Synthesis and characterization of polyrotaxanes comprising α-cyclodextrins and poly(ε-caprolactone) end-capped with poly(butyl methacrylate)s

Biodegradable polyrotaxane (PR)-based triblock copolymers were synthesized via the bulk ATRP of BMA initiated with PPRs built from self-assembly of a distal 2-bromoisobutyryl end-capped PCL with α-CDs in the presence of Cu(I)Br/PMDETA at 45 ^oC. Those movable α-CDs made a great contribution to the mechanical strength enhancement, blood anticoagulation activity and protein adsorption repellency of the resulting copolymers. Biodegradable polyrotaxane-based triblock copolymers were synthesized via the bulk atom transfer radical polymerization (ATRP) of n-butyl methacrylate (BMA) initiated with polypseudo-rotaxanes (PPRs) built from a distal 2-bromoisobutyryl end-capped poly(ε-caprolactone) (Br-PCL-Br) with α-cyclodextrins (α-CDs) in the presence of Cu(I)Br/N,N,N',N″,N″-pentamethyldiethylenetriamine at 45 ^oC. The structure was characterized in detail by means of ¹H NMR, gel permeation chromatography, wide-angle X-ray diffraction, DSC and TGA. When the feed molar ratio of BMA to Br-PCL-Br was changed from 128 to 300, the degree of polymerization of PBMA blocks attached to two ends of the PPRs was in the range 382-803. Although about a tenth of the added α-CDs were still threaded onto the PCL chain after the ATRP process, the movable α-CDs made a marked contribution to the mechanical strength enhancement, blood anticoagulation activity and protein adsorption repellency of the resulting copolymers. Meanwhile, they could also protect the copolymers from the attack of H₂O and Lipase AK Amano molecules, exhibiting a lower mass loss as evidenced in hydrolytic and enzymatic degradation experiments.