Complexation of Thermoresponsive Dialkoxynaphthalene End-Functionalized Poly(Oligoethylene Glycol Acrylate)S with Cbpqt(4+) in Water

Four different oligoethylene glycol acrylates (OEGA), namely hydroxypropylacrylate (HPA), methoxy diethylene glycol acrylate (mDEGA), methoxy triethylene glycol acrylate (mTEGA) and 2-hydroxyethyl-acrylate (HEA) were homopolymerized via RAFT polymerization employing a naphthalene functionalized chain transfer agent resulting in thermoresponsive naphthalene-functionalized POEGAs with different hydrophilicities. Supramolecular inclusion complexes of these POEGAs with electron-deficient cyclophane cyclobis(paraquat-p-phenylene) tetrachloride (CBPQT(4+)) in water were studied. The association constants (K-a) were determined to study the effect that polymer hydrophilicity has on the K-a and results indicated that the nature of the polymer did not significantly influence the complexation strength and the association is mostly enthalpy driven. The impact of temperature on the host-guest complexes was also investigated. A continuous partial thermally induced dissociation of complexes was observed upon raising the temperature with a more distinct decrease in complexation around the cloud point temperature (T-CP) of the POEGA employed, indicating the importance of the polymer phase transition for tuning the recognition properties of dialkoxynaphthalene end-decorated poly(oligoethylene glycol acrylate)s in water.