Photochemical Sciences Ph.D. Dissertations


Photoreactivity and Enhanced Toughness and Stability in Polysaccharide-Based Materials Using Metal Ion Coordination

Date of Award


Document Type


Degree Name

Doctor of Philosophy (Ph.D.)


Photochemical Sciences

First Advisor

Alexis D. Ostrowski (Committee Chair)

Second Advisor

Xiangdong Xie (Other)

Third Advisor

Alexander Tarnovsky (Committee Member)

Fourth Advisor

Joseph C. Furgal (Committee Member)


Nature provides a wide range of biopolymers that have been used over the years to create different materials with different properties. Among these biopolymers, we used polysaccharides to develop sustainable materials with unique properties. To enhance their properties, we tried recreating the hierarchal assemblies found in nature between soft organic and hard inorganic components. In other words, our approach was to use metal coordination to ligand groups present in the polysaccharides to make materials with unique mechanical properties and water stability. We also wanted to be able to use light to modify the properties of these materials or degrade them. We chose to work with Fe(III) and V(V) metal ions because these two metals ions showed photoreactivity with different ligands such as carboxylate-containing polyuronates such as alginate and pectin, and other polysaccharides such as chitosan and cellulose and small hydroxy acids such as tartaric acid. First, we studied the photoreactivity of V(V) with two polysaccharides, alginate and chitosan in aqueous solution. In both solutions, a decrease in viscosity was observed with light irradiation accompanied by a change in color from an initial yellow color to a blue color corresponding to the photochemical reduction of V(V) to V(IV) according to previous studies. Second, we made solid films from pectin and chitosan and improved their properties using V(V) ion coordination. V(V)-coordinated films showed increased strength and water stability compared to V(V)-free films. The photochemical reaction observed in solution was also observed in solid state. Finally, to further understand the photochemical reaction in solid state, we made films by blending two of the three polysaccharides, either pectin and chitosan or pectin and ᴋ-carrageenan with different Fe-species. We learned that rheological properties and photochemical properties can be tuned by changing the blend of polysaccharides or the metal species used to make the material.