Dynamic Compression of in Situ Grown Living Polymer Brush: Simulation and Experiment

Abstract

A comparative dynamic Monte Carlo simulation study of polydisperse living polymer brushes, created by surface initiated living polymerization, and conventional polymer monodisperse brush, comprising linear polymer chains, grafted to a planar substrate under good solvent conditions, is presented. The living brush is created by end-monomer (de)polymerization reaction after placing an array of initiators on a grafting plane in contact with a solution of initially non-bonded segments (monomers). At equilibrium, the monomer density profile φ(z) of the LPB is found to decline as φ(z) ∝ z −α with the distance from the grafting plane z, while the distribution of chain lengths in the brush scales as c(N ) ∝ N −τ . The measured values α ≈ 0.64 and τ ≈ 1.70 are very close to those, predicted within the framework of the Diffusion-Limited Aggregation theory, α = 2/3 and τ = 7/4. At varying mean degree of polymerization (from L = 28 to L = 170) and effective grafting density (from σg = 0.0625 to σg = 1.0), we observe a nearly perfect agreement in the force-distance behavior of the simulated LPB with own experimental data obtained from colloidal probe AFM analysis on PNIPAAm brush and with data obtained by Plunkett et. al., [Langmuir 2006, 22, 4259] from SFA measurements on same polymer.

Molecular dynamics simulation of brushes formed by star polyelectrolytes under theta solvent conditions

“…The thickness of the brush H was considered equal to H = 2 < z> . The results for the construction of diagram of states are presented in Supporting Information Table S1.…”

GALAMOST: GPU-accelerated large-scale molecular simulation toolkit

“…[34][35][36][37] Surface-initiated polymerization is not trivial as it is of great relevance with the performance of the designed materials of polymer brushes. [38][39][40] The properties of polymer brushes fabricated via surface-initiated polymerization are synergistically controlled by excluded volume effect, diffusion of monomers, and polymerization. [35] The implementation of the stochastic chain-growth polymerization model in GALAMOST supplies a powerful tool to deal with these types of problems.…”

“…To study the phenomena related to polymerization, a stochastic chain‐growth polymerization model coupled with CGMD was proposed recently by Liu et al This model has its applications in, for example, polymerization‐induced phase separation, surface‐initiated polymerization, and so on . Surface‐initiated polymerization is not trivial as it is of great relevance with the performance of the designed materials of polymer brushes . The properties of polymer brushes fabricated via surface‐initiated polymerization are synergistically controlled by excluded volume effect, diffusion of monomers, and polymerization .…”

Mixed brushes consisting of oppositely charged Y‐shaped polymers in salt free, monovalent, and divalent salt solutions

“…Symmetric mixed brushes, consisting of n + = 32 Y(+) and n − = 32 Y(−)‐shaped PE chains with spacer length S + = S − = 80 and charged units fractions α + = α − = 0.2 were simulated in order to elucidate the effects of the grafting density and salt concentration on both the total brush height H and the internal stratification of the mixed brush. The brush height is considered equal [ 36 ] to H = 2 <z> , where <z> is the mean distance z of each polymer unit from the surface, which is defined as the first moment of the probability distribution P(z) according to: …”