Using nanocapsules as building blocks to fabricate organic polymer nanofoam with ultra low thermal conductivity and high mechanical strength
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The nanocapsules and the nanofoam powder
The building blocks, nanocapsules, were synthesized by the interfacial reversible addition-fragmentation chain transfer (RAFT) miniemulsion polymerization, which we invented recently [29], [30]. Miniemulsion is a dispersed system, where oil minidroplets of 30 nm–500 nm are kinetically stabilized by surfactant and co-stabilizer (some compound with extremely low water solubility) in water [31], [32]. Miniemulsion polymerization, where the polymer particles are directly converted from the monomer
Summary
We demonstrated that the high performance polymeric nanofoam of air could be fabricated, for the first time, at normal drying conditions in the forms of powder and monolith. The polymer nanofoam showed the ultra low thermal conductivity, only half those of the conventional polymer foam. The crush strength of the monolith of the polymer nanofoam was as high as 8.55 MPa. The compressive strain at break was 45%. The key for the success is to use the performed nanocapsules with well-defined highly
Preparation of nanocapsules
The nanocapsules were made by the interfacial RAFT miniemulsion polymerization according to the previous report [37]. The recipe to synthesize the nanocapsules used in each experiment is listed in Table 4. The conversion was close to 100%. The solid content of the final products was 20 wt%.
Preparation of the powders of the hollow nanocapsules
The product latex of nanocapsules was demulsified by HCl solution and re-dispersed in tetrahydrofuran (THF) with magnetic stirring for over 12 h to dissolve paraffin out of the nanocapsules. Then the
Acknowledgements
The authors would like to thank the financial support from National Natural Science Foundation (Grant No. 21125626, 21076181, 20836007) and Program for Changjiang Scholars and Innovative Research Team in University.
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