Abstract
Mixed-matrix membranes based on amorphous and semi-crystalline polyimides with zirconium dioxide (ZrO2) nanostars were synthesized. Amorphous poly(4,4′-oxydiphenylenepyromellitimide) and semi-crystalline polyimide prepared from 1,4-bis(4-aminophenoxy)benzene and 4,4’-oxydiphthalic anhydride were used. The effect of ZrO2 nanostars on the structure and morphology of nanocomposite membranes was studied by wide-angle X-ray scattering, scanning electron microscopy, atomic force microscopy, and contact angle measurements. Thermal properties and stability were investigated by thermogravimetric analysis and differential scanning calorimetry. Transport properties of hybrid membranes containing 5 wt % ZrO2 were tested for pervaporation of a mixture of butanol–water with 10 wt % H2O content. It was found that a significant amount of the ZrO2 added to the semi-crystalline polyimide is encapsulated inside spherulites. Therefore, the beneficial influence of inorganic filler on the selectivity of mixed-matrix membrane with respect to water was hampered. Mixed-matrix membranes based on amorphous polymer demonstrated the best performance, because water molecules had higher access to inorganic particles.
Highlights
Aromatic heterocyclic polyimides and their composites are promising membrane materials [1,2,3,4,5]due to their superior chemical stability, good mechanical properties, and excellent thermal stability.The effectiveness of most membrane processes is mainly controlled by the selection of membrane material with appropriate structural, physical, and chemical properties [6]
The initial polymer membrane (Figure 5a) is characterized by considerable variation of spherulite sizes from to μm, while for matrix membranes (MMMs), this parameter lies in the considerable variation of spherulite sizes from 4 to 10 μm, while for MMM, this parameter lies in the range1–4
Novel MMMs based on polyimides and ZrO2 nanostars were successfully prepared and investigated
Summary
Aromatic heterocyclic polyimides and their composites are promising membrane materials [1,2,3,4,5]due to their superior chemical stability, good mechanical properties, and excellent thermal stability.The effectiveness of most membrane processes (such as pervaporation) is mainly controlled by the selection of membrane material with appropriate structural, physical, and chemical properties [6]. The introduction of inorganic nanoparticles into an organic membrane can: (1) decrease chain mobility near polymer–particle interface [12]; (2) change the membrane’s free volume [13,14]; and (3) change both the degree of crystallinity and the sizes of polymer spherulites [11]. All of these factors affect the permeability of the membrane. The level of such an increase may be reduced by the blockage of selective channels because of the crystalline nature of the polymer and/or a decrease of chain mobility near polymer–particle interface
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