Semi-flexible polymers, such as actin filaments, can deform the shape of membrane when confined in a membrane vesicle, playing an important role in biological processes. Here, we use dynamic Monte Carlo simulations to study an active polymer chain confined in a membrane vesicle. For flexible polymer chains, the membrane shape is governed by the competition between membrane bending rigidity and polymer activity.
View Article and Find Full Text PDFReversible chemistries have been extensively explored to construct highly crystalline covalent organic frameworks (COFs) via defect correction. However, the mechanisms of defect correction that can explain the formation of products as single crystals, polycrystal/crystallites, or amorphous solids remain unknown. Herein, we employed molecular dynamics simulations combined with a polymerization model to investigate the growth kinetics of two-dimensional COFs.
View Article and Find Full Text PDFSynthesis of covalent organic frameworks with long-range molecular ordering is an outstanding challenge due to the fact that defects against predesigned topological symmetries are prone to form and break crystallization. The physical origins and controlling parameters of topological defects remain scarcely understood. By virtue of molecular dynamics simulations, we found that pentagons for combination [C + C] and [C + C] and heptagons for [C + C] and [C + C] were initial defects for growth dynamics with both uncontrolled and suppressed nucleation, further inducing more complex defects.
View Article and Find Full Text PDFPolymerization of monomers into two-dimensional covalent organic frameworks with precise porous structures exhibits desired catalytic, gas separation, and optoelectronic properties. However, the defects arising from covalent bonding in a polymerization process always result in amorphous films with small crystalline domains or polycrystalline powders. It is still a tremendous challenge to synthesize high-quality crystalline products, even single crystals with a large size over the micrometer scale.
View Article and Find Full Text PDFWe present a systematic investigation on the effect of adding nanoparticles on the dynamics of polymer chains by using coarse-grained molecular dynamics simulation. The dynamics is characterized by three aspects: molecular motion, relaxation at different length scales, and dynamical heterogeneity. It is found that the motion of polymer chains slows down and the deviation from Gaussian distribution becomes more pronounced with increasing nanoparticle volume fractions.
View Article and Find Full Text PDFIn this work, hydroxyl-functionalized boron nitride nanosheet (OH-BNNS) was prepared and was blended with poly(l-lactide) (PLLA) to yield PLLA/OH-BNNS nanocomposites with excellent dispersion of OH-BNNS via the interaction of carbonyl in PLLA and hydroxyl in OH-BNNS. The effects of OH-BNNS on the crystallization and melting behaviors, isothermal crystallization kinetics, macroscopic crystal morphology and crystal structure of PLLA were studied by means of various techniques. The addition of OH-BNNS nanofillers can effectively accelerate the crystallization of PLLA and enhance the nucleation density, leading to a smaller spherulite size, increased crystallinity, a more obvious crystallization peak upon cooling but weakened cold crystallization behavior upon heating.
View Article and Find Full Text PDFThe crystallization process of Hertzian spheres is studied by means of molecular dynamics simulations in an NPT ensemble where the total number of particles N, the pressure P, and the temperature T are kept constant. It has been observed that the bond orientational ordering rather than the translational ordering (density) plays a primary role. The crystal polymorphs are determined by the state points.
View Article and Find Full Text PDFPolymer gel exists ubiquitously in our daily life, as in food, cosmetics, drugs, and so on. From the structural point of view, the 3D network can be found in a structural gel. In most experimental work, the gel is identified by the sharp increase in modules; that is, the gel should have similar properties as those of a solid, which is named as mechanical gel.
View Article and Find Full Text PDFWe perform lattice Monte Carlo simulation using the bond-fluctuation model to examine the conformation and dynamic properties of a single small flexible ring polymer in the matrix of linear chains as functions of the degree of polymerization of the linear chains. The average conformation properties as gauged by the mean-square radius of gyration and asphericity parameter are insensitive to the chain length for all the chain lengths examined (30, 100, 300, and 1000). However, in the longer chain (300 and 1000) samples, there is an increased spread in the distribution of the value of these quantities, suggesting structural heterogeneity.
View Article and Find Full Text PDFThe influence of molecular topology on the structural and dynamic properties of polymer chain in solution with ring structure, three-arm branched structure, and linear structure are studied by molecular dynamics simulation. At the same degree of polymerization (N), the ring-shaped chain possesses the smallest size and largest diffusion coefficient. With increasing N, the difference of the radii of gyration between the three types of polymer chains increases, whereas the difference of the diffusion coefficients among them decreases.
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