Wichai Kamonthira, Vao-Soongnern Visit
Laboratory of Computational and Applied Polymer Science (LCAPS), School of Chemistry, Institute of Science, Suranaree University of Technology, Nakhon Ratchasima, 30000, Thailand.
J Mol Model. 2021 Sep 28;27(10):301. doi: 10.1007/s00894-021-04927-6.
Molecular and structural properties of random copolymer thin films were studied by Monte Carlo simulation of coarse-grained copolymer model on the high coordination lattice. Random copolymer thin films with 50% comonomer fraction with varied interaction strength between comonomer units were studied. Intramolecular interaction was represented by Flory's rotational isomeric state (RIS) model of polyethylene (PE). The non-bonded interactions were treated by Lennard-Jones potential with different parameter sets for comonomer units. When the interaction strength of comonomer is increased, the density of thin films is higher in the inner region and significantly dropped near the free surface along the normal direction of the film. Higher bulk densities and narrower interfacial thicknesses are observed for random copolymer with stronger bead interaction. End beads were segregated at the free surface region and tend to orient perpendicularly to the surface. Copolymer size and shape were significantly changed as a function of bead interaction. For orientation of the whole chain, the largest molecular axis tends to orient along the film surface, but changed toward random orientation for weaker bead interaction. The intra-chain energies were decreased at the surface region while the non-bonded energies were increased. The stronger the comonomer bead attraction, the more change in energetics across the thin film.
通过在高配位晶格上对粗粒化共聚物模型进行蒙特卡罗模拟，研究了无规共聚物薄膜的分子和结构性质。研究了共聚单体分数为50%、共聚单体单元间相互作用强度不同的无规共聚物薄膜。分子内相互作用由聚乙烯（PE）的弗洛里旋转异构体状态（RIS）模型表示。非键相互作用采用Lennard-Jones势处理，共聚单体单元采用不同的参数集。当共聚单体的相互作用强度增加时，薄膜内部区域的密度较高，并且沿薄膜法线方向在自由表面附近显著下降。对于具有较强珠子相互作用的无规共聚物，观察到更高的体密度和更窄的界面厚度。末端珠子在自由表面区域分离，并倾向于垂直于表面取向。共聚物的尺寸和形状随珠子相互作用而显著变化。对于整个链的取向，最大分子轴倾向于沿薄膜表面取向，但对于较弱的珠子相互作用则向随机取向变化。表面区域的链内能量降低，而非键能量增加。共聚单体珠子吸引力越强，整个薄膜的能量变化就越大。
