Study On The Synthesis Of Polyfluorenes-based Rod-coil Block Copolymers Via Double-controlled Polymerization And Its Self-assembled Behavior

The rod-coil block copolymers contained flexible coil-like chain segment and rigid rod-like chain segment are kinds of special copolymers which are very different to coil-coil block copolymers in self-assembling stucture and phase behavior,have gained great instreasting in many fields.In this paper,we proposed a method for preparing polyfluorenes-based rod-coil block copolymers via double-controlled polymerization.And then,we researched its self-assembled behavior and stimuli-responsiveness in selective solvent.The main conclusions are listed blow:(1)A series of rod-coil block copolymers poly[2,7-(9,9-dihexyl-fuorene)]-b-poly[2-(dimethylamino)ethyl methacrylate](PFH-b-PDMAEMA)were synthesized by double-controlled polymerization of combainning controlled suzuki cross-coupling and atom transfer radical polymerization(ATRP).Comparing to traditional method,this polymerization method could been controlled well and the copolymers showed low polydispersity index(PDI)with well-defined structure.The research of PFH-b-PDMAEMA has shown that the PFH is crystalline conjugated polymer but will be amorphous in the copolymer system.The advanced block PDMAEMA played main role in polymer thermal performance(TGA and DSC).The spectrum showed PFH block controlled the fluorescence properties of copolymer and lead to the aggregation induced fluorescence decrease in THF solution.(2)The self-assembling of PFH-b-PDMAEMA in selective solvent for coil block has been researched.The PFH-b-PDMAEMA could self-assemble into nanofiber-like micelles in aqueous,THF-water mixed solutions and alcohols.The morphologies of the micelles could be varied from nanofibers,to cylinders,and spheres by changing the composition of the selective solvents and gradually transited from the short stick to ball with the decline of polarity of the alcohol solvent,observed by TEM and AFM.The spectrum showed the H-type aggregation by ?-? stacking of cored PFH block may be the key of various assembled morphologies.And the proportion of solvent orsolvent polarity may affect the ?-? stacking between PFH,lead to the change in assembled morphology.(3)The morphology and photoluminescence of these micelles were p H-or temperature-responsive in aqueous.Instreastingly,the fluorescence intensity increased with temperature increased and became stronger as the p H increased(p H < 9)but reduced again when the p H further increased(p H > 9).And the morphologies of micelles transited into shorter linear or shuttle-like structures with the change of p H and are aggregated as temperature-induced.Such specific phenomenon may mainly caused by the changes or transition in PDMAEMA chains and the effect of aggregated state of micelles.