Chemical and Biological Engineering PhD Thesis Defense by Derya Aydın

*******************************************************************

KOC UNIVERSITY

GRADUATE SCHOOL OF SCIENCES & ENGINEERING

CHEMICAL AND BIOLOGICAL ENGINEERING

PHD THESIS DEFENSE BY DERYA AYDIN

******************************************************************

Title: Design of Functional Materials via Emulsion Templating: Energy and Biomedical Applications

Speaker: Derya Aydın

Time: June 16, 2017, 10:30

Place: ENGB05

Koç University

Rumeli Feneri Yolu

Sariyer, Istanbul

Thesis Committee Members:

Assoc. Prof. Seda Kızılel (Advisor, Koc University)

Prof. Burak Erman (Koc University)

Prof. A. Levent Demirel (Koc University)

Prof. Ebru Toksoy Öner (Marmara University)

Assoc. Prof. Başak Kayıtmazer (Boğaziçi University)

Abstract:

Incorporating functional materials into immiscible mediums has been a conventional challenge in materials science. Solid-like structures are formed via templating stable liquid emulsions to overcome this challenge. The technique we introduce here involves incorporation of a hydrophilic functional domains into hydrophobic styrene-butadiene-styrene (SBS) matrix using emulsion templating method to enable controlled release of molecules such as anti-icing agents for surfaces or drugs for therapeutic applications. In the first part of thesis, we designed a bitumen compatible functional polymer composite for anti-icing property on asphalt roads. Bitumen, an asphalt binder, is generally modified SBS for improved strength and thermomechanical properties. However, an anti-icing function has not been considered in those previous designs.  Here, we developed a functional polymer composite consisting of potassium formate (HCOOK) salt pockets dissolved in a hydrophilic gel medium and dispersed in a hydrophobic SBS polymer matrix via silica particle stabilization. Next, we investigated modification of bitumen with this functional polymer composite and demonstrated significant increase in freezing time of composite-modified bitumen compared to base bitumen in a custom-made and camera-attached temperature controlled chambers with temperatures of -14 and -2 °C, respectively. In addition, we investigated morphological and salt release properties of composite modified bitumen and observed potassium formate (HCOOK) release for 67 days.  Furthermore, we investigated altered ionic salts consisting of HCOOK, sodium chloride (NaCl) or magnesium chloride (MgCl₂₎ and observed that identity of salts have altered effects on mechanical, morphological and functional properties of the composite incorporated or coated bitumen. These results are promising and suggest the potential of this polymer composite-modified bitumen for anti-icing functionality and for industrially relevant applications.

In the second part of thesis, we investigated synthesis of polyethylene glycol (PEG) nanospheres via water-in-water emulsion templating method for biomedical applications. This method is promising for the synthesis of PEG micro/nanospheres for biological systems, since the emulsion is aqueous and do not require organic solvents or surfactants. We prepared w/w emulsions based on phase separation of dextran and PEG prepolymer and achieved the synthesis of nano-scale PEG hydrogel particles. Next, we investigated the release kinetics of a model drug, pregabalin from PEG nanospheres and fitted experimental data to a stretched exponential function to predict half-time and drug release rates from the model equation. In the last part of thesis, we crosslinked SBS polymer via photo-initiated thiol-ene reactions ad incorporated PEG particles into crosslinked SBS network to obtain SBS-PEG hybrid gels for sustained drug release purposes. In literature, SBS was only used in few biomedical applications and drug release kinetics of this rubber elostomer was unknown. We observed extended release of an anti rheumatoid arthritis drug from SBS-PEG gels up to 28 days which show their potential for sustained drug delivery applications. Cell viability results suggested that PEG nanospheres and SBS-PEG gels are non-toxic, and can be considered for controlled drug/molecule delivery.