Monte Carlo Simulations of Copolymer Adsorption from Copolymer / Homopolymer Melts at Planar Chemically Patterned Surfac
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Monte Carlo Simulations of Copolymer Adsorption from Copolymer / Homopolymer Melts at Planar Chemically Patterned Surfaces
James J. Semler and Jan Genzer Department of Chemical Engineering, North Carolina State University, Raleigh, NC 27695-7905, U.S.A. ABSTRACT We investigate the adsorption of copolymers from copolymer / homopolymer mixtures at planar chemically patterned surfaces. The Monte Carlo bond fluctuation model is used in conjunction with configurational biased Monte Carlo moves to study the effect of: i) the copolymer microstructure, ii) the size and spatial distribution of chemical heterogeneities on the substrate, and iii) the polymer/substrate interactions on the ability of the copolymer to recognize the substrate chemical pattern. Our results confirm that the surface pattern recognition occurs whenever the characteristic size of the copolymer distribution sequence matches that of the surface heterogeneity domain. Moreover, the copolymer sequence distribution plays a crucial role in determining the extent of the surface pattern transfer into the bulk material. Our results reveal that more pronounced surface pattern transfer into the bulk occurs for small attractions of the adsorbing species to particular surface domains relative to the large attractions. INTRODUCTION Organization of polymers near solid surfaces embodies a vast area of both practical and fundamental interest. These systems are relevant to many large-scale technological applications including fiber-filled polymer composites, antireflection coatings, and adhesives. In addition, much research has been done on small-scale applications including chemical sensors and nanoscale patterning and masking [1-3]. In order to exploit these applications in their entirety, it is necessary to understand the key features and trends associated with polymer adsorption at solid surfaces. Over the past few decades numerous theoretical and experimental reports have appeared that aimed at describing the adsorption of homopolymers and copolymers at chemically homogeneous surfaces [4]. These studies have provided a fundamental understanding of the basic physics and chemistry governing polymer adsorption. However, in many situations the substrates are not completely chemically homogeneous. The substrates may be composed of more than one chemical species or possibly contain impurities, which will directly influence the adsorption properties of polymers. Such “chemically rough” substrates are often encountered in biological situations, examples of which include pathogen-host interactions and biopolymer adhesion for transmembrane signaling and shape transformation of membranes [5-7]. The idea of a chemically rough surface adds a new dimension to the current issues related to polymer adsorption. In such cases one might expect that the polymer adsorption characteristics will not only depend upon the chain length and monomer sequence distribution along the macromolecule, but also on the sizes, shapes, and spatial distributions of the heterogeneous domains on the surfa
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