Evaluation of Aldrich® RAFT Agents

Jeremy Bartels, Sebastian Grajales, Kaushik Patel, Kanth V. B. Josyula, Gangadhar Panambur and Scott Batcheller
Aldrich Materials Science, 6000 N. Teutonia Ave. Milwaukee, WI 53209



RAFT polymerization process

In 1998, members of an Australian Commonwealth Scientific and Research Organization (CSIRO) team discovered the RAFT polymerization method.1



Why use RAFT methods?

  • The process allows radical-initiated growing polymer chains to degeneratively transfer reactivity from one to another through the use of key functional groups (dithioesters, trithiocarbonates, xanthates and dithiocarbamates).
  • RAFT agents help to minimize out-of-control growth and prevent unwanted termination events from occurring, effectively controlling polymer properties like molecular weight and polydispersity.
  • RAFT agents are commercially available.
  • RAFT does not use any cytotoxic heavy metal components (unlike ATRP).


Classes of RAFT agents


  • Dithiocarbamates Z1 is typically -Me or other alkyl
    Z2 is typically -Ph or other aromatic
  • Xanthates Z is typically an alkyl chain (Et)
  • Dithioesters Z can vary widely, but is typically -Ph
  • Trithiocarbonates Z is typically an alkyl group (C12H25, etc.)

Versatility of RAFT

  • RAFT is compatible with most functional groups and solvents, including water.
  • RAFT polymerizations are often mildly tolerant to oxygen content, especially when compared to living anionic polymerizations.
  • RAFT agents may be tuned to give polymers with telechelic functionality, for further processing/ binding events.
  • The RAFT technique requires no special equipment or vacuum glassware.
  • RAFT polymers can be applied to any field, from electronics to cell biology.


Compatibility table



RAFT efficacy

A series of five RAFT polymerizations were carried out using Aldrich® RAFT agents, monomers, and initiators:


Polymer Conv (%) MnTheo (Da) MnNMR (Da) MwGPC (Da) MnGPC (Da) PDI
1. PtBA 33% 4,600 4,800 5,000 4,700 1.06
2. PtBA-b-PS 35% 7,400 7,200 7,200 6,300 1.15
3. PEO-b-PS 29% 7,300 7,400 7,000 6,300 1.04
4. PVAc 65% 12,300 12,300 18,000 14,800 1.21
5. PMMA 60% 15,400 15,000 16,400 14,900 1.10



New class of RAFT CTAs: Universal, pH-switchable RAFT agents



Materials

     

References

  1. Chiefari, J., Chong, Y. K., Ercole, F., Kristina, J., Jeffrey, J., Le, T. P. T., Mayadunne, R. T. A., Meijs, G. F., Moad, G., Rizzardo, E., Thang, S. H. Macromolecules, 1998, 31, 5559.

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Acknowledgements

  • Shashi Jasty, Ph.D.
  • John Radke
  • Ilya Koltover, Ph.D.
  • Angel Thompson