Adding Nonconnected Monomers to Manage the Layering Crystallization of Polymers on Athermal Substrate

Abstract

crystal of polymers, like lamellar crystal, has emerged as a matrix basis for the design of advanced functional materials with significant physical reinforcement and/or multifunctional capabilities. [8][9][10][11][12] Inducing polymer crystallization through adding parallel confinement is a strategy increasingly considered to obtain lamellar crystal of polymers. [13][14][15][16][17][18][19][20] When polymers are confined in a space with dimension comparable to or smaller than the radius of gyration of the polymer chains, the occurrence and growth of polymer crystal can be dramatically influenced by the confinement. The presence of a substrate further complicates the formation of polymer crystal, which leads to the crystallization of polymer chains hard to be controlled. Layering crystal of polymers is generally formed on adsorbing substrate having enthalpical polymersubstrate attraction. For an athermal substrate without direct polymer-substrate attraction, it has been reported that there is small part of polymer chains sacrificing their own conformational entropy by flattening against the substrate surface to maximize the total conformational entropy of whole polymer chains. [21,22] Finally, 2D thin layer of polymer chains, with thickness as large as about one monomer diameter, develops at the substrate surface when system is in the concentrated regime of polymers. [23] However, polymer chains beyond the first layer keep their 3D structure, and the corresponding monomer distribution is thereby amorphous without order appearing in the dimension perpendicular to the substrate surface. [24] In this communication, after a large scale of molecular dynamics (MD) simulations and theory analysis, we confirm and clarify that layering crystallization of polymers beyond the first layer can be intrigued after blending polymers with nonconnected monomers, and the thickness of polymer layering crystal is targetedly controllable. Simulation SetupIn the simulations, polymers were modeled as bead-spring chains without explicit twisting or bending potential. Each chain is composed of Lc = 20 Lennard-Jones (LJ) spheres with mass m and diameter σ m , connected by anharmonic springs governed by a finite extensible nonlinear elastic (FENE) potential. [25,26] The FENE potential is defined as Layering crystallization of polymers has extensive interests for achieving multifunctional materials with tailored applications. However, it is difficult to form polymer crystal on athermal substrate due to the conformational entropy loss of polymer chains if they are flattened against the substrate surface. Using molecular dynamics (MD) simulations, it is confirmed that layering crystallization of polymers can be intrigued after blending the polymers with nonconnected monomers in between two athermal parallel substrates. The layering crystal area of polymers extends as increasing the bulk volume fraction of nonconnected monomers. It is proposed that the conformational entropy loss of the crystallized polymers is compensated by an increase of the...