Honeycomb-Structured Porous Films Controlled by the Temperature of Water Bath

Abstract

The highly ordered porous films were fabricated from the solution of polystyrene with one carboxyl terminal group in carbon disulfur in a chamber with a water bath. It is found that the pore size can be readily controlled by changing the temperature of water bath. The pore size increases with an increase in the water-bath temperature in a given range. And the porous film from the ''dilute'' solution can be readily formed even at a low relative humidity (RH), while the porous film from the ''concentrated'' solution can be fabricated only at a rather high RH. The regularity of porous film becomes better at the higher RH and higher concentration. It suggests that there exists a synergetic effect of solution concentration and RH on the formation of porous film. These phenomena are explained by the slow evaporation rate of the solvent under the conditions. 9,10 microphase-separation of block copolymers. 11,12 The templates employed in the methods are often sacrificial, though they are not readily produced. [13][14][15][16] Recently, a breath figures (BF) method in which water droplets act as easily available templating medium draws increasing interests. [17][18][19] In this method, the evaporation of solvent in polymer solution leads to a decrease in the temperature of solution surface, and water vapor starts to condense onto the cold solution surface to form water droplets. And then the water droplets are packed by the precipitated polymers and self-assembled into a BF array. Upon further evaporation of solvent and water, the ordered porous structure is effectively locked in place. 17 The morphology of pores mocking the water droplets can be readily controlled by varying the process conditions (such as relative humidity, concentration and airflow rate across the polymeric solution surface, etc.) and the types of materials used. 17,[19][20][21][22] The basic techniques related to BF method also markedly affected the formation of pores. In the airflow technique, an airflow parallelly across the solution surface results in cooling of solution surface due to fast evaporation of the solvent, which is beneficial to formation of highly ordered porous film and widely used in BF method. 19,20,23 Recently, Li et al. 24developed a new method that the airflow blew across the solution surface along the direction having a small angle with respect to the normal of the solution surface. The shape of the pores could be controlled, that is, elliptical pore morphology with different aspect ratios was obtained. Stenzel et al. 25switched the airflow from parallel to vertical stream, better porous size control over the whole film surface was achieved, but at the cost of regularity of the film. In the above techniques, the airflow containing a certain amount of moisture, which is often additionally fed, played a key role in inducing a decrease in solution temperature and the formation of ordered porous film. Bormashenko et al.26,27 employed a fast dip-coating technique to fabricate porous film on different solid substrates. They found tha...

Tailoring pore distribution in polymer films via evaporation induced phase separation

“…[1][2][3][4][5][6][7] The liquid-liquid phase separation (LLPS) route is undoubtedly a well-known and established technique to prepare porous polymeric structures. [8][9][10][11][12][13][14][15][16] In this process, a thermodynamically unstable polymer solution phase separates into two coexisting liquid phases in thermodynamic equilibrium. One of these phases, i.e., the polymer-rich phase solidies to form a solid matrix, while the other phase, viz., a polymer-lean phase which is rich in nonsolvent, eventually forms the pores in the matrix.…”

Fabrication of Durable Honeycomb‐Patterned Films of Poly(ether sulfone)s via Breath Figures

“…The mean pore sizes ( D ) of PES films are demonstrated in Figure b. It is obvious that there are two main differences between the results of the current system and previous reported systems . Firstly, D does not always change monotonically with the increase of C A or RH.…”

“…It is obvious that there are two main differences between the results of the current system and previous reported systems. [ 71,[76][77][78][79] Firstly, D does not always change monotonically with the increase of C A or RH. Secondly, C A and RH have synergetic effects on D , i.e., the infl uence of C A differs at different RHs.…”

Photoluminescent Honeycomb Structures from Polyoxometalates and an Imidazolium‐Based Ionic Liquid Bearing a π‐Conjugated Moiety and a Branched Aliphatic Chain

“…[4] The preparationo fh oneycombs tructures has been expanded from solid substrates to the air/waterinterface and the templates have been extended from droplets of watert ot hose formed by nonaqueous solvents or microemulsions.I nfluences of various factors on the morphology of the honeycombs tructures, such as humidity,g as flow,t emperature, concentration of the materials, type of substrate, and organic solvent,h ave been fully investigated. Up to now,v arious candidates have been explored to form honeycomb structures.B esides polymers with diversec ompositions and structures, [12][13][14][15] av ariety of materials with attractive properties have also been tried, including carbon nanotubes( CNTs), [16,17] grapheneo xide (GO), [18] proteins, [19] small organic molecules, [20][21][22] and inorganic-organic hybrids. [10,11] Ab ig advantage of the honeycombs tructures fabricated by the BF methodi st hat the functions of the films can be facilely tuned by engineeringt he starting materials.…”

“…[10,11] Ab ig advantage of the honeycombs tructures fabricated by the BF methodi st hat the functions of the films can be facilely tuned by engineeringt he starting materials. Up to now,v arious candidates have been explored to form honeycomb structures.B esides polymers with diversec ompositions and structures, [12][13][14][15] av ariety of materials with attractive properties have also been tried, including carbon nanotubes( CNTs), [16,17] grapheneo xide (GO), [18] proteins, [19] small organic molecules, [20][21][22] and inorganic-organic hybrids. [23][24][25][26][27] The films containing honeycombs tructures with varying sizes and morphologies have been successfully used as molecular sieves, [28] sensors, [29] superhydrophobic coatings, [30] antibacterial surfaces, [31] cell culture reservoirs, [32] and templates for electrodeposition of Au or Ag particlesfor surface-enhanced Ramanscattering (SERS).…”