Chiral Imprinting of Diblock Copolymer Single-Chain Particles

Abstract

This Article reports the molecular imprinting of polymer single-chain particles that have a radius ∼3.7 nm. For this, the template l-phenylalanine anilide or l-ΦAA and a diblock copolymer PtBA-b-P(CEMA-r-CA) were used. Here, PtBA denotes poly(tert-butyl acrylate), and P(CEMA-r-CA) denotes a random block consisting of cinnamoyloxyethyl methacrylate (CEMA) and carboxyl-bearing (CA) units. In CHCl3/cyclohexane (CHX) with 64 vol % of CHX or at fCHX = 64%, a block-selective solvent for PtBA, PtBA-b-P(CEMA-r-CA) formed spherical micelles. The core consisted of the insoluble P(CEMA-r-CA) block and l-ΦAA, which complexed with the CA groups. Pumping slowly this micellar solution into stirred CHCl3/(CHX) at fCHX = 64% triggered micelle dissociation into single-chain micelles, which comprised presumably a solubilized PtBA tail and a collapsed P(CEMA-r-CA)/l-ΦAA head. Because the solvent reservoir was under constant UV irradiation, the photo-cross-linkable units in the P(CEMA-r-CA) head cross-linked, and the single-chain micelles were converted into cross-linked single-chain micelles or tadpoles. Synchronizing the micelle addition and photoreaction rates allowed the preparation, from this protocol, of essentially pure tadpoles at high final polymer concentrations. Imprinted tadpoles were procured after l-ΦAA was extracted from the tadpole heads. Under optimized conditions, the produced imprinted tadpoles had exceptionally high binding capacity and high selectivity for l-ΦAA. In addition, the rates of l-ΦAA release from and rebinding by the particles were high