Millimeter-Size Spherical Polyurea Aerogel Beads with Narrow Size Distribution

Area of Science:

• Materials Science
• Polymer Chemistry

Background:

• Aerogels are advanced porous materials with unique properties.
• Developing scalable and cost-effective synthesis methods for aerogels is crucial for their wider application.

Purpose of the Study:

• To report a novel, simple, and cost-efficient method for synthesizing spherical polyurea (PUA) aerogel beads at room temperature.
• To characterize the morphology, size, and properties of the synthesized PUA aerogel beads.

Main Methods:

• Spherical wet-gels of polyurea were formed by dripping an aliphatic triisocyanate solution into a mixture of ethylenediamine and heavy mineral oil.
• Supercritical fluid (SCF) CO₂ drying was employed to obtain the final aerogel beads.
• Characterization included SEM for morphology, and NMR (IR, ¹H MAS, ¹³C CPMAS) for chemical structure confirmation.

Main Results:

• Room temperature synthesis yielded millimeter-size spherical PUA aerogel beads (mean diameter 2.7 mm) with narrow size distribution.
• The PUA aerogel beads exhibited low density (0.166 g cm⁻³), high porosity (87%), and high surface area (197 m² g⁻¹).
• SEM revealed a porous skin on the bead surface, distinct from the interior morphology.

Conclusions:

• The reported method is simple, cost-efficient, and scalable for producing spherical PUA aerogel beads.
• The synthesized PUA aerogel beads possess desirable properties for various potential applications.
• The room temperature synthesis avoids complex procedures, enhancing accessibility for PUA aerogel production.