Relationship Between Interfacial Dynamics and Chain Entanglement in Confined Polymer Films†

doi:10.7503/cjcu20150077

Abstract

Abstract:

We investigated the relationship between the interfacial dynamics and chain entanglement of polymer melts in confinement by means of the lattice Monte Carlo simulations using the bond-fluctuation model, combining the primitive path analysis. When the wall-polymer interaction varies from weakly attractive interaction to strongly repulsive interaction, chain mobility in the interfacial region is higher than that in the inner region. Only when the wall-polymer attraction is stronger than a critical adsorption strength will chain mobility in the interfacial region be lower than that in the inner region. The facilitation or retardation of interface dynamics may be directly related to the degree of entanglement in the interfacial and inner regions: the entanglement degree in the interfacial region retains the bulk level despite of the wall-polymer interaction; the entanglement degree in the inner region is lower than that in the interfacial region when the polymer film is confined between strongly attractive walls, but it is higher when the film is between weakly attractive or repulsive walls. The variations of the confinement degree of polymer chains in both interfacial and inner regions also have an impact on the interface dynamics. Analysis on chain density distribution in the film as a function of the wall-polymer interaction provides a certain explanation for the related physical mechanisms.

Key words: Monte Carlo simulation, Confinement, Dynamics, Entanglement, Interfacial region of polymer film

CLC Number:

TrendMD:

LI Sijia, ZHANG Wanxi, YAO Weiguo, SHI Tongfei. Relationship Between Interfacial Dynamics and Chain Entanglement in Confined Polymer Films^†[J]. Chem. J. Chinese Universities, 2015, 36(6): 1133.

Figures/Tables 6

Fig.1 Proportion of the chain(A) and migration probability of chains’ center-of-mass(B) in the interfacial region or inner region as a function of the wall-polymer interactiona. Layer-Ⅰ; b. layer-Ⅱ.

Fig.2 Center-of-mass diffusion coefficient of the chain in the interfacial region or inner region as a function of the wall-polymer interactiona. Layer-Ⅰ; b. layer-Ⅱ.

Fig.3 Density profile of the monomer(A) and of the chain(B) as a function of the distance from the wall for different wall-polymer interactionsSince the profiles are symmetric around the middle of the film, only the left half is shown.εw/kBT: a. -3.0; b. -0.6; c. -0.3; d. 0; e. 3.0.

Fig.4 Number of the nearest-neighboring particles per monomer in the interfacial region or inner region as a function of the wall-polymer interaction(A) and number of the nearest-neighboring particles per monomer as a function of the distance from the wall for different wall-polymer interactions(B)(A) a. Layer-Ⅰ; b. layer-Ⅱ; (B) a. εw=-3.0 kBT; b. εw=-0.6 kBT; c. εw=0; d. εw=3.0 kBT.

Fig.5 Primitive paths of confined chains for a strong attractive(εw=-3.0 kBT)(A), neutral(εw=0)(B) or strong repulsive(εw=3.0 kBT)(C) interaction with the walls

Fig.6 Number of entanglements per chain in the interfacial region or inner region as a function of the wall-polymer interaction(A) and number of entanglements per chain as a function of the distance from the wall for different wall-polymer interactions(B)(A) a. Layer-Ⅰ; b. layer-Ⅱ; c. bulk; (B) a. εw=-3.0 kBT; b. εw=-0.6 kBT; c. εw=0; d. εw=3.0 kBT; e. bulk.

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