Memory of Surface Patterns in Mixed Polymer Brushes:  Simulation and Experiment

Abstract

The correlation between the morphology of mixed polymer brushes and fluctuations of the grafting points is investigated by single-chain-in-mean-field simulations and experiments. The local topography of two types of mixed polystyrene-polymethylmethacrylate (PS-PMMA) brushes that differ in their modes of attachment has been studied during repeated microphase separation into laterally structured and homogeneous morphologies upon changing solvents. In the first type of brush (conventional), each of the surface-attached initiator groups starts the growth of either a PS or a PMMA chain in a random fashion. In the second case (Y-shaped mixed brushes), two chains of different types are attached to the same anchor group on the substrate. Whereas in the first case statistical fluctuations of the chemical composition occur on a local scale, such composition fluctuations are strongly suppressed in the latter case. The microphase-separated morphology is similar in both cases, but Y-shaped brushes exhibit a significantly weaker domain memory than do conventional PS-PMMA mixed brushes. The results of the experiment are compared with simulations, and a simple phenomenological argument and qualitative agreement are found. The observations demonstrate that small fluctuations in the grafting points are amplified by the microphase separation and nucleate the location of the domains in the mixed brush.

Preparation and characterization of V-shaped PS-b-PEO brushes anchored on planar gold substrate through the trithiocarbonate junction group

“…Based on the universal phase diagram of block copolymer [70], However, considering the constrain effect in the V-shaped brushes due to sharing a single grafting site for one PS chain and one PEO chain [8], the critical segregation force needed for microphase separation in the V-shaped brush should be larger than that in the corresponding free block copolymer. Therefore, whether microphase separation occurs in these three mixed PS-b-PEO brushes cannot be inferred only from the values of vN.…”

“…Firstly, like diblock copolymers, when the molecular weights of the two types of polymer chain in the mixed brush are sufficiently high, microphase separation may take place [3][4][5][6][7]. However, the segregation force needed for microphase separation in the mixed brush is different from that for the corresponding free diblock copolymers [8]. The microphase-separated pattern of the mixed brush may lead to some particular properties of the surface in lubrication, friction, adhesion, and wettability [9][10][11].…”

Scanning Force Microscopy as Applied to Conformational Studies in Macromolecular Research

“…Their exposure to vapours of selective solvents also induced reorganisation to be observed with SFM in real time. [233] Finally, it is commonly accepted that vapours are convenient and powerful means to induce reorganisation of adsorbed polymer structures. [234,235] Concurrently with our works there were published results on SFM observations of the motion of individual brush-like molecules on a surface during process of spreading of macroscopic polymer droplets deposited on a substrate.…”

Local chemical composition of nanophase-separated polymer brushes

“…For example, a mixed brush of hydrophilic and hydrophobic homopolymers that is exposed to a hydrophilic solvent should chemically segregate, and the hydrophilic component should accumulate at the surface, which is a process called perpendicular segregation. 13,14 Although reversible switching from hydrophilic to hydrophobic character has been observed, the local chemical structure has remained unknown; especially due to the switchable properties of the top-layer polymer brushes which play an important role in the wetting properties of surfaces.…”