Synthesis and multi-stimuli-responsive behavior of copolymer of N,N′-dimethylacrylamide and complex pseudorotaxane

Abstract

Novel water-soluble side-chain copolymer with the pseudorotaxane structure threaded by cucurbit[6]uril (CB[6]) was synthesized by N′-(4-vinylbenzyl)-1,4-diaminobutane dihydrochloride with CB[6] threaded (4VBCB) and N,N′-dimethylacrylamide (DMAA) as monomers. SEM results show that the diameter of the spherical particles increases and the crosslinking in spherical particles occurred with the decrease of the molar ratio of DMAA/4VBCB. Interestingly, 1H NMR spectra show that the threading and dethreading of CB[6] on the side chains could be controlled by the addition of CaCl2 or BaCl2, but CB[6] cannot drop from the side chains by the addition of NaCl. DLS data indicate that the copolymers have thermal sensitivity and their jump temperature could be controlled by adjusting the molar ratio of DMAA/4VBCB, and RLS data show that the size of aggregation increases with increasing the concentration of NaCl. At the same time, the copolymers have pH-responsive behavior. Novel water-soluble side-chain copolymer with the pseudorotaxane structure threaded by cucurbit[6]uril (CB[6]) was synthesized. Interestingly, the threading and dethreading of CB[6] on the side chains could be controlled by the addition of CaCl2 or BaCl2, but CB[6] cannot drop from the side chains by the addition of NaCl. And Na2CO3 or Na2SO4 was added into the CaCl2 or BaCl2 solution of copolymer for the removal of Ca2+ or Ba2+. As expected, CB[6] could thread on the side chains again as shown in Fig. 6a.