Synthesis Of Main Chain Bile Acid Polymers And The Construction Of Supramolecular Systems

The natural occurring bile acids with the curved rigid steroidal skeleton anddistinctive facial amphiphilicity have attracted great attentions in polymer chemistry andsupramolecular chemistry. Until now, the preparation of high molecular weight mainchain bile acid polymers is still a great challenge. The supramolecular functionalmechanisms of bile aicd polymers, which are controlled by the unique steroidal skeletonand facially amphiphilic properties, is still in its infancy. In this dissertation, based onthe bile acid building blocks and their unique structures, we design and synthesis aseries of main chain bile acid polymers and focused on their supramolecular assembly,multi-level hierarchical assembly as well as the wrinkle phenomenon. The major workis as follow:A series of bile acid derivatives with terminal alkyne and azide reaction groupshave been synthesized. Due to their rigid steroidal skeleton and facial amphiphilicity,the single crystals of three compounds were obtained by crystallization. The alkyne andazide groups are paralleled to each other in the crystal lattice. By topochemicalpolymerization, the high molecular weight main chain bile acid polymers were obtainedin the absense of metal catalysts and the organic solvents. With the advantages of100%monomers conversion, the polymerization of the alkyne and azide groups occurred inthe crystal lattice and the resulted polymers don’t need further purification. Comparedwith the polymerization process in the amorphous solid state and solution phase, thereaction efficiency and the molecular weight as well as the selectivity of the1,4-triazolegroups were greatly improved.The supramolecular assembly behavior of main chain cholic acidbiopolymers was studied. Depending on the unique rigid skeleton and facialamphiphilicity, the supramolecular assemblies were characterized by thevesicles stability, adaptability and reversible adjustment as well as the uniquehydrophilic and hydrophobic binding pockets in the vesicle membranes. Due tothe presence of triazole groups in the polymer chains, the permeability of thevesicle membrane was response to the pH changes and this process is reversiblefor several cycles. The main chain cholic acid polymers with regioselective1,4-triazolegroups as linkages were synthesized and their multi-level hierarchical assemblyas well al wrinkling phenomenon were developed. Induced by the polar solvents,the folded structures with one-dimensional hydrophilic cavity were firstlyformed and then stacked together leading to the multi-lamellar membraneassemblies. Based on the multi-level ordered assembly structures, which werecontrolled by the rigid steroidal skeleton and their unique facial amphiphilicity,and the physical assembly process, the large scale ordered wrinkles wereobtained. By combination of supramolecular multi-level assembly and physicalassembly, the biopolymer wrinkels with the potential applications in the celladhesion were developed.