TY - JOUR

T1 - Exact results and the effect of monomer–monomer bond type for a grafted ideal chain

AU - Yeung, Chuck

AU - Friedman, Barry A.

N1 - Publisher Copyright:
© 2022, The Author(s), under exclusive licence to EDP Sciences, SIF and Springer-Verlag GmbH Germany, part of Springer Nature.

PY - 2022/10

Y1 - 2022/10

N2 - We determine the equilibrium chain end probability density PN(x) for a one-dimensional ideal chain of N monomers grafted to a planar surface. This distribution is also the distribution function of a three-dimensional chain where the tangential dimensions y, z are integrated out of the distribution. With a small modification of the analysis of Erukhimovich, Johner, and Joanny for free chains near a wall, we are able to obtain exact results for PN(x) for any monomer number N though with the restriction that the monomer–monomer bonds lengths are exponentially distributed. In particular, we obtain exact values for PN and its derivative d PN/ d x at the surface for any N and the full profile PN(x) for selected values of N. To determine the effect of the bond distribution, we find PN(x) numerically for Gaussian and uniformly distributed one-dimensional bonds and compare with the exact results for exponential bonds. We suggest several ways to quantify the effect of bond type based both on PN(x) near the surface and in the scaling region x∼Na. We then extract the large N limit of PN(x) and show that it is similar to the chain end probability for continuous chains but shifted toward smaller x. We show the amount of shift is a measure of the magnitude of the correction to the continuous chain PN(x). We derive the value of the shift for exponential bonds and show that the value is different for other bond types. We argue the shift can be interpreted as an effective surface behind the actual surface.

AB - We determine the equilibrium chain end probability density PN(x) for a one-dimensional ideal chain of N monomers grafted to a planar surface. This distribution is also the distribution function of a three-dimensional chain where the tangential dimensions y, z are integrated out of the distribution. With a small modification of the analysis of Erukhimovich, Johner, and Joanny for free chains near a wall, we are able to obtain exact results for PN(x) for any monomer number N though with the restriction that the monomer–monomer bonds lengths are exponentially distributed. In particular, we obtain exact values for PN and its derivative d PN/ d x at the surface for any N and the full profile PN(x) for selected values of N. To determine the effect of the bond distribution, we find PN(x) numerically for Gaussian and uniformly distributed one-dimensional bonds and compare with the exact results for exponential bonds. We suggest several ways to quantify the effect of bond type based both on PN(x) near the surface and in the scaling region x∼Na. We then extract the large N limit of PN(x) and show that it is similar to the chain end probability for continuous chains but shifted toward smaller x. We show the amount of shift is a measure of the magnitude of the correction to the continuous chain PN(x). We derive the value of the shift for exponential bonds and show that the value is different for other bond types. We argue the shift can be interpreted as an effective surface behind the actual surface.

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U2 - 10.1140/epje/s10189-022-00239-6

DO - 10.1140/epje/s10189-022-00239-6

M3 - Article

C2 - 36269469

AN - SCOPUS:85140251194

SN - 1292-8941

VL - 45

JO - European Physical Journal E

JF - European Physical Journal E

IS - 10

M1 - 84

ER -