A Shish-kebab superstructure in low-crystallinity elastomer nanocomposites: Morphology regulation and load-transfer

Abstract

In this paper, a regulated morphology of multi-walled carbon nanotube bundles (CNTBs) in olefin block copolymer (OBC) is achieved via a facile method of short-time strong sonication and solution blending. Inside the CNTBs which consist of several to dozens of nanotubes, the nanotubes exhibit a well aligned structure. With the incorporation of CNTBs, a hybrid shish-kebab superstructure is formed that nanotubes in CNTBs form the central stems and OBC crystals form kebabs on the surface of nanotubes. Superior reinforcement is achieved, e.g., the tensile strength and Young's modulus can be both tripled with 2 wt% CNTB incorporation. A downshift of G' band of CNTBs in nanocomposites in in situ Raman Spectra can be strikingly 10.09 cm -1 , presenting remarkably effective load-transfer and leading to significant reinforcement. Additionally, unique morphology of CNTBs and the low compliance of rigid shish-kebab superstructure with large stereo hindrance could also contribute to the reinforcement of OBC/CNTB nanocomposites. In rheological tests, the nanocomposites exhibit quite low rheological percolation threshold of 0.34 wt% and gel point of 0.634 wt% as well as notable difference in terminal behavior in low frequency zone compared to that of neat OBC, revealing that the rigid bundle structure of CNTBs has remarkable effect on the viscoelastic behavior of OBC.

Competition Between Interfacial Interaction and Microphase Separation in Crystallization of Filled Block Copolymers

“…Ochoa observed that the addition of cellulose nanofibers (CNFs) can increase the final crystallinity of polyethylene‐b‐polyethylene glycol (PE‐b‐PEG) diblock copolymers . Moreover, a nanohybrid shish‐kebab (NHSK) structure, which consists of central nanofiller (shish) and surrounding lamellar crystals (kebabs), has been observed in olefin block copolymers incorporating one‐dimensional nanofillers . Similar structure has also been found in PE‐b‐PEG block copolymers containing carbon nanotubes (CNTs) .…”

“…In the system without the repulsive interaction ( B 2 = 0), a central nanofiller periodically decorated with disk‐shaped lamellae, which is similar with the reported NHSK structure, can be observed. In experiments, such a structure has also been induced by different one‐dimensional nanofiller in diblock copolymer solutions . For instance, it has been reported that a small amount of nanofiller in the olefin diblock copolymer solution is sufficient to induce heterogeneous crystallization of the block copolymer, ultimately forming a typical NHSK structure .…”

“…In experiments, such a structure has also been induced by different one‐dimensional nanofiller in diblock copolymer solutions . For instance, it has been reported that a small amount of nanofiller in the olefin diblock copolymer solution is sufficient to induce heterogeneous crystallization of the block copolymer, ultimately forming a typical NHSK structure . In our previous research, we have investigated the formation mechanism of the NHSK structure in different polymer systems containing nanofiller, such as homopolymers, random copolymers, and crystalline‐amorphous diblock copolymers .…”

“…In general, nanofillers act as nucleating agents to promote crystallization and induce the formation of crystal structures with various morphologies, which remarkably depend on filler size, filler content, and polymer–filler interaction . In particular, the incorporation of nanofillers also affects crystallization behaviors of block copolymers . Ochoa observed that the addition of cellulose nanofibers (CNFs) can increase the final crystallinity of polyethylene‐b‐polyethylene glycol (PE‐b‐PEG) diblock copolymers .…”

Properties and preparation of olefin block copolymer/thermoplastic polyurethane blends

“…Owning to these nanocrystalline hard domains, OBCs exhibit high melting temperature, but still remains soft elastomeric feature, a difficult balance hard to reach for general elastomers, like metallocene‐catalyzed polyethylene elastomer. Several recent works have investigated the relationships between structure and properties of novel OBCs . However, only a few OBC blends available in the literature includes OBC/PP (polypropylene), OBC/SEBS (styene‐ethylene‐butylene‐styrene copolymer), and OBC/ethylene‐octene (EO) copolymer …”