ABSTRACT
The helical insertion behavior of poly(para-phenylene) (PP) chains into confined cylindrical slits constructed by two carbon nanotubes (CNTs) with different diameters is studied by molecular dynamics simulations. The contribution of system energy and each energy component to helical self-assembly is discussed to further explain the conditions, driving force and mechanism. The width and length of the slit, the diameter of the outer tube and the temperature have a great impact on the helical insertion of PP chains. Two equations are proposed to confirm the diameter and the distances between the PP helix and the inner and outer walls of the given CNTs. The helical self-assembly of PP with different numbers of chains inserted into the slits is further studied. This study has a great benefit in understanding the conformational behavior of polymers, even biological macromolecules in confinements.
ABSTRACT
Background: Ischnothyreus Simon, 1893 is one of the most speciose genera of Oonopidae, with 124 extant species mainly distributed in the Old World. Currently, 27 species are known in China. New information: A new species, Ischnothyreusruyuanensis Tong, sp. n., is described from Guangdong Province, China. Morphological description and illustrations are provided.
ABSTRACT
Background: Ablemma Roewer, 1963 is a species-rich genus of the family Tetrablemmidae O. Pickard-Cambridge, 1873, currently comprising 28 known species. This genus is mainly distributed in Southeast Asia. Currently, only one species, A.prominens Tong & Li, 2008 is known to occur in China. New information: The species Ablemmashimojanai (Komatsu, 1968), presently only known from the Ryuku Islands in Japan, is reported from China for the first time on the basis of material collected in Guangdong Province. A morphological description and detailed images are provided.
ABSTRACT
Helical nanomaterials represent an emerging group of nanostructures because of their multiple functionalities enabled by unique spiral geometry and nanoscale dimensions. This study demonstrates that several trans-transoid polyacetylene (Tt-PA) chains can self-spiral limitlessly over the whole length of polymers to form regular multiple helices under the inducement of water cluster, fullerene ball and metallic nanoparticles (NPs). Multi-helices possess random chirality selection which have equal probability of left-handedness and right-handedness. Energy components, geometric parameters and differences of helices induced by different NPs are analyzed to deeply probe the possible mechanism and the nature of the limitless spiral of the PA polymer. Furthermore, the helical self-assembly of cis-formed cis-transoid (Ct-PA) and trans-cisoid (Tc-PA) isomers is further studied. The spiral ability of Ct-PA is much higher, but Tc-PA is much lower than that of Tt-PA. Remarkably, Tc-PAs are always form five-helix at room temperature.
ABSTRACT
Molecular dynamics simulations demonstrate that several polyacetylene (PA) chains can encapsulate and self-assemble into multi-stranded helical structures in confined inner space of carbon nanotubes (SWCNTs). The driving van der Waals force and curvature provided by the tube wall enable polymers to bend and spiral to maximize the π-π stacking area with the tube wall when filling the inside of the SWCNT. Structural forms and knitting patterns of multiple helices are influenced by the combined effect of the tube space, the number of PA chains and the temperature. The knitting pattern of a six-helix is unique and a knitted six-helix can exist steadily after removing the SWCNT while a two- to five-helix will recover intrinsic straight configurations.
ABSTRACT
Molecular dynamics simulations demonstrate that the cut defect can induce and guide the self-assembly of an isolated graphene nanoring (GNR) to form multi-layered funnel morphology. The vdW force is the driving force; the tangent component drives the self-assembly of GNR and the normal component adjusts and maintains the vertical distance between graphene layers, which is two times of the vdW radius. Moreover, the offset π-π stacking aids the adjacent layers to achieve the lowest energy of AB stacking. With different diameters of the annular GNRs, the final configurations experience multilayered cone, funnel and tube-shaped structures. It also illustrates the influence of temperature in the funnel-forming process. The wide gap with two edges beyond the cutoff distance of vdW force can utilize fullerenes to help and induce the assembly of the GNR. Cutting defect fissure would be a new way to induce the self-assembly of isolated graphene to design and fabricate new carbon nanostructures without impurities.
ABSTRACT
The polymer possessing with planar structure can be activated and guided to encapsulate the inner space of SWNT and form a helix through van der Waals interaction and the π-π stacking effect between the polymer and the inner surface of SWNT. The SWNT size, the nanostructure and flexibility of polymer chain are all determine the final structures. The basic interaction between the polymer and the nanotubes is investigated, and the condition and mechanism of the helix-forming are explained particularly. Hybrid polymers improve the ability of the helix formation. This study provides scientific basis for fabricating helical polymers encapsulated in SWNTs and eventually on their applications in various areas.
ABSTRACT
Novel scroll peapods are fabricated simply by utilizing the spontaneous scrolling mechanism of graphene onto fullerene string. The basic interaction between the graphene and the fullerene string is investigated, and the mechanism of the formation of the scroll peapod is explained in particular. The formation of the scroll peapod and its formation time are influenced by the combined effects of fullerene number, diameter and graphene size. It is also worth noting that narrow graphene nanoribbon wrapped onto a C720 bean can form a particular helical peapod. Higher temperature slows the scrolling dynamics, and even hinders the formation of the scroll peapod. This study provides a scientific basis for producing scroll peapods simply, and eventually their applications in various areas.