Computer simulations of the early stages of crystal nucleation of linear and short chain branched polyethylene on carbon nanotubes

Jerónimo, K.; Cruz, Víctor L.; Ramos, Javier; Vega, Juan Francisco; Trujillo, Mariselis; Müller, Alejandro J.; Martínez‐Salazar, Javier

doi:10.1016/j.eurpolymj.2014.04.021

Cited by 15 publications

(6 citation statements)

References 43 publications

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“…It is expected that the inclusion of explicit solvent can favor the unwrapping of the PFO-BPy:Re polymer since the SWCNT is more exposed to the solvent molecules leading to a phase separation . To rigorously quantify the dynamics of both polymer systems, we can numerically evaluate the radius of gyration, R g , given by − R g 2 = (1/ N ) ∑ i =1 N ( r i – r cm ) 2 , where r i and r cm are the position vectors of each atom and the center of mass of the oligomer, respectively, and N is the number of atoms in the oligomer. The radius of gyration provides a numerical measure of the folding of the polymer chain and its global shape, with higher values of R g 2 corresponding to an expanded and stiff molecular configuration.…”

Section: Resultsmentioning

confidence: 99%

Isolation of Pristine Electronics Grade Semiconducting Carbon Nanotubes by Switching the Rigidity of the Wrapping Polymer Backbone on Demand

et al. 2015

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Conjugated polymers are among the most selective carbon nanotube sorting agents discovered and enable the isolation of ultrahigh purity semiconducting singled-walled carbon nanotubes (s-SWCNTs) from heterogeneous mixtures that contain problematic metallic nanotubes. The strong selectivity though highly desirable for sorting, also leads to irreversible adsorption of the polymer on the s-SWCNTs, limiting their electronic and optoelectronic properties. We demonstrate how changes in polymer backbone rigidity can trigger its release from the nanotube surface. To do so, we choose a model polymer, namely poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(6,60-(2,20-bipyridine))] (PFO-BPy), which provides ultrahigh selectivity for s-SWCNTs, which are useful specifically for FETs, and has the chemical functionality (BPy) to alter the rigidity using mild chemistry. Upon addition of Re(CO)5Cl to the solution of PFO-BPy wrapped s-SWCNTs, selective chelation with the BPy unit in the copolymer leads to the unwrapping of PFO-BPy. UV-vis, XPS, and Raman spectroscopy studies show that binding of the metal ligand complex to BPy triggers up to 85% removal of the PFO-BPy from arc-discharge s-SWCNTs (diameter = 1.3-1.7 nm) and up to 72% from CoMoCAT s-SWCNTs (diameter = 0.7-0.8 nm). Importantly, Raman studies show that the electronic structure of the s-SWCNTs is preserved through this process. The generalizability of this method is demonstrated with two other transition metal salts. Molecular dynamics simulations support our experimental findings that the complexation of BPy with Re(CO)5Cl in the PFO-BPy backbone induces a dramatic conformational change that leads to a dynamic unwrapping of the polymer off the nanotube yielding pristine s-SWCNTs.

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Section: Resultsmentioning

confidence: 99%

Isolation of Pristine Electronics Grade Semiconducting Carbon Nanotubes by Switching the Rigidity of the Wrapping Polymer Backbone on Demand

et al. 2015

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“…34 Recent computer simulation studies performed by us were able to reproduce many of the above experimental facts on linear and branched PE/CNT nanocomposites. 40 The simultaneous effect of chain branching and molecular weight on the rheology and crystallization behavior of PE/CNT nanocomposites has been seldom studied. Therefore, the aim of the present study is to investigate the way in which the properties of well dispersed nanocomposites are affected by the molecular architecture of the matrix.…”

Section: Introductionmentioning

confidence: 99%

Influence of Chain Branching and Molecular Weight on Melt Rheology and Crystallization of Polyethylene/Carbon Nanotube Nanocomposites

et al. 2014

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In this paper, the synergistic effects that carbon nanotubes (CNTs) produce on the basic rheological properties and crystallization of polyethylenes with different branch contents and molecular weights was investigated. Multiwalled carbon nanotubes coated with polyethylene (as produced by in situ polymerization) were blended in the melt (in a 1% wt. ratio) with three polyethylene matrices of different molecular weights and branch contents. Transmission electron micrographs demonstrated excellent carbon nanotube dispersion in all samples and the existence of a geometrical percolation network. The rheological and calorimetric properties of the nanocomposites were determined and the results compared to those obtained for neat polyethylene resins. Both Newtonian viscosity and steady-state shear recoverable compliance increased with the addition of CNTs in all cases. However, the increase was strongly dependent on the molecular weight (and dispersity index) of the matrices regardless of the branch content. A novel screening effect of the CNTs network due to the high relaxation times of the matrix with the highest molecular weight was detected. This important result demonstrates that viscoelasticity can hinder the measurement of the rheological percolation threshold of CNTs network depending on the scale of relaxation times involved. Additionally, it was found that in relative terms (comparing each nanocomposite with its neat polyethylene matrix), the M w values also play a vital role in CNT nucleation besides chain branching content. Both nonisothermal and isothermal nucleation effects caused by CNTs increased as the M w of the polyethylene matrix decreased in spite of the role played by short chain branches in decelerating their overall crystallization kinetics. The capability for producing more stable lamellae through successive annealing of the nanocomposites as compared to their neat matrices also followed a decreasing trend with molecular weight increases, as indicated by SSA thermal fractionation results. Nevertheless, the presence of branches played a major role, since fractionation quality improved greatly as the branch content increased in the samples, as expected on the basis of the sensitivity of thermal fractionation to the presence of defects along crystallizable sequences.

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“…To better characterize the morphology and orientation of the SWCNT, we calculate the global SWCNT order parameter Q, experssed as − where N is the number of particles that composed the SWCNT and θ ij is the angle between the vectors b i and b j . The vector b i = ( r i – r i –1 )/2 is the one formed by the midpoint of two adjacent particles i and i – 1.…”

Section: Resultsmentioning

confidence: 99%

Self-Assembled Morphologies and Percolation Probability of Mixed Carbon Fillers in the Diblock Copolymer Template: Hybrid Particle-Field Molecular Dynamics Simulation

Zhao

Milano

et al. 2015

J. Phys. Chem. C

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The self-assembly of polymer composites of mixed carbon fillers including single-walled carbon nanotube (SWCNT) and carbon black nanoparticles (CB NPs) in diblock copolymer (BCP) template are investigated using hybrid particle-field molecular dynamics simulations in this work. Simulations show, in agreement with experiments, that composites of BCP template with SWCNT have lower percolation threshold than that of BCP template with CB NPs. Moreover, the ratio between SWCNT and CB NPs has a strong influence on the percolation threshold of composites. The results of percolation probability show that adding more SWCNT (compared with CB NPs) to the BCP template could decrease the percolation threshold. However, a synergistic effect of percolation of the mixed carbon fillers in BCP template has been found. In particular, a nonlinear relation following the Boltzman function has been found, and the lowest percolation threshold exists with the volume ratio 4:1 (SWCNT/CB NPs) compared with the volume ratios of 1:1, 2:1, and 8:1 (SWCNT/CB NPs). The mixed carbon fillers also affect the morphologies of the BCP template, and the calculated radius of gyration of BCP shows that, in a higher concentration of the mixed fillers, the stretching of BCP is stronger, which results in the deformation of BCP template

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Computer simulations of the early stages of crystal nucleation of linear and short chain branched polyethylene on carbon nanotubes

Cited by 15 publications

References 43 publications

Isolation of Pristine Electronics Grade Semiconducting Carbon Nanotubes by Switching the Rigidity of the Wrapping Polymer Backbone on Demand

Isolation of Pristine Electronics Grade Semiconducting Carbon Nanotubes by Switching the Rigidity of the Wrapping Polymer Backbone on Demand

Influence of Chain Branching and Molecular Weight on Melt Rheology and Crystallization of Polyethylene/Carbon Nanotube Nanocomposites

Self-Assembled Morphologies and Percolation Probability of Mixed Carbon Fillers in the Diblock Copolymer Template: Hybrid Particle-Field Molecular Dynamics Simulation

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