Things to Consider Before Conducting an ATRP
In many of the examples reported in the literature detailing preparation of copolymers using ATRP by the Matyjaszewski group, and indeed most other academic laboratories, the monomers and other components of the reaction medium have been subjected to rigorous purification. This is conducted because academicians are often interested in following the kinetics of the reaction and wish to ensure reproducible conditions not necessarily because rigorous purification is required; indeed some of the examples below describe conducting the reaction in the presence of limited amounts of air or in the presenc of radical inhibitors or antioxidants which is normally not advised for a radical polymerization. Deoxygenation may not be a problem when monomers, initiators, solvents and catalyst components are provided in an industrial setting but is a potential problem at all levels below commercial scale.
In some of the starting points listed in this section of the web-page, see menu on left hand side, detailed conditions are provided. Once a set of detailed conditions are provided, we generally use the same reaction conditions for a later example using the same components, with different ratios of reagents.
Listed below are some of the tasks that should be undertaken if one wishes to conduct a successfull ATRP. As alluded to throughout the site one set of conditions does not work for every monomer and every catalyst complex.
- Transition metal, almost all examples described on the web site use copper based complexes as catalyst,
- Homogeneous or Heterogeneous
- Targeted polymerization rate and degree of polymerization
- Most appropriate procedure for initiation of the reaction
- Structure/topology of molecule
- Order of addition of monomers
3) Problems encountered
- Getting control over the process
- Reaction too fast
- Reaction too slow
- Reaction stops
- Reaction does not start
- Control over MW, PDI, Functionality
- Formation of byproducts
Selection ProblemsHow do you select initiator, catalyst, solvent and reaction conditions for a specific reaction?
- Selecting catalysts for different monomers, PMDETA or Me6TREN are not the best ligands for everything!
- Appropriate selection of halogen or other transferable atom or group
- Selecting solvents for different monomers
- Use of water or another polar solvent
- Correct order of polymerization of monomers
- Is halogen exchange required?
- Is there an alternative to halogen exchange for low copper ATRP
- Complex topology
- Selecting/targeting an appropriate ratio of activator to deactivator
- Determine the role of solvent
- Concentration of monomers/solubility/viscosity
- Temperature/temperature control
- Catalyst removal