Formation of Ordered Two‐Dimensional Polymer Latticeworks With Polygonal Meshes by Self‐Organized Anisotropic Mass Transfer

Abstract

This manuscript addresses the formation of self-assembled two-dimensional (2D) polymer latticeworks with multiple polygonal meshes packed in various ordered arrays. Firstly, ordered arrays of water droplets were formed in the hydrophilic regions of patterned self-assembled monolayers (SAMs) consisting of isolated hydrophilic circles surrounded by a continuous hydrophobic region. After dip-coating this water-patterned surface into a polymer solution in chloroform, dewetting of the polymer solution led to the formation of a crater-like porous polymer film. Next, the resulting polymer film with round pores arranged in a 2D ordered array was subjected to a thermal treatment carried out at a temperature higher than the glass-transition temperature (T g ) of the polymer. The thermal annealing process resulted in a morphological transformation from circular pores into polygonal meshes packed in either a similar or different ordered array. This morphological transition is self-organized, involving mass transfer, an anisotropic process, and is controlled by the minimization of the Gibbs free energy. An empirical equation was established to guide the experiments. Thus, the patterned features of the polymer meshes can be designed via the ordered arrays of the hydrophilic circles of the SAMs as well as by experimental parameters such as the concentration of the polymer solution. The formation of the polymer latticework with polygonal meshes reveals that selforganized mass transfer can be applied in micropatterning by elaborate experimental design.

Preparation and potential application of functional ordered microstructures

“…Further take the advantage of anisotropy dewetting phenomenon induced by a thermal annealing process, we have succeeded in preparing polymer lattice works with multiple polygonal meshes packed in various ordered arrays [22]. AFM results of the samples before and after thermal annealing revealed that this morphological transition was a thermal-initiated, Gibbs free energy-controlled anisotropic dewetting process.…”

“…Our research group has been engaged in the preparation and application of functional ordered microstructures for many years. We have set up a series of methods for preparing microscopic patterned surface, which includes the lift-up [13] and micro-contact print (CP) of colloidal crystals [14,15], colloidal crystal assisted lithography (CCAL) [16][17][18][19], water droplet molding and controllable dewettings [20][21][22], etc. Based on these methods, we have prepared lots of ordered microstructures with special functionalities, controllable components, size and properties [23][24][25][26][27][28][29][30][31][32][33][34][35][36].…”

“…(c) and (d) show the polymer latticeworks with complex meshes fabricated by designing the patterned templates (as shown by the insets)[22].…”

Control of Morphology in Pattern Directed Dewetting of a Thin Polymer Bilayer

“…as film integrity is essential for these applications . However, the morphological self-organization during dewetting of an unstable polymer thin film has the potential to become a nonlithographic technique for engineering meso and nanoscale patterns, where the feature size and the periodicity of the structures can be controlled by varying the initial film properties such as the film thickness ( h 0 ) and surface/interfacial tensions. − Typically instability in a homopolymer film is manifested only when it is heated above the glass transition temperature ( T G ) of the polymer or is exposed to its solvent vapor. This allows additional morphology control of the structures, as the evolution sequence can be arrested at any intermediate stage by simply quenching the film to a lower temperature, or by removing it from the solvent chamber.…”

“…The only limitation of instability mediated patterning approaches lies in the inherently random nature of the structures, which hinders their practical utility. − Strategies have therefore been worked out to align the structures for their potential use in in fabrication of devices and functional surfaces. In this regard, dewetting a thin polymer film on a chemically, − or a topographically patterned substrate ,− is a promising route, which has been successfully used to align the instability patterns. Theoretical studies based on nonlinear simulations, − as well as experiments − have shown that a perfectly ordered structure on a patterned substrate results only within a narrow parameter range, which depends on the commensuration between the natural instability length scale of the film (λ) and the periodicity of the substrate patterns (λ P ). − , Additionally, on a topographically patterned substrate, the positioning of the dewetted features can be tailored by adjusting the nature of the initial adhesion of the film with the substrate. , A recent work outlines the influence of substrate feature height on the dewetting dynamics and pattern morphology …”