Hemisilicone Elastomers That Are Recyclable to the Monomer

Area of Science:

• Polymer Chemistry
• Organosilicon Chemistry
• Materials Science

Background:

• Polydimethylsiloxane (PDMS) is a widely used silicone polymer.
• The synthesis and properties of novel silicone-based polymers are of interest for advanced material applications.

Purpose of the Study:

• To synthesize and characterize methyl-, vinyl-, and hydride-terminated polymers from the heterocyclic monomer 2,2,5,5-tetramethyl-2,5-disila-1-oxacyclopentane (c-M2E).
• To investigate the properties of these polymers, including their viscosity and potential for cross-linking into elastomers.
• To evaluate the suitability of these novel polymers for applications in curable elastomer formulations and assess their recyclability.

Main Methods:

• Ring-opening equilibration polymerization of c-M2E catalyzed by sulfuric acid.
• End-capping of polymers using hexamethyldisiloxane (MM), divinyltetramethyldisiloxane (MVMV), and tetramethyldisiloxane (MH MH).
• Molecular weight control by adjusting monomer to end-capping agent ratios.
• Cross-linking of vinyl-terminated polymers via platinum-catalyzed hydrosilylation with tetramethylcyclotetrasiloxane (DH4).

Main Results:

• Successfully prepared methyl-, vinyl-, and hydride-terminated polymers from c-M2E with controlled molecular weights.
• Polymers exhibited oil-like properties and molecular weight-dependent viscosities comparable to PDMS analogs.
• Vinyl-terminated polymers were cross-linked into transparent solid elastomers with moduli increasing as molecular weight decreased.
• Evidence suggests potential practical recyclability of the synthesized resins and elastomers.

Conclusions:

• Polymers derived from c-M2E show promise as alternative silicone materials with tunable properties.
• These polymers can be formulated into curable elastomers, expanding options for material design.
• The potential for recyclability enhances the sustainability profile of these novel silicon-based materials.