Lityum metakrilat içeren iyonik hidrojellerin sentezi ve karakterizasyonu
Synthesis and characterization of ionic hydrogels containing lithium methacrylate
Yazar: NECLA İPEK
Danışman: PROF. DR. CEMAL ÖZEROĞLU
İstanbul Üniversitesi / Fen Bilimleri Enstitüsü / Kimya Ana Bilim Dalı
Derece: Yüksek Lisans, 2014
Konu: Kimya = Chemistry

Özet:
Bu çalışmada, akrilamid monomeri ile birlikte komonomer olarak lityum metakrilat kullanılarak kimyasal çapraz bağlı kopolimerler sentezlenmiştir. Çapraz bağlı akrilamid/lityum metakrilat polimerleri (AAm/LiMA) N,N'-metilenbis(akrilamid) (MBAA) çapraz bağlayıcısı kullanılarak oda sıcaklığında sulu asidik çözeltide serbest radikalik polimerleşme tepkimesi ile hazırlanmıştır. Tepkimede redoks başlatıcı sistemi olarak DL-penisilamin-seryum(IV)sülfat ve pH düzenleyici olarak etilendiamintetraasetikasit tetra sodyum tuzu (EDTANa4) kullanılmıştır. Penisilamin-Ce(IV) başlatıcı sisteminin kullanılmasının amacı düşük sıcaklıklarda hidrojelleri sentezlemek içindir.

Abstract:
In this study, chemically crosslinked copolymers were Synthesized using lithium methacrylate as comonomer with together acrylamide monomer. Crosslinked acrylamide/lithium methacrylate (AAm/LiMA) polymers were prepared by free radical polymerization in aqueus-acid solution at room temperature using N,N'-methylenebisacrylamide (MBAA) as crosslinker. DL-penicillamine-cerium(IV) sulfate as redox initiator system and ethylenediaminetetraaceticacid tetra sodium salt (EDTANa4) were used in the reaction as pH adjuster. The purpose of using pencillamine-Ce(IV) initiator system is to synthesize hydrogels at low temperatures.
 pH-dependent swelling behaviour of AAm/LiMA hydrogels and the effects of LiMA and the crosslinker MBAA concentration on the equilibrium swelling values (SD) were been investigated by determining their SDD values in distilled water, in the buffer solutions at various pH's (2.0, 3.0, 5.0 and 6.3) and in the NaCl salt solutions of different concentrations (0.02 M, 0.05 M and 0.20 M) at room temperature. Furthermore, in other group of experiments, acrylamide was polymerized with two co-monomers which are sodium methacrylate and potassium methacrylate. In the obtained hydrogels, water absorption capacity of hydrogels increases with the increase in hydrophilic comonomer content.  It was also observed that the increase in crosslinker content decreased the equilibrium swelling values. When pH dependent equilibrium swelling values of synthesized hydrogels were examined, maximum equilibrium swelling value was found at pH: 6.3 (in distilled water) and minimum equilibrium swelling value was found at acidic media at pH: 2.0.
Parameters about swelling kinetic and diffusion mechanism were calculated by using of the results of swelling studies. In the measurement of swelling kinetics of hydrogels, it was observed that the amount of absorbed water increased with increase of the amount of hydrophilic comonomer in structure. When swelling cinetics of hydrogels were investigated, the type of diffusion mechanisms of hydrogels which do not contains LiMA was found as Fickian. The type of diffusion mechanism of hydrogels containing LiMA was found as non-Fickian.
Structural characterization of chemically crosslinked polymers was made by Fourier Transform Infrared Spectroscopy (FT-IR) analysis.

Keywords: Redox polymerization, hydrogel, lithium methacrylate, acrylamide, 
penicillamine.