Synthesis of Agarose-graft-poly[3-dimethyl (methacryloyloxyethyl) ammonium propanesulfonate] Zwitterionic Graft Copolymers via ATRP and Their Thermally-Induced Aggregation Behavior in Aqueous Media.

A novelpolysaccharide-based zwitterionic copolymer, agarose-graft-poly[3-dimethyl (methacryloyloxyethyl) ammonium propanesulfonate](agarose-g-PDMAPS) with UCST, depending both on hydrogenbonding and electrostatic interaction, was synthesized by ATRP, andits aggregation behavior in aqueous media was investigated in detail.Proton nuclear magnetic resonance spectroscopy, Fourier transform-infraredspectroscopy, and gel-permeation chromatography were performed tocharacterize the copolymer. Thermosensitive behaviors of the copolymersin water, NaCl, and urea solution were tracked by ultraviolet, dynamiclight scattering, and transmission electron microscopy analysis. Itwas found that the copolymers existed as “core–shell”spheres at an elevatedtemperature, as a result of the self-assembly of the agarose backboneslocated in the “core” driven by hydrogen-bonding interactions.When the copolymer solution was cooled below UCST, the core–shellspheres began to aggregate because of the electrostatic interactionsand collapse of PDMAPS side chains in the “shell” layer.UCST of the copolymer could be tuned in a wide range, depending onthe chain lengths of PDMAPS. This is the first example to investigatethe thermosensitivity, combining ionic interactions of the zwitterionicside chains with hydrogen bondings from the biocompatible agarosebackbones. The synthetic strategy presented here can be employed inthe preparation of other novel biomaterials from a variety of polysaccharides. [ABSTRACT FROM AUTHOR]