Filamentous Virus-based Assembly: Their Oriented Structures and Thermal Diffusivity

Abstract

Organic polymers are generally regarded as thermal insulators because amorphous arrangement of molecular chains reduces the mean free path of heat-conducting phonons. However, recent studies indicated that single chains of polymers with highly oriented structures could have high thermal conductivity than bulk polymers because stretched polymer chains effectively conduct phonons through polymeric covalent bonds. Here, we demonstrated the possibility of non-covalent virus assembly prepared by simple flow-induced methods toward high thermal conductive polymeric materials. Films with high thermal diffusivity composed of non-covalent bond-based assemblies of liquid crystalline filamentous viruses were prepared using a simple flow-induced orientation method. Structural and thermal characterization demonstrated that highly oriented structures of the viruses in the film were attributed to the high thermal diffusivity. Our results will open attractive opportunities for biomolecular-based thermally conductive soft materials even though the assemblies are based on non-covalent bonds.

High Thermal Diffusivity in Thermally Treated Filamentous Virus-Based Assemblies with a Smectic Liquid Crystalline Orientation

“…POM was performed to evaluate the ordered structures of the M13 phages in the films before and after thermal treatment. In the POM images before thermal treatment, it was observed that the M13 phage films possessed differently oriented structures at the different positions on the film, as previously reported [ 34 ] ( Figure 3 a–c, inset). In brief, M13 phages on the film outside showed highly oriented smectic liquid crystal structures through a clearly layered birefringence ( Figure 3 a, inset).…”

“…M13 phage-based films of highly oriented liquid crystalline assembled structures with high thermal diffusivity were prepared according to a previously reported flow-induced method on a glass plate that had been circularly patterned with a hydrophobic coating based on fluororesin [ 34 ] ( Figure 1 b). We have previously found that the film thickness at the outside edge of the circular pattern (outside) is thicker than at the center (center) or part-way between the center and the outside (midpoint).…”

“…To characterize the effects of the thermal treatment on the thermal conductive properties of the M13 phage-based assemblies, thermal diffusivity values of the phage films at the three positions (outside, midpoint, and center) were measured by temperature wave analysis ( Figure 2 a). It was previously found that the thermal diffusivity value on the outside of the as-prepared film was approximately 10 times greater than that of non-oriented films due to the formation of extremely oriented structures in the assemblies, which might lead to a decrease in phonon scattering at structural defects [ 34 ]. The thermal diffusivity value at the outside of the thermally treated films was the same within experimental error as the as prepared films (that is, untreated films).…”

“…The M13 phages expressed were amplified using the Escherichia coli and purified by precipitation and re-dispersion procedures using a mixed solution composed of 5 w / v % poly(ethylene glycol) (average molecular weight of 7000–10,000) and 2.5 M NaCl. M13 Phage solutions (15 mg/mL, 500 µL) were mounted on glass plates circularly patterned with a highly water-shedding coating based on fluororesin (glass diameter: 15 mm, Matsunami Glass Ind., Ltd., Osaka, Japan) followed by incubation for 24 h at 25 °C in a dry atmosphere [ 34 ].…”

“…Such liquid crystalline properties have been utilized for the construction of M13 phage-based materials with ordered structures [ 11 , 14 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 ]. Recently, we developed M13 phage-based assemblies with ordered structures in various scale (so called hierarchical assemblies) with high thermal diffusivity, even though the assemblies were based on non-covalent bonds, and found that macroscopic phage orientation in the assemblies is essential for high thermal diffusivity [ 34 ]. Despite the promising potential of biomacromolecular assemblies as thermal conductive materials, the stability against heating of the assemblies, which are generally regarded as low heat resistance objects, have rarely been investigated.…”