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Pirol'ün akrilik asit ile kopolimerizasyonu

Oxidative polymerization of pyrrole with acrylic acid

  1. Tez No: 68900
  2. Yazar: HALE AYŞE ERDEM
  3. Danışmanlar: PROF. DR. SEZAİ SARAÇ
  4. Tez Türü: Yüksek Lisans
  5. Konular: Kimya, Chemistry
  6. Anahtar Kelimeler: Belirtilmemiş.
  7. Yıl: 1997
  8. Dil: Türkçe
  9. Üniversite: İstanbul Teknik Üniversitesi
  10. Enstitü: Fen Bilimleri Enstitüsü
  11. Ana Bilim Dalı: Fizikokimya Ana Bilim Dalı
  12. Bilim Dalı: Belirtilmemiş.
  13. Sayfa Sayısı: 86

Özet

ÖZET Bu çalışmada seryum (IV) tuzları başlatıcı olarak kullanılarak, H2SO4 içeren ve H2SO4 içermeyen ortamlarda akrilik asit (AA) -pirol (Py) kopolimerizasyonu gerçekleştirilmiştir. Sıcaklığın, akrilik asit, seryum (IV) sülfat, pirol ve H2S04 konsantrasyonlarının kopolimerizasyon üzerindeki etkisi UV- Visible spektrofotometresiyle, çöken kısımların yapısı fiziksel karışım, tek başına poliakrilik asit ve tek başına polipirol ile karşılaştırmalı olarak FT-IR spektrofotometresiyle incelenmiştir. Ayrıca bu polimerizasyon poliakrilik asit kullanılarak da denenmiş, poliakrilik asit kullanılması durumunda akrilik asit monomerinin kullanımına göre farklı sonuçlar gözlenmiştir. Poliakrilik asit ile yapılan çalışmaların matris üzerinden gerçekleştiği bilinmektedir. Bu sonuç monomer kullanıldığında elde edilen ürünün matris polimerizasyon ürünü olmadığını gösterir niteliktedir. Polimerizasyonun ilerleme süreci ve kinetiği UV-Visible absorbsiyon spektrofotometresiyle incelenmiştir. Bunun sonucunda reaksiyon süresinin sıcaklığa bağlı olarak kısaldığı ve konsantrasyonlara bağlı olduğu görülmüştür. Ayrıca reaksiyon hız sabitleri ve aktivasyon enerjileri hesaplanmıştır. Reaksiyon iletkenlik, pH ve döngülü voltamogram ile izlenmiş, elde edilen bulgulardan reaksiyon mekanizması önerilmiştir. Bütün bu deneysel çalışmalar sonucunda :. Seryum (IV) sülfat başlatıcısımn, seryum (IV) amonyum nitrat başlatıcısına göre reaksiyonu hızlandırdığı,. Akrilik asit-pirol konsantrasyonu oram belirli bir değere ulaştıktan sonra kopolimerizasyonun gerçekleştiği,. Sıcaklığın kopolimerizasyon hızını oldukça arttırdığı,. Ortamda H2SO4 bulunduğunda oligomer ve kopolimer oluşum hızlarının hemen hemen aynı olduğu gözlenmiştir. IX

Özet (Çeviri)

SUMMARY Electrically conducting polymers made from heterocyclic monomers have been the subject of much research in recent years. Polyopyrrole has received considerable interest, partly because it can be prepared both electrochemically and by chemical oxidation with mild oxidative transition metal ions and partly because of it's relatively good stability oxidised form. But it is hard and brittle, and these poor mechanical properties greatly restrict it's potential for applications in bateries. Polymerization of a conducting polymer inside an insulating host matrix is used to improve the mechanical properties of polypyrrole. Conducting polymers have novel electrical and optical properties that are potentially usefull for applications in electroluminescence display, rechargable batteries, electrocromic windows, chemical sensors, electromagnetic shielding and antielectrostatic films. One of the problems İs that conducting polymers are difficult to be solubilized in any solvent because of their delocalized 7t-electronic structures which are the very same molecular characteristics that gives rise to their novel optical and electronic properties necessary for device applications. Polymerization conditions in aqueous solution at concentrations of 25% or less were effective. Polymerization of more concentrated solutions or of undiluted monomer is not recomended because the high heat content of polymerization makes polymerization difficult to control and produces insoluble polymer The polymerization of undiluted monomer is hazardous. Aqueous solutions of acrylic and methacrylic acids can be polymerized in the presence of a peroxydisulfate initator at 90-100°C. If methacrylic acid is used, the polyacid precipitates at the temperature of polymerization but goes into solution again at lower temperatures. When acrylic acid is used the polymerization solution remains homogeneous. The use of redox initators, especially at low temperatures, requires efficient purging of solvent and aparatus with nitrogen or other inert gas to remove molecular oxygen, which inactivates the initator. The polymers can be used as aqueous solutions or they can be dried to flaky white solids. It is advisable to allow at least 5% moisture to remain in the dried polymer to facilitate re-solution. Preparations which dissolve instantaneously can be made by freeze-drying. Attempt have been made to copolymerize different kinds of heterocyclic compound with the aim of impoving the properties of the resulting copolymers. For this purpose pyrrole was copolymerized with acrylic acid due to mechanical properties of it's homopolymer which is better then pyrrole.Although the presence of some literatüre on the electrochemical copolymerization of pyrrole with substituted carbazole and substituted pyrrole, in literature copolymerization with acrylic acid by using eerie salts is not known in literature. In this thesis, oxidative copolymerization of acrylic acid with pyrrole by using eerie salts in water were studied. The effect of monomers,metal ion, sulphiric acid concentration, temperature, addition order of components and type of cerium (IV)salts were investigateted. Depending on relative concentration of pyrrole, acrylic acid and eerie salts different type precipitate is formed. After the filtration colored solution was investigated by UV- Visible spectrophotometer as well as pH and conductivity measurements. The precipitation was investigated by FT-IR spectrophotometer and elemental analysis. Pyrrole concentration was varied in the range 0.0035M-3.00M with fixed concentrations of other parameters. As the amount of the pyrrole increased the properties of polymer became to closer homopolymer of pyrrole. Acrylic acid concentration was varied from 0.03M to 3M, wheras all the other parameters remained constant. The observation of UV- Visible absorbtion peak only occurs at certain acrylic acid concentration. Below this concentration it seems acrylic acid does not incorporate to the copolymer structure. The effects of eerie salts on the copolymerization was examined varying the cerium (IV) salts concentration in the range of 1.23.10“^- 2.46.10”3M, wheras all the other parameters remained constant. The absorbance of the peak which corresponds to copolymerization of pyrrole and acrylic acid increases with increasing cerium (IV) salts concentration, up to 1.23.10“3M but after this certain concentration the absorbance remained constant. In addition to these results polymerization performed in the presence and absence of acrylic acid and reactions were followed by UV- Visible measurements (Figure 1). In the absence of acrylic acid only one maximum absorbance at A,=464 nm corresponding to oligomer formation of pyrrole was observed (Figure 1-a). While in the presence of acrylic acid in adition to peak at X=464 nm,a new peak at X=593 nm attributed to copolymer formation between acrylic acid and pyrrole was also observed (Figure 1-b) When H2SO4 was added in this medium (i.e. pyrrole- acrylic acid- cerium (IV) sulphatefCS]) absorbance of two peaks (X=464 nm and X=593 nm ) became almost equal, which means rate of oligomer and copolymer formation is the same in the presence of H2S04 (Figure 1-c). XI200 400 600 800 1000 1100 Wave length, nm Figure-1 Oligomer formation of pyrrole in the presence and absence of acrylic acid a-) b-) c-) -3 During the reaction change in conductivity and pH was followed by time in the presence of acrylic acid ( Figure 2 ) and results were compared in the case of polyacrylic acid ( Figure 3 ). In the case of acrylic acid, pH decrease while the conductivity increase with time. Polymerization of pyrrole begins with the oxidation of monomer to cation radicals reacting further with the formation of polymeric bond between the pyrrole or acrylic acid. At the same time IT”ions are split off, which cause increase in pH and decrease in conductivity ( Figure 2). On the other hand in the case of PAA change in pH and conductivity shows different profile than acrylic acid case of polyacrylic acid change in pH and conductivity shows different profile than acrylic acid case ( Figure 3 ). This result supports the idea that while in the case of monomer copolymer formation occures and in the case of polymerization goes through matrix. Xll1000 2000 time,t(sn) 3000 4000 Figure-2 Pyrrole, acrylic acid and cerium (IV) sulphate copolymerization change in conductivity and pH by time [AA] = 0.3M [Py] = 0.0007M [CS] =1.23xl(T*M Temperature = 50°C X a 28.00 27.00 E 26.00 -25.00 24.00 4000 time, t (sn) Figure 3- Pyrrole, acrylic acid and cerium(TV) sulphate copolymerization change in conductivity and pH by time [PAA] = 0.3M [Py] = 0.0007M [CS] = 1.23xl(rM Temperature = 50°C xuiIn conclusion at a certain concentrations of pyrrole,acrylic acid, eerie salts and sulphuric acid copolymer formation occurs between pyrrole and acrylic acid in solution in adition toprecipitated form. In the case of electrochemical copolymerization of pyrrole and acrylic acid, copolymer film occurs on the electrode surface. Mother liquere remains clear, showing that copolymerization reaction occurs at only electrode surface unlike the chemical polymerization in which both soluble and insoluble products can be obtained. XIV

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