Bioinspired Gradient Materials via Blending of Polymer Electrolytes and Applying Electric Forces

Abstract

Free-standing and supported films with lateral gradient in composition were prepared using blends of poly(acrylic acid) (PAA)/sodium salt and its copolymers with acrylamide (AAm) in an applied electric field. The gradients were stabilized by complexation of carboxylate groups with metal species. To find the favorable conditions and components for successful blending and interaction with Fe and Ce species, we studied blending of the two PAA samples with molecular weights of 2,000 and 15,000 Da with two copolymers of AA and AAm (with 10 and 70 wt. % of AA units) and interaction of these blends with Fe(III) and Ce(IV) ions. The structure of the hybrid (blend) films was studied using differential scanning calorimetry (DSC), X-ray photoelectron spectroscopy (XPS), UV-vis spectroscopy, X-ray diffraction and optical microscopy. To ensure blend miscibility and efficient interaction with metal ions, the copolymer containing 70 wt.% of AA units has been used. The surface enrichment with metal species was observed at all experimental conditions studied in this work. For lateral gradient film formation, 15,000 Da PAA has been used to avoid uneven distribution of the homopolymer in the film, observed for 2,000 Da PAA. The gradient films were characterized by XPS. The lateral gradient of functionality such as COONa group or Fe content, has been obtained at different strengths of electric field applied during film formation. The use of lower voltage allows one to prevent NaOH formation and creates more favorable conditions for development of a gradient polymer film. The Ce content gradient was not observed due to formation of large Ce oxide particles (≥750 nm), masking the gradient of functionality. For the first time, free-standing films with lateral gradient in composition were prepared using an applied electric field.

Tuning gradient microstructures in immiscible polymer blends by viscosity ratio

“…In polymer blends, this task is quite challenging due to the complex relationships between their properties, microstructures, and processing conditions. Recently, bioinspired gradient polymer materials have attracted a lot of attention due to their characteristic morphologies and properties . Most natural plants, such as bamboo, have different layers forming hierarchical microstructures with specific properties .…”

“…The tensile strength of the bamboo culm increases parabolically with radial distance and reaches its maximum value in the outer region due to the gradient distribution of fibers. By applying similar ideas to synthetic immiscible polymers, desirable morphologies and properties can be achieved by controlling the external field (e.g., gradient temperature field and electric fields), polymer diffusion in interpenetrating polymer networks, and phase separation in multicomponent blends . Recently, we produced polymer fibers with gradient microstructures by tuning melt processing parameters and capillary die design .…”

Chelation Gradients for Investigation of Metal Ion Binding at Silica Surfaces

“…For example, using polymer blends containing poly(acrylic acid), Stucky and coworkers 30 established the composition and conditions for the optimal interaction of a gradient with Fe and Ce. Most previous studies, however, have involved a detailed study of one surface prepared from one set of experimental conditions.…”

Effect of annealing on self-organized gradient film obtained from poly(3-[tris(trimethylsilyloxy)silyl] propyl methacrylate-co-methyl methacrylate)/poly(methyl methacrylate-co-n-butyl acrylate) blend latexes

“…FGMs are of interest to the study of orchestrated responsive behaviors, aerospace materials, and photoelectric and nuclear energy conversion materials [3][4][5][6]. Despite that FGMs are well known in the field of ceramics, metals, and other inorganic materials [7], functional gradient polymeric materials (FGPMs) have been extensively used because of their excellent properties, such as optical properties and mechanical stress relaxation [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22].…”

“…Many ways to achieve this structure have been developed, including dissolution diffusion [17][18][19], blend [20][21][22], and other novel approaches [9][10][11][12], over the past few years. Of Electronic supplementary material The online version of this article (doi:10.1007/s00396-011-2582-x) contains supplementary material, which is available to authorized users.…”