Aijuan Zhang

Fabrication of robust honeycomb polymer films: A facile photochemical cross-linking process

Highly ordered honeycomb films are prepared by breath-figure method using an amphiphilic diblock copolymer of polystyrene-block-polyacrylic acid (PS-b-PAA). By simply cross-linking PS matrix via deep ultraviolet (UV) irradiation, both the solvent and thermal stability of the porous films was significantly improved while retaining the three-dimensional (3D) structures. The film surface wettability was changed from hydrophobicity to hydrophilicity by the formed polar groups during the photochemical process. After 6 h UV cross-linking, the honeycomb structures could be preserved up to 320 degrees C, an increase of more than 200 K as compared to the non-cross-linked films.

Breath figure in non-aqueous vapor

In this paper we reported the preparation of porous honeycomb polymer film using a static breath figure (BF) method under non-aqueous atmospheres. Methanol and ethanol vapors were chosen as the atmosphere in which the BF process was conducted. It is found that honeycomb films with ordered pores can be obtained with methanol and ethanol droplets arrays as the templates. The influence of the atmosphere on the film morphology, including the pore shape, size and the degree of pore packing order, was investigated. Furthermore, the formation process of the BF arrays under these alcohol vapors was investigated using a non-planar substrate method. Finally it is shown that the honeycomb films with different pores can be used to prepare highly ordered ceramic micropatterns with adjustable sizes, as well as the siloxane-based soft stamps. Our results prove that the BF method is not only suitable for water vapor, but is also compatible with other organic vapors. Also this paper develops a facile way to control the morphology features of the BF honeycomb films by changing the vapor atmospheres, which is valuable when designing and fabricating ordered microstructures.

One-step synthesis of polyhydroquinone–graphene hydrogel composites for high performance supercapacitors

Electroactive polymers constitute an important class of electrode materials for supercapacitors based on pseudocapacitance. However, it is difficult to utilize low-conductive electroactive polymers in supercapacitors, although these polymers may have large theoretical specific capacitance. In this article, we designed and prepared a novel type of electrode material, with a unique structure of low-conductive electroactive polyhydroquinone (PHQ) coated on a highly conductive three-dimensional (3D) porous graphene hydrogel (GHG). PHQ–GHG composites were prepared via a one-step reaction between graphene oxide and hydroquinone under mild conditions. Because PHQ has a large theoretical specific capacitance, and GHG possesses a 3D porous structure, large specific surface area and high electrical conductivity, the composites showed a high specific capacitance of 490 F g−1 at a current density of 24 A g−1, as well as excellent rate performance and cycling stability. These results demonstrate that PHQ–GHG composites are promising electrode materials for supercapacitors, and the method developed in this paper paves a new way for utilizing those electroactive polymers of low electrical conductivities in supercapacitors.

Multi-length scale porous polymer films from hypercrosslinked breath figure arrays

Multi-length scale porous polymer (MLSPP) films were fabricated using commercially available polystyrene (PS) via static breath figure (BF) process and sequent hypercrosslinking reaction. One level of ordered pores in microscale were introduced using static BF process, and the other level in nanoscale were produced by the sequent Friedel-Crafts hypercrosslinking reaction. The chemical structure of the PS MLSPP film was investigated by Fourier transformation infrared spectrometry and solid state nuclear magnetic resonance, and the morphology of the film was observed with electron microscopes. The MLSPP films showed large specific surface areas and excellent chemical and thermal stabilities, owing to the micropores and the crosslinked chemical structure produced by the Friedel-Crafts reaction. The methodology reported in this paper is a template-free, low cost and general strategy for the preparation of MLSPP films, which has potential applications in the areas of environment and energy.