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Materials and Synthesis of pH-Responsive Membranes
Published in Randeep Singh, Piyal Mondal, Mihir Kumar Purkait, pH-Responsive Membranes, 2021
Randeep Singh, Piyal Mondal, Mihir Kumar Purkait
The temperature-induced grafting method is a simple and easy-to-use method for the grafting of pH-responsive groups or polymers over a membrane surface. The basic requirement of this method is a chemical initiator or a cleavage agent, such as Azobisisobutyronitrile (AIBN). Generally, the polymerization is performed in a heterogeneous polymer-monomer reaction system in a solvent, such as water, toluene, ethanol, and others. Later, this prepared pH-responsive polymer is used to synthesize PRM. Both the “graft to” and “graft from” routes can be used. Sinha et al. [3] used this method for the preparation of pH-responsive flat sheet polysulfone ultrafiltration membranes. In this study, the copolymer poly(acrylic acid)-co-poly(ethylene glycol methyl ether methacrylate) (poly(AA-co-PEGMA)) was prepared by precipitation polymerization in toluene using AIBN as the chemical initiator. The reaction components were taken in a round-bottom three-neck flask having a condenser and an inlet and outlet for nitrogen gas. The reaction was carried out in an inert atmosphere in a boiling oil bath for ~2 h. On completion of the reaction, the reaction mixture was brought to room temperature by cooling and then vacuum filtered. Lastly, the final product was heat dried at 50°C for 4 days. The presence of pH-responsive groups in the copolymer was checked by using Fourier transform infrared spectroscopy (FTIR). Later, this pH-responsive copolymer was blended in the polysulfone membranes to impart pH responsiveness and tested for pH response with pH-based bovine serum albumin rejections.
Molecular-Imprinting-Based Sensors
Published in Banshi Dhar Gupta, Anand Mohan Shrivastav, Sruthi Prasood Usha, Optical Sensors for Biomedical Diagnostics and Environmental Monitoring, 2017
Banshi Dhar Gupta, Anand Mohan Shrivastav, Sruthi Prasood Usha
Polymerization initiators: Molecular imprinting is broadly performed by free radical polymerization, electropolymerization, and photopolymerization methods. The rate of free radical polymerization is strongly affected by the initiator properties (Lanza et al. 2001). 2-Azobisisobutyronitrile (AIBN) is the mostly used initiator for polymerization. This is because of thermal decomposition of AIBN which results in the formation of two isobutyronitrile radicals, which initiate the polymerization process. For free radical polymerization, mostly azo-group compounds are used as the initiators. Figure 6.2 shows the few initiators used for the synthesis of the polymerization. The removal of oxygen bubbles from prepolymerized solution is also important before starting the polymerization process because the presence of oxygen molecules may lead to the instability of the final product. The oxygen removal is usually performed by keeping the prepolymerization complex in an inert gas atmosphere such as nitrogen or argon.
Considerations for Development and Manufacture
Published in Richard J. LaPorte, Hydrophilic Polymer Coatings for Medical Devices, 2017
Other components added to the formulation, which do not constitute a significant fraction of the gel structure or the carrier volume, will be viewed as additives. Granted, this definition is rather nebulous, but it is suggested as a means of isolating a diverse group of components that contributes some unique function or property to the final hydrogel coating. Additives in hydrogel coatings are not used as fillers or extenders, because cost is usually not a major consideration in designing a formulation. Rather, their function is to initiate or catalyze matrix formation, provide a therapeutic function, stabilize solution or dispersion formulations, or impart antithrombogenicity or biocompatibility to the coated devices. Examples of initiators include AIBN or peroxides (e.g., hydrogen peroxide and benzoyl peroxide). Conventional catalysts (e.g., organotin catalysts) are not employed because of their toxic nature. Enzyme catalysis has been reported, although these systems do not seem to have met with commercial success as yet [12]. Therapeutic agents can include a range of bioactive molecules, such as proteins, enzymes, and a variety of drugs, whereas biostats used to promote biocompatibility include heparin, as well as other proprietary materials. The list of additives is conceivably unlimited as hydrogel technology continues to expand.
Using Digital Microfluidics to Dispense, Combine, and Transport Low-Surface-Energy Fluids
Published in Fusion Science and Technology, 2018
B. P. Chock, D. R. Harding, T. B. Jones
Polystyrene shells that are made using the digital microfluidic process must use water-in-oil-in-water (W/O/W) emulsions with styrene as the oil phase. A fluid (e.g., butanol or higher-order alcohols) that is miscible with styrene, but has limited solubility in water, is added to styrene to raise the dielectric constant and change the density so it matches that of the inner and outer water phases. Similarly, a fluid (e.g., acetonitrile) that is miscible with water but has limited solubility in styrene is added to water to match the density of the styrene/alcohol mixture. Many possible solvent combinations exist; however, this is a constrained problem because the fluids must have the right combination of dielectric constants, densities, solubilities, and surface energies. Finally, an initiator (e.g., AIBN) is needed in the oil phase to initiate the free-radical polymerization process.13,14
A green and facile method to fabricate superhydrophobic coatings
Published in Surface Engineering, 2019
Yanfen Huang, Zaosheng Lv, Zhe Cao, Chi Huang
Dodecafluoroheptyl methacrylate (DFMA) was purchased from the Xuejia Company of Harbin in China and was used as received. Butyl acrylate (BA), methyl methacrylate (MMA) and acrylic acid (AA) were obtained from Shanghai Chemical Reagents Company and used after distillation under reduced pressure to eliminate inhibitors. Azobisisobutyronitrile (AIBN) (analytic grade) was recrystallised from methanol and used as initiator. Ethanol was purchased from Shanghai Chemical Reagents Company and used as received. TiO2 nanoparticles (P25) were purchased from Germany AEROXIDE Company.