Fluorescence Monitoring Of Rheological Behavior Of Supramolecular Elastic Network

The movement of polymeric segments is a basic problem in the field of polymer science.With the gradual development of materials research methods,the understanding of the dynamic behavior of the polymer chain is also changing.The flow and deformation of the polymer is called rheology.The rheological behavior of the polymer segment can be measured indirectly through its rheological properties during processing,but this process cannot be visualized.The fluorescence probe technology based on aggregation-induced emission?AIE?is a method that uses the photophysical and photochemical characteristics of AIE molecules to monitor the changes in the structure and physical properties of materials at the molecular level.It has the advantages of environmental sensitivity,real-time dynamic tracking of samples and simple operation.It has advantages over infrared spectroscopy and nuclear magnetic resonance spectroscopy in studying various dynamic processes of polymers.And some molecules with AIE effect will change the fluorescence characteristic parameters?fluorescence wavelength,intensity and fluorescence lifetime?due to environmental changes.After the TPE molecule is combined with the polymer segment,the rotation of the benzene ring around the TPE molecule is affected by the movement of the polymer segment,which affects the degree of fluorescence emission and wavelength shift,thereby mapping a series of changes in the molecular chain during the movement of the polymer segment.Therefore,it is theoretically feasible to use fluorescent probes to study the motion behavior of polymer segments.This paper focus on the monitor of the motion behavior of polymer segments using the fluorescence properties of AIE molecules under the shear force field,to realize the visual operation of the rheometer.?1?Through rational molecular design and the use of click chemistry reactions,1,2-polybutadiene with a large amount of unsaturated bonds in the main chain was successfully modified with amino groups,blended with different amounts of TPE-4COOH to form supramolecular elastic networks with different degrees of hydrogen bonding crosslinking,and their structures were characterized by ¹H NMR,GPC,FTIR,variable temperature FTIR and viscoelastic properties.?2?Through the construction of fluorescence-rheology equipment and the design of test parameters,the supramolecular elastic network at different temperatures and different hydrogen bond contents was sheared,and the change of fluorescence intensity with shear strain was observed.The results show that the fluorescence intensity increases as the shear strain increases,and then the shear strain increases again,and the fluorescence intensity keeps fluctuating around the maximum value.The mechanism was explored by infrared-rheology combined test.This fluorescence characteristic is based on the energy dissipation mechanism of ionic hydrogen bonding.And set the control group PB-4%NH₂/TPE,after fluorescence-rheological testing,it was found that the fluorescence intensity showed a slight increase first and then decreased,because the effect of shear force increased the intermolecular force and made the system viscosity reduced,thereby promoting non-radiative transitions.The self-healing properties of supramolecular elastic networks were tested.Because the supramolecular elastic network contains a large number of dynamic ionic hydrogen bonds,when the material is damaged,the reversible dissociation and reorganization of the ionic hydrogen bonds give the material good self-healing ability.