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An organic peroxide that can initiate radical polymerization by O–O bond homolysis. Benzoyloxy radicals, and radicals formed by their further reaction, can initiate monomer addition.

Controlled radical polymerization based on reversible trapping of growing radicals by a nitroxide, forming dormant alkoxyamines. Initiation and end-group retention must be controlled to obtain predictable chain length.

Radical polymerization, a type of chain-growth polymerization. Peroxide bond cleavage initiates reactive chains; propagation adds monomer to a radical end while regenerating a radical end on the longer chain. Termination and chain transfer can then stop or redirect growth. In the propagation step there is no obligatory small-molecule condensate, so this is not a step-growth condensation.

For the ideal equimolar step-growth polymerization, $p=0.5$ givesThis counts individual starting molecules, so it is only roughly one diamine–diester pair per average chain, rather than a long polymer. In a successful radical polymerization, many monomers normally add between initiation and radical termination. The styrene–maleic anhydride copolymer in (iv) therefore has the larger expected degree of polymerization.

Conversion alone does not specify the radical-chain length: the conclusion assumes ordinary polymer-forming conditions, rather than arbitrarily high initiator concentration or extremely strong chain transfer in chain polymerization.

Radical polymerization in which growing chain ends reversibly exchange between active radicals and dormant species. Keeping the active-radical concentration small can reduce bimolecular termination and narrow the molar mass distribution. Termination and chain transfer may still occur, so reversible deactivation alone does not guarantee ideal living polymerization.