Synthesis Of Poly (Tert-butyl (Meth) Acrylate)-b-Poly (N-isopropylacrylamide) By Atom Transfer Radical Polymerization And Their Self-assembly Behavior

It is well-known that the amphiphilic diblock copolymers enable them to self-assemble to form spherical micelles with a core of hydrophobic segment and a shell of hydrophilic segment in aqueous medium.Over the past decades,self-assembly of amphiphilic block copolymers in aqueous solution has attracted much attention for their wide range of applications in drug delivery,metal nanoparticles,surface modification,etc.In this thesis,two series of AB type amphiphilic block copolymers were synthesized by atom transfer radical polymerization(ATRP).Their structures were precisely characterized.The assembly behavior of the block copolymers in selective solvents and the characteristics of their morphology were studied in detail.The main results achieved are as follows: 1.Both poly(tert-butyl acrylate)(PtBA-Cl)and poly(tert-butyl methacrylate)(PtBMA-Cl)were synthesized by using l-Chlorophenylethane(1-PECl)as initiator and CuCl/ N,N,N',N",N"-Pentamethyldiethylenetriamine(PMDETA)as catalyst. Then,poly(tert-butyl acrylate)-b-poly(N-isopropylacrylamide) (PtBA-b-PNIPAM)and poly(tert-butyl methacrylate)-b-poly (N-isopropylacrylamide)(PtBMA-b-PNIPAM)were synthesized by using PtBA-Cl and PtBMA-C1 as macroinitiator respectively and CuCl/PMDETA as catalyst.The molecular weights and polydispersity indexes(PDI)of PtBA-Cl,PtBMA-Cl,PtBA-b-PNIPAM and PtBMA-b-PNIPAM were determained by gel permeation chromatography (GPC).The results showed that the number average molecular weights of PtBA-Cl,PtBMA-Cl,PtBA-b-PNIPAM and PtBMA-b-PNIPAM approach the theoretical values and their molecular-weight distributions are narrow.The structures of PtBA-Cl,PtBMA-Cl,PtBA-b-PNIPAM and PtBMA-b-PNIPAM were characterized by FTIR and ~1H NMR.2.Micelles solutions were prepared by block copolymers of PtBA-b-PNIPAM and PtBMA-b-PNIPAM in aqueous solution.The morphologies of the micelles were observed by scanning electron microscopy(SEM)and transmission electron microscopy(TEM).The results revealed that both PtBA-b-PNIPAM and PtBMA-b-PNIPAM can form core-shell micelles with PtBA or PtBMA as core and PNIPAM as shell in aqueous solution via self-assembly.3.The self-assembly behaviors of the block copolymers were investigated by dynamic light scattering(DLS).The results indicated that at the same temperature,the hydrodynamic diameters of PTN1,PTN2 and PTN3 micelles are reduced in turn while the hydrodynamic diameters of PTN2-1,PTN2 and PTN2-3 micelles are raised in turn.The hydrodynamic diameters of PNT1,PTN2 and PNT3 micelles are also reduced in turn.With increasing temperature,the hydrodynamic diameters of all micelles tended to decrease,indicating that the micelles are sensitive to temperature.The VPTT of the micelles is around 31℃. Furthermore,the hydrodynamic diameters of PtBA-b-PNIPAM micelles is in a range of 150-215nm.At the same temperature,the hydrodynamic diameters of PMN1, PMN2 and PMN3 micelles are reduced in turn while the hydrodynamic diameters of PMN2-1,PMN2 and PMN2-3 micelles are raised in turn. The hydrodynamic diameters of PNM1,PMN2 and PNM3 micelles are also reduced in turn.With increasing temperature,the hydrodynamic diameters of all micelles tended to decrease,indicating that the micelles are sensitive to temperature.The VPTT of the micelles is around 31℃. Furthermore,the hydrodynamic diameters of PtBMA-b-PNIPAM micelles is in a range of 155-290nm.4.The effects of the concentration of the block copolymers in solution and the solvents on the self-assembly behavior were preliminarily studied.The results showed that with increasing of PtBMA-b-PMPAM/THF solution in aqueous solution,the hydrodynamic diameters of micelles are raised.The sizes of the micelles are significantly affected by the solvents.