Polyimide Microspheres Research Articles

Electroactive PI sphere generated by electrospraying

AbstractIn this study, electroactive polyimide microspheres (EPSs) based on conjugating segments of electroactive aminocapped aniline trimer as diamine and 4,4′‐(4,4′‐isopropylidenediphenoxy)‐bis(phthalic anhydride) as dianhydride were successfully prepared by electrospraying technology and characterized by time of flight mass spectroscopy, 1H‐NMR, Fourier transform infrared spectroscopy and cyclic voltammetry. The prepared electroactive polyimide was then dissolved in a suitable organic solvent (N,N‐dimethylformamide; N‐methyl‐2‐pyrrolidone) followed by electrospraying treatment under four different operational parameters (i.e. solution concentration, applied voltage, feeding rate and deposition distance) to give EPSs of various diameters. Moreover, EPSs deposited on the Pt electrode were tested in a 1.0 mol L−1 H2SO4 aqueous solution by cyclic voltammetry which showed an obvious redox peak similar to polyaniline. Copyright © 2011 Society of Chemical Industry

Fabrication of polyimide microspheres with high precursor polymer concentration

Polyimide (PI) microspheres with high precursor polymer concentration were successfully prepared using non-aqueous reverse emulsion polymerisation. The emulsion was composed of N, N-dimethyl formamide and liquid paraffin, in which Span85 was used as surfactant. The effect of Span85 concentration on the resulting PI product has been investigated. The results indicated that with the increase in Span85 concentration, the average diameter declined, and the size distribution became narrow. When the concentration of surfactant Span85 was around 0.15 w/w, a yellow-to-brown-coloured powder of PI microfine spheres was obtained, with an average particle size of 25.6 µm. As an emulsifier and a chain termination agent, surfactant Span85 chemically bonded to the growing polymer chains, and not only formed stable non-aqueous inverse emulsion but also increased precursor polymer concentration.

Intrinsically electroactive polyimide microspheres fabricated by electrospraying technology for ascorbic acid detection

In this paper, we present the first fabrication of intrinsically electroactive polyimide microspheres (EPS) based on conjugated segments of an electroactive amino-capped aniline trimer (ACAT) of a diamine, 4,4′-(4,4′-isopropylidenediphenoxy)-bis(phthalic anhydride) (BSAA) and a dianhydride. EPS was successfully prepared using electrospraying technology and applied in the detection of ascorbic acid (AA). The particle size of EPS can be controlled by varying the concentration of spraying solution, while the electrocatalysis oxidation properties can be influenced by the different particle sizes of EPS. A sensor constructed using an EPSS (EPS with a small particle size)-modified carbon paste electrode (CPE) was found to show 4.38-fold and 1.81-fold higher electrocatalytic activities towards the oxidation of AA than those constructed using an EPI (electroactive polyimide) thin film and EPSL (EPS with large particles size), respectively.

Superhydrophobic Polyimide Films with a Hierarchical Topography: Combined Replica Molding and Layer-by-Layer Assembly

Artificial superhydrophobic surfaces with a hierarchical topography were fabricated by using layer-by-layer assembly of polyelectrolytes and silica nanoparticles on microsphere-patterned polyimide precursor substrates followed with thermal and fluoroalkylsilane treatment. In this special hierarchical topography, micrometer-scale structures were provided by replica molding of polyamic acid using two-dimensional arrays of polystyrene latex spheres as templates, and nanosized silica particles were then assembled on these microspheres to construct finer structures at the nanoscale. Heat treatment was conducted to induce chemical cross-linking between polyelectrolytes and simultaneously convert polyamic acid to polyimide. After surface modification with fluoroalkylsilane, the as-prepared highly hydrophilic surface was endowed with superhydrophobicity due to the bioinspired combination of low surface energy materials and hierarchical surface structures. A superhydrophobic surface with a static water contact angle of 160 degrees and sliding angle of less than 10 degrees was obtained. Notably, the polyimide microspheres were integrated with the substrate and were mechanically stable. In addition, the chemical and mechanical stability of the polyelectrolyte/silica nanoparticle multilayers could be increased by heat-induced cross-linking between polyelectrolytes to form nylon-like films, as well as the formation of interfacial chemical bonds.

Chemical composition of plasma treated polyimide microspheres

Synthetic carbon microspheres for chromatography were obtained from porous copolymer of 4,4′-bis(maleimidodiphenyl)methane (BM) and divinylbenzene (DVB) using arc discharge argon plasma treatment. Chemical structure of the obtained material was determined by elemental analysis, scanning electron microscopy with X-ray detector, acid and base titrations, and atomic absorption spectroscopy. The results suggest that the carbon microspheres contain copper coming from the plasma reactor electrodes. To remove it two complexion agents were used: EDTA and 20% HNO3. Copper can be removed from the surface using these methods. The other amount was permanently built into internal structure of the microspheres.