Influence of CNT Length on Dispersion, Localization, and Electrical Percolation in a Styrene-Butadiene-Based Star
Ulrike Staudinger1, Andreas Janke1, Christine Steinbach1
1Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Str. 6, 01069 Dresden, Germany.
Polymers
|July 9, 2022
Summary
Shortening carbon nanotubes (CNTs) via ball milling influenced their localization in block copolymer (BCP) nanocomposites. This tuning affected electrical properties, increasing resistivity and percolation thresholds with shorter CNT lengths.
Area of Science:
- Materials Science
- Polymer Science
- Nanotechnology
Background:
- Block copolymers (BCPs) offer nanostructured domains for material property tuning.
- Carbon nanotubes (CNTs) are known for their exceptional electrical and mechanical properties.
- Controlling CNT dispersion and localization is key to optimizing nanocomposite performance.
Purpose of the Study:
- To investigate the effect of shortened multiwalled carbon nanotubes (MWCNTs) on the electrical and mechanical properties of BCP nanocomposites.
- To explore selective localization of CNTs within BCP nanostructures for potential sensor applications.
- To understand how MWCNT length reduction impacts electrical percolation and mechanical behavior.
Main Methods:
- Ball milling to shorten MWCNTs into different size fractions.
- Transmission electron microscopy (TEM) and dynamic light scattering (DLS) for MWCNT length analysis.
- Atomic force microscopy (AFM) and TEM for investigating CNT localization within BCP nanostructures.
- Electrical conductivity and mechanical (stress-strain) testing of the resulting nanocomposites.
Main Results:
- BCP nanostructure and glass transition temperatures were largely unaffected by CNT addition up to 2 wt%.
- Shortened CNTs showed partial localization in the PB-rich phase or at phase interfaces.
- Mechanical properties (Young's modulus, strain at break) showed minor changes attributed to CNT localization.
- Electrical percolation threshold increased with decreasing CNT length; shortened CNTs exhibited surface resistivity changes due to sedimentation.
Conclusions:
- MWCNT shortening via ball milling allows for tuning of electrical properties in BCP nanocomposites.
- CNT localization, influenced by length, plays a role in the observed mechanical property variations.
- Sedimentation of shortened CNT agglomerates during processing significantly impacts electrical conductivity, particularly surface resistivity.
Keywords:
CNT dispersionCNT lengthCNT localizationball millingblock copolymercarbon nanotubeselectrical conductivitymechanical behaviorMore Related Videos
11:42Synthesis of Monodisperse Cylindrical Nanoparticles via Crystallization-driven Self-assembly of Biodegradable Block Copolymers
Published on: June 20, 2019
7.9K
11:09Grafting Multiwalled Carbon Nanotubes with Polystyrene to Enable Self-Assembly and Anisotropic Patchiness
Published on: April 1, 2018
8.2K
Related Concept Videos
01:14Polymer Classification: Architecture
2.9K
Polymers are classified as linear or branched on the basis of their chain architecture. The polymer chains in linear polymers have a long chain-like structure with minimal to no branching at all. Even if a polymer features large substituent groups on the monomer, which appear as branches to the skeleton, it is not considered a branched polymer. A branched polymer contains secondary polymer chains that arise from the main polymer chain. The branching occurs when the polymer growth shifts from...
2.9K
01:08Molecular Weight of Step-Growth Polymers
2.3K
Step growth polymerization involves bi or multifunctional monomers. Bifunctional monomers react to form linear step growth polymers, whereas multifunctional monomers react to form non-linear or branched polymers.
As the step-growth polymerization involves step-wise condensation of monomers, the molecular weight also builds up eventually. Consequently, high molecular weight polymers are obtained at the late stages of the polymerization, where 99% of monomers have been consumed.
The extent of the...
As the step-growth polymerization involves step-wise condensation of monomers, the molecular weight also builds up eventually. Consequently, high molecular weight polymers are obtained at the late stages of the polymerization, where 99% of monomers have been consumed.
The extent of the...
2.3K
01:26Polymer Classification: Stereospecificity
2.6K
Polymerization generates chiral centers along the entire backbone of a polymer chain. Accordingly, the stereochemistry of the substituent group has a significant effect on polymer properties. Polymers formed from monosubstituted alkene monomers feature chiral carbons at every alternate position in the polymer backbone. Relative to the predominant orientation of substituents at the adjacent chiral carbons, the polymer can exist in three different configurations: isotactic, syndiotactic, and...
2.6K
01:24Characteristics and Nomenclature of Copolymers
2.7K
Copolymers are the products obtained from the polymerization of multiple monomer species. So, in a polymer chain itself, there can be multiple repeating units that come from different monomers. The process of synthesizing a polymer from different monomer species is called copolymerization. When two monomers are involved, the polymer is known as a bipolymer. Polymers with three and four monomers are termed terpolymers and quaterpolymers, respectively. Figure 1 depicts the copolymerization of...
2.7K
01:10Polymers: Molecular Weight Distribution
3.7K
For any given polymer, the weight average molecular weight (Mw) is higher than, if not equal to, the number average molecular weight (Mn). The only situation in which the weight average molecular weight and the number average molecular weight are equal is when a polymer consists only of chains with equal molecular weight. However, this never happens in a synthetic polymer, since it is difficult to control the polymerization process up to a molecular level with accuracy to a hundred percent.
3.7K
01:17Radical Chain-Growth Polymerization: Chain Branching
2.0K
The skeletal structure of polymers synthesized via radical polymerization is always branched. For example, the polymerization of ethylene by radical polymerization results in a low-density grade of polyethylene with a heavily branched skeletal structure. Here, the radical site abstracts hydrogen from the growing chain, and the radical site shifts from the end (a primary carbon center) to anywhere within the growing chain (a secondary carbon center). Consequently, the part of the chain from the...
2.0K