Poliakrilamid jellerinin sentez şartları ve ağ yapı özellikleri arası ilişkiler
Relationship between the synthesis conditions and network properties of polyacrylamide gels
- Tez No: 67071
- Danışmanlar: PROF. DR. OĞUZ OKAY
- Tez Türü: Yüksek Lisans
- Konular: Kimya, Chemistry
- Anahtar Kelimeler: Serbest radikal polimerizasyonu, çapraz bağlı polimerizasyon, polimerik jeller hidrojeller, poliakrilamid jelleri, jellere çözücü difüzyonu, şişme derecesi, çapraz bağ yoğunluğu
- Yıl: 1997
- Dil: Türkçe
- Üniversite: Kocaeli Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Kimya Ana Bilim Dalı
- Bilim Dalı: Fizikokimya Bilim Dalı
- Sayfa Sayısı: 178
Özet
POLİAKRİLAMİD JELLERİNİN SENTEZ ŞARTLARI İLE AĞ YAPI ÖZELLİKLERİ ARASI İLİŞKİLER Nurgül Kalyoncu BALIMTAŞ
Özet (Çeviri)
RELATIONSHIP BETWEEN THE SYNTHESIS CONDITONS AND NETWORK PROPERTIES OF POLYACRYLAMIDE GELS Key Words : Polymer gels, hyrogels, polyacrylamide gels, free-radikal polymerization, crosslinking polymerization, solvent diffusion into the gels, swelling, crosslink density ABSTRACT: In this study, a series of hydrophilic gels called hyrogels were prepared in order to clarify the relationships between their synthesis conditions and swelling properties. Hydrogels were prepared at room temperature by radical copolymerization of acrylamide (AAm ) monomer, sodium acrylate (NaAc) ionic comonomer, and N,N'- methylenebis(acrylamide) (BAAm) croslinkinker in the presence of ammonium persulfate (APS) / N,N,N\N'-tetramethylenediamine (TEMED) iniator system. Swelling ratios of the hyrogels thus obtained as well as their swelling rates in water were measured and the dependence of the swelling properties on the amounts of the crosslinker BAAm and the ionic comonomer NaAc used in the jel synthesis was studied. Moreover, various amounts of isopropyl alcohol (IP A) as a chain transfer agent were included into the polymerization system and the influence of IP A on the gel properties was studied. To clarify the mechanism of solvent diffusion into the hydrogels, dynamic swelling experiments were also carried out within the framework of this study. Experimental results showed that non-ionic polyacrylamide (PAAm) gels prepared at low BAAm concentrations exhibit relatively high swelling rates and swelling ratios in water. Addition of NaAc into the polymerization system further increase the swelling ratios of PAAm gels. It was found that one gram of the gel prepared at 31 % NaAc concentration absorb about 800g of water. The crosslink densties of the hyrogels calculated from their swelling ratios and by use of Flory's swelling equation were found to be much less than the values found from the amunts of the crosslinker BAAm used in the gel synthesis. It was shown that only 20 % of BAAm used in the feed form effective crosslinkages, whereas the rest was consumed by cyclization reactions. Moreover, addition of IPA into the reaction system as a chain transfer agent increased both the swelling ratios and the swelling rates of PAAm gels. Calculations using the Flory and Mayo equations indicated that the crosslink density of the Flory and Mayo eguations indicated that the crosslink density of the gels remains constant for IPA / AAm mole ratio < 0,2, whereas it decreases continously on rising the IPA concentration above this value. Dynamic swelling experiments showed that water diffusion into the non-ionic PAAm gels proceeds according to the Fick's law of diffusion. However, including ionic units into the hydrogel structure changes the mechanism of solvent diffusion into the gels according to a mechanism called in the literature as“anormal solvent diffusion”.
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