Precise control over the location of monomers in a polymer chain has been described as the ‘Holy Grail’ of polymer synthesis. Controlled chain growth polymerization techniques have brought this goal closer, allowing the preparation of multiblock copolymers with ordered sequences of functional monomers. Such structures have promising applications ranging from medicine to materials engineering. Here we show, however, that the statistical nature of chain growth polymerization places strong limits on the control that can be obtained. We demonstrate that monomer locations are distributed according to surprisingly simple laws related to the Poisson or beta distributions. The degree of control is quantified in terms of the yield of the desired structure and the standard deviation of the appropriate distribution, allowing comparison between different synthetic techniques. This analysis establishes experimental requirements for the design of polymeric chains with controlled sequence of functionalities, which balance precise control of structure with simplicity of synthesis.

This article is the first comprehensive review on the study and use of vinyl ester monomers in reversible addition fragmentation chain transfer (RAFT) polymerization. It covers all the synthetic aspects associated with the definition of precision polymers comprising poly(vinyl ester) building blocks, such as the choice of RAFT agent and reaction conditions in order to progress from simple to complex macromolecular architectures. Although vinyl acetate was by far the most studied monomer of the range, many vinyl esters have been considered in order to tune various polymer properties, in particular, solubility in supercritical carbon dioxide (scCO₂). A special emphasis is given to novel poly(vinyl alkylate)s with enhanced solubilities in scCO₂, with applications as reactive stabilizers for dispersion polymerization and macromolecular surfactants for CO₂ media. Other miscellaneous uses of poly(vinyl ester)s synthesized by RAFT, for instance as a means to produce poly(vinyl alcohol) with controlled characteristics for use in the biomedical area, are also covered.

Dispersity is firmly established as the standard measure of dispersion in molecular weight distributions. However, it can be misleading, particularly when applied to the relatively narrow molecular weight distributions obtained via living or reversible deactivation polymerizations. The use of the standard deviation is recommended as an alternative. In complex structures, a representative sample of chains provides a better illustration of structural variation than any single number.

The 7-membered cyclic thionolactone, ε-thionocaprolactone (TCL), undergoes radical copolymerization with vinyl esters to form degradable copolymers. While most radical ring-opening monomers require laborious and low-yielding syntheses, TCL can be prepared in one step from caprolactone (75% yield). TCL copolymerizes readily with vinyl esters, but is unreactive towards more activated monomers and does not homopolymerize under radical conditions. The molecular weight and to some extent the dispersity of the TCL/vinyl ester copolymers can be controlled via xanthate-mediated RAFT polymerization in the range of 5–20 kg mol⁻¹. Analysis of the copolymer structure shows a high level of TCL–TCL dyads, suggesting that the terminal copolymerization model does not accurately describe TCL copolymerization.