Integrated process for preparing porous, surface functionalized polyetherimide microparticles

Abstract

Highly porous polyetherimide (PEI) microparticles achieved by a spraying/coagulation process are candidate absorber materials for apheresis applications. Hydrophobic PEI surfaces tend to be rapidly coated with proteins when in contact with blood. Therefore, a hydrophilic modification of such particles is required. In this study, we explored the formation of porous, surface functionalized PEI microparticles by low molecular weight polyethyleneimine (Pei) or potassium hydroxide (KOH) in an integrated process combining chemical modification and particle formation. The integrated process resulted in smaller microparticles with diameters of 70 to 80 μm compared to the chemical twostep process. All particles exhibited similar bulk densities, ranging from 0.09 to 0.015 g cm À3 , and average pore sizes around 180-250 nm. A successful modification of the particles' surface by both processing approaches could be confirmed by X-ray photoelectron spectroscopy measurements and microwetting experiments, where hydrophilic advancing contact angles of 57°to 64°were determined. Integrated particle processing further resulted in changes of the bulk properties, i.e. molecular weight, thermal decomposition behavior or glass transition temperature. Hydrophilic modified PEI microparticles have been successfully prepared by different approaches. In a next step their absorption capacity for uremic toxins will be investigated with regard to a potential application in blood detoxification.

Morphological analysis of differently sized highly porous poly(ether imide) microparticles by mercury porosimetry

“…Shape and size of the microparticles were characterized by SEM with a Phenom G2 pro (L.O.T.‐Oriel, Darmstadt, Germany). The sample preparation followed a recently described procedure . For analysis of the average particle diameters, the image processing software ImageJ (version 1.51; National Institutes of Health, USA) was applied and the standard deviation (error) was determined by measuring 500 particles.…”

“…The obtained high resolution SEM images were analyzed by ImageJ processing software (version 1.51d; Fiji distribution, National Institutes of Health, USA) regarding the average pore size by introducing a suitable threshold (a grayscale transition in the histogram) to separate polymer and free space (pores). The cross‐sectional samples were prepared via cryo‐ultramicrotomy as described before …”

“…The cross-sectional samples were prepared via cryo-ultramicrotomy as described before. [10] Pore size and particle size calculations Mercury intrusion porosimetry is based on the Washburn equation, [20] r ¼ À2γcosθ…”

“…porogen‐based methods, spraying methods, or phase separation methods) have been employed for preparation of porous microparticles with controlled pore sizes and morphologies . Examples are poly( ε ‐caprolactone) based microparticles with aligned pores prepared by an emulsion freezing approach, hierarchically structured poly(methyl methacrylate) particles prepared via non‐solvent assisted electrospraying or highly porous poly(ether imide) (PEI) microparticles where the internal pore structure can be altered by variation of the solvent applied in the spraying/coagulation process, and by surface modifications . Porous PEI particles (Fig.…”

“…[1,6] Examples are poly(εcaprolactone) based microparticles with aligned pores prepared by an emulsion freezing approach, [7] hierarchically structured poly(methyl methacrylate) particles prepared via non-solvent assisted electrospraying [8] or highly porous poly(ether imide) (PEI) microparticles where the internal pore structure can be altered by variation of the solvent applied in the spraying/coagulation process, [4,9] and by surface modifications. [10] Porous PEI particles ( Fig. 1) are discussed as candidate adsorber materials for apheresis applications, e.g.…”