Poly-A-isopropylacrylamide PNIPAM

Functional biomaterial surfaces have been created to change between being hydrophobic and hydrophilic, in response to external signals, such as differences in temperature, solvent environment, light, or electrical current. Temperature-sensitive poly(A/-isopropylacrylamide) (PNIPAm)-coated substrate is hydrophobic at a cell culture temperature of 37°C that favors cell adhesion and becomes hydrophilic at a lower temperature of 20°C, causing the detachment of cell sheets. These reversible responsive surfaces have been used to culture and harvest layers of endothelial, epithelial, lung, liver, cardiac, and kidney cells, and could eventually enable assembly of complex tissues and organs. 

Hydroalkoxylation of alkynes, or the addition of alcohol to alkynes, is a fundamental reaction in organic chemistry that allows the preparation of enol ethers and a variety of oxygen-containing heterocycles such as furan, pyran, and benzofuran derivatives. Bergbreiter et al. found that a Mnear poly-(A-isopropylacrylamide) (PNIPAM) polymer exhibited inverse temperature solubility in water (i.e., soluble in cold water but insoluble in hot water). A recoverable homogeneous palladium catalyst was prepared based on the polymer. The PNIPAM-bound Pd(0) catalyst was effective for the reaction of 2-iodophenol with phenylacetylene in aqueous THE media to give the target product... 

Plasmid analysis is often used in recombinant DNA technology. Anew separation matrix, consisting of poly(A-isopropylacrylamide) (PNIPAM) polymer and mannitol as small molecule additive, was used for CE-based plasmid DNA separation. Supercoiled, linear, and nicked conformers of lambda plasmid were separated in 1% PNIPAM + 6% mannitol. The effect of the applied mannitol concentration on the separation quality is shown in Figure 6.6 [117]. 

By polymerizing poly(A -isopropylacrylamide) (PNIPAM) [55] or poly (2-(diethylamino)ethyl methacrylate) (PDEAEMA) [56] as a stimuli responsive polymer/hydrogel layer around a colored nanoparticle of PS-co-PMMA, the local refractive index and consequently the color intensity of the latex could be switched by the temperature [55] or pH [56]. 

The idea of thermomorphic catalysts, which is largely similar to the concept of catalysts with modified poly(ethylene oxide)s, was implemented by the example of modified poly(A -isopropylacrylamides) (PNIPAMs). At low temperatures, PNIPAMs can dissolve in water and at high temperatures, in two-phase systems, PNIPAMs pass into the organic phase, and also retain partly in water (Fig. 11-4). The upper critical solution temperature depends on substituents at the amide group [83, 91-93]. Several macromolecular metal complexes with PNIPAM ligands have been designed. 

Recently, Liu s group also reported the fabrication of thermoresponsive cross-linked hollow poly(A-isopropylacrylamide) (PNIPAM) nanocapsules with controlled shell thickness via the combination of surface-initiated atom transfer radical polymerization (ATRP) and click cross-linking. Cross-linked PNIPAM nanocapsules were fabricated by the click cross-linking of PNIPAM shell layer with a tri-functional molecule, l,l,l-fm(4-(2-propynyloxy) phenyl)ethane. Due to the thermo-responsiveness of PNIPAM, cross-linked PNIPAM nanocapsules exhibit thermo-induced collapse/swelling transitions that make it possible to classify them as nanogels. 

Our work employs electrochemically initiated polymerization (EIP) which is an easy and flexible method to produce surface coatings of various kinds. The technique makes use of the decomposition of an electro-active initiator at an electrode to start a free-radical polymerization. The polymer is formed directly at the electrode surface. As a consequence, the films adhere tightly to the surface. Adhesion is based on physisorption of the hydrogel to the metal. Note in this context that EIP is different from electrografting of conductive polymers. In EIP, the initiator is the electro-active species, rather than the monomer. Recently, we reported on the formation of thermoresponsive poly-A -isopropylacrylamide (pNIPAm) hydrogel coatings on gold surfaces based on this approach. ... 

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... 

Structures of poly(A/-isopropylacrylamide) (PNIPAM) and poly(A/-vinyl caprolactam) (PVCL). 

Soon after this report, Liu and coworkers [80] reported the successful synthesis of cyclic poly(A-isopropylacrylamide) (PNIPAM) by the same procedure. This method was also successful in preparation of cyclic block copolymers. 

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(A-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 proUne. Polypeptides composed of the pentapeptide repeat unit VPGXG possess a reversible lower critical solution temperature (LCST). Below the LCST, the peptide is soluble... 

Kobayashi M, Matsumoto Y, Uchiyama M, Ohwada T (2004) A new chemoselective anionic polymerization method for poly(A-isopropylacrylamide) (PNIPAm) in aqueous media design and application of bulky zincate possessing little basicity. Macromolecules 37 4339-4341. doi 10.1021/ma0400261... 

---