Novel Water-Soluble Cyclodextrin-Based Conjugated Polymer for Selective Host–Guest Interactions of Cationic Surfactant CTAB and Reverse FRET with Rhodamine B Tagged Adamantyl Guest

Abstract

A new water-soluble π-conjugated main-chain polymer P1 bearing a β-cyclodextrin (β-CD) pendant was designed and synthesized. The aggregation and disaggregation of P1 generated faded yellow-greenish and bright-yellow emissions, respectively. The inclusion complexation capability of P1 through β-CD pendant with a cationic surfactant cetyltrimethylammonium bromide (CTAB) guest and associative interactions of P1 with Fe3+ through triazole spacers resulted in significantly enhanced and completely diminished emission profiles of P1 in pure water, respectively. Interestingly, ADRhB as another rhodamine B (RhB) tagged adamantyl guest was transformed into ADRhB(O), i.e., the open form of ADRhB, to generate RhB emission in the presence of Fe3+ ion selectively for the pendent host β-CD of P1, and the further interaction of ADRhB(O)/Fe3+ with P1 prevailed a completely quenched RhB emission via the inclusion complexation of adamantyl terminal of ADRhB(O) in β-CD. Moreover, stronger interactions of CTAB with β-CD further generated RhB emission of ADRhB(O) even in the presence of acceptor P1. Finally, a novel β-CD bearing water-soluble P1 with selective and strong interactions of CTAB toward disaggregation events in pure water, and further electrostatic repulsion and utilization of RhB via RhB-tagged adamantyl guest ADRhB(O) as a donor revealed the reverse-fluorescence resonance energy transfer (FRET) process of P1.