Phosphoramidite conjugates and methods of forming synthetic oligonucleotides therefrom

A method of synthesizing a polynucleotide composition, comprising:

• performing a synthesis of the polynucleotide composition via phosphoramidite chemistry, solid-phase supported synthesis, to create a polynucleotide chain;
• during at least one cycle of the synthesis, coupling a reversible-deactivation-radical-polymerization-(an RDRP)-phophoramidite reagent in a growing chain of the polynucleotide composition, the RDRP-phophoramidite reagent comprising a phosphoramidite compound conjugated to an RDRP initiator or a chain transfer agent for RDRP via a moiety comprising a protected hydroxyl group, wherein a hydroxyl protecting group of the protected hydroxyl group is stable to polynucleotide synthesis conditions.