An efficient process for the copper(0)-mediated controlled radical synthesis of acrylate-methacrylate block copolymers
Cu(0)-mediated polymerization using tris[2-(dimethylamino)ethyl]amine (Me6TREN) as ligand is a promising method to polymerize acrylates at ambient temperature with fast reaction rates that also maintains the high chain-end functionality needed for the synthesis of block copolymers. However, higher ligand levels are required to successfully control methacrylate chain growth, and the cost of Me6TREN presents a significant barrier to commercialization. Thus, reaction conditions suitable for continuous production of low molecular weight poly(methyl acrylate) (p(MA)) macroinitiator with target chain length of 10 in the continuous copper tubular reactor were developed using the less expensive N,N,N′,N′′,N′′-pentamethyldiethylenetriamine (PMDETA) as ligand by increasing reactor temperature to 70°C and using the initiator ethyl α-bromoisobutyrate. The resulting macroinitiator solution could be stored and chain-extended with MA to high conversion in a semi-batch reactor using either PMDETA or Me6TREN, increasing the versatility of a newly developed process to efficiently produce block copolymers using either ligand, or a combination of the two. PMDETA ligand also provides a route for semi-batch chain extensions of the p(MA) macroinitiator using methacrylates, as significantly higher ligand levels are required to promote controlled chain growth while achieving high conversions. Successful operating conditions were developed with diethylene glycol methyl ether methacrylate (DEGMEMA), to overcome solubility issues found with poly(methyl methacrylate), p(MMA). It was demonstrated that MA as comonomer is not necessary to achieve high DEGMEMA conversions in the process, but that increased concentrations of both the ligand (by a factor of 10) and the ascorbic acid reducing agent (by a factor of 2) are required for chain extensions using methacrylates compared to the conditions used for acrylate chain extensions. Addition of 5 wt% water as cosolvent increased DEGMEMA conversion to > 90% for room temperature operation in 4 h, as well as improved the initiation efficiency of the macroinitiator. These optimized reaction conditions with PMDETA were successfully applied to chain extensions with butyl methacrylate and MMA, although the conversions achieved were not as high. Polymers containing hydrophobic and hydrophilic blocks were also synthesized from the p(MA) macroinitiator by sequential feeding of DEGMEMA and MMA or MA. The reaction rates achieved with methacrylates are much faster than reported in literature, and the use of PMDETA as ligand provides an economically favorable and versatile system to produce block copolymers using acrylates or methacrylates.
URI for this recordhttp://hdl.handle.net/1974/28720
Request an alternative formatIf you require this document in an alternate, accessible format, please contact the Queen's Adaptive Technology Centre
The following license files are associated with this item: