Multiwall carbon nanotubes (MWCNTs) have been functionalized via addition of undecyl (C 11 -) radicals generated by thermal decomposition of lauroyl peroxide. The functionalized MWCNTs (C 11 -MWCNTs) were characterized by Raman, IR spectroscopy, and thermogravimetric analysis (TGA). Isotactic polypropylene (iPP) and syndiotactic polypropylene (sPP) nanocomposites containing both purified and alkyl-functionalized MWCNTs have been synthesized via in situ polymerization method with the use of C 2 -and C s -symmetry zirconocenes activated by MAO in liquid propylene medium. The effect of incorporating C 11 -MWCNTs on structural, electrical, and mechanical properties of the polypropylene-based nanocomposites has been studied. Analysis of electrical properties in the microwave range elucidates interfacial transformations in the composites induced by MWCNT functionalization and evaluates relative aspect ratios for the filler particles in different systems. The synthesized materials demonstrate improved filler dispersion and mechanical characteristics as a result of nanotube chemical functionalization. The MWCNT functionalization leads to markedly improved nanocomposite plasticity and noticeable enhancement of sPP tensile modulus.

Isotactic polypropylene and elastomeric stereoblock polypropylene nanocomposites containing 0.1−3.5 wt % multiwall carbon nanotubes (MWCNTs) have been synthesized via the in situ polymerization approach using MAO-activated C 2- and C 1-symmetry ansa-zirconocenes, a technique that has not been previously reported in literature. Fracture morphology examination of the nanocomposites revealed very efficient distribution of the MWCNTs within the isotactic polypropylene matrix, yet interfacial adhesion level and the reinforcement efficiency were dependent on the nanotube loadings. The elastomeric stereoblock polypropylene/MWCNT and the isotactic polypropylene-based nanocomposites exhibited different morphologies depending on the synthesis peculiarities. For isotactic polypropylene, Youngʼs modulus increased by ∼22% even at 0.1 wt % MWCNT loading, and further modulus growth was observed at higher filler contents. Relatively low permittivity values and considerable dielectric losses in microwave range infer that the obtained nanocomposites can find use as efficient electromagnetic shielding materials and microwave absorbing filters. Outstanding improvement of thermal stability (∼60 °C at maximum weight loss rate temperature) has been achieved for isotactic polypropylene upon incorporating only 3.5 wt % of carbon nanotubes.

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