N-heterocyclic olefins have been employed in polymer field as a catalyst. There is a comparison between the efficiency of metal complexes and organ-catalyst toward ring opening polymerization for degradation purpose. This slides presents two selected papers demonstrating the influence of olefins as a part of N-heterocyclic chemical structure in the rate of degradation.

1. Ring opening polymerization
by N-heterocyclic olefins
Hiren, Mohammed 09/12/2016

2. Paper 1 – N-heterocyclic olefins as organic catalysts for
polymerization: preparation of well defined poly(propylene
oxide)
Paper 2 – Highly polarized alkenes as organocatalysts for the
polymerization of lactones and trimethylene carbonate

3. Essential points
• Advantages of using organic catalysts
• Differences in the catalysts
• Mechanisms
• HNMR

4. • N-heterocyclic olefins
• Used alongside benzyl alcohol initiator to ring open propylene oxide,
lactones and trimethylene carbonate.
• Over the 2 papers there are 5 catalysts
• Anionic ring opening polymerization

5. Paper 1

6. Catalysts 1-4 + monomer
Propylene oxide

7. Bulk polymerization table

8. Catalyst 3
• Less control over the reaction
• Produced a primary carbanion
• Impurities in the polymer produced
• 2 proposed mechanisms

9. Mechanism
Deprotonation
Nucleophilic attack

10. CATALYST 4
• More control over the reaction
• It forms a tertiary carbanion which favors the anionic polymerization
over the zwitterionic polymerization.
• Abstracts protons from the initiator better than catalyst 3, as it’s a
stronger base.

12. Changing the concentration of initiator

13. HNMR Green = aromatic
Red = methylene unit
BnOH

14. Advantages of 4 over 3
• Stronger base
• More stable, able to predict the outcome
• Produces less impurities in polymer

15. Paper 2

16. N-heterocyclic olefins
-More active than NHCs in ROP.
-Exocyclic carbon partially anionic.
-Ring size + substitutions affect the activity.
-The stability of the carbanion.
-
S. Naumann, A. W. Thomas, and A. P. Dove, ACS Macro Lett. 2016, 5

17. The monomers used:
L- lactide Delta- valerlactone Trimethyl carbonate(TMC)
ω- pentadecalactone (PDL) ε-caprolactone

18. S. Naumann, A. W. Thomas, and A. P. Dove, ACS Macro Letters. 2016, 5

19. S. Naumann, A. W. Thomas, and A. P. Dove, ACS Macro Letters. 2016, 5
The deactivation of the
catalyst occurred.
Substitutions avoid the
deprotonation.

20. S. Naumann, A. W. Thomas, and A. P. Dove, ACS Macro
Letters. 2016, 5
High Conversion (No BnOH).
The ratio increases the activity.
No improvement in control.
Broad Mwt distribution.
 Low catalyst loading.

22. Advantages of NHO’s
• Less toxic than organometallic compounds.
• They produce a high conversion with and without initiators.
• Easy to edit the structure in order to change the activity.
• ability to operate under alternative polymerization mechanisms.