Linear polyethylene/branched polyethylene blends (LPE/BPE) were prepared using the homogeneous binary catalyst system composed by Ni(alpha-diimine)Cl-2 (1) (alpha-diimine = 1,4-bis(2,6-diisopropylphenyl)-acenaphthenediimine) and rac-ethylenebis(IndH(4))ZrCl2 (2) (IndH(4) = 4,5,6,7-tetrahydro-1-eta(5)-indenyl) activated with methylaluminoxane in hexane at three different polymerization temperatures (0, 30 and 50 degreesC) and by varying the zirconium loading molar fraction (x(Zr)). The polymerization runs carried out at 30 degreesC have shown that the productivity decreases linearly with x(Zr) On the other hand, at 0 and 50 degreesC, a non-linear dependence was observed between the x(Zr) and the productivity. The molecular weight of the LPE/BPE blends varied from 222 to 470 x 10(3) g mol(-1) with polydispersities around 2.0. Differential scanning calorimetry results showed that the dependence of the T-m values with respect to the x(Zr) it is higher for the LPE/BPE blends produced at 0 degreesC. Dynamic mechanical thermal analysis shows the formation of different polymeric materials where the stiffness varies according to the x(Zr). The surface morphology of the BPE/HDPE blends produced at 30 degreesC revealed a low miscibility between the PE phases resulting in the formation of a 'cobweb structure' (for x(Zr) = 0.25) after etched with hot o-xylene. (C) 2003 Elsevier Science Ltd. All rights reserved.