Ethylene‐co‐Norbornene Copolymers Grafted Carbon Nanotube Composites by In Situ Polymerization

Abstract

Vinyl functionalized multiwalled carbon nanotubes (MWCNT-vinyl) are synthesized and used as monomers to prepare poly(ethylene-co -norbornene)-grafted carbon nanotube composites by in situ polymerization with [Ti( η 5 -C 5 Me 5 )(NϭC t Bu 2 )Cl 2 ] activated with methylalumoxane (MAO). The glass transition temperatures ( T g ) of grafted MWCNT composites are more than 30 ° C higher than those of copolymers. This difference is rationalized by the immobilization of the copolymer chain to the MWCNT surface by a covalent bond. The Young's modulus is shown to increase by more than 200% compared to poly(ethylene-co -norbornene) by incorporating 3.4 wt% functionalized MWCNT.blending methods generally used for preparing nanocomposites are not suitable for polyolefi ns. [ 4 ] The in situ polymerization of monomers in the presence of nanoparticles and CNT is a promising method for obtaining nanocomposites in which nanotubes are dispersed individually at nanometer level. [5][6][7] Copolymers of ethylene (E) with norbornene (N) [P(Eco -N)] are thermoplastic materials that have recently received great attention because of their attractive properties [ 8 , 9 ] such as high T g , high optical transparency, excellent moisture barrier, and chemical resistance. These distinctive properties enable them to be utilized for a wide variety of uses in advanced packaging, engineering components, and optical applications.Among the in situ methodologies hitherto reported, P(E-co -N)-MWCNT were obtained with MAO-activated metallocenes by polymerization fi lling technique (PFT), [ 6 ] and more recently by in situ synthesis with a highly active methylalumoxane (MAO) free catalytic system. [ 9 ] Another method involves in situ polymerization in the presence of functionalized nanotubes which can be inserted into the polymer chain, resulting in covalent attachment of nanotubes to the polymer. Consequently, better dispersion and formation of a strong interface between nanotubes and polymer matrix are achieved.

Study on single and binary catalytic systems of pyridine‐imine catalysts based on nickel and iron in synthesis of reactor blends and low‐density polyethylene nanocomposites

“…54 In fact, the nanofiller (such as CNTs) could increase the chain transfer reaction and β-hydrogen elimination due to an electronic effect that consequently increases the branching content. 23,24 As exhibited in Figure 8 and Table III (Entries 2-5), the values for LDPE/ nanocomposite samples varied between 11.5 and 70.8 methyl branches/1000 carbon atoms. Furthermore, nanocomposite samples containing MWCNT [20][21][22][23][24][25][26][27][28][29][30] showed the lowest vinyl content (0.12 vinyl groups/1000 carbon atoms) among all the samples.…”

“…23,24 As exhibited in Figure 8 and Table III (Entries 2-5), the values for LDPE/ nanocomposite samples varied between 11.5 and 70.8 methyl branches/1000 carbon atoms. Furthermore, nanocomposite samples containing MWCNT [20][21][22][23][24][25][26][27][28][29][30] showed the lowest vinyl content (0.12 vinyl groups/1000 carbon atoms) among all the samples. However, the addition of MWCNT into the polymerization media led to a greater vinyl content in the products, up to 5.30 vinyl groups/1000 carbon atoms.…”

“…LDPE/nanocomposite samples containing different types and content of MWCNTs were successfully prepared via in situ polymerization. By increasing the content of MWCNT [20][21][22][23][24][25][26][27][28][29][30] , the activity of the catalysts was improved, which can be attributed to adsorption of catalyst on the CNT surface, but overall the performance of the catalyst mixture decreased in the presence of MWCNTs. The LDPE/nanocomposites with lower melting point and degree of crystallinity compared to the neat polyethylene blend implied higher chain walking, degree of branching, and vinyl content.…”

“…10,28 Morphology of LDPE/Nanocomposites SEM images were used to investigate the influence of the different type and content of MWCNTs as well as different preparation techniques on the morphology of the final products. Figure 9(b), a uniform morphology is not seen for the sample obtained in the presence of MWCNT [20][21][22][23][24][25][26][27][28][29][30] (entry 3, Table III); however, virtually a single fraction of the crystalline phase in DSC traces was observed for the sample containing MWCNT [entry 5, Table III, and Figure 7(a)], in which the presence of nanotubes is obvious in the polymer matrix [ Figure 9(c)].…”

“…The activity of the catalyst N in polymerization, as well as the melting point and crystallinity of the resultant sample, dropped as the MWCNT [20][21][22][23][24][25][26][27][28][29][30] was added into the polymerization reactor. However, the branching and vinyl content trends in these samples are not the same as in the sample produced by the dual catalyst system under the same conditions.…”