Preparation And Fluorescence Properties Of Cylindrical Molecular Brushes

Molecular brushes are a special type of graft copolymers with multiple polymer chains end tethered to a linear polymer.Owing to their typical worm conformation,remarkable chain end effect,precise adjustable aspect ratio and unique stimuli-responsive properties,molecular brushes have shown wide applications ranging from catalysis,drug delivery and optoelectronics.Furthermore,with the development of polymer chemistry,various living polymerization methods have been successfully used to prepare molecular brushes.However,the development of simple and efficient methods to synthetize molecular brushes with precise and controllable chemical composition,structure and properties is still a key problem to be solved.In order to develop new preparation method,further understand the effect of the chain structure on the performance of molecular brushes and explore the new features,we designed and synthesized a series of molecular brushes,and studied the morphology,thermal properties and fluorescence properties using modern testing methods.The specific research contents are as follows:1.The first application of Lewis pair-mediated polymerization(LPP)in the simple and efficient synthesis of molecular brushes has been demonstrated.Poly(NHO)as a Lewis base backbone was firstly prepared by RAFT polymerization and the successive deprotonation.Together with Al(C6F5)3,the polymerization of methyl methacrylate and?-valerolactone can be promoted,leading to the formation of side chains via the grafting-from approach.NMR,GPC,AFM and DSC characterization indicate the successful formation of worm-like molecular brushes.Polymerization kinetics investigation confirms that LPP is highly efficient and controllable.The current strategy provides a new method for the synthesis of polymers with well-defined topological structures.2.A novel molecular brush fluorescence sensor was designed and developed for the detection of intracellular zinc ions.The molecular brush of poly(2-oxazoline)was synthesized via REM-GTP and the grafting-from LCROP,and end-capped by a Zn2+-responsive functionality.Ion response fluorescence investigation reveals the molecular brush response to zinc with high selectivity.Fluorescence experiment explains the mechanism of the molecular brush toward zinc.Cytotoxicity experiment and living cell imaging experiment proved that the molecular brush fluorescence sensor can be used for the detection of zinc ions in the cell due to the good biological compatibility and membrane permeability.Poly(2-oxazoline)molecular brush fluorescence sensor provides a practical tool in the field of biological imaging.3.Based on the fluorescence response to zinc ion mentioned above,we further expanded and obtained a series of tunable fluorescence(including white light)polymeric hydrogels through a simple blending method and by adjusting the stoichiometry of different ions(Zn2+,Eu3+and Tb3+).FT-IR,GPC and rheological data confirms the formation of the gel system.The tensile shear test proves that the polymer gel has high strength(?b,0.53 MPa)and good mechanical properties(E 0.12 MPa,?b 133%).Furthermore,the experiments show that the white light gel has obvious fluorescence response to the stimuli of external acid and alkali.It can be used to prepare highly reversible pattern gel for information storage and display.The pattern gel is an ideal information security material and is expected to be applied in other relevant fields such as biology.