Abstract
The use of anhydrous alcohols for Cu-catalysed reversible-deactivation radical polymerisation of a wide range of hydrophobic methacrylates has been explored in detail.
Highlights
We have previously reported the highly controlled nature of the Cu-catalysed reversible-deactivation radical polymerisation (RDRP) of n-butyl methacrylate at elevated temperature in anhydrous methanol (MeOH; generally considered a poor solvent for the resulting polymer), to give poly(nBMA) of controlled molecular weight and low dispersities (Đ = 1.03–1.10).[80]
Monomer–MeOH miscibility was assessed visually and showed homogeneous mixtures for all monomers under conditions representative of Cu-catalysed RDRP, with the exception of stearyl methacrylate (SMA); at ambient temperature (
An attraction of RDRP reactions is the ability to conduct controlled polymerisations at high solids contents, leading to final polymer solutions of >50% w/w; it is clear that monomer selection has the potential to impact the initial solvent environment, whilst monomer depletion during propagation, and formation of polymer, may lead to a transition from a “good” solvent environment to a “poor” solvent condition, as exploited by the so-called polymerization-induced self-assembly, or PISA, reactions.[71]
Summary
The level of control provided by RDRP techniques has permitted the generation of numerous novel macromolecular architectures including: block copolymers,[16,17,18] multi-block copolymers,[19,20,21,22,23,24,25,26,27] star polymers,[27,28,29,30,31,32,33] branched polymers[34,35,36,37,38] and hyperbranched polymers.[39,40,41,42,43,44] One approach which relies heavily on the ability to control the number of propagating polymer chains to avoid the formation of an insoluble gelled network is the generation of branched polymers via statistical copolymerisation of mono- and bifunctional monomers (BFM).[45] The mechanism of branched polymer architecture formation, and the branching processes occurring during copolymerisation, are well understood;[46,47,48,49,50] this approach has been used to generate branched polymers using. Many factors can influence the prevalence of branching reactions during polymerisation; the feedstock ratio of BFM to initiator ([B]0/ [I]0) determines the fraction of polymer chains theoretically capable of partaking in branching reactions,[58] whilst the statistical distribution of BFM is dependent on the level of electronic interaction between co-monomers.[59,60] The inclusion of BFM into the polymer structure, whether via intermolecular branching or intramolecular cyclisation, impacts the extent of branching and may be heavily influenced by the concentration at which polymerisations are conducted.[61,62,63,64] These factors must always be considered when designing new branching copolymerisation reactions using this approach
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