Preparation and surface properties of polyrotaxane-containing tri-block copolymers as a design for dynamic biomaterials surfaces

A tri-block copolymer series containing hydrophilic polyrotaxane and hydrophobic poly(iso-butylmethacrylate) (PiBMA) segments was prepared by atom transfer radical polymerization (ATRP), starting from a pseudopolyrotaxane consisting of 2-bromoisobutyryl end-capped poly(ethylene glycol) (PEG) and α-cyclodextrin (α-CD) and followed by methylation. The dynamic wettability and molecular mobility of the copolymer surfaces were evaluated by dynamic contact angle (DCA) and quartz crystal microbalance with dissipation (QCM-D) measurements, respectively. The polyrotaxane tri-block copolymer surfaces were found to show pronounced dynamic wettability and molecular mobility compared to the control surfaces-a tri-block polymer consisting of PEG and PiBMA, and a PiBMA homopolymer-suggesting that a polyrotaxane loop-like structure exists at the outermost surface in an aqueous environment and exhibits dynamic properties attributable to the possible mobile nature of hydrated α-CD molecules along the PEG backbone. Finally, excellent protein adsorption repellency was achieved on the polyrotaxane tri-block copolymer surface, presumably due to the mobile nature of the supramolecular architecture on the surface.