Poliakrilamidin poliakrilikaside kontrollü dönüşümü
Başlık çevirisi mevcut değil.
- Tez No: 55695
- Danışmanlar: PROF.DR. NİYAZİ BIÇAK
- Tez Türü: Yüksek Lisans
- Konular: Kimya Mühendisliği, Chemical Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1996
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 23
Özet
ÖZET Bilindiği gibi suda çözünen polimerlerin en önemlilerinden birisi poliakrilik asittir. Poliakrilikasit monomerinden itibaren polimerleştirme yolu ile hazırlanabildiği gibi poliakrilamid, poliakrilonitril ve poli(alkil akrilat)ların hidrolizi ile de hazırlanabilir. Monomerden itibaren çok büyük miktarlarda polimer elde edilmesi; akrilik asit monomerinin polimerleşme reaksiyonunun ekzotermik(ısı veren) olması sebebiyle oldukça zordur. Yine aynı sebeple akrilik asit monomerinin depolanması çok özel önlemleri gerektirir. Poliakrilik asidin yukarıda belirtilen polimerlerin asit ya da alkali hidrolizi ile elde edilmesi sık sık başvurulan bir yöntemdir. Kısmen hidroliz yapmak suretiyle burada akrilik asit kopolimerlerihin hazırlanması da mümkün olmakla beraber reaksiyonun kontrollü bir şekilde yürütülmesi imkansız denecek kadar zordur. Biz bu çalışmada polİakrilamidin sulu çözeltide nitroz asitle etkileştirilmesiyle, azot çıkışıyla birlikte poliakrilik asidin hazırlanabileceğini kanıtladık. Bu çalışmanın ortaya koyduğu en önemli sonuç, buradaki nitroz asit mol oranının ayarlanmasıyla poliakrilamiddeki amid gruplarının istenen oranda karboksil gruplarına dönüştürülebileceğinin ortaya çıkmış olmasıdır. Böylece istenilen bileşimde akrilikasit-akrilamid kopolimerlerinin elde edilmesinin mümkün olduğu bu çalışmayla ortaya çıkmış bulunmaktadır.
Özet (Çeviri)
SUMMARY CONTROLLED CONVERSION OF POLYACRYLAMIDE INTO POLYACRYLICACID Interaction of nitrous acid with aqua solution of poly(acrylamide) gives poly(acrylic acid) in quantitative conversion yields. The reaction proceeds smoothly, with simultaneous evolution of nitrogen, provided that the temperature below 5°C. The procedure presented provides a versatile route to prepare acrylic acid-acrylamide copolymers in any desired composition, by adjusting molar ratio of nitrous acid. Introduction Poly(acrylic acid) is öne of the most important water-soluble polymers. it has found many applications in textile sizing, adhesives and coatings. Incorporation of a few percent of acrylic acid into a copolymer imparts a degree of hydrophylicity to the copolymer. Those copolymers gain adhesion capability. Also, presence of acrylic acid moieties in a copolymer provides post-crosslinking capabilities, by treating with appropriate difunctional reagents, such as diamines, diols and epoxides. Since poly(acrylic acid) has ionizable carboxyl groups in each repeating unit, it shows unusual solution behavior in polar solvents, which differs from those of non-ionic polymers. This behavior is termed as polyelectrolyte behavior. There are two main routes to prepare poly(acryliC acid): i) Polymerization of acrylic acid monomer and ü) acid ör alkaline hydrolysis of suitable prepolymers, such as polyacrylic acid esters, poly(acrylonitrile) and poly(acryl amide) Polymerization of acrylic acid monomer is fairly exothermic and may cause to severe explosions. For this reason only small quantities (up to 10 mi) of acrylic acid is recommended to homopolymerize. Another limitation is that, acrylic acid monomer itself shows storage and handling problems because of its spontaneous polymerization capability. it polymerizes thermaly even in presence of inhibitors. Its storage in large containers is not safe and extreme çare should be undertaken. For preparing large quantities of poly(acrylic acid) hyrolysis of polyacrylic acid esters, poly(acrylamide) ör poly(acrylonitrile) is often prefered. By partial hydrolysis of these polymers it is possible to obtain the corresponding copolymers. For instance, viC-nitroso compounds. In our case, the most activated methylene group in poly(acrylic acid) is the one carrying carboxyl group. Having one hydrogen atom this methylene group can give C-nitroso compounds. On the other hand, the inherent viscosities of the copolymers obtained by this method do not change linearly with their compositions. Obviously this is because of the polyelectrolyte behavior of acrylic acid segments in the copolymers. XIAlso İR spectra of poly(acrylamide), acrylic acid-acrylamide copolymer (l/l) and poly(acry!ic acid) obtained by this method have been given in fig. 1 for comparision. IR spectra of the later two match well with those given in the literature. These evidences estabüshe the proposed transformations qualitatively. 4 0 00 3000 2000 looo 4oo cm rl Fig. 1. IR spectra of poly(acrylamide)(a), acrylic acid-acrylamide copolymer(l/l) (b) arid poly(acryllc acid) (c) İt is important to note that, excess of nitrous acid is not recommended for the preparation of poly(acrylic acid). Because in that case surprisingly the resulting pf oduct contains nitrogen. Indeed, when we used two-fold excess of nitrous acid, the elementary microanalysis showed 1.9% nitrogen. This little nitrogen content can not be ascribed to the unreacted amide groups. Most probably this must be because of the formation of C-nitroso compounds through the main chain carbon atom carrying carboxyl group. Because nitrous acid is known to react with activated methylene groups to form oximes as in case for the reaction of acetone with nitrous acid yielding acetone oxim. Where as methylene groups possesing one hydrogen atom giveC-nitroso compounds. In our case, the most activated methylene group in poly(acrylic acid) is the one carrying carboxyl group. Having one hydrogen atom this methylene group can give C-nitroso compounds. On the other hand, the inherent viscosities of the copolymers obtained by this method do not change linearly with their compositions. Obviously this is because of the polyelectrolyte behavior of acrylic acid segments in the copolymers. XIAlso İR spectra of poly(acrylamide), acrylic acid-acrylamide copolymer (l/l) and poly(acry!ic acid) obtained by this method have been given in fig. 1 for comparision. IR spectra of the later two match well with those given in the literature. These evidences estabüshe the proposed transformations qualitatively. 4 0 00 3000 2000 looo 4oo cm rl Fig. 1. IR spectra of poly(acrylamide)(a), acrylic acid-acrylamide copolymer(l/l) (b) arid poly(acryllc acid) (c) İt is important to note that, excess of nitrous acid is not recommended for the preparation of poly(acrylic acid). Because in that case surprisingly the resulting pf oduct contains nitrogen. Indeed, when we used two-fold excess of nitrous acid, the elementary microanalysis showed 1.9% nitrogen. This little nitrogen content can not be ascribed to the unreacted amide groups. Most probably this must be because of the formation of C-nitroso compounds through the main chain carbon atom carrying carboxyl group. Because nitrous acid is known to react with activated methylene groups to form oximes as in case for the reaction of acetone with nitrous acid yielding acetone oxim. Where as methylene groups possesing one hydrogen atom giveC-nitroso compounds. In our case, the most activated methylene group in poly(acrylic acid) is the one carrying carboxyl group. Having one hydrogen atom this methylene group can give C-nitroso compounds. On the other hand, the inherent viscosities of the copolymers obtained by this method do not change linearly with their compositions. Obviously this is because of the polyelectrolyte behavior of acrylic acid segments in the copolymers. XI
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