To synthesize cyclic polymers with definite topological structure is always a challenging topic in polymer chemistry. Recently

Xie and coworkers at East China Normal University developed a blocking cyclization route to synthesize cyclic polymers with controllable topology

and synthesized a series of A(B

2

A)

n

(

n

= 1

2

and 3) type cyclic copolymers with well-defined ring size (the repeat unit was 40 − 400) and ring number (1 − 3)

mainly by successive ring-opening metathesis polymerization (ROMP) of alternating addition of di- and monofunctional norbornene monomers in a one-pot process. This blocking cyclization strategy

unlike the traditional ring-closure and ring-expansion techniques

can precede at high monomer concentration (0.02 mol L

−1

) producing very high cyclization efficiency

which has broken through the limitation of the previous two traditional cyclizing routes

and thus can be considered as the third route as a versatile platform to cyclic polymers by commercial Grubbs catalyst and conventional ROMP.