Polymer brushes stimuli-responsive surfaces

Chen, T., Ferris, R., Zhang, J., Ducker, R., Zauscher, S. Stimulus-responsive polymer brushes on surfaces transduction mechanisms and applications. Prog. Polym. Sci. 35, 94-112 (2010)... 

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. 

Lipid-bilayer membranes on solid substrates are often used as cell-surface models connecting biological and artificial materials. They can be placed either directly on solids or on ultrathin polymer supports, such as brushes or hydrogels, which mimic the extracellular matrix. A similar approach has been applied to polymer membranes with the advantage of tunable thickness, easier chemical modifications to allow stimulus responsiveness, or the attachment of active molecules by incorporation of reactive end groups. In addition, incorporated proteins have lower interactions with the support because of the increased membrane thickness, and therefore behave as in a natural environment. ... 

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. 

Stimulus-Responsive Polymer Brushes on Polymer Particles Surfaces and Applications... 

When stimuli-responsive polymers are attached to a surface, changes in the physicochemical properties of the surface layer that result from an external stimulus can be assessed by AFM in situ. Micropattemed thermoresponsive polymers, such as poly(A-isopropylacrylamide) (PNIPAm), were characterized via AFM height imaging and the brush adhesiveness measured by force spectroscopy during... 

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