The Effect of Grafting Density on the Crystallization Behaviors of Polymer Chains Grafted onto One-Dimensional Nanorod

Abstract

The crystallization behaviors of five polymer chain systems grafted on a nanorod and the corresponding effect of grafting density were investigated by dynamic Monte Carlo simulations. The segment density near the interfacial regions, the number of crystallites, and the mean square radius of gyration (<Rg2>) increase with increasing grafting density, which are beneficial to the enhancement of crystallizability. Meanwhile, the crystalline morphology is greatly influenced by grafting density and polymer-nanorod interaction. For the grafted system with 52 chains, a nanohybrid shish-kebab (NHSK) structure is formed, when the polymer-nanorod interaction (Eb/Ec) is -0.4. For the system with 128 chains, a NHSK structure is formed, when Eb/Ec is -1.0. For the system with 252 chains, NHSK structure cannot be formed. The findings in this work can supply important theoretical reference for the design, preparation, and application of polymer nanocomposites.

Insights into the Crystallization of Polymer Nanocomposite Systems Blended with Grafted and Free Chains Studied by Molecular Simulation

“…In order to investigate the crystal morphologies of polymer nanocomposite systems with different numbers of grafted chains, an orientation parameter F is introduced in our simulation as follows where θ denotes the angle between the crystal bond orientation and the Z -axis direction, and ⟨...⟩ means the average value of all corresponding crystal segments . According to formula 3, when bond orientations are parallel to the Z -axis, F = 1; when bond orientations are perpendicular to the Z -axis, F = −0.5; when bond orientations are random, F = 0.…”

Interspecific grafting between Gossypium hirsutum, G. barbadense and G. herbaceum lines

“…Because cotton is a tropical plant and some reports suggest that cold and wet soils increase disease susceptibilities; therefore, seedling grafting shows great promise to improve cotton yields in temperate-tropical production areas when using superior, cold tolerant and/or disease resistant rootstocks. Also transplanting could make wheat–cotton intercropping system possible by planting cotton after winter wheat harvest 43 in June, for instance in Turkey, and immediately transplanting 30–50 days old cotton seedlings in soil without tilling. It is reported that transplantation of cotton after the winter wheat harvest has become a more common planting pattern in some region of China 25 , 26 .…”

Simulations on polymer nanocomposite crystallization

“…It has been reported that the crowding effect of molecular chains is relatively weak for the polymer systems with lower grafting density, which leads to the tendency of molecular chains to participate in the nucleation and growth of crystals in the form of intramolecular chain-folding nucleation. [123][124][125] However, for the polymer systems with higher grafting density, the crowding effect of molecular chains is very strong and the degree of conformational extension is high, which results in the preferential crystallization of the molecular chains through intermolecular fringed-micelle nucleation. Due to the different nucleation modes, the systems with different grafting densities exhibit different crystal morphologies.…”

“…Previously, our group systematically investigated the crystallization behaviors of polymers grafted on the surface of nanofillers with different dimensions based on dynamic MC simulations, and found that a higher grafting density can result in a shorter nucleation induction period and a higher final crystallinity. [122][123][124][125][126][127][128][129][130][131] This phenomenon can be attributed to the decreased conformational entropy of the grafted chains and the decreased critical free energy nucleation barrier caused by the increased segment density in the regions near the grafting points and the chains with highly stretched conformations. 123 Second, grafting density also affects the nucleation mode and the orientation of chain segments, which in turn changes the crystalline morphology.…”