Synthesis And Self-assembly Of Amphiphilic Thermo-sensitive Block Copolymer And Copolymers Brush

Aggregation of amphiphilic block copolymer is very important in self-assembly of supramolecular. Copolymers could assemble in bulk, in solution and in thin film. With the combination of hydrophilicity and hydrophobicity, block copolymers could assembly into a rich variety of morphologies in aqueous solutions. So self-assembly of amphiphilic block copolymer in aqueous media is of fundamental interest for applications in delivery drugs, sewage treatment and production of nanoparticles.As we all know, the structures of block copolymers are relatively simple and block copolymers could self-assemble into periodic microdomains by changing the chain composition, chain length, and so on. Thus, self-assembly of amphiphilic block copolymer is becoming a hot spot of technical research in the world of the preparation of nanomaterials over two decades.Firstly, an amphiphilic block copolymer PGMA-b-PNIPAM was prepared by the addition of N-isopropyl acrylamide (NIPAM) to macro-RAFT agent poly(glycidyl methacrylete) (PGMA), which was synthesized first via reversible addition-fragmentation chain transfer polymerization (RAFT) using cumyl dithiobenzoate (CDB) as the RAFT agent. The polymers obtained were characterized in detail by IR,1H NMR, gel permeation chromatography (GPC). Furthermore, we investigated the self-assembly of amphiphilic block copolymers in aquous solution and core-shell micelles can be obtained. To obtain more stable micelles, cross-linking reactions between ethylenediamine and epoxy groups were performed. Finally, thermo-sensitive behavior of micelles was investigated by using DLS and LSS.Brush copolymers are a special class of graft copolymers in which side chains are grafted densely onto a polymer backbone. Those side chains of brush copolymers are stretched away from the backbone to form a brushlike or a wormlike cylindrical conformation because of their crowding arrangement. On the same time, brush copolymers could self-assemble into spherical micelle, vesicle and lamellar structure, which have been verified experimentally and theoretically.To obtain some richer types of aggregates, we prepared amphiphilic brush copolymers containing poly(poly(ethylene glycol)methyl ether methacrylate), poly(s-caprolactone) and poly(N-isopropyl acrylamide) side segments. The amphiphilic brush copolymers with poly(poly(ethylene glycol)methyl ether methacrylate), poly(s-caprolactone) and poly(N-isopropyl acrylamide) side segments were prepared via reversible addition-fragmentation chain transfer polymerization (RAFT), ring-opening reaction (ROP) and click chemistry. The syntheses combined ring-opening polymerization of s-caprolactone (ε-CL) through a "grafting from" strategy and "click" reaction with alkyne-poly(N-isopropyl acrylamide) (alkyne-PNIPAM) through a "grafting to" strategy, using multifunctional poly(glycidyl methacrylete)-b-poly(poly(ethylene glycol)methyl ether methacrylate) that bears hydroxyl and azide groups from junction points. The reaction procedures were controlled, and the structures of obtained brush copolymers were well characterized by IR,1H NMR, gel permeation chromatography (GPC). These brush copolymers can self-assemble into micellar structures in THF/H2O and the thermo-sensitive behavior of micelles were investigated by using DLS and LSS.