Photo-controlled Reversible Self-assembly Of Block Copolymer Based On Inclusion Complexation Of β-cyclodextrin

Self-assembly of amphiphilic block copolymer has attracted much attention in recent decades. In this thesis, we separately prepared a series of hydrophobic azobenzen-containing diblock and triblock copolymers and further studied their photo-controlled reversible self-assembly hehavior though inclusion complexation between β-cyclodextrin((3-CD) and azobenzen (Azo).1. Azobenzen-containing diblock copolymer. The azobenzen monomer was first synthesized from phenylamine in three steps. Then a series of hydrophobic azo-contained PAzo-b-PS diblock copolymers were successfully synthesized using reversible addition-fragmentation chain transfer polymerization (RAFT). The hydrophobic PAzo-b-PS diblock copolymers formed stable spherical micelles in aqueous solution though inclusion complexation between azobenzen and β-cyclodextrin. DLS results showed that the size of the micelles increased with the increase of polymerization degree of styrene. Transmission electron microscope (TEM) result indicated that the assembled structure of PAzo-b-PS with β-CD micelles should be a core-shell structure. The reversible assembly and disassembly process of the micelles were realized by alternating visible and UV irradiation, which were confirmed by DLS and TEM. This non-covalently connected photo-controlled reversible assemblies system might have potential applications in many fields.2. Azobenzen containing triblock copolymer. Similar to PAzo-b-PS diblock copolymer, the azobenzen monomer (AzoMA) which contained a methyl acrylate and a difunctional atom transfer radical polymerization (ATRP) initiator EBriB were first synthesized. Then we synthesized Azo-containing triblock copolymers (PAzoMA-b-PMMA-b-PAzoMA) using ATRP. Additionally, β-CD-terminated methoxypolyethylene glycols (MPEG-β-CD) was prepared using Click Chemistry. This hydrophobic PAzoMA-b-PMMA-b-PAzoMA copolymer with MPEG-β-CD self-assembled into mixed aggregates of spherical micelles and hollow vesicles in aqueous solution through β-cyclodextrin-azobenzene host-guest inclusion complexation. The DLS result indicated the size of aggregates increased with the increase of polymerization degree of AzoMA. And the aggregates also showed reversible photo-isomerization by alternating UV and visible light irradiation.