Publication YXY 2012
G.-J. M. Gruter, L. Sipos, M. A. Dam, Comb. Chem. High Throughput Screening 2012, 15, 180.
High Throughput experimentation was well established as a tool in early stage catalyst development and catalyst and process scale-up today. One of the more challenging areas of catalytic research is polymer catalysis. The main difference with most non-polymer catalytic conversions is the fact that the product is not a well defined mol. and the catalytic performance cannot be easily expressed only in terms of catalyst activity and selectivity.
In polymn. reactions, polymer chains are formed that can have various lengths (resulting in a mol. wt. distribution rather than a defined mol. wt.), that can have different compns. (when random or block co-polymers are produced), that can have crosslinking (often significantly affecting phys. properties), that can have different end-groups (often affecting subsequent processing steps) and several other variations. In addn., for polyolefins, mass and heat transfer, oxygen and moisture sensitivity, stereoregularity and many other intrinsic features make relevant high throughput screening in this field an incredible challenge.
For polycondensation reactions performed in the melt often the viscosity becomes already high at modest mol. wts., which greatly influences mass transfer of the condensation product (often water or methanol). When reactions become mass transfer limited, catalyst performance comparison is often no longer relevant. This however does not mean that relevant expts. for these application areas cannot be performed on small scale.
Relevant catalyst screening expts. for polycondensation reactions can be performed in efficient small scale parallel equipment. Both transesterification and polycondensation and post condensation through solid-stating in parallel equipment were developed. Next to polymer synthesis, polymer characterization also needs to be accelerated without making concessions to quality to draw relevant conclusions.