Master Thesis Defense: Kinyas Aydın
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SELF-CROSS LINKABLE SUPERABSORBENT HYDROGELS BASED ON DIFFERENT VINYLALKOXYSILANES AS CROSSLINKERS

Kinyas Aydın
Materials Science and Engineering, M.Sc. Thesis, 2013

Thesis Jury
Prof. Dr. Yusuf Z. Menceloğlu (Thesis Supervisor), Asst. Prof. Fevzi Çakmak Cebeci, Asst. Prof. Gözde İnce, Assoc. Prof. Selmiye Alkan, Asst. Prof. Murat Çokol

Date &Time: June, 03rd, 2013 - 10.00

Place: FENS G032

Keywords: Superabsorbent, Free Radical Solution Precipitation, Acrylamide, AMPS, Vinylalkoxysilanes, Equilibrium Swelling Ratio, Cross linking

Abstract

Novel superabsorbent hydrogels were synthesized through the Free Radical Solution Precipitation polymerization technique. The synthesized materials were characterized by Differential Scanning Calorimetry (DCS), Simultaneous Thermal Analysis (STA), FTIR (Fourier Transmittance Infrared) ,1H Nuclear Magnetic Resonance Spectroscopy (NMR), 29Si  Nuclear Magnetic Resonance Spectroscopy. Thin film surfaces of polymers were characterized by Drop Shape Analysis (DSA). These characterization methods provide valuable information to understand chemical structure and performance level of water uptake synthesized hydrogels, effect of synthesis parameters; change in cross linker agents, and thermal behavior of polymers.

Equilibrium Swelling ratio (ESR) of synthesized superabsorbent hydrogels were measured  gravimetrically and highest ESR value with correspoding polymer structure and concentration were optimized.

 Due to chemical structure and reactivity relationship, in terms of hydrolysis and condensation reactions, three different type of cross linking agents reactions were used  in polymerization. Based  on three  different  chemical structures of vinylalkoxysilane cross linking agents, namely Triethoxyvinylsilane (TEVS), Vinyltrimethoxysilane(VTMS)  and  Tris(2-methoxyethoxy)vinylsilane (TMEVS), the ESR value  was obtained  for each  based samples.

According to 1H – NMR  analysis, monomer reactivities  of AMc  and AMPS  were found as 1.32  and 1.25  respectively. Based on monomer reactivity results, it is clear to conclude that for the Free radical solution precipitation polymerization of acrylamide and AMPS occurred randomly.

Experimentally three  different  polar  aprotic solvents  were  used  as  solvent medium in reactions,1,4-dioxane,Dimethylacetamide  and Dimethylformamide. A significant difference result from using these three polar solvents was the comparable change in ESR under same conditions.

Solution viscosity of prepared  standard 6 %(wt/ml)  of  polymers  were measured  in Brookfield DV-III Rheometer  while keeping torque  value  15%.

Molecular weight of synthesized  polymers  based on three  different vinylalkoxysilanes  were calculated  according the results  obtained  from Dilute  Solution Viscometery  experiment, while using the constants  for  polyacrylamide since approximately about 90 % of synthesized polymers  are  acrylamide.