UVM Theses and Dissertations
Format:
Print
Author:
Naik, Sandeep Shahikant Smeeta
Dept./Program:
Chemistry
Year:
2010
Degree:
PhD
Abstract:
This dissertation work will focus on three different areas, temperature and pH-responsive block copolymers, poly(lysine) based organogels and functional lipid mimetic using "thiol-yne" reaction. Double e hydrophilic block copolymers provide a unique opportunity to obtain two different types of aggregates. One of the blocks can be alternately rendered insoluble with an external stimulus to drive the self-assembly. The first research project primarily focuses on pH and temperature as an external stimulus for formation of these aggregates. Poly(propylene oxide), PPO is used as the temperature-responsive block whereas poly(Llysine), PLL is used as the pH responsive block. In addition to forming two different types of aggregates, the secondary structure changes of the poly (L-Iysine) block affect the size of the morphologies formed over the pH range. The morphologies formed were studied as models for drug-delivery applications.
Polypeptides possess secondary structures (e.g., [alpha]-helix and [beta]-sheet) in solution due to cooperative hydrogen bonding. These secondary structures contribute strongly to the selfassembly properties of polypeptide chains and lead to hierarchical three-dimensional supra-molecular arrangements. The second research work is a study of the assembly of poly(L-lysine) in organic solvents like tetrahydrofuran and chloroform to give organogels. The effect of the non-peptide block of the copolymer on gel strength was studied thoroughly. These organogels can be used as rheology modifiers and viscosity enhancers.
The third research area deals with the use of emerging thiol-yne "click" reactions to achieve a molecular geometry which closely mimics a phospholipid structure, with the polypetide block as the head group and dodecyl groups as the two hydrophobic tails. The polypeptide blocks were synthesized, by ring-opening polymerization using propargylamine as the initiator to yield alkyne-terminated polypeptide. These peptides were then coupled with a dodecylthiol group using photoinitiator-mediated thiol-yne chemistry. These block copolymers assemblies have potential application as phospholipid mimics in biological sytems.
Polypeptides possess secondary structures (e.g., [alpha]-helix and [beta]-sheet) in solution due to cooperative hydrogen bonding. These secondary structures contribute strongly to the selfassembly properties of polypeptide chains and lead to hierarchical three-dimensional supra-molecular arrangements. The second research work is a study of the assembly of poly(L-lysine) in organic solvents like tetrahydrofuran and chloroform to give organogels. The effect of the non-peptide block of the copolymer on gel strength was studied thoroughly. These organogels can be used as rheology modifiers and viscosity enhancers.
The third research area deals with the use of emerging thiol-yne "click" reactions to achieve a molecular geometry which closely mimics a phospholipid structure, with the polypetide block as the head group and dodecyl groups as the two hydrophobic tails. The polypeptide blocks were synthesized, by ring-opening polymerization using propargylamine as the initiator to yield alkyne-terminated polypeptide. These peptides were then coupled with a dodecylthiol group using photoinitiator-mediated thiol-yne chemistry. These block copolymers assemblies have potential application as phospholipid mimics in biological sytems.