Thermodynamic approach to enhanced dispersion and physical properties in a carbon nanotube/polypeptide nanocomposite

Abstract

A high molecular weight synthetic polypeptide has been designed which exhibits favorable interactions with single wall carbon nanotubes (SWCNTs). The enthalpic and entropic penalties of mixing between these two molecules are reduced due to the polypeptide's aromatic sidechains and helical secondary structure, respectively. These enhanced interactions result in a well dispersed SWCNT/Poly ( L -Leucine-ran-L -Phenylalanine) nanocomposite with enhanced mechanical and electrical properties using only shear mixing and sonication. At 0.5 wt% loading of SWCNT filler, the nanocomposite exhibits simultaneous increases in the Young's modulus, failure strain, and toughness of 8%, 120%, and 144%, respectively. At one kHz, the same nanotube loading level also enhances the dielectric constant from 2.95 to 22.81, while increasing the conductivity by four orders of magnitude.Keywords: copolypeptide, single wall carbon nanotube (SWCNT), nanotube/polymer interactions, nanotube/polymer nanocomposite Next generation aerospace applications will demand strong and lightweight materials that offer additional intrinsic functionalities such as electrical conductivity, sensing, or actuation. Incorporation of single wall carbon nanotubes (SWCNTs) into certain high performance polymers yields a lightweight material with dramatically improved mechanical and electrical properties that also exhibits sensing and actuating behavior 1,2 . Achieving these improved properties depends on the SWCNTs being 1 https://ntrs.nasa.gov/search.jsp?R=20090017801 2018-05-09T15:57:46+00:00Z

Polyvinylferrocene for Noncovalent Dispersion and Redox-Controlled Precipitation of Carbon Nanotubes in Nonaqueous Media

“…Atomic force microscopy (AFM) images were taken with a Veeco Nanoscope V AFM with Figure 1b) is believed to be completely debundled nanotubes with an average diameter around 2 to 5 nm, co-existing with another group of slightly bundled SWCNTs with an average diameter around 10 to 12 nm. Moreover, the CNT loadings obtained by using PVF as the dispersant (2.3 ± 0.1 mg mL −1 for SWCNTs and 2.2 ± 0.1 mg mL −1 for MWCNTs) exceeded significantly most of the reported values for CNT dispersions in organic solvents using other noncovalent-type dispersants [23][24][25][26][27][28][29][30]48 ( Figure 1c). The method of determining the CNT solubility is presented in the Supporting Information (SI) Section S1.1.…”

Fluorescent PLLA-nanodiamond composites for bone tissue engineering

“…Therefore, a major issue in manufacturing ND-polymer composites is to thwart the strong tendency of ND to aggregation by improving dispersion quality [21]. In order to achieve this goal, various approaches similar to those used for CNTs have been utilized, including high shear mixing, extrusion, in situ polymerization, wrapping the nanoparticles with surfactants, and covalent chemical functionalization [22,23]. In this study we use chemically functionalized ND produced via covalent attachment of octadecylamine (ODA) to its surface [16].…”

Shear piezoelectricity in single‐wall carbon nanotube/poly(γ‐benzyl‐L‐glutamate) composites

“…Based on this information, the SWCNTs also do not interfere with the backbone dipoles responsible for last component of eq 2, the single crystal constants d and d . Building upon previous reports of favorable interactions between aromatic species and SWCNTs through dispersion interactions,23, 33, 34 the benzyl‐terminated PBLG side chains may be inhibiting interactions between the SWCNTs and the backbone dipoles responsible for shear piezoelectricity. This theory may explain how the SWCNTs can exist in concentrations sufficient to enhance several physical properties and impart multifunctionality to PBLG without degrading its shear piezoelectricity.…”

“…In addition, its biocompatibility, commercial availability (Sigma Aldrich), and similarity to many other α‐helical biopolymers and polypeptides22 make it an excellent initial selection for this study. PBLG also contains aromatic sidechains and possesses a size/shape similar to SWCNTs, both of which have been shown to improve SWCNT dispersion in polymer composites 23. Induced dipole‐dipole interactions between the PBLG aromatic sidechains and SWCNT π‐bonds lead to a reduction in the enthalpy of mixing for these two species, while their similar size/shape result in an increase in entropy of mixing 23.…”

“…PBLG also contains aromatic sidechains and possesses a size/shape similar to SWCNTs, both of which have been shown to improve SWCNT dispersion in polymer composites 23. Induced dipole‐dipole interactions between the PBLG aromatic sidechains and SWCNT π‐bonds lead to a reduction in the enthalpy of mixing for these two species, while their similar size/shape result in an increase in entropy of mixing 23. Two polymer lots, labeled PBLG and PBLG2, were used in the experiments for this study.…”