A device and method for efficiently synthesizing diverse molecular products on substrates. A parent vessel 200 contains a suspension of substrates. The suspension is pressurized with argon and transferred to a plurality of reaction vessels 201-209 in one or more reaction vessel banks where monomer addition reactions take place. Optionally, the substrates may be tagged with a tag monomer. A vortexing motor 300 vortexes the contents of reaction vessels 201-209 during monomer addition reactions to enhance synthesis. After the desired monomer and/or tag monomer addition reaction, the suspension is pressurized with argon and transferred back to parent vessel 200 for mixing. Thereafter, the suspension may be pressurized with argon and reallocated among reaction vessels 201-209 for further synthesis.