Temperature-responsive atom-transfer radical

Thermally responsive polymers, such as poly( V-isopropyl acrylamide) (NI-PAm), have also been studied extensively for applications related to those previously discussed [112], De las Heras et al. described the synthesis and patterning of NIPAm brushes on SAMs and their subsequent performance during temperature-dependent adhesion assays of BSA and Streptococcus mutans (Fig. 7). The authors employed p.CP to pattern features of hydrophobic hexadecanethiol and backfilled the surface with an initiator-functionalized alkanethiol. Polymer brushes were grown via surface-initiated atom transfer radical polymerization (ATRP). FITC-BSA was then... 

Huang, J. Cusick, B. Pietrasik, J. Wang, L. Kowalewski, T. Lin, Q. Matyjaszewski, K. Synthesis and in situ atomic force microscopy characterization of temperature-responsive hydrogels based on poly(2-(dimethylamino)ethyl methacrylate) prepared by atom transfer radical polymerization. Langmuir 2007, 23 (1), 241-249. 

Lately, surface-initiated atom transfer radical polymerization (ATRP) has been used to obtain a surface-grafted membrane (Liu et al. 2010). A porous PTFE membrane was treated by the hydrogen plasma and the C-F groups of the modified surface became effective initiators of ATRP. PEG methacrylate or its copolymer with A-isopropylacrylamide was grafted in such a way and the modified membranes showed temperature-responsive and protein repulsion features (Liu et al. 2010). 

An early attempt on stimulus-responsive polymer-incorporated nanochannels was conducted by Yameen et al. The authors started with PI microfilms at the thickness of 12 pm/ The conical nanochannels were fabricated through the ion-etching technique as mentioned above. In the nanochannels, the PNIPAAm polymer brushes were produced via surface-initiated atom transfer radical polymerization. As PNIPAAm responds to thermal stimuli in the form of extension and retraction, the functionalized nanochannels can be opened/closed according to the environment temperature. 

Wohlfarth, C., Upper critical (UCST) and lower critical (LCST) solution temperatures of binary polvmer solutions, in CRC Handbook of Chemistry and Physics, Lide, D.R. (ed.), 87 ed., Taylor Francis, CRC Press, Boca Raton, 13-19,2006. Xia, Y., Burke, N.A.D., and Stoever, H.D.H., End group effect on the thermal response of narrow-disperse poly(V-isopropylaciylamide) prepared by atom transfer radical polymerization. Macromolecules, 39, 2275, 2006. 

This technology has been expanded to prepare intelligent nanocapsules with temperature-responsive cross-linked shells and pH-responsive brushes on their inner walls. These nanocapsules have been prepared by the surface-initiated atom transfer radical polymerization (SI-ATRP) technique with sihca NP as the sacrificial templates. The two-step, sequential SI-ATRP procedure provided the poly(tert-butyl acrylate) (PtBA) brushes on the inner walls of the temperature-responsive cross-linked poly(A-isopropylacryl-amide) (PNIPAA) shells. Then the ester groups in the nanocapsules were transformed chemically into carboxyl groups after etching the silica templates with HF (Mu and Liu, 2012). 

Mu, B. and Liu, P. (2012). Temperature and pH dual responsive crosslinked polymeric nanocapsules via surface-initiated atom transfer radical polymerization. Reactive and Functional Polymers, 72,983-989. 

Zhang et al. controlled the size of nanoparticles by exploiting the pH and temperature responsiveness ofa poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) brush [68]. Briefly, a PDMAEMA bmsh was synthesized onto a polystyrene latex nanoparticle via atom transfer radical polymerization (ATRP). Dynamic light-scattering events indicated that pH changes led to temperature changes in solution, which resulted in an alteration in particle size. This approach could be useful in enzyme immobilization or protein separation. 

Reactions (2b) and (3b) formally involve H-atom transfer reactions from the —OH and —CHO groups, respectively, to the peroxy group and fragmentation of the hydroperoxide so formed. This type of chemistry is common in reactions of alkyl radicals in hydrocarbon combustion, but at temperatures in the 700-800 K range (Walker and Morley, 1997) this chemistry is responsible for the phenomenon... 

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