An Associative Pathway Enables Highly Controlled Ring-Opening Polymerization of Cyclosiloxane with ppm-Level...

Area of Science:

• Polymer Chemistry
• Organocatalysis
• Materials Science

Background:

• Precise control over molar mass and structure of polysiloxane is critical for its applications.
• Traditional methods often require harsh conditions or complex catalysts.

Purpose of the Study:

• To develop a highly active and selective organocatalyst for the ring-opening polymerization (ROP) of cyclosiloxanes.
• To achieve controlled synthesis of polysiloxanes with defined molar mass and low dispersity.

Main Methods:

• Ring-opening polymerization (ROP) of cyclotrisiloxane (D3) and cyclotetrasiloxane (D4) using anionized 1,3-diphenylurea (UA1) with a tetra-n-butylammonium counterion.
• Characterization of resulting polysiloxanes for molar mass and dispersity.
• Computational analysis of catalyst-monomer interactions.

Main Results:

• UA1 demonstrated high catalytic activity (TOF up to 52,000 h⁻¹ for D3) with low catalyst loadings (5-100 ppm).
• Polydimethylsiloxane with controlled molar mass (2-140 kg mol⁻¹) and low dispersity (1.06-1.18) was obtained.
• The catalyst successfully polymerized D4 to high molar mass (1,660 kg mol⁻¹).
• Hydrogen bonding between the catalyst and silanol species/monomer was identified as key to efficiency and selectivity.

Conclusions:

• Anionized 1,3-diphenylurea is a highly efficient organocatalyst for controlled ROP of cyclosiloxanes.
• The catalyst enables precise control over polysiloxane synthesis with minimal loading.
• This approach offers a greener and more effective route for polysiloxane material production.