M.Sc Thesis


M.Sc StudentFoqara Mohammad
SubjectOne Pot Energy Efficient Process for Forming a Transparent,
Flexible and Protonic Conductive Casein Plastics
DepartmentDepartment of Chemistry
Supervisor ASSOCIATE PROF. Nadav Amdursky
Full Thesis textFull thesis text - English Version


Abstract

Over the years, several approaches have been made in the search for a greener alternative solution for traditional plastics. One of them is in the form of a bioplastic, meaning the use of natural sources for the making of the bioplastic. However, in most cases, bioplastics do not meet all the criteria to compete with petrochemical-based plastics. In general, proteins have been used for the development of plastic materials for a long time. The topic of this thesis is making bioplastics using the casein protein. Casein-based materials have a long history and they have been used decades ago as plastic replacement, albeit with the advancement in modern plastic formation, their use has been abandoned. Here, we introduce a new methodology for the use of the casein protein for making bioplastics that are free-standing, transparent, insoluble, flexible, degradable with fast degradation profile, which is capable to mediate ions, i.e., conductive bioplastic. Our choice of the casein protein is due to its sustainable nature, resulting in being one of the most commercially affordable protein among all proteins, and even more affordable than most of the plant-derived polysaccharides. Importantly, we use the commercially available protein as is, and no purification stage is needed, while the plastic formation is a one-pot simple process. An important part of the plastic formation stage is the sulfonation of the casein protein, which drastically alter various properties of the bioplastic, as well as the use of the low concentration of plasticizer and cross-linker. In terms of their mechanical properties, our casein bioplastics exhibit a wide range of properties, whereas the sulfonated bioplastic are more elastic (stretchable) but not very strong with Yong’s modulus in the order of a few MPa, compared to the non-sulfonated bioplastics that are less elastic but much stronger (~200 MPa). One as the important features of our sulfonated casein bioplastics is the efficient ion conductivity across them, thus making them the first conductive casein-based plastic. We show that the presence of the sulfate group together with water molecules inside the bioplastic can result in a high ionic conductivity in the order of 0.4 mS•cm-1, whereas the non-sulfonated bioplastic is much less conductive (~0.01 mS•cm-1). We attribute the ionic conductivity to proton transport within the bioplastic due to the high kinetic isotope effect upon deutoration. Our new material opens the field of ionic conductive bioplastics that are highly affordable and can be manufactured on very large scales, where we envision several lines of applications, from common plastic replacement, to biomedical applications (as conductive patches in vivo), and common conductive plastic applications as  corrosion protectors, compact capacitors, antistatic coating, and electromagnetic shielding of electrical components.