Polystyrenes with Hydrophilic End Groups: Synthesis, Characterization, and Effects on the Self-Assembly of Breath Figure Arrays

Abstract

We report the synthesis and characterization of a series of hydroxyl-end-functionalized polystyrenes (PS-OH) and the formation of patterned porous films. The polymers were synthesized by chain end reaction of polystyrene having a bromide end group (PS-Br) with hydramines including ethanolamine, diethanol amine, 2-amino-1,3-propanediol, and 2-(2-aminoethoxy) ethanol. The polymers were characterized by gel permeation chromatography (GPC), nuclear magnetic resonance (NMR), matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS), and differential scanning calorimetry (DSC). It was found that the end groups can influence the glass transition temperature (T(g)) of the polystyrenes. The polymers with different end groups were then used to prepare honeycomb-patterned porous films by the breath figure method. Results reveal that the subtle chain-end modification leads to a dramatic change in the morphology of the films. Honeycomb films with large area ordered structure can be easily prepared from PS-OH. Effects of the end groups as well as blending PS-OH with PS-Br on the surface pore diameter, pore center distance, and the hierarchical structure were studied in detail. As supported by the results of polymer hydrophilicity, in situ observation of the film formation process, as well as the chain mobility, the film structure is supposed to be mainly determined by the precipitation of polystyrene at the solution/water droplet interface and the interfacial activity enhanced by the end groups.

Breath-Figures Self-Assembly, the Versatile Method of Manufacturing Membranes and Porous Structures: Physical, Chemical and Technological Aspects

“…These results were supported by findings reported in Ref. 38, where the authors reported that the hydrophilic end groups can dramatically improve the filmforming property of polystyrene and that the regularity of the film is mainly influenced by the interaction of film-forming polymers with condensed water droplets. Amirkhani polymer produced a large area of regular spherical bubbles, whereas adding particles to the polymer solution leads to smaller arrays of the flattened bottom bubbles.…”

Breath Figure: A Nature-Inspired Preparation Method for Ordered Porous Films

“…It is widely accepted that the morphology shown in Figure 11a results from the coalescence of water droplets during the BF process. 42,114,115 This coalescence is easy to understand: when two droplets touch each other, they tend to merge. 116,117 However, experimental results show that, in most BFAs, pore arrays are mostly regular over a larger area, as shown in Figure 11b.…”

“…116,117 However, experimental results show that, in most BFAs, pore arrays are mostly regular over a larger area, as shown in Figure 11b. 42 It is difficult to imagine such uniform pores being templated from water droplets that underwent coalescence. Thus, the water droplets on the solution surface are quite stable; they rarely coalesce even when they are closely packed.…”

Breath Figures: Fabrication of Honeycomb Porous Films Induced by Marangoni Instabilities

“…Thus, with an appropriate design of the polymer, a desired functionality can be homogeneously distributed in the entire film, exclusively inside the cavities, both inside/outside the pores or on the top surface (Scheme 10.1). A variety of techniques have been employed to analyze the chemical distribution of the surfaces, such as fluorescence microscopy [114,140], transmission electron microscopy [75], atomic force microscopy [144], time-of-flight secondary-ion mass spectrometry [145], X-ray photoelectron spectroscopy [146], energy-dispersive X-ray (EDX) measurements [147] and Raman microscopy [148].…”