This document discusses the use of n-heterocyclic olefins as organic catalysts in ring opening polymerization, focusing on their advantages and the mechanisms involved. It highlights two papers that detail the properties and performance of various catalysts with respect to the polymerization of different monomers. Key findings include the effectiveness and stability of these catalysts, their lower toxicity compared to organometallic compounds, and their ability to produce high conversion rates.

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.