Synergetic binary organocatalyzed ring opening polymerization for the precision synthesis of polysiloxanes

Area of Science:

• Polymer Chemistry
• Organocatalysis
• Materials Science

Background:

• Organocatalytic ring-opening polymerization (ROP) offers control over polymer synthesis but faces challenges with polysiloxane production.
• Existing methods struggle with polarity mismatches and side reactions like transetherification during cyclic siloxane polymerization.
• Achieving well-defined polysiloxanes with controlled architectures remains a significant hurdle in polymer science.

Purpose of the Study:

• To develop a precision synthesis method for polysiloxanes using a novel binary organocatalytic system.
• To overcome limitations in current organocatalytic ROP for nonpolar monomers like hexamethylcyclotrisiloxane (D3).
• To investigate the synergistic effects of organic bases and (thio)ureas in controlling polymerization.

Main Methods:

• Employed a binary organocatalytic ring-opening polymerization (BOROP) approach for hexamethylcyclotrisiloxane (D3).
• Utilized organic bases, specifically triazabicyclodecene (TBD) and 1,8-bis(tetramethylguanidino)naphthalene (TMGN), as catalysts.
• Incorporated (thio)ureas as co-catalysts to modulate the polymerization activity and selectivity.

Main Results:

• Generated polydimethylsiloxanes (PDMS) with narrow dispersity (M_w/M_n < 1.1) using TBD and (thio)ureas.
• Demonstrated that TMGN alone is inactive, but synergistic effects with urea enable controlled BOROP of D3.
• Produced PDMS elastomers with uniform network structures, enhanced stretchability, and excellent mechanical properties.

Conclusions:

• The developed binary organocatalytic system (BOROP) effectively controls the ring-opening polymerization of D3.
• Synergistic activation-deactivation equilibrium between catalysts and co-catalysts is key to achieving high-quality PDMS.
• This method provides a pathway for synthesizing advanced polysiloxane materials with tailored properties.