Competitive Molecular‐/Ion‐Recognition Responsive Characteristics of Poly( N ‐isopropylacrylamide‐ co ‐benzo‐12‐crown‐4‐acrylamide) Copolymers with Benzo‐12‐crown‐4 as Both Guest and Host Units

Novel dual molecular‐ and ion‐recognition responsive poly( N ‐isopropylacrylamide‐ co ‐benzo‐12‐crown‐4‐acrylamide) (PNB 12 C 4 ) linear copolymers with benzo‐12‐crown‐4 (B12C4) as both guest and host units are prepared. The copolymers exhibit highly selective sensitivities toward γ ‐cyclodextrin ( γ ‐CD) and Na + . The presence of γ ‐CD induces the lower critical solution temperature (LCST) of PNB 12 C 4 copolymer to shift to a higher value due to the formation of 1:1 γ ‐CD/B12C4 host‐guest inclusion complexes, while Na + causes a negative shift in LCST due to the formation of 2:1 “sandwich” B12C4/Na + host‐guest complexes. Regardless of the complexation order, when γ ‐CD and Na + coexist with PNB 12 C 4 , competitive complexation actions of B12C4 as both guest and host units toward γ ‐CD and Na + finally form equilibrium 2:2:1 γ ‐CD/B12C4/Na + composite complexes, and the final LCST values of PNB 12 C 4 copolymer reach almost the same level. The results provide valuable guidance for designing and applying PNB 12 C 4 ‐based smart materials in various applications.