Poly stimuli-responsive

Kaholek M, Lee W-K, LaMattina B, Caster KC, Zauscher S. Preparation and characterization of stimulus-responsive poly(n-isoptDpylacrylamide) bmshes and nanopattems. Polym Mater Sci Eng 2004a 90 226-227. 

In addition to the assessment of pore sizes and quality control, AFM provides direct access to the dynamic changes of smart pores, for instance pores that are equipped with a stimulus-responsive coating. Iwata et al. reported on the pH control of pore opening and closing of poly (acrylic acid) (PAA) -functionalized pores, as shown in Fig. 3.83. [174] The pores of two different membranes are closed, as seen by CM-AFM, at high pH due to the deprotonation of the PAA coating and concomitant expansion of the polymeric layer into the opening of the pore. 

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. 

A novel approach to immobilization of enzymes via covalent attachment is the use of stimulus-responsive smart polymers, which undergo dramatic conformational changes in response to small alterations in the environment, such as temperature, pH, and ionic strength [401 03], The most prominent example is a thermo-responsive and biocompatible polymer (poly-iV-isopropyl-acrylamide), which exhibits a critical solution temperature around 32°C, below which it readily dissolves in water, while it precipitates at elevated temperatures due to the expulsion of water molecules from its polymeric matrix. Hence, the biolransformation is performed under conditions, where the enzyme is soluble. Raising the temperature leads to precipitation of the immobilized protein, which allows its recovery and reuse. In addition, runaway reactions are avoided because in case the reaction temperature exceeds the critical solution temperature, the catalyst precipitates and the reaction shuts down. 

Vasani, R. B. Mclnnes, S. J. R Cole, M. A. Jani, A. M. M. Ellis, A. V. Voelcker, N. H. Stimulus-responsiveness and drag release from porons sUicon films ATRP-grafted with poly(iV-isopropylacrylamide). Langmuir 2011, 27, 7843-7853. 

Vasani RB, Mclnnes SJP, Cole MA, Jani AMM, EUis AV, Voelcker NH (2011) Stimulus-responsiveness and drug release from porous sihcon films ATRP-grafted with poly(-V-isopropylacrylamide). Langmuir 27 7843... 

Besides self-cleaning, the application of hydrogels can also be extended to other areas such as capture and regulation of oil drops underwater. The key question is to realize hydrogels with stimulus-responsive adhesion properties. Chen et al. reported that a poly(N-isopropylactylamide) (PNIPAAm) hydrogel exhibited a wettability and underwater oil adhesion switch... 

Y-shaped double-hydrophilic block copolymers, with a poly(EO-co-PO) sequence and two blocks of various hydrophilic methacryKc polymers, were synthesized by an elaborated ATRP technique by Armes and co-workers [239]. pH and thermal stimulus-responsive micelles could be obtained by these authors. 

Elastin-like polypeptides (ELPs) have been extensively studied due to the fact that they combine similar stimulus response properties to other artificial polymers such as poly(iV-isopropylacrylamide) (pNIPAM) with the advantages of a biologically derived material, that is, it is biocompatible, modular in its composition, and can be obtained by biological processes. ELPs are polypeptides that contain a short, repetitive peptide sequence, most commonly (VPGXG) that is derived from tropoelastin, the precursor of elastin. In this sequence, X represents any amino acid sequence except proline. Polypeptides composed of the pentapeptide repeat unit VPGXG possess a reversible lower critical solution temperature (LCST). Below the LCST, the peptide is soluble... 

Peter, M., R. G. H. Lammertink, M. A. Hempenius, and G. J. Vancso. 2005. Electrochemistry of surface-grafted stimulus-responsive monolayers of poly(ferrocenyldimethylsilane) on gold. 21 (H) 5115-5123. 

If the liposomes in question are treated with the polymer after their formation, the polymer binds only to the outer surface of the liposomes. If the liposomes are formed from a lipid-polymer mixture, on the other hand, the polymer is present on both sides of the liposome membrane. Such liposomes respond even faster to temperature changes. The change of the liposome surface properties caused by the phase transition of stimulus-responsive polymers in also known to affect their interaction with cells. The phenomenon has been used in an attempt to develop a targeted drug delivery system. Liposomes modified with a pH-sensitive polymer, namely succinylated poly(glycidol), were shown to deliver the dye cacein more efficiently into cultured monkey kidney cells than nonmodified liposomes. ... 

Poly(acrylamide) (PAAm) Permanent matrix for stimulus-responsive DD... 

Zou S, Hempenius MA, Schonherr H, Vancso GJ (2006) Force spectroscopy of individual stimulus-responsive poly(ferrocenyldimethylsilane) chains towards a redox-driven macro-molecular motor. Macromol Rapid Commun 27 103-108... 

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