Preparation And Characterization Of Helical Structure In Block Copolymer Film Induced By Hydrogen Bond

Polymer with precisely helical structure has wide applications in chiral recognition,chiral light emission,chiral catalysis and so on.Present research on this topic are mainly focused on the solution environment,and the preparation and control of the helical structure in the film system is still in the initial stage.Block copolymer can self-assemble into various ordered nanostructures and can be used as template in microelectronics,selective separation and so on.Combining the helical structure with block copolymer to prepare block copolymer helical structure is expected to achieve applications in chiral optical,chiral separation,especially in mesostructured materials preparation.How to simply prepare the helical structure in block copolymer film and control its rotation becomes one of the hot spots of research.In this paper,the helical structure of block copolymer was prepared by the method of chiral small molecule doping.The details are as follows:(1)PS-b-PEO/TA hybrid films were prepared by doping chiral tartaric acid molecules(TA)in PS-b-PEO.PEO blocks can form intermolecular hydrogen bonds with carboxyl and hydroxyl groups in the chiral TA calculated by software simulation.The chiral signals of the carboxyl groups on the hybrid films increase with the increase of the doping ratio,and the chiral signals of the PS blocks appear,indicating that the chiral transfer of TA not only occurred on the PEO chain directly,but also on the non-hydrogen bonding PS chain.This chiral transfer does not depend on the formation of helical structures.Compared with undoped PS-b-PEO,the incorporation of TA reduced the crystallization peak of PEO block,enhanced the microphase separation.The glass transition temperatures of PS block and PEO block were improved.The results of TEM showed that when the TA ratio was 22%,the helical structure can be formed,and the helicity of helical structure could be controlled by chirality of TA.(2)We further investigated the chiral transfer behavior of the crosslinkable block copolymers PIP-b-PEO and PBd-b-PEO by chiral molecular doping.The chiral signal of the sample increased with the increase of the TA doping ratio,and the chiral signal of carbon-carbon double bond in the block copolymer appeared.However,it was not found in the solution,indicating that the chiral transfer of TA to the macromolecular skeleton can only occur in the solid film,which can not be achieved in the solution.And this chiral transfer capability is closely related to the segment mobility.PBd-b-PEO / TA hybrid films were cross-linked by UV then removed the chiral molecule,which resulted in chiral controllable porous block copolymer films.