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Isopropyl Acrylamide (isopropyl + acrylamide)
Selected AbstractsGlucose-Responsive Bioinorganic Nanohybrid Membrane for Self-Regulated Insulin ReleaseADVANCED FUNCTIONAL MATERIALS, Issue 9 2010Claudia R. Gordijo Abstract A bioinorganic nanohybrid glucose-responsive membrane is developed for self-regulated insulin delivery analogous to a healthy human pancreas. The application of MnO2 nanoparticles as a multifunctional component in a glucose-responsive, protein-based membrane with embedded pH-responsive hydrogel nanoparticles is proposed. The bio-nanohybrid membrane is prepared by crosslinking bovine serum albumin (BSA),MnO2 nanoparticle conjugates with glucose oxidase and catalase in the presence of poly(N -isopropyl acrylamide- co -methacrylic acid) nanoparticles. The preparation and performance of this new nanocomposite material for a glucose-responsive insulin release system is presented. The activity and stability of immobilized glucose oxidase and the morphology and mechanical properties of the membrane are investigated. The enzymatic activity is well preserved in the membranes. The use of MnO2 nanoparticles not only reinforces the mechanical strength and the porous structure of the BSA-based membrane, but enhances the long-term stability of the enzymes. The in vitro release of insulin across the membrane is modulated by changes in glucose concentration mimicking possible fluctuations of blood-glucose level in diabetic patients. A four-fold increase in insulin permeation is observed when the glucose concentration is increased from normal to hyperglycemic levels, which returns to the baseline level when the glucose concentration is reduced to a normal level. [source] Thermo-Switchable Charge Transport and Electrocatalysis Using Metal-Ion-Modified pNIPAM-Functionalized ElectrodesADVANCED FUNCTIONAL MATERIALS, Issue 15 2009Michael Riskin Abstract Metal ions (Ag+, Cu2+, Hg2+) are incorporated into an electropolymerized, poly(N -isopropyl acrylamide), pNIPAM, thermosensitive polymer associated with an electrode using the "breathing-in" method. The ion-functionalized pNIPAM matrices reveal ion-dependent gel-to-solid phase-transition temperatures (28,±,1,°C, 25,±,1,°C, 40,±,1,°C for the Ag+, Cu2+, and Hg2+ -modified pNIPAM, respectively). Furthermore, the ion-functionalized polymers exhibit quasi-reversible redox properties, and the ions are reduced to the respective Ag0, Cu0, and Hg0 nanocluster-modified polymers. The metal-nanocluster-functionalized pNIPAM matrices enhance the electron transfer (they exhibit lower electron-transfer resistances) in the compacted states. The electron-transfer resistances of the metal-nanocluster-modified pNIPAM can be cycled between low and high values by temperature-induced switching of the polymer between its contracted solid and expanded gel states, respectively. The enhanced electron-transfer properties of the metal nanocluster-functionalized polymer are attributed to the contacting of the metal nanoclusters in the contracted state of the polymers. This temperature-switchable electron transfer across a Ag0 -modified pNIPAM was implemented to design a thermo-switchable electrocatalytic process (the temperature-switchable electrocatalyzed reduction of H2O2 by Ag0 -pNIPAM). [source] Control of Molecular Transport Through Stimuli-Responsive Ordered Mesoporous Materials,ADVANCED MATERIALS, Issue 15 2003Q. Fu External and reversible control of the size and surface energy of the pores in mesoporous architectures has been achieved. The method involves modification of mesoporous silica by atom transfer radical polymerization of N -isopropyl acrylamide (the precursor to a stimuli- responsive polymer). The resulting polymer-grafted particles allow the adsorption and transport of molecular species to be dynamically controlled as illustrated in the Figure for the release of rhodamine 6G from the particles at 50,°C. [source] Pectin and acrylamide based hydrogels for environment management technologies: Synthesis, characterization, and metal ions sorptionJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2007Ghanshyam S. Chauhan Abstract The present article describes various aspects of preparation and characterization of hydrogels based on pectin and three different amide monomers viz: acrylamide (AAm), N -isopropyl acrylamide (N -i-PAAm), and 2-acrylamido-2-methyl-1-propane sulfonic acid (AAmPSA). Hydrogels have been prepared by graft copolymerization as well as in the presence of crosslinker N,N -Methylene bisacrylamide ((N,N -MBAAm) and initiated by redox system comprising of ammonium peroxysulphate,ferrous ammonium sulfate (APS: FAS) at two temperatures. Hydrogels thus synthesized have been characterized by SEM, FTIR, and water uptake studies. The later has been carried as a function of time, temperature, pH, crosslinker concentration, and temperature at which the hydrogels were prepared. Candidate hydrogels have been used for the sorption of some common metal ions pollutants found in soil, industrial, and mining water bodies. Biodegradability studies have been carried by soil burial method to investigate the effect of chemical modification on biodegradability of pectin and to understand the possibility of eco-friendly nature and to explore the scope of reusability of the hydrogels and waste minimization. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source] Effect of molecular weight of poly(N -isopropyl acrylamide) temperature-sensitive flocculants on dewateringAICHE JOURNAL, Issue 8 2009Haihong Li Abstract The influence of molecular weight (MW) and dose of Poly(N-isopropyl acrylamide) (PNIPAM) (temperature-sensitive flocculant) on sedimentation rate, sediment density, and supernatant clarity of silica suspensions was investigated. The addition of PNIPAM resulted in rapid sedimentation (T > critical solution temperature, CST) and low sediment moisture (T < CST). Higher MW polymers resulted in more effective flocculation and sediment consolidation. At 10 ppm, PNIPAM (3.6 million Da) produced 20 m/h settling rate and 48 vol % solids sediment density, whereas 0.23 million Da polymer produced 0.1 m/h settling rate. PNIPAM produces effective flocculation and consolidation by cycling the interparticle interactions between repulsion and attraction as temperature is cycled around the CST. The change in temperature produces a hydrophilic/hydrophobic transition of the polymer, influencing adsorption onto the surface and the inter-particle forces. Conventional polyacrylamide flocculants (not influenced by temperature), cannot be used to produce both rapid sedimentation and dense sediments. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Synthesis of oily core-hybrid shell nanocapsules through interfacial free radical copolymerization in miniemulsion: Droplet formation and nucleationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 3 2010Z. H. Cao Abstract Nanocapsules with an oily core and an organic/inorganic hybrid shell were elaborated by miniemulsion (co)polymerization of styrene, divinylbenzene, ,-methacryloyloxy propyl trimethoxysilane, and N -isopropyl acrylamide. The hybrid copolymer shell membrane was formed by polymerization-induced phase separation at the interface of the oily nanodroplets with water. It was shown that the size, size distribution, and colloidal stability of the miniemulsion droplets were extremely dependent on the nature of the oil phase, the monomer content and the surfactant concentration. The less water-soluble the hydrocarbon template and the higher the monomer content, the better the droplet stability. The successful formation of nanocapsules with the targeted core-shell morphology (i.e., a liquid core surrounded by a solid shell) was evidenced by cryogenic transmission electron microscopy. Both nanocapsules and nanoparticles were produced by polymerization of the miniemulsion droplets. The proportion of nanoparticles increased with increasing monomer concentration in the oil phase. These undesirable nanoparticles were presumably formed by homogeneous nucleation as we showed that micellar nucleation could be neglected under our experimental conditions even for high surfactant concentrations. The introduction of ,-methacryloyloxy propyl trimethoxysilane was considered to be the main reason for homogeneous nucleation. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 593,603, 2010 [source] Macromolecular brushes synthesized by "grafting from" approach based on "click chemistry" and RAFT polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2010Dongxia Wu Abstract Well-defined macromolecular brushes with poly(N -isopropyl acrylamide) (PNIPAM) side chains on random copolymer backbones were synthesized by "grafting from" approach based on click chemistry and reversible addition-fragmentation chain transfer (RAFT) polymerization. To prepare macromolecular brushes, two linear random copolymers of 2-(trimethylsilyloxy)ethyl methacrylate (HEMA-TMS) and methyl methacrylate (MMA) (poly(MMA- co -HEMA-TMS)) were synthesized by atom transfer radical polymerization and were subsequently derivated to azide-containing polymers. Novel alkyne-terminated RAFT chain transfer agent (CTA) was grafted to polymer backbones by copper-catalyzed 1,3-dipolar cycloaddition (azide-alkyne click chemistry), and macro-RAFT CTAs were obtained. PNIPAM side chains were prepared by RAFT polymerization. The macromolecular brushes have well-defined structures, controlled molecular weights, and molecular weight distributions (Mw/Mn , 1.23). The RAFT polymerization of NIPAM exhibited pseudo-first-order kinetics and a linear molecular weight dependence on monomer conversion, and no detectable termination was observed in the polymerization. The macromolecular brushes can self-assemble into micelles in aqueous solution. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 443,453, 2010 [source] Synthesis and characterization of synthetic polymer colloids colloidally stabilized by cationized starch oligomersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 7 2009Marianne Gaborieau Abstract A method is developed for anchoring enzymatically degraded cationized starch as electrosteric stabilizers onto synthetic latices, using cerium(IV) to create free-radical grafting sites on the starch. Direct anchoring of debranched starch onto a poly(methyl methacrylate) seed latex yields a latex stabilized by well-defined oligosaccharides. Using ,-amylase to randomly cleave starch to form (1,4)-,-glucans, and a comonomer, N -isopropyl acrylamide (NIPAM), whose corresponding polymer exhibits a lower critical solution temperature (LCST), creates a means to synthesize block (or graft) oligomers of oligosaccharide and synthetic polymer, which are water soluble at room temperature. Above 30 °C, they become amphiphilic and form self-emulsifying nanoparticles (sometimes termed "frozen micelles") from which a synthetic latex is grown after addition of methyl methacrylate, the collapsed NIPAM-containing entities functioning as a type of in situ seed. This synthesis of stable synthetic latex particles is shown to have a high grafting efficiency. The starch fragments were characterized by 1H solution-state NMR before grafting, and 13C solid-state cross-polarization magic-angle spinning (CP-MAS) NMR was used to characterize the starch oligomers actually grafted on the final latex. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1836,1852, 2009 [source] Stability and utility of pyridyl disulfide functionality in RAFT and conventional radical polymerizationsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2008Cyrille Boyer Abstract Two RAFT agents, suitable for inducing living radical polymerization in water, have been synthesized. Both RAFT agents were shown to be effective over the temperature range 25,70 °C. One RAFT agent was functionalized with a pyridyl disulfide group. RAFT efficacy was demonstrated for the polymerizations of N -isopropyl acrylamide (NIPAAM) and poly(ethylene oxide)-acrylate (PEG-A) in both water and acetonitrile. The kinetic data indicates that the pyridyl disulfide functionality is largely benign in free radical polymerizations, remaining intact for subsequent reaction with thiol groups. This result was confirmed by studying conventional radical polymerizations in the presence of hydroxyethyl pyridyl disulfide. The utility of the pyridyl disulfide functionality at the terminus of the polymers was demonstrated by synthesizing polymer-BSA conjugates. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7207,7224, 2008 [source] Thermo-Responsive Hydrogels with Nanodomains: Rapid Shrinking of a Nanogel-Crosslinking Hydrogel of Poly(N -isopropyl acrylamide)MACROMOLECULAR RAPID COMMUNICATIONS, Issue 8 2008Nobuyuki Morimoto Abstract Rapidly shrinking poly(N -isopropyl acrylamide) (PNIPAM) hydrogels are prepared by crosslinking with self-assembled nanogels that consist of cholesteryl- and methacryloyl-substituted pullulan (CHPMA). The CHPMA nanogel (Rh,=,26.4 nm) was used as a crosslinker for a hydrophilic nanodomain. Transmission electron microscopy images of the nanogel-crosslinked PNIPAM hydrogel reveal a well-defined nanoporous structure. The nanogel-crosslinked PNIPAM hydrogel shows rapid shrinking based on its structure. The shrinking half-time was ,2 min, which is about 3,400 times faster than that of a PNIPAM hydrogel crosslinked by methylene(bisacrylamide). [source] | ||||||||||||||||||||||