Structure and Conformation of Stereoregular Poly(methyl methacrylate) Chains Adsorbed on Graphene Oxide and Reduced Graphene Oxide via Atomistic Simulations Alireza F. Behbahani, †,‡ G. Hashemi Motlagh, ‡ S. Mehdi Vaez Allaei, §,∥ and Vagelis A. Harmandaris* ,⊥,† † Institute of Applied and Computational Mathematics, Foundation for Research and TechnologyHellas, Heraklion GR-71110, Greece ‡ Advanced Polymer Materials and Processing Lab, School of Chemical Engineering, College of Engineering, University of Tehran, Tehran 11155-4563, Iran § Department of Physics, University of Tehran, Tehran 14395-547, Iran ∥ School of Physics, Institute for Research in Fundamental Sciences (IPM), Tehran 19395-5531, Iran ⊥ Department of Mathematics and Applied Mathematics, University of Crete, Heraklion GR-71110, Greece *S Supporting Information ABSTRACT: A detailed analysis of the structure and conformation of stereoregular and atactic poly(methyl methacrylate) (PMMA) chains confined between oxidized graphene sheets is provided through long-time atomistic molecular dynamics simulations. Low-molecular-weight isotactic-, atactic-, and syndiotactic-PMMA chains confined between graphene oxide (GO) and reduced graphene oxide (RGO) sheets have been simulated at different temperatures ranging from 520 to 580 K. The interfacial properties of PMMA/pristine graphene (PG) are also discussed. GO and RGO structures have been generated based on the Lerf−Klinowski structural model of graphite oxide with carbon-to-oxygen ratios of 3 and 10, respectively. The interfacial packing and adsorption of PMMA chains on PG, RGO, and GO model surfaces are studied through the calculation of interfacial mass density profiles and distribution of monomer/surface distance. Furthermore, the arrangement of PMMA atoms in the vicinity of functional groups of nanosheets and their hydrogen bond formation are investigated. The conformations of adsorbed chains, that is, chains with at least one adsorbed monomer, are analyzed in detail as trains, loops, and tails. It is observed that the number of adsorbed monomers and the average size of trains, that is, consecutive adsorbed monomers of a chain, increase with the concentration of functional groups of the nanosheets. This is related to the strength of the polymer/substrate interactions and the increase of the roughness of model nanosheets which enhances the probability of polymer/surface contacts. The tacticity-dependent adsorption of PMMA chains is also examined in detail. Isotactic-PMMA chains, compared to atactic and syndiotactic ones, exhibit a better interfacial packing and form longer trains. i-PMMA chains are stiffer and, moreover, become more extended in the vicinity of model surfaces. The formation of longer trains by isotactic stereoisomers is found to be consistent with their higher stiffness, that is, higher characteristic ratio and gyration radius. Results reported here suggest a clear correlation between chain dimensions, size of trains, and interfacial packing of the adsorbed PMMA chains. 1. INTRODUCTION Graphene-based polymer nanocomposites have appeared as a promising class of materials. Pristine single layer graphene is an exceptionally strong material with a very high electrical and thermal conductivity as well as an enormous specific surface area. 1,2 One of the most promising scalable synthesis routes for production of graphene-like materials is based on the exfoliation of graphite oxide. 1−4 Exfoliation of graphite oxide in polar solvents, like water, leads to production of graphene Received: March 20, 2019 Article pubs.acs.org/Macromolecules Cite This: Macromolecules XXXX, XXX, XXX-XXX © XXXX American Chemical Society A DOI: 10.1021/acs.macromol.9b00574 Macromolecules XXXX, XXX, XXX−XXX Downloaded via BUFFALO STATE on May 10, 2019 at 11:30:42 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.