Solvent-Assisted Synthesis of Polyborodimethylsiloxane (PBDMS) and its Rheological Research

Polyborodimethylsiloxanes (PBDMS) are supramolecular elastomers known for their unique viscoelastic and shear-stiffening properties, attributed to weak Si–O: B dative bonding and hydrogen bonding. This enables a transition between liquid-like and elastic behavior, making PBDMS suitable for smart coatings, flexible electronics, and energy-dissipating materials. PBDMS is also a key component in strain-sensitive Interpenetrating Polymer Networks (IPNs), such as the commercially available D3O, which combines PBDMS with polyurethane matrix. Most PBDMS synthesis studies focus on high-temperature bulk methods (200 °C), which, despite being contamination-free, suffer from poor mixing, chain scission, and scalability issues. This study explores a solvent-assisted approach using hydroxy-terminated PDMS of varying viscosities and boric acid (BA) at 120 °C in toluene, ensuring uniform mixing and controlled molecular scission. Fourier transform infrared (FTIR) spectroscopy confirmed Si–O-B linkage formation within 2 h, while gel permeation chromatography (GPC) showed a 90.4% molecular weight reduction. Rheological analysis indicated increased storage (G’) and loss (G’’) moduli, with elastic behavior dominating after 6 h. This solvent-assisted method provides a scalable and reproducible alternative for PBDMS synthesis, offering precise control over viscoelastic properties for advanced applications.