Organic Small Molecular Crystals Based On The Properties Of Bending Response To Stimulation

Organic elastic materials have aroused major attention because of their important potential application in the flexible and wearable devices as new organic materials.Generally speaking,traditional organic molecule crystals tend to be brittle when they are applied with external stress,which considerably hampers their application in the flexible devices field.However,the discover of organic small molecule elastic crystals perfectly compensate for this disadvantage of traditional organic materials.In contrast with some organic complex,it is quite easy to synthesize and purify the organic small molecule compounds which own a broad source,meanwhile,it is also very convenient to obtain their crystals.Additionally,with the rapid development of optical waveguide research in recent years,this new application field of organic elastic crystals have been opened up at the same time.In this thesis,we designed and synthesized two simple organic small molecule elastic crystals.These two crystal materials were deeply investigated by a series of tests such as the three-point bending test,spectrum and Raman spectrum test,which disclosed the relationship between structure and property of crystals.Our investigation provided a new idea for the design of new organic elastic materials.Furthermore,we also carried out the investigation on their application in the organic crystal waveguide.1.In the second chapter,we successfully designed and synthesized another molecule based on the skeleton of(Z)-2,3-diphenylacrylonitrile that mentioned above.We introduced a totally new group,trifluoromethoxy,into the origin skeleton to synthesize a new compound(Z)-4-(2-cyano-2-(4-(trifluoromethoxy)phenyl)vinyl)benzonitrile,CN-TFMOPB.We obtained elastic acicular crystals and plastic lamella crystals by recrystallization.XRD data indicates that two kinds of crystal belong to one single crystalline phase.Single crystal data indicates that crystal possesses layer structure.Molecules in each layer also grow along a axis by ?–? stacking,moreover,because of the tetrahedral configuration of trifluoromethyl group,there are weak F···F interaction which is likely to regenerate between molecular layers.When crystals were applied with external stress,subtle motion of a part of molecules occurred.The molecules in the outer part extended and molecules in the inner part contracted,resulting in the elastic deformation of crystals.Nevertheless,there also exist weak interactions between layers due to the tetrahedral molecular configuration.Therefore,the molecular layer slips slightly when the crystal is applied with external force.The new weak interaction generates accompanied with the rupture of original interaction to fix the molecular layers.Therefore,although the external force is removed,the molecular layers that slip will not return to its original position,causing the crystal to exhibit plastic deformation.In addition,the elastic and plastic optical waveguide loss of this kind of material was also tested.The test results showed that this kind of material has a crucial potential application value in the relevant optical field.2.In the third chapter,we successfully designed and synthesized a derivative of(Z)-2,3-diphenylacrylonitrile which has been already reported,CN-DPVB,(Z)-4-(1-cyano-2-(4-(dimethylamino)phenyl)vinyl)benzonitrile.We obtained a large number of single crystals by slow diffusion of 1,2–dichloroenthane and ethanol system.CN-DPVB single crystals were long yellow needle–like crystals.CN-DPVB single crystals could be bent into a half loop without rupture when the ends were applied with force by tweezers.After the withdraw of the force,the crystal restored instantly and this whole process could repeat for many times.Moreover,it was found that the crystals could bend automatically under the hydrochloric acid atmosphere.The data of single crystal indicates that the molecules in the crystal are obviously layered,where molecules in each layer grow along a axis by ?–? interaction.Therefore,the plentiful weak interactions endow the whole crystal exceptional elasticity.However,when molecules are protonated by hydrochloric acid,the dimethyl amino group will drastically rotate 70 degree.Hence,when crystals were under hydrochloric acid atmosphere,the dimethyl amino group of the molecules on the surface would rotate,which resulted in the subtle motion of molecules and finally bent the whole crystal.In addition,the optical waveguide loss of this kind of material was also tested.The test results showed that this kind of material has a crucial potential application value in the relevant optical field.In conclusion,we successfully designed and prepared two organic crystals with different elasticity properties,which were investigated deeply under various condition.The relationship between the structure and property of these two molecules conspicuously illustrated the relationship between the molecular structure and elasticity property of organic small molecule elastic materials.Our research would provide some new ideas and strategies for the development of organic small molecule elastic materials.