Polycarbosilane-Grafted Nanoparticles: Free-Flowing Hairy Nanoparticle Liquids That Convert to Ceramic

Abstract

Here, we report a new class of hybrid nanoparticles (NPs) that are self-supporting and display viscous flow behavior in the absence of solvent, yet convert to a purely inorganic material on heating. Hairy nanoparticles (HNPs) composed of silica nanoparticle cores (10−20 nm diameter) and preceramic poly(1,1-dimethylpropylsilane) (l-PCS) brushes were synthesized via a grafting-from approach utilizing hydrosilylation chemistry. The l-PCS polymer brush was grown from the nanoparticle core by anchoring the Pt(0) Karstedt's catalyst to Si−H groups functionalized on the silica surface. The resulting l-PCS-based HNPs were easily dispersed in a variety of organic solvents, displaying Newtonian rheological behavior at low weight percent solvent loadings, while neat HNPs displayed relatively low viscosities. The Krieger−Dougherty equation was used to evaluate viscosity trends as related to corona size, with the corona size being determined through dynamic light scattering. Thermally cured HNPs were successfully converted to SiO 2 /SiC nanocomposites, as evidenced by X-ray diffraction and attenuated total reflection (ATR)-Fourier transform infrared (FTIR). These unique preceramic HNPs hold considerable promise as a route to high-temperature materials, offering enhanced processability and compositional tailorability compared to neat resins.

Biomorphic Ceramics: Synthesis and Characterization of Preceramic Polymer-Modified Melanin

“…After silanization, SiH–ghosts were functionalized by either a graft-to reaction with SMP-10 or a graft-from reaction with ADS (Figure ). Functionalization with ADS results in poly­(ADS), a polymer with a well-known structure. However, previous work has shown that poly­(ADS) has a low ceramic yield .…”

“… Functionalization with ADS results in poly­(ADS), a polymer with a well-known structure. However, previous work has shown that poly­(ADS) has a low ceramic yield . Functionalization with SMP-10 has the benefit of using a commercially available material with high ceramic yields, approaching 80% according to the manufacturer, but is prone to cross-linking between polymer chains due to the allyl groups and SiH groups present in the polymer.…”

“…In order to minimize reactions that occur away from the melanin particles, leading to free polymer in solution in the case of ADS or a cross-linked polymer unassociated with melanin if SMP-10 is used, the catalyst and SiH–ghosts are first reacted together. This allows the Karstedt’s catalyst to insert into the Si–H bond to initiate reactions off the surface of the melanin, instead of in solution . ADS or SMP-10 is then added to the solution and the reaction is allowed to proceed.…”

“…This allows the Karstedt's catalyst to insert into the Si−H bond to initiate reactions off the surface of the melanin, instead of in solution. 84 ADS or SMP-10 is then added to the solution and the reaction is allowed to proceed. After the reaction is completed, the mixture is centrifuged to remove the free polymer and unreacted melanin, separating the soluble and insoluble material, and both the precipitate and supernatant are dried.…”

Impact of the Backbone Structure on the Rheological and Thermal Properties of Preceramic Polymer-Grafted Nanoparticles and Derived Ceramics

“…We recently reported the first example of using hydrosilylation to graft preceramic polymers from nanosilica. 34 Hydrosilylation is a straightforward route toward the fabrication of poly(1,1-dimethylpropylsilane)-grafted silica particles, and these particles are very dispersible in organic solvents. Solvent removal revealed a stable free-flowing composite with low viscosity compared to a physical mixture of poly(1,1-dimethylpropylsilane) and silica nanoparticles.…”