Cyclic poly(n-butyl acrylate)-block-poly(methyl methacrylate) (cyclic-PBA-b-PMMA) can be synthesized successfully by the combination of ATRP and click reactions.The cyclic copolymers were obtained by the intramolecular cyclization reactions between the linear precussors at high dilution.The chemical structures

molecular weights and molecular weight distributions of the cyclic block copolymers obtained were well characterized by Fourier transform infrared spectroscopy

nuclear magnetic resonance spectroscopy and gel permeation chromatography.The thermal properties of these cyclic block copolymers and their linear counterparts were characterized by differential scanning alorimetry and thermogravimetric analysis.It is interesting that the cyclic block copolymers have similar glass transition temperatures but higher degradation temperatures compared to their linear counterparts.The morphologies of the prepared samples were investigated via transmission electron microscopy.Unlike the linear block polymers

the cyclic block copolymers exhibited unique morphologies.Obviously

the cyclic block copolymers displayed a continuous dispersed morphology

and the dispersed phase had a worm-like structure.Meanwhile

nano-scaled phase separation was also observed between PBA and PMMA phasees.By means of annealing above the glass transition temperatures of the two blocks

PBA and PMMA

both linear and cyclic copolymers possessed well ordered nano-structures

and the size of these separated domains increased after annealing.