Chengao Li,Licheng Wang,Liuyun Wei,Mingqing Yuan,Hua Yang
Bilayer hydrogels composed of poly(N-isopropylacrylamide) (PNIPAm) and poly(acrylic acid-co-acrylamide) (P(AAc-co-AAm)) are commonly utilized as anisotropic hydrogels with temperature and pH sensitivity. Nonetheless, PNIPAm is known to possess poor mechanical properties, a slow thermal response, and brittleness, which greatly restricts its application for temperature sensitivity. In order to overcome these limitations, a semi-interpenetrating network (semi-IPN) structure was created by combining PNIPAm with sodium alginate. This structure effectively addressed the issue of PNIPAm’s brittleness, increased its tensile stress, and improved its tensile strain. Notably, a porogen such as sodium carbonate was incorporated to increase the porosity of the thermo-sensitive layer hydrogel, resulting in a faster thermal response rate. The bilayer hydrogel obtained can be used as a bidirectional hydrogel driver with both temperature and pH sensitivity. Mechanical manipulation through temperature changes or pH shifts can cause significant deformation in the hydrogel, making it a promising material for soft actuator applications.
Jinxiong Song,Lijun Song,Biao Ai,Youcai Chen,Ying Liu,Yuzhang Zhu,Jian Jin
Thin-film composite (TFC) polyamide (PA) nanofiltration (NF) membranes are essential for separating ions and small molecules in the industries, including water treatment, chemical processing, energy production, and pharmaceuticals. These membranes are typically fabricated via interfacial polymerization (IP) on polysulfone (PSf) or polyethersulfone (PES) ultrafiltration (UF) supports. Apparently, optimizing the physicochemical properties of the UF support is very important for achieving TFC-PA NF membranes with superior separation performance. This study systematically investigated the influence of common pore-forming agents used in UF membrane fabrication, specifically polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), and lithium chloride (LiCl), on the desalination performance of resulting TFC-PA NF membranes. We characterized the zeta potential, pore structure, and surface wettability of PSf UF membranes prepared with each pore agent. These characteristics were then correlated with the adsorption and desorption behavior of piperazine (PIP) monomers during the IP process. Our findings indicate that employing PVP as a pore-forming agent not only enhanced PIP adsorption within the UF support but also facilitated its rapid release during the IP reaction. This dual effect resulted in a PA selective layer with reduced thickness and smaller pore size. Consequently, the TFC-PA NF membrane fabricated on the PVP-modified UF support exhibited both higher water permeance and improved salt rejection. This research highlights the significant role of the pore-forming agent in determining the performance of TFC-PA NF membranes. The results suggest that UF supports prepared using PVP as a pore agent may be optimal for creating NF membranes with enhanced overall performance.
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