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. 2022 Aug 1;14(15):3137.
doi: 10.3390/polym14153137.

Effect of MWNT Functionalization with Tunable-Length Block Copolymers on Dispersity of MWNTs and Mechanical Properties of Epoxy/MWNT Composites

Jingwei Liu  1   2 , Yunsheng Ye  3 , Xiaolin Xie  2 , Xingping Zhou  2
Affiliations

Effect of MWNT Functionalization with Tunable-Length Block Copolymers on Dispersity of MWNTs and Mechanical Properties of Epoxy/MWNT Composites

Jingwei Liu et al. Polymers (Basel). .

Abstract

The dispersion level of carbon nanotubes (CNTs) and interface design are two of the most crucial roles in developing the superior mechanical performance of polymer/CNT nanocomposites. In this work, a series of azide-terminated poly(glycidyl methacrylate)-block-poly(hexyl methacrylate) (PGMA-b-PHMA) copolymers with different PHMA chain lengths and similar PGMA chain lengths were grafted on the surface of multiwall carbon nanotubes (MWNTs). PHMA length changes significantly impact the grafting density and solubility in organic solvents of as-prepared block copolymer functionalized MWNTs(bc@fMWNTs). Then, the bc@fMWNTs were introduced to epoxy, and the resulted epoxy/bc@fMWNT composites show better mechanical properties than neat epoxy and epoxy/p-MWNT composites. The results suggest that longer PHMA chains cause the two competitive and opposing effects on the dispersion state and soft interface. On the one hand, the longer PHMA chains on the surface of MWNTs would afford higher deformation for the matrix and enhanced mobility for MWNTs because of the soft and flexible nature of PHMA, enhancing the energy dissipation during strain. On the other hand, as the length of PHMA extends, the dispersion level of bc@fMWNTs in epoxy declines, which is harmful to the composite's mechanical properties. Hence, epoxy/bc@fMWNTs composites with relatively short PHMA chains show the best tensile and fracture properties.

Keywords: MWNTs; block copolymer; epoxy; interface; regulation; toughness.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
GPC curves of block copolymers (A) B1 (Mn = 10,700 g mol−1, Mw/Mn = 1.12); (B) B2 (Mn = 15,150 g mol−1, Mw/Mn = 1.13); (C) B3 (Mn = 19,500 g mol−1, Mw/Mn = 1.12); (D) B4 (Mn = 27,300 g mol−1, Mw/Mn = 1.15).
Figure 2
Figure 2
TGA curves (a) and solubility and grafting density (b) of bc@fMWNTs brushes with different PGMA-b-PHMA-N3 average molecular weights.
Figure 3
Figure 3
Optical density at 500 nm of bc@fMWNTs in THF at different concentrations. The straight line is a linear fit to the data having a slope of 0.01145. (Note: The concentration for UV–Vis measurement has been diluted several times) (a), and photograph, the solubility of different block copolymer modified MWNTs in THF (b), toluene (c), and DMF (d) after 24 h.
Figure 4
Figure 4
TOM images of the epoxy nanocomposites with 0.05 wt% (a) p-MWNTs, (b) B1@fMWNTs, (c) B2@fMWNTs, (d) B3@fMWNTs, (e) B4@fMWNTs, and TEM images of the epoxy nanocomposites with 0.05 wt%: (f) p-MWNTs, (g) B1@fMWNTs, (h) B4@fMWNTs.
Figure 5
Figure 5
Storage modulus (a) and tan δ (b) of epoxy composites with 0.05 wt% of p-MWNTs and bc@MWNTs.
Figure 6
Figure 6
Tensile properties (a) and fracture toughness (b) of epoxy-based nanocomposites.
Figure 7
Figure 7
Stress–strain curves of epoxy, epoxy composites with 0.05 wt% B1@fMWNTs and B4@fMWNTs.
Figure 8
Figure 8
Proposed epoxy/bc@fMWNTs nanocomposite formation mechanism (a), interphase structures around MWNTs and their effects upon loading (b).
Figure 9
Figure 9
SEM fractographs of the epoxy nanocomposites with 0.05 wt%: (a) p-MWNTs, (b) B1@fMWNTs, (c) B2@fMWNTs, (d) B3@fMWNTs, (e) B4@fMWNTs.
See this image and copyright information in PMC

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