A novel composite PCMs nanocapsules (nanoPCMs) with PMMA and SiO2 as hybrid shell material and paraffin as core were successfully synthesized by concerted reaction of interfacial polymerization, sol gel and self-assembly methods. SEM images showed that the structure of nanocapsules was affected by the mass ratio of TEOS and MMA. When the mass ratios of TEOS/MMA were 1:3.5 and 1:5.75, the nanocapsules were spherical and homogeneous with the diameter around 120 nm. However, the nanocapsules were inhomogeneous and irregular when the mass ratio of TEOS/MMA was 1:12.5. Based on the results of DSC, moderate mass ratio of TEOS/MMA can improve thermal properties of nanocapsules. When the mass ratio of TEOS/MMA was 1:3.5, the thermal properties of paraffin@PMMA-SiO2 nanocapsules was improved with the average enthalpy about 71 J/g and encapsulated efficiency of paraffin was 57.4%, which was higher than paraffin@PMMA nanocapsules. Besides paraffin which was encapsulated in nanocapsules has a better thermal stability than that of unencapsulated, and the nanocapsules prepared with different mass ratio of MMA/TEOS can provide almost the same thermal stability. (C) 2015 Elsevier B.V. All rights reserved.