PMMA nano-encapsulated phase change material colloids for heat management applications

•RT21HC, a commercial organic PCM, has been nano-encapsulated into PMMA shells.•Organic nucleating agents have been incorporated into the nano-capsules to mitigate PCM supercooling.•Stable, concentrated suspensions into water of PMMA nano-capsules containing PCM have been obtained.•The apparent thermal capacity of the obtained colloids can be more than 10 % higher with respect to pure water.