Ideal polymer chains of various architectures at a surface

Abstract

We study the macroscopic behavior of ideal polymer chains of various architectures in the vicinity of a surface, by considering that at least one of the units of the chains is in contact with the surface. The probability that any unit will be in contact with the surface is employed and the macroscopic properties are determined as averages over this probability. The present model is an amendment to the model used previously with the one end of a linear chain fixed at the surface, and though it is a simplification to the full problem where the chains can move freely in the whole space, it is free from the necessity to include the volume and the polymer concentration in order to describe chains in the vicinity of the surface. We estimate the mean number of contacts between a chain and the surface for the cases of linear, ring, regular star, and regular comb polymers as the basic quantity for the description of both the thermodynamics of chains at a surface and the degree of adsorption of polymers of various architectures.

Computer Simulation of Adsorbed Polymer Chains with a Different Molecular Architecture

“…The degree of adsorption of linear and star-branched polymers is comparable but the latter are slightly less adsorbed (92-96% of linear ones). This behavior is quite opposite to theoretical predictions [15] where 3-arm stars are slightly (6%) better adsorbed than linear chains. Ring chains are considerably better adsorbed (40-45%) than linear ones.…”

“…[15] He found that for non-excluded volume chains (in H temperature) the number of contacts of the polymer chain with the surface comparing with linear chain is as follows:…”

“…In the case of weak adsorption (v S = 0.5) ring polymers are adsorbed more (ca. 60% -see Recently Kosmas et al [15] have developed a theoretical treatment to study the properties of adsorbed linear, ring, star, and comb polymer chains with no excluded volume. This theory predicts that the adsorption of ring polymers is 18% higher than the linear ones.…”

Wetting of a Multiarm Star-Shaped Molecule

“…1d. These results are consistent with the notion that star-shaped polymers exhibit significant interfacial activity; [13] they suffer a significantly lower entropic penalty than their linear analogs of the same N upon adsorption at an interface [11]; the number of segments of a star-shaped molecule in contact with an interface is large compared to linear chains of the same N [12]. Moreover, the frustrated segmental packing in the bulk is responsible for the decrease in the cohesive energy density of star-shaped molecules, leads to lower surface tensions than their linear chain counterparts of the same N [14,15].…”

“…Theory and simulations reveal that star-shaped molecules are known to suffer a much smaller entropic loss when adsorbed onto substrates [11][12][13] and they possess lower surface energy, than their linear analogs of the same degree of polymerization, N. [14,15] We show that star-shaped polymers possess considerably lower contact angles and line tensions than their linear analogs. Unlike linear chains, star-shaped polymers of sufficiently high functionality, f, exhibit evidence of structuring at a substrate, stable (or metastable) wetting layer formation, due evidently to entropic effects.…”