Microsphere Pattern Prepared by a “Reverse” Breath Figure Method

Abstract

We have reported an interesting method, named reverse breath figure, for the preparation of polymeric microsphere patterns. By the same procedure as breath figure, instead of under a humid atmosphere, linear and star-shaped poly(styrene-block-butadiene) copolymers dissolved in solvents such as toluene, trichloroform, and dichloromethane were cast onto the surface of a glass substrate in methanol or ethanol vapor. After the complete evaporation of the solvent, microspheres with the diameters ranging from hundreds of nanometers to several micrometers were prepared. The microsphere patterns are the reverse of the honeycomb porous structure of breath figure. The mechanism of the microsphere formation has been studied to show that when the surface tension of the polymer solution is 1.5 mN/m higher than that of the condensed liquid, microsphere patterns can be prepared, whereas a honeycomb porous film of breath figure can be obtained when the surface tension of the polymer solution is lower than that of the condensed liquid. The viscosity of the polymer solution is also an important factor to influence the fabrication of the microsphere patterns.

Honeycomb-patterned porous films fabricated via self-organization of Tb complex-loaded amphiphilic copolymers

“…While for the THF, the surface morphology is demonstrated as microspheres shape rather than porous lms (Fig. 3d) which is named reverse breath gures by Ferrari et al 23 and Xiong et al 44 They concluded that only solvents with low boiling point, high vapor pressure and low water solubility can form regular porous lms. The THF has relative higher boiling point and evaporates too slowly at room temperature, leading to no condensation of water drops on the surface of the solution and resulting in reverse breath gures.…”

The Preparation of NC Microspheres and BuNENA Modified NC Microspheres by the Breath Figures Method

“…There are several views as to whether, or not, the final morphology obtained by the 'breath figures' method is microspherical or akin to a porous film. Xiong [16] considered that the morphology of a polymer (either microspherical or as a porous film) after assembly mainly depended on the differences in surface tension between the polymer solution and the non-solvent. In general, if the difference was positive and higher than 1.5 mN/m, microspheres were obtained, otherwise, porous films were produced.…”

“…Using this method, Francois et al made ordered, porous, polymer films in 1994 [12] and investigated the films prepared by the 'breath figures' method thereafter [13][14][15]. In 2009, a polymer microsphere was obtained for the first time by Xiong et al, by changing the atmosphere in which the specimen was prepared from water to an organic solvent, methanol [16]. NC microspheres and BuNENA modified NC microspheres (BMNM) were prepared using the 'breath figures' method in this research.…”

Ordered patterns formed on polymer film through trapping and locking

“…The ordered patterns can be obtained through conventional lithography techniques, yet the high price of the equipment remains a problem . During recent years, the non‐conventional approaches such as soft lithography, dewetting, embossing, and breath figure method, have received considerable attention . However, in most cases, they still involve some challenges such as harsh preparation conditions, time‐consuming steps, or restriction to special polymers.…”

“…6 During recent years, the non-conventional approaches such as soft lithography, dewetting, embossing, and breath figure method, have received considerable attention. [7][8][9][10][11][12][13][14][15] However, in most cases, they still involve some challenges such as harsh preparation conditions, time-consuming steps, or restriction to special polymers. For example, block copolymers have been extensively used for research on ordered patterns, which results from the balance of repulsive interactions between dissimilar segments and the self-assembly behavior.…”