Synthesis and characterization of the thermo- and pH sensitive star polymers with a rigid core of β-cyclodextrin

Two kinds of chemical modified beta-cyclodextrin(beta-CD) with different acylation degree were synthesized relying on the content of chloroacetyl chloride agent used. The structures of beta-CD with different degree of acylation were characterized using infrared spectroscopy, C-13-NMR, H-1-NMR and titration analysis. Infrared spectroscopy and C-13-NMR indicated that acylations occurred at C-2 and C-6 position in beta-CD, H-1-NMR and titration analysis suggested that the acylation degrees of beta-CD are 3.2 and 4.5, respectively. A series of star polymers having different average length, of poly ( N, N-dimethylaminoethyl methacrylate) were synthesized by atom transfer radical polymerization (ATRP) using anterior acylated beta-CD as the initiator. The branch chain structure and their compositions were characterized using infrared spectroscopy, H-1-NMR, element analysis and DSC. The star polymers prepared here had a hard beta-CD core with the potential to form inclusion complexes with certain small organic compounds, and also their aqueous solutions were studied by UV spectroscopy in order to explore their thermo- and pH sensitivities. The results showed that the novel star polymers exhibited clearly thermo- and pH respondings in accordance with the change of the environment.