Methods to make polymer composites comprise melt and solution blending, but in the particular case of polyolefins they are not appropriate due to the weak interfacial adhesion. In the present work, in situ blended (ISB) together with in situ polymerization (ISP) processes have been employed and compared using MAO/(nBuCp)2ZrCl2 as catalytic system and sepiolite clay as additive in ethylene polymerization. A new method as a combination of the previous ones (ISB + ISP) has been developed and applied to the synthesis of linear low-density polyethylene (LLDPE). When ISB + ISP method is employed high catalytic activities are observed and this combination allows to increase the storage modulus at 25 degrees C up to 26% with 2.8 wt % of clay in LLDPE when silica is employed as catalyst carrier; in that way, copolymer particles with good morphology with higher storage modulus are obtained, useful properties for their use in specific applications. (c) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012