Fabrication of pH-Responsive Polyimide Polyacrylic Acid Smart Gating Membranes: Ultrafast Method Using 248 nm Krypton Fluoride Excimer Laser

Abstract

pH-responsive smart gating membranes were developed using a two-step fabricating process. In the first step, a porous polyimide (PI) support membrane with ordered, regular, and welldefined pores was obtained with a 248 nm KrF excimer laser using a lithography technique. The porous membranes were then grafted with poly(acrylic acid) (PAAc) hydrogel by free radical polymerization using the same excimer laser. The number of pulses and frequency could be varied to obtain a range of water permeabilities. Permeability of membrane changed significantly due to swelling and deswelling of PAAc inside the pores at pH 7 and pH 3, respectively. These hydrogel networks were firmly grafted inside pores and remained mechanically intact even after using high pressure during permeability studies. PAAc grafting was confirmed using ATR-FTIR. PAAc hydrogel distribution inside membrane pores was analyzed using SEM and fluorescence microscopy. To quantify the amount of polymer grafted, TGA studies were carried out. Diffusion studies were also carried out using caffeine as a drug molecule to evaluate the application of membrane in drug delivery devices. The linear drug release profile obtained from the study confirmed the potential application of membrane for drug delivery purposes. Results obtained also suggest that the fabrication method developed is fast, efficient, solvent-free, and economical.

Metal–Organic Enzyme Nanogels as Nanointegrated Self-Reporting Chemobiosensors

“…The insertion of phosphate groups is also evidenced in the FTIR spectra (Figure A). A band corresponding to the symmetric stretching vibration of the carbonyl group of the acrylate ester, i.e., 1723 cm –1 , can be identified only in MAEPm containing samples (pGOx_1 to pGOx_3). , Same samples show a differential shoulder that arises at 1150 cm –1 , which is typically attributed to the antisymmetric stretching of phosphate groups. , …”

Ordered Alignment of Liquid Crystalline Graphene Fluoride for Significantly Enhancing Thermal Conductivities of Liquid Crystalline Polyimide Composite Films

“…The T HRI (277.6 °C) of 15 wt % GeF/LC-PI composite film is significantly higher than that of pure LC-PI film. This is because the introduction of GeF fillers hinders the overflow of decomposition products during heating . The T HRI of 15 wt % LC-GeF/LC-PI composite film is 278.7 °C, which is 12.1, 16.3, and 1.1 °C higher than the pure PI film, pure LC-PI film, and 15 wt % GeF/LC-PI composite film, respectively, due to the pyrolysis of TMN making the gas products generated escape into the boundary layer, forming a thermal blocking effect and improving the thermal resistance of LC-GeF/LC-PI composite films, therefore broadening application in extreme working environments, such as extremely high temperatures.…”

Method Development for Separation and Analysis of Tire and Road Wear Particles from Roadside Soil Samples

“…There are several common peaks in the reference cryogrinds and TRWPs (Figure a). These peaks include aliphatic hydrocarbon bands (C–H stretching at 2920 and 2845 cm –1 and C–H bending at 1450 cm –1 ), , C–O–C stretching at 954 cm –1 , ester bands (C–O bending at 1027 cm –1 ), and out of plane bending of aromatic C–H at 700 cm –1 . It was evident that TRWPs 1 and 2 had similar peaks as that of the PC-Si cryogrind, whereas TRWP 3 revealed common peaks with T-NR cryogrind.…”