LAUSR

In contrast to traditional polymers, the monomers or polymer segments in supramolecular polymers (SPs) are connected by directional and reversible noncovalent interactions, including electrostatic interactions, hydrogen bonds, host–guest recognition, van der Waals forces, coordination, π–π stacking, etc. In some aspects, SPs have shown intrinsic outstanding properties, such as a highly dynamic molecular structure, abundant stimuli-responsiveness and self-adjusting or self-healing characteristics, and the advantage of facile preparation over the traditional covalent polymers (CPs). As a result, SPs are very promising in applications such as optoelectronics, biomedical or selfhealing materials. However, despite the progress, the topological structures of SPs are still insufficient when compared with a large number of CPs. Most of the reported SPs have only a linear structure, and the SPs with topological structures such as graft, block, hyperbranched, dendritic, star-shaped, and network structures are quite limited. It is still highly challenging to develop new SPs with unique topological structures. A shish-kebab-like (SK) structure is a typical structure in polymer crystals, nanohybrids, small molecule assemblies and some inorganic nanomaterials. However, to our knowledge, there are few reports on SPs with a SK structure, mainly due to the difficulty in synthesis. In our previous work, we reported linear-branched, Janus, dumbbell-like and dandelionlike SPs and studied their self-assembly behaviours. On the basis of these works, herein, we report the construction of a light-responsive shish-kebab-like supramolecular polymer (SKSP). As shown in Scheme 1, we first synthesized a functional molecule of β-cyclodextrin (CD) grafted with hyperbranched glycidyl ether (HPG) on the surface and one azobenzene (AZO) group at the end (CD-g-HPG-AZO). Then the SKSP was prepared through the noncovalent host–guest interaction between the CD and AZO groups of CD-g-HPG-AZOs (Scheme 2). It was found that such an amphiphilic SKSP could self-assemble into nanofibers in water, which transformed into micelles under UV light due to the trans-to-cis isomerization of the AZO groups (Scheme 2). The synthesis of CD-g-HPG-AZO was based on the clickchemistry reaction between the alkynyl group of AZO-Alk and the azide group of CD-N3-g-HPG (Scheme 1). 30 AZO-Alk was prepared in two steps. In the first step, 4-hydroxyazobenzene and 6-bromohexanol were reacted under the catalysis of potassium carbonate to give 6-hydroxyoxo-4-azobenzene (AZO-gOH). Then, AZO-g-OH was reacted with bromopropyne under the catalysis of potassium hydroxide and a crown ether to form 6-(propynyloxy)hexyloxy-4-azobenzene (AZO-Alk) (Fig. S1–S6, ESI†). CD-N3-g-HPG (Mn, GPC = 1800 Da, Mn, NMR = 5000 Da,