Dewetting Behavior of Hydrogen Bonded Polymer Complex Film under Hydrothermal Condition

Morphological Variation of an LB Film of Giant Amphiphiles Composed of Poly(ethylene oxide) and Hydrophobically Modified POSS

Hydrophobically modified polyhedral oligomeric silsesquioxanes (XPOSS) are linked to one end of water-soluble poly(ethylene oxide) (PEO) to synthesize giant amphiphiles (XPOSS-PEO). XPOSS-PEO exhibit an interesting surface activation capacity owing to the synergy of the soft PEO segment and hydrophobic XPOSS when they are spread on the water surface and compressed by the barrier. The monolayers of XPOSS-PEO at the air-water interface are transferred onto the silicon substrate at different surface pressures using the Langmuir-Blodgett (LB) film deposition protocol. The modification of the POSS head significantly changes the crystallinity of the PEO tail, which affects the LB film morphologies of the giant amphiphiles. When the POSS are modified with fluorinated agents, the assembled LB films show a fractal growth pattern, but when the POSS are decorated with a pure alkane chain, the fractal growth pattern does not present in the resulting LB film.

Aquaporin-Containing Proteopolymersomes in Polyelectrolyte Multilayer Membranes

The field of membranes saw huge developments in the last decades with the introduction of both polyelectrolyte multilayer (PEM)-based membranes and biomimetic membranes. In this work, we combine these two promising systems and demonstrate that proteopolymersomes (PP+) with the incorporated aquaporin protein can be distributed in a controlled fashion using PEMs, even on the inner surface of a hollow fiber membrane. In this way, various proteopolymersome multilayers (PPMs) are fabricated using PP+ as the positively charged species in combination with the polyanions poly(styrene 4-sulfonate) (PSS) and poly(acrylic acid) (PAA). It is shown by reflectometry through alternately adsorbing the polyanions and PP+ that, for both PAA and PSS, a good layer growth is possible. However, when the multilayers are imaged by SEM, the PAA-based PPMs show dewetting, whereas vesicular structures can only be clearly observed in and on the PSS-based PPMs. In addition, membrane permeability decreases upon coating the PPMs to 2.6 L∙m⁻²∙h⁻¹∙bar⁻¹ for PAA/PP+ and 7.7 L∙m⁻²∙h⁻¹∙bar⁻¹ for PSS/PP+. Salt retentions show that PAA/PP+ layers are defective (salt retentions <10% and high molecular weight cut-off (MWCO)), in line with the observed dewetting behavior, while PPMs based on PSS show 80% MgSO₄ retention in combination with a low MWCO. The PSS/PP+ membranes show a Donnan-exclusion behavior with moderate MgCl₂ retention (50%–55%) and high Na₂SO₄ retention (85%–90%) indicating a high amount of negative charge present within the PPMs. The corresponding PEMs, on the other hand, are predominately positively charged with MgCl₂ retention of 97%–98% and Na₂SO₄ retention of 57%–80%. This means that the charge inside the multilayer and, thus, its separation behavior can be changed when PP+ is used instead of a polycation. When comparing the PPM membranes to the literature, similar performances are observed with other biomimetic membranes that are not based on interfacial polymerization, but these are the only ones prepared using a desired hollow fiber geometry. Combining PEMs and biomimetic approaches can, thus, lead to relevant membranes, especially adding to the versatility of both systems.

Interpolymer complexes of carbopol® 971 and poly(2-ethyl-2-oxazoline): Physicochemical studies of complexation and formulations for oral drug delivery

Carbopol® 971 and poly(2-ethyl-2-oxazoline) form hydrogen-bonded interpolymer complexes in aqueous solutions and their complexation is strongly dependent on solution pH. This work investigated the complexation between these polymers in aqueous solutions. The compositions of interpolymer complexes as well as the critical pH values of complexation were determined. The structure of these complexes was studied in solutions using transmission electron microscopy and in solid state using elemental analysis, FTIR spectroscopy and differential scanning calorimetry. Solid compacts were prepared based on interpolymer complexes and physical blends of these polymers and their swelling behaviour was studied in aqueous solutions mimicking the fluids present in the gastrointestinal tract. These materials were used to prepare oral formulations of mesalazine and its release from solid matrices was studied in vitro. It was demonstrated that the complexation between Carbopol® 971 and poly(2-ethyl-2-oxazoline) has a profound effect on the drug release from matrix tablets.