The radical copolymerization of cyclic disulfide-type monomers (ethyl lipoate or lipoic acid) with ethyl acrylate (1 : 1 molar feed ratio) yielded copolymers containing a significant fraction of backbone disulfide groups, which were degradable upon reduction. A compound containing two types of radically polymerizable groups (cyclic disulfide (1,2-dithiolane) and vinyl), 2-acryloyloxyethyl lipoate (AOELp), was synthesized and demonstrated to be a useful precursor for highly branched sulfur-containing polymers. Under radical polymerization conditions, AOELp served as a crosslinker, but up to moderate to high conversions and prior to gelation, soluble highly branched polymers were produced containing reductively degradable disulfide moieties, originating from the attack of a sulfur-centered radical on a 1,2-dithiolane group from AOELp or the polymer (pendant group), or the coupling of two sulfur-centered radicals. Alternatively, the reduction of AOELp afforded the corresponding dithiol acrylate (an AB₂-type monomer), which participated in radical or ionic step-growth thiol–ene reactions, yielding highly branched reductively non-degradable polymers with thioether-type sulfur atoms in the backbones.

A method for the preparation of azide-containing linear and branched polymers was developed that takes advantage of the efficient exchange of the acetoxy “ligands” in (diacetoxyiodo)benzene PhI(O₂CCH₃)₂ (Ph = phenyl) with azides, for instance in the presence of sodium azide. The in situ generated azide-containing hypervalent iodine(III) compounds PhI(N₃)(O₂CCH₃) and PhI(N₃)₂ decomposed rapidly, even at temperatures close to ambient, to the monovalent iodine compound (iodobenzene) and azide (and – in the former case – also acetoxy and/or methyl) radicals. The reactive azide radicals initiated the polymerization of methyl methacrylate at 40–100 °C, yielding polymers with an azide functionality at the α-terminus. Fast termination by coupling of the propagating radicals with azide radicals and possibly azide transfer from PhI(N₃)_x(O₂CCH₃)_2−x (x = 1, 2) were responsible for the formation of low-molecular-weight linear polymers with an azide group at the ω-end. When the polymerizations were carried out in the presence of divinyl compounds (crosslinkers), highly branched polymers were produced prior to gelation. The network formation was delayed in these systems until moderate to high monomer conversions were reached due to the aforementioned termination and/or transfer, which limited the size of the interconnected chains and therefore the average number of incorporated pendant vinyl groups per chain. The use of the PhI(O₂CCH₃)₂–NaN₃ initiating system proved to be an efficient one-pot route to mono- and diazide-capped linear or multi-azidated branched polymers that could be easily functionalized, e.g., under azide–alkyne “click” coupling conditions with alkynes, such as propargyl 4-(1-pyrenyl)butyrate.

Polymeric phosphonium salts are an important class of polyelectrolytes that are currently gaining increasing interest due to their solution properties and reactivity. The successful controlled/living radical polymerization of a phosphonium salt-type monomer, 4-vinylbenzyltriphenylphosphonium tetrafluoroborate (4VBTPPBF₄), under initiators for continuous activator regeneration atom transfer radical polymerization (ICAR ATRP) conditions employing a low concentration of catalyst is reported. After optimization of the reaction conditions, high monomer conversions to the polymeric phosphonium salt, poly4VBTPPBF₄, were reached with very good polymerization control. The living character of the polymerizations was further evidenced via chain extension experiments that yielded either higher molecular weight homopolymers or block copolymers. It is also shown that poly4VBTPPBF₄ can be efficiently converted to linear poly(4-vinylstyrene) using the Wittig olefination reaction.