Tunable Water-soluable Supramolecular Polymers Via Visible Light Regulated Host-guest Interactions

The development of photoresponsive supramolecular polymers through the noncovalent-interaction-driven self-assembly between the monomers incorporated with photoactive functional modules;will facilate the construction of novel photoresponsive functional supramolecular materials by taking the combined advantages of both supramolecular polymers and photoresponsiveness.In this dissertation,a unique CB[8]/azobenzene based host-guest system featured with visible-light regulated encapsulation behavior was constructed,by using which as noncovalent conjugations the novel visible-light responsive water-soluble host-guest supramolecular polymer could be further fabricated.First of all,we have designed and synthesized two types of water-soluble ortho-difluoro-substituted azobenzene(FAB)guest molecules with a univalent pyridine cation unit(F1)and a divalent viologen unit(F2),respectively.In the absence of light,experimental investigation showed that F1 E molecule containing trans-FAB unit could be co-encapsulated with a viologen(MV)molecule by the cavity of CB[8] to form a hetero-ternary host-guest complex of CB[8]·F1E·MV.Upon irradiating this complex with visible light of λ > 500 nm could induced the E→Z photoisomerization of the encapsulated azo guest,resulting in the formaton of CB[8]·F1Z binary host-guest complex by excluding the MV guest out from the cavity of CB[8].In the case of F2,without irradiation,two F2 E molecules could be encapsulated by two CB[8] hosts to form the host-guest complex of CB[8]2·F2E2,in which each of the CB[8]’s cavity was filled with an trans azo unit and a MV unit.Exposing this complex to the visible light of λ > 500 nm could trigger the E→Z photoisomerization of the encapsulated F2 E,leading to the formation of CB[8]2·F2Z complex with each CB[8]’s cavity occupied by the cis-FAB module of F2 Z.Furthermore,an ABBA type linear monomer(F3)was synthesized whose terminuses were modified with FAB and MV units,by the assembly of which with CB[8] unique visible light responsive water-soluble host-guest supramolecular polymer could be fabricated.Upon the irradiation by visible light of λ > 500 nm,the obtained supramolecular polymer was found to exhibit unique photoinduced disassembly behavior,during which the CB[8]2·F3Z complex was formed.It could be expected that the construction of such unique CB[8]-mediated host-guest system with visible light regulated encapsulation features as well as the unique visible light responsive host-guest supramolecular polymer,will positively impact on the development of novel visible light responsive supramolecular soft materials and biocompatible supramolecular materials.