Construction Of Chiral Nematic Structural Dual Response Composite Films By Self-coassembly Method

Cellulose nanocrystals(CNCs)is prepared by acid hydrolysis of cellulose raw materials.CNCs have unique evaporation-induced self-assembly(EISA)characteristics,and can form one-dimensional photonic crystals with chiral nematic structure.Its important functional applications are based on the assembly characteristics.Many functional materials can be obtained by using the assembly characteristics and template function of CNCs,which have been applied in the fields of chiral catalysis,anticounterfeiting,humidity and optical induction.Based on the composite assembly and template function of nanocellulose,a functional film with color/drive dual response to water was constructed in this paper.1.Preparation and characterization of Latex/GO/CNCs(LGC)chiral nematic ternary composite films.LGC ternary composite membranes were prepared by evaporation and induction of Latex/GO/CNCs water dispersions.A series of characterizations show that the ternary films have asymmetric chiral nematic structure.Due to the self-assembly characteristics of CNCs sevaporation,the ternary composite films have chiral nematic structure,and GO is asymmetrically distributed in the upper and lower layers during evaporation due to gravity and entropy effects.At the same time,GO doping also induces a gradient change in pitch of chiral nematic structure from top to bottom.2.Study on preparation and properties of Latex/GO binary composite membranes(LG)with double response.On the basis of LGC composite films,the CNCs templates were removed by alkali treatment.The results show that the chiral nematic structure and the asymmetric distribution of GO in the dried LG films can be maintained.The structure and optical properties of the films are obviously different,and the flexibility of the films is greatly improved.Due to the different wettability of LG film in the upper and lower layers,the expansion degree of water is different,and the pitch of LG film also changes at the same time,which results in synchronous response of color/drive.3.ER/GO(EG)composite films were prepared by evaporative composite assembly of epoxy resin(ER),GO and CNCs and alkali treatment.Unlike LGC system,CEG system can add a lot of GO.In addition to the similar color change and driving response behavior of the final EG film,it is also found that the driving response behavior will gradually disappear with the increase of GO.However,when adding GO equivalent to LGC system,the EG film can show large-scale response to water and bend into a more complex spiral structure.