A nanodiamond nanomatrix structure is formed into natural rubber, generating not only entropic elasticity but also energetic elasticity. The radical reaction with tert-butylhydroperoxide (TBHP)/tetraethy-lenepentamine (TEPA) in the latex stage forms a chemical linkage between the nanodiamond and natural rubber particles after removing proteins from the rubber. To investigate the relationship between morphology and mechanical properties, the as-cast films prepared from nanodiamond-grafting deproteinized natural rubber (DPNR-ND) latex are subjected to transmission electron microscopy (TEM), tensile tests, and dynamic mechanical analyses. The nanodiamond nanomatrix structure markedly increases the tensile strength of natural rubber. The values of the storage modulus and loss modulus are about ten times higher than those of natural rubber in the rubbery plateau region when DPNR-ND contains 40 w/w% ND. Thus, an energetic elasticity is realized in conjunction with the entropic elasticity. (c) 2017 Elsevier Ltd. All rights reserved.