Abstract
The radical copolymerization of butyl acrylate (BA) and 2-hydroxyethyl acrylate (HEA) was investigated under batch and semi-batch operations, with a focus on the influence of hydrogen-bonding on acrylate backbiting. The effect of hydrogen bonding on HEA to BA relative incorporation rates during copolymerization, previously seen in low-conversion kinetic studies, was also observed under high-conversion semi-batch conditions. However, overall reaction rates (as indicated by free monomer concentrations), polymer molar masses, and branching levels did not vary as copolymer HEA content was increased from 0 to 40 wt % in the semi-batch system. In contrast, introduction of a H-bonding solvent, n-pentanol, led to an observable decrease in branching levels, and branching levels were also reduced in batch (co)polymerizations with HEA. These differences can be attributed to the low levels of unreacted HEA in the starved-feed semi-batch system.
Highlights
Radical Polymerization (RP) is one of the most common and significant methods to produce polymers at a commercial scale [1]
As final conversions are similar, the resulting branching levels (BLs) values measured provide insights as to how solvent and monomer choice affects the relative rate of backbiting to chain-growth
Monomer conversions of 75–80% were reached for butyl acrylate (BA) polymerized in xylenes and toluene, with the polymer produced in both solvents having a very similar number average (Mn ) and weight-average (Mw ) molar masses, as well as final branching levels (~3%)
Summary
Radical Polymerization (RP) is one of the most common and significant methods to produce polymers at a commercial scale [1]. Despite the development of controlled radical polymerization [2,3,4], living polymerization [5], and other catalytically supported approaches [6], RP is still favored in industry due to its simplicity and high tolerance towards impurities in either organic or aqueous media [1], and its high productivity at a comparably low cost to produce a diverse range of polymeric products from a wide range of monomers, including ethylene, (meth)acrylates, or styrene derivatives [7]. Functional groups raise the value of the crude product as they allow post-modifications (e.g., crosslinking); whereas, lower molar masses decrease the viscosity when handling or applying the coating to a surface. The reactive functionality is often introduced by hydroxyl containing monomers, from which a wide range of post-modifying chemistry is accessible
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