Synthesis And Self-assembly Of Amphiphilic Rod-coil Molecules Based On DSA Unit

Aggregation-induced emission/aggregation-induced emission enhancement(AIE/AIEE)has recently attracted intense research,and a large number of AIE/AIEE luminogens(AIE/AIEEgens)have been constructed for application in diverse scientific fields.The AIE and AIEE effects are similar,but not identical,photophysical behaviors,which are closely related to molecular architectures.However,the current understanding of the inherent differences between AIE and AIEE is still obscure.It is well known that there are two different photoluminescence phenomena aggregation-caused quenching(ACQ)and AIE in the aggregation of luminescent materials.In general,ACQ and AIE effects are competitive in the photoluminescence.The dominant role of ACQ and AIE effects depends on the molecular structure and the intermolecular packing.For J-aggregates,because of their highly ordered intermolecular packing,the red shift phenomenon and the increase of emission intensity have been widely recognized in various aggregates.In the study of supermolecular self-assembly with 9,10-distyrylanthracene(DSA)as the framework,DSA molecules have good application prospects in fluorescent probes and optical materials due to the AIE effect.In this thesis,amphiphilic rigid flexible block molecule with rigid part of DSA was designed and synthesized.The flexible part was a straight-line chain and a branch chain containing nitrogen atoms.Because containing anthracene unit in the structure of DSA,it can interact with the electron deficient molecules form a charge transfer complex through the donor acceptor interaction.Hence,we connected DSA with the linear polyepoxyethane chain to obtain the target molecule.By adding the electron deficient small molecule tetranitrofluorenone,we studied the effect of the molecular assembly and the change of the morphology by the donor acceptor interaction.The results show that the charge transfer complex was formed through the interaction between donor and acceptor.With the addition of acceptor,the molecular assembling morphology changes from dendrite to spiral fiber to strip like.The introduction of nitrogen into the molecular structure was usually used for pH responsiveness.The rod builing blocks incorporating DSA unit have the different lengths of the dendrimers with nitrogen atoms.Subsequently,we studied the effect of the length of the flexible chain and the pH of the solution on the molecular assembly performance.The results show that the increase of the length of the flexible chain weakens the intermolecular force and leads to the looser arrangement of the molecules.As the increase of the acidity of the system,the morphology of the molecular assembly is changed.Interestingly,under the irradiation of 365 nm UV light,the original UV absorption of the molecule decreases,and the fluorescence were obviously quenched.With the increase of irradiation time,this phenomenon was more obvious,which were the same as that under the irradiation of 254 nm UV light.