Applying Catching-by-Polymerization for the Preparation of Long Sequence-Defined Polymers

Catching-by-polymerization (CBP) is a recently developed DNA purification strategy that works by covalently anchoring target sequences within a hydrogel. In this study, we evaluated CBP for purifying non-biological poly(phosphodiester)s. These polymers were produced via automated solid-phase synthesis using 2-cyanoethyl (3-dimethoxytrityloxy-propyl) diisopropylphosphoramidite as a model monomer. At the final step of the iterative synthesis, a specially designed CBP linker was attached to the polymer chains. This linker includes (i) a reactive phosphoramidite group, (ii) a preloaded monomer unit, (iii) a cleavable trityl moiety, (iv) a spacer, and (v) a polymerizable methacrylamide terminus. Following cleavage from the solid support, the polymers were incorporated into a hydrogel network through aqueous radical copolymerization with N,N-dimethylacrylamide and bis-acrylamide. Subsequent washing removed defective chains, which had been capped during synthesis and, therefore, lacked the covalent linkage required for hydrogel attachment. The correctly synthesized sequences were then released from the gel by detritylation and analyzed by HPLC and Mass Spectrometry. These analyses demonstrate that CBP provides an effective and straightforward method for purifying polymers across a range of lengths. Notably, it enabled the isolation of long chains that had not previously been obtained from this monomer, including 150-mer and 170-mer for the first time.