Tez özetleri Astronomi ve Uzay Bilimleri Anabilim Dalı

Tezin Yabancı Dildeki Adı :
THE PREPARATION AND CHARACTERIZATION OF POROUS, IONIC SUPER ABSORBENT POLYMER GELS

Yabancı Dildeki Özet :

In this thesis, crosslinked poly(N,N-(dimethylamino)ethyl methacrylate sulfate) (PDMAEMASA or 100 DESA) homopolymer and poly(N,N-(dimethylamino)ethyl methacrylate sulfate-co-N,N-dimethylacrylamide) (P(DMAEMASA-co-DMAm)) copolymers were prepared from N,N-(dimethylamino)ethyl methacrylate sulfate (DMAEMASA) ve N,N-dimethylacrylamide (DMAm) monomers for the first time. Both homopolymer and copolymer gels were also prepared in the presence of 5 wt. % 10 wt. % sucrose (SUC), poly(ethylene glycol) 2000 (PEG) ve sodium bicarbonate (NaHCO₃) in order to increase the stimuli-responsive properties. Thus, these gels have gained porous structure. Polimerization reactions were performed in aqueous solution, at 40^oC in 24 hours by using ammonium persulphate (APS) (1mol % of the total monomer content) as initiator; N,N,N’,N’-tetramethylenediamine (TEMED) (same weight of APS) as accelerator; and N,N’-methylene bis acrylamide (NMBA) (1 mol % of total monomer content) as crosslinker. The initial total monomer content was kept constant at 1 M. In the preparation of DMAEMASA-DMAm copolymers, the content of DMAm in monomer feed was 20 and 40 mol % for 80 DESA and 60 DESA copolymers, respectively.

Swelling behavior of DMAEMASA homopolymer and DMAEMASA-DMAm copolymer, prepared for the first time in this work, as a function of time and pH of swelling medium were investigated by determining their equilibrium swelling values (ESV) in distilled water at 20, 30, 40, and 60^oC and in buffer solutions at constant ionic strength (0.1 M) with various pH’s at 20^oC for 24 h. In addition, the polymers were prepared in the presence of pore-foaming agents, so that the effect of pore-forming agents on their swelling behavior was studied. The structural and thermal characterization of polymers were performed by elemental analysis, FTIR, DSC and SEM methods.
Elemental analysis results showed that DMAEMASA content in both homopolymer and copolymer was nearly the same, and it was 70% of theoretical value. This result shows the presence of DMAEMA units in addition to DMAEMASA and DMAEMASA-DMAm in homopolymer and copolymer, respectively. Glass transition temperature (Tg) of homopolymer was determined to be 168.4^oC. With the introduction of DMAm into the polymer structure, Tg values of 80 DESA and 60 DESA copolymers decreased to 154.6 and 147.8^oC, respectively. While the use of pore-forming agent during the polymerization of 80 DESA and 60 DESA copolymers decreased the Tg values in the order of NaHCO₃ , PEG , SUC; NaHCO₃ and PEG had nearly no effect on Tg values these polymers, but sucrose led to approximately 7^oC decrease in Tg of same polymers.

Equilibrium swelling values of polymers in distilled water decreased with DMAEMASA content in monomer feed and the lowest ESV is belong to non-porous homopolymer. ESV’s of homopolymer and copolymers increased with temperature, the use of pore-forming agent during the polymerization, and the amount of pore-former. While NaHCO₃ had the highest positive effect on the ESV’s of polymers, the performances of PEG and SUC were nearly same.

ESV’s of both porous and non-porous homopolymer and copolymers displayed a minimum at pH=5. In acidic and basic medium, higher ESV’S were observed, especially ESV’s in low pH-region were higher than those in basic medium.

Key Words: N,N-(dimethylamino)ethyl methacrylate sulfate, N,N-dimethylacrylamide, sucrose, poly(ethylene glycol) 2000, sodium bicarbonate, porous gel.