"Click" Synthesis Of Amphiphilic Copolymers With Different Topological Structures And Their Self-Assembly

As a set of highly efficient and specific reactions that capable of being conducted in a range of environments under relatively mild conditions, click chemistry has recently attracted increased attention. Since their development, click chemistry strategies have been rapidly integrated into the field of macromolecular engineering, and offered great potential in the synthesis of macromolecular with increasing complexity and functionality through its efficiency and broad applicability. Self-assembly of polymeric supramolecules is a powerful tool for producing functional nano-materials with regular structure and has been successfully applied in various fields such as drug delivery, catalysis, nano-reactor and sensor. Induction of click chemistry into polymer synthesis and functionalization not only enriches the structural of amphiphilic copolymer, but also enable the efficient generation of polymeric assemblies with diversified function. In this dissertation, a series of amphiphilic copolymer with distinct topological structures have been successfully synthesized by using click chemistry strategies. The solution self-assembly behaviors of them were investigated. This dissertation can be divided into four major sections, and the main research contents and conclusions are shown as follows:1. Ultrathin polymeric nanotubes prepared form self-assembly of alternating copolymer and their surface functionalizeAmphiphilic alternating copolymer P(DHB-a-BDT) was synthesized through an epoxy-thiol click reaction between 1,4-butanedithiol and butadiene diepoxide. The self-assembly of P(DHB-a-BDT) was achieved by adding selected solvent (Water) to common solvent (DMSO). TEM, Cryo-TEM and AFM were used to directly detect the morphology of the self-assemblies. The results indicated that the alternating copolymer self-assembled into nanotube in DMSO/water mixed solution. Those nanotubes were constructed with an ultrathin wall of 2 nm. Several types of functional groups, such as carboxyl groups, amino groups, or peptides, have been introduced into the nanotubes by click copolymerization with functionalized dithiols or amines, and the functionalized nanotubes were verified by TEM, AFM, CLSM and Zeta potential measurement. In addition, the details of the self-assembly process as well as the nanotube structure have been disclosed by a dissipative particle dynamics (DPD) simulation.2. Physical gel prepared form self-assembly of alternating copolymer and their properity.Amphiphilic alternating copolymer P(DHB-a-EDT) was synthesized through the through an epoxy-thiol click reaction between 1,2-ethanedithiol and butadiene diepoxide. The resulting polymer can form physical gel in DMSO/water mixed solution with the critical gelation concentration (CGC) as low as 2.5 mg/mL. SEM and TEM were used to directly detect the morphology of the gel. The results indicated that P(DHB-a-EDT) first self-assembled into micelles than the micelles aggregate together to form continuous and open fibrous network in the gel formation process. FTIR and DLS study at various temperatures further revealed that the driving force of the gelation is ascribed to the hydrogen bonding interaction together with hydrophobic interaction. Besides, The gel also exhibits typical dynamic mechanical behavior of physical gels in rheological measurement.3. Synthesis of comb-like copolymer with amphiphilic side chain and its photo-responsive self-assembly behavior.Amphiphilic comb-like copolymer PAzoAM was synthesized through fast click-like Menschutkin reaction of PDMAEMA with propargyl bromide, followed by Cu(I)-catalyzed azide-alkyne cyclo-addition (CuAAC) with 4-azidoazobenzene. The self-assembly of PAzoAM was achieved by adding selected solvent (Water) to common solvent (DMF). TEM and SEM results indicated that the amphiphilic comb-like copolymer self-assembled into vesicle in water. Those assemblies show dynamic/switchable morphology in response to light.4. Synthesis of amphiphilic hyperbranched multiarm copolymer with thiol as focal point (SH-HBPO-star-PEO) and its applications in gold surface modification.Amphiphilic hyperbranched multiarm copolymers with thiol as focal point (SH-HBPO-star-PEO) were synthesized via a combination of cationic ring-opening polymerization and thiol-yne click chemistry. The water dispersibility of SH-HBPO-star-PEO modified Au nanoparticles was examined by TEM, DLS and UV-vis spectra. The protein adsorption on these SH-HBPO-star-PEO self-assembled monolayers on Au surface was examined by using a quartz crystal microbalance with dissipation (QCM-D) using bovine serum albumin (BSA) as model protein. All polymers demonstrated good antifouling properties, a correspondence between antifouling properties and degrees of branching (DB) of HBPO core was observed and the highest protein-resistance was achieved with a SH-PEHO-star-PEO with a DB of 17%. The antifouling ability seems to decrease with the increase of DB in the HBPO core, which may be caused by lower chain flexibility of the copolymer with a higher DB.