Dual responsive coatings

During the period of 1962 to 1964 we made significant improvements in the technology. Thanks to Yembrick s work, coatings achieved a high level of stability. Bob Cohen s work had resulted in the replacement of o-Cl-HABI with the preferred biimidazole, CDM-HABI, with a spectrum that maximized the imaging and deactivation peaks of the dual response spectrum (structures depicted in Scheme 4.8). 

V. Sundaresan, J.U. Menon, M. Rahimi, K.T. Nguyen, and A.S. Wadajkar, Dual-responsive polymer-coated iron oxide nanoparticles for drug delivery and imaging applications. Inter. J. Pharm., 466 (1-2), 1-7,2014. 

Magnetic and pH dual responsive system consisting of Fe304 Si02 nanoparticles coated with mPEG-poly[L-Asparagine]... 

A dual SAW delay line oscillator is illustrated in Figure 3. It consists of two SAW delay lines fabricated on the same ST-quartz substrate. One delay line is coated with the chemically sensitive film and the other is left uncoated. The frequencies of the two delay line oscillators are mixed and filtered to provide a frequency equal to the difference of the two oscillator frequencies. This scheme has several advantages when used in chemical vapor sensor applications. First, it helps to compensate for SAW frequency drift caused by ambient temperature and pressure fluctuations. Additionally, the difference frequency is much lower than the frequency of the oscillators themselves. This permits SAW vapor response measurements using inexpensive digital circuitry. 

Due to the relative ease of control, temperature is one of the most widely used external stimuli for the synthesis of stimulus-responsive bmshes. In this case, thermoresponsive polymer bmshes from poly(N-isopropylacrylamide) (PNIPAM) are the most intensively studied responsive bmshes that display a lower critical solution temperature (LOST) in a suitable solvent. Below the critical point, the polymer chains interact preferentially with the solvent and adopt a swollen, extended conformation. Above the critical point, the polymer chains collapse as they become more solvophobic. Jayachandran et reported the synthesis of PNIPAM homopolymer and block copolymer brushes on the surface of latex particles by aqueous ATRP. Urey demonstrated that PNIPAM brushes were sensitive to temperature and salt concentration. Zhu et synthesized Au-NPs stabilized with thiol-terminated PNIPAM via the grafting to approach. These thermosensitive Au-NPs exhibit a sharp, reversible, dear opaque transition in solution between 25 and 30 °C. Shan et al. prepared PNIPAM-coated Au-NPs using both grafting to and graft from approaches. Lv et al. prepared dual-sensitive polymer by reversible addition-fragmentation chain transfer (RAFT) polymerization of N-isopropylacrylamide from trithiocarbonate groups linked to dextran and sucdnoylation of dextran after polymerization. Such dextran-based dual-sensitive polymer is employed to endow Au-NPs with stability and pH and temperature sensitivity. 

As mentioned above, two-component flocculants often present advantages over a single-component flocculant, such as better control of flocculation kinetics and improved floe strength. Most dual-component flocculants consist of two polyelectrolytes, two pol5miers, or a polyelectrolyte and a nanocolloid. Usually, one of the components adsorbs on the surface of the particles to be flocculated and the second component bridges these polymer-coated particles. Therefore, this combination of patching and bridging is believed to be responsible for excellent results, as described for instance for retention systems (Fig. 5) [10]. 

J. Shi, N.M. Alves, and J.E Mano, Chitosan coated alginate beads containing poly (N-iso-propylacrylamide) for dual-stimuli-responsive drug release. Journal of Biomedical Materials Research Part B Applied Biomaterials, 84 (2), 595-603,2008. 

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