The invention provides methods and compositions for production of a cyclic polymer in a cell free system. In general, the methods of the invention involve ligating first and second recombinant intein domains to a linear synthetic polymer to form a compound containing the structure: D1-X(n)-D2, where D1 is a first catalytic domain of an intein; D2 is a second catalytic domain of an intein; where the second catalytic domain has at its N-terminus a first reactive site for the intein; and X(n) is a polymer of a number n of monomer X, where the polymer N-terminus has a second reactive site for the intein. D1-X(n)-D2 compounds autocatalytically cyclize the X(n) polymer to produce a cyclic polymer. The invention finds use in a variety of drug discovery, clinical and therapeutic applications.