Formation Of Chiral Supramolecular Composite Films In Block Copolymer Induced By Hydrogen Bond

In recent years,supramolecular helical structure assembly in bulk copolymers have attracted intensive attention due to their unique structures and advantages,especially in designing functional materials.Based on the previous study in our group,additive driven self-assembly has been employed as a method to enhance block copolymer phase saparation and form a well-ordered chiral system.This method is based on the selective interaction between tartaric acid and on segement of block copolymer.At the same time,it can achieve precise control of the chirality and the size of the assembled structure.In this work,we selected tartaric acid?TA?as chiral source to induce assembly of achiral block copolymers for preparation hybrid films with chiral helical structure.?1?Firstly,the effect of molecular weight of polymer segment on the helical self-assembly in bulk was investigated.The linear block copolymers,PBMA-b-PEO,with different PEO mass fractions,were synthesized by atom transfer radical polymerization?ATRP?method.Then,helical structure with controlled handedness was prepared by incorporating TA molecule into block copolymer PBMA-b-PEO.In the hybrid film,intermolecular hydrogen bonding acted as a driving force to induce helical phases self-assembly.Experimental results proved that intermolecular hydrogen bonding between PEO block as a minority phase and TA can enhance the segregation strength of the systems.At the same time,the chiral information was transferred from TA molecular to achiral block copolymer to yield supramolecular helical structure.When PEO mass fraction was in the range of 0.17 to 0.24,the block copolymer could assemble into helical structures;when the mass fraction of PEO was up to 0.26,a regular layer structure was formed,in which chirality transfer occurred,but helical structure was not formed.Based on these results,chiral functional composite film with fluorescence responsive was prepared by co-assembly of PBMA-b-PEO,TA and 1-hydroxyindole(C₁₆H₁₀O)fluorescent small molecule.The chiral helical arrangement of C₁₆H₁₀O in the composite film was achieved,and the composite film shows a clear fluorescent chiral information.?2?Further,block copolymer PS-b-P4VP oriented perpendicular to the substrate was selected as achiral block copolymer.And helical structure was prepared by incorporated with TA molecule.The structure characterization of PS-b-P4VP/TA hybrid film indicated that a well-ordered chiral structure of the block copolymer was formed by annealed for 72 h.After soaked in ethanol,the P4VP phase swelled and rearranged.So that the contact angle was significantly reduced.The CD and VCD spectra in the film state showed that the chiral information was transferred from the TA molecule to the PS-b-P4VP/TA hybrid film.This method provided a new way for preparation of composite films with controlled chiral porous structure.?3?Finally,the chiral information transfer behavior from TA to bottle brush block copolymer P?NBPS?-b-P?NBPEO?was investigated.In this system,bottle brush block copolymer P?NBPS?-b-P?NBPEO?has larger size domain spacing and more rapid assembly kinetics compared with line block copolymer.P?NBPS?-b-P?NBPEO?with narrow molecular weight distribution by ROMP was prepared for hybrid films by blended with TA molecule.In which intermolecular hydrogen bonding acted as a driving force to induce chiral information transferred.Circular dichroic?CD?and vibration circular dichroism?VCD?were used to characterize the chirality of hybrid film.The experimental results proved that after the composite film annealed,the chiral information was transferred to the bottle brush copolymer from TA molecule and at the same time the segregation of the system was increased.