Charge Transfer Effects In Supramolecular Gels From Diphenylalanine Derivatives

Compared with conventional polymer gels,supramolecular gels have lower critical gel concentration(CGC),thermal reversibility and easy degradability,which make them more adaptable to a variety of applications.Although supramolecular gels can largely replace polymeric(natural)gels,they need to be modified and functionalized to further broaden their applications.Charge transfer(CT)interaction,as a hot topic in the field of supramolecular interactions nowadays,should be an effective strategy for the modification of supramolecular gels.For this purpose,a study on the charge transfer effect in supramolecular gel systems was carried out,which is mainly included as follows:(1)Tuning rheological behaviors of supramolecular aqueous gels via charge transfer interactions.The first part of this thesis achieves the tuning of the rheological behavior of supramolecular gels through CT interactions:we synthesized a pyrene-containing derivative of diphenylalanine as an electron donor gelator and derivatives of naphthalenediimide or 3,5-dinitrobenzene as matching electron acceptor additives;Through the comparison of single-component gels and the CT gels,we found that the viscoelastic properties and strength of the original gels were modulate by adding different acceptor molecules to the original gels or changing the ratio of selected acceptor molecules in the system.More importantly,by changing the ratio of the acceptor in the system,the storage modulus can be continuously adjusted in a wide range of 190 000 to 50 000 Pa.These findings are expected to be a new strategy to tune the mechanical properties of functional supramolecular materials and provide new ideas to expand the application situations of supramolecular gels.(2)Tuning photophysical properties of gels by photoinduced charge transfer effects.The second part of this thesis achieves photophysical property modulation of supramolecular gels through photoinduced CT effects:we synthesized an anthraquinone-containing derivative of diphenylalanine as an electron acceptor gelator and the commercial fluorescent probe 1,3,6,8-pyrenetetrasulfonic acid tetrasodium salt as an electron donor additive;Comparison with single-component gels and composite gels we found a novel photoinduced enhanced CT effect;Through the study of photophysical behavior of the composite gels,it was found that the photoinduced CT interaction makes a dramatic change in the photophysical properties of the composite gels,with a threefold increase in fluorescence quantum yield(15.1%to 46.7%)compared to that before illumination.These findings are expected to provide a new strategy for the study of the photophysical properties of CT composite supramolecular gels and provide a helpful reference for the development of supramolecular gel-based luminescent soft matter materials.Based on the fundamental understanding of charge transfer interactions,the paper explores the feasibility of its applications in related fields by exploring its tuning effect in supramolecular gel systems.It provides a new strategy for the functionalization of supramolecular gels,which will be of enlightening significance for future fields involving supramolecular self-assembly and soft materials.