Fabrication Of Smart And Responsive Supermolecular System Based On Self-assembly Of Block Copolymer

It is well known that amphiphilic block copolymer can self-assembly into core-shell micellar structures in selective solvents which offer a powerful method for fabricating ordered and regular nanostructure as scaffolds and templates. As a result, the block copolymer containing functional organic molecule enable to form stable and highly regularity nanometer scale pattern. Functional organic molecule with block copolymer self-assembly has been widely developed and provides a simple and effective method of preparing responsive multifunctional system in solution and in thin film.To begin with, we systematically investigated the effects of the solvent nature, solution concentration and solvent-induced on the self-assembling behaviors of two amphiphilic block copolymers poly (styrene-b-2-vinylpyridine) PS-b-P2VP and poly (2-vinylpyridine-b-cyclohexyl methacrylate) PCMA-b-P2VP. The affinity of the solvent to different blocks defined by the polymer-solvent interaction parameter,χP-S seriously affected the solubility and self-assembly behavior of the block copolymers. In addition, we used a selective solvent-induced method to achieve nanopatterns by core-corona inversion of micelles in situ. Due to the different solubility of the block chains, thin films were responsive to acid and ethanol treatment to obtain nanoporous or nanoring templates. The morphology of thin film with selective solvent-induced method offers a powerful method for fabricating ordered and regular nanostructure as scaffolds and templates.In the second, we tried to use the block copolymer micelles to incorporate 4- hydroxyl-stilbazole, a simple photoswitching molecule, and investigate how it affected their self-assembly behavior in the micelle structure. Photochromic process of 4-hydroxyl stilbazole molecule with c=c bond cause the changes of the micellar aggregations within the microenvironment of block copolymer. Furthermore, the stilbazole group can not only undergo trans-cis isomerization but also coordinate to Zn2+ ion and have pH response. Therefore the incorporation of the 4- hydroxyl stilbazole generated simulative signal to influence and control the micellar aggregations. We obtained multiple responsive systems in the assembly process such as UV light, metal ion and pH signal. We assured that the incorporation of the stimuli-responsive materials into the block copolymer will have an amount of potential applications in biochemistry and medicine areas.F?rster energy transfer (FRET) is a nonradiative process whereby an excited state donor transfers energy to a proximal ground state acceptor through long-range dipole-dipole interactions. The rate of energy transfer is highly dependent on many factors, such as the extent of spectral overlap, the relative orientation of the transition dipoles, and most importantly, the distance between the donor and acceptor molecules. In our work, Pyrene (donor) and Salicylidene Schiff Base (acceptor) has been successfully coated in the PS-b-P2VP micellar nanostructure which provides as scaffold to qualify the F?rster radius (1-10 nm) between donor and acceptor. In the FRET without AIE, since fluorescence quantum yield of SPEA is zero, only the fluorescence emission intensity of Pyrene has been considerably quenching through energy transfer. With the time growth, SPEA molecule can occur aggregation induced emission(AIE). Under the excitation wavelength of Pyrene, the solution displays a remarkable green light emission which can observe easily by the naked eyes. Moreover, the increased temperature will accelerate the movement of SPEA-AIE molecules leading to destruct the AIE effect and also the change of FRET efficiency. We achieved a controllable smart response system with both AIE and FRET methods. The novel preparation of FRET on-off-on switch and aggregation induced emission in the same system has a wide potential application in biological detection and drug carries.