טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentTamar Gitli
SubjectBicontinuous Systems Combining Hydrogels and Hydrophobic
Polymers Through Emulsion Templating
DepartmentDepartment of Materials Science and Engineering
Supervisor Full Professor Silverstein Michael
Full Thesis textFull thesis text - English Version


Abstract

A high internal phase emulsion (HIPE) is an emulsion in which most of the volume (more than 74%) is occupied by the internal, dispersed phase. A polyHIPE is a highly interconnected, porous polymer that results from the polymerization of monomers within the external phase of a HIPE. The porous structure and its interconnectivity can be tailored by varying the HIPE composition and the polyHIPE synthesis parameters. Typical polyHIPEs are hydrophobic and exhibit poor water absorption. Hydrogels, on the other hand, are hydrophilic crosslinked polymer networks that can undergo extensive, reversible swelling in water. Due to their high water contents and their ability to be reversibly hydrated and dehydrated, hydrogels are promising controlled release systems.

In this research, the unique properties of hydrogels and polyHIPEs were combined into one novel system by polymerizing monomers within both the external, organic phase of a HIPE and within the internal, aqueous phase of a HIPE. The resulting materials consisted of interconnected hydrogel domains within continuous hydrophobic polyHIPE scaffolds. The ability to reversibly dry and hydrate these materials demonstrated their bicontinuous, interconnected structure.

The hydrophobic monomer used in this research was primarily styrene (S). The hydrophilic monomer used in this research was primarily acrylamide (AAm). The structures and properties of these systems were investigated using a combination of spectroscopy, microscopy, mechanical analysis, and thermal analysis. The potential for controlled release was investigated by loading and release experiments using a hydrophilic dye (Eosin Y) as a model drug.

The molecular and porous structures of these bicontinuous systems were found to be more complex than originally assumed and were sensitive to changes in the synthesis procedure and in the HIPE composition. The loading and release profiles of the model drug were also affected by these changes. Most importantly, release times of up to 3 weeks could be achieved through control of the polyHIPE's molecular and porous structures.