesis of novel block copolymers of thienyl end capped poly (dimethylsiloxane) and polypyrrole via chemical oxidative polymerization by iron (III) chloride. Mono hydroxy terminated poly (dimethylsiloxane) (MH.PDMS) was reacted with 2-thiophenecarbonyl chloride (ThCCl) in order to synthesize a polymer containing thienyl end-group (PDMS-ThC). Then copolymers of PDMS-ThC and pyrrole were synthesized by chemical oxidative polymerization using iron (III) chloride as an oxidant. The synthesized block copolymers (PDMS-ThC -b-PPy) were characterized by spectroscopic analysis and morphologically by Scanning Electron Microscope (SEM).
According to the experimental results, it was observed that the thienylation reaction was successfully carried out and the polypyrrole mean particle size decreased with the effect of the thienyl-terminated poly (dimethylsiloxane) group. By optimally calculating the molar ratios during the copolymerization process, the expected loss of conductivity was kept to a minimum, so that a polypyrrole copolymer was obtained which was processable and had high conductivity.