Connecting Monotonic and Oscillatory Motions of the Meniscus of a Volatile Polymer Solution to the Transport of Polymer Coils and Deposit Morphology

Abstract

We study the deposition mechanisms of polymer from a confined meniscus of volatile liquid. In particular, we investigate the physical processes that are responsible for qualitative changes in the pattern deposition of polymer and the underlying interplay of the state of pattern deposition, motion of the meniscus, and the transport of polymer within the meniscus. As a model system we evaporate a solution of poly(methyl methacrylate) (PMMA) in toluene. Different deposition patterns are observed when varying the molecular mass, the initial concentration of the solute, and temperature; these are systematically presented in the form of morphological phase diagrams. The modi of deposition and meniscus motion are correlated. They vary with the ratio between the evaporation-driven convective flux and the diffusive flux of the polymer coils in the solution. In the case of a diffusion-dominated solute transport, the solution monotonically dewets the solid substrate by evaporation, supporting continuous contact line motion and continuous polymer deposition. However, a convection-dominated transport results in an oscillatory ratcheting dewetting-wetting motion of the contact line with more pronounced dewetting phases. The deposition process is then periodic and produces a stripe pattern. The oscillatory motion of the meniscus differs from the well documented stick-slip motion of the meniscus, observed as well, and is attributed to the opposing influences of evaporation and Marangoni stresses, which alternately dominate the deposition process.

Connecting Surface‐Forces‐Based Energy Barriers to Nonhomogeneous Colloidal Structures to Appear from Volatile Binary Mixtures of Same Size Nanoparticle Species

“…The confinement is advantageous for rendering physical parameters in the experiment, for example, temperature, rate of water evaporation, linear geometry of the three phase contact line between the liquid, vapor, and solid substrate and its position (where the majority of the deposit is usually found), well defined. [34,[45][46][47][48] In this work, a rectangular micro-chamber is employed, which is composed of silica as a substrate (<100 >, 550 µm thickness, with 1 µm wet thermal oxide layer, Silicon Materials) and glass (microscopy slide, Marienfeld) as a cover. The inner thickness of the chamber was 125 µm, according to the choice of the polyamide film (Kapton, DuPont) spacer, which separated between the substrate and the glass cover.…”

Pattern Formation in Slot-Die Coating

“…A recent detailed analysis of patterns obtained in evaporative dewetting is given in Ref. [17]. In the case of the well studied "passive systems" the contact line velocity is selected by the system and not externally imposed as in "active systems" like slot-die coating and many other coating processes.…”

Two-dimensional patterns in dip coating - first steps on the continuation path

“…Depending on the properties of the liquid, wetting behaviour of the liquid on the substrate and withdrawal speed (or strength of evaporation), a large variety of homogeneous and patterned coatings can be produced. For instance, well controlled experiments with particle suspensions [10,11,12] or polymer solutions [13,14,15,16] may produce regular line patterns orthogonal or parallel to the withdrawal direction [11,13,16]. Other described patterns include interconnected or wavy stripes [16], ladder structures [13], hierarchical line patterns [17], droplet or hole arrays [13,14,16], and branched structures [18,19].…”

“…For instance, well controlled experiments with particle suspensions [10,11,12] or polymer solutions [13,14,15,16] may produce regular line patterns orthogonal or parallel to the withdrawal direction [11,13,16]. Other described patterns include interconnected or wavy stripes [16], ladder structures [13], hierarchical line patterns [17], droplet or hole arrays [13,14,16], and branched structures [18,19]. Overviews are given in [9,6].…”

“…Overviews are given in [9,6]. Note that systematic accounts of parameter dependencies of properties of deposition patterns and of the transitions between different patterns are rare [10,16].…”