N-isopropyl acrylamide

Uenoyama, S and Hoffman AS. Synthesis and characterization of acrylamide-N-isopropyl acrylamide copolymer grafts on silicone rubber substrates. Radiat. Phys. Chem., 1988, 32, 605-608. 

Polydiallyldimethylammonium Chloride-co-N-Isopropyl Acrylamide 1.0-5.0 Synthesized by R. Pelton, McMaster Univ. 

Polydiallydimethylammonium Chloride-co-N-Isopropyl Acrylamide Medium Permanent Medium Flexible Cyclic Side Chain Weak... 

Fig. 19. Turn-over frequencies for hydrogenation of allyl alcohol and N-isopropyl acrylamide obtained in water using dendrimer-encapsulated Pd nanoparticles of constant average size. The hydroxyl-terminated PAMAM dendrimer generation varies from G4 to G8...

An interesting family of polymeric ligands show inverse temperature dependence of solubihty in water, i.e. they can be precipitated from aqueous solutions by increasing the temperature above the so-called cloud point. Typically these ligands contain poly(oxyalkylene) chains, but the phenomenon can be similarly observed with poly(N-isopropyl acrylamide) derivatives (e.g. 132) and methylated cyclodextrins, too. At or above their cloud points these compounds fall off the solution, due to the break-up and loss of the hydration shell which prevents aggregation and precipitation of their molecules. Conversely, upon cooling below this temperature (also called the lower critical solution temperature, LCST) these substances dissolve again. 

The hyperbranched hydrogen-bond grafts formed in these self assembly processes are stable to solvent extraction. This was shown by preparing fluo-rescently labeled poly(N-isopropyl acrylamide) 11 and poly(acryhc acid) 12. 

Hydrogels synthesized from polymers and copolymers of N-isopropyl acrylamide (NIPAAm) shrink or swell as the temperature is raised or lowered through their lower critical solution temperature (LCST). 

We report here on copolymer hydrogels of N-isopropyl acrylamide (NIPAAm) and acrylamide (AAm) which are crosslinked with mediylene-bis-acrylamide (MBAAm) and which contain the enzyme asparaginase immobilized within the gel. 

High polymers of N-isopropyl acrylamide (NIPAAM) exhibit a lower critical solution temperature (LCST) in phosphate buffered saline above 31 C precipitation occurs, with minimal concentration dependence. 

Figure 1. Lower critical solution temperatures of copolymers of N-isopropyl acrylamide with other N-alkyl acrylamides as a function of monomer input ratios.

Figure 2. Sephacryl S-400 Chromatogram of Acrylamide/N-isopropyl Acrylamide (10/90) Copolymer.

Figure 3. Turbidity versus Temperature Curves for poly-N-isopropyl acrylamide and its copolymers ...

Figure 4. Copolymerization plot for acrylamide and N-isopropyl acrylamide (NIPAAM).

Figure 5. Lower Critical Solution Temperatures of Copolymers of N-isopropyl Acrylamide and N-n- and N-t-butyl Acrylamide as a Function of Monomer Input Ratios.

Using N-isopropyl acrylamide and acrylamide or other N-substituted acrylamides it is possible to design copolymers that will precipitate at any desired temperature between 0 and 65 C. It is not surprising that acrylamide is the most effective comonomer in raising the LCST. 

AAM, acrylamide NMAAM, N-methyl acrylamide NEAAM, N-ethyl acrylamide NNBAAM, N-n-butyl acrylamide NTBAAM, N-t-butyl acrylamide NIPAAM, N-isopropyl acrylamide LCST, lower critical solution temperature TEMED, Tetramethylethylenediamine PBS, phosphate-buffered saline AIBN, 2,2 azobis(isobutyronitrile). 

Zhao et al (70) developed a method for the synthesis of dendrimer-encapsulated metal nanoparticles based on sorbing metal ions into (modified) PAMAM dendrimers followed by a reduction. Dendrimers encapsulating copper, palladium, and platinum nanoparticles have been prepared. Hydroxyl-terminated PAMAM dendrimers were used to prepare encapsulated palladium (PAMAM generations 4, 6, and 8) and platinum (PAMAM generations 4 and 6) nanoparticles. The dendrimer-encapsulated palladium and platinum nanocomposites catalyzed the hydrogenation reaction of allyl alcohol and N-isopropyl acrylamide in water 71). 

Many recent studies on polymer gels are related to volume phase transition phenomena of poly(acrylamide) PAAm gel [7] and poly(N-isopropyl acrylamide) PNIPAAm gel [8, 9]. The volume phase transition in gels was extensively studied by Tanaka and his coworkers [10, 11]. 

Fig. 6.2. Electrochromatographic separation of benzyl alcohol (1), resorcinol (2), methylparaben (3), and p-naphthol (4) using a soft gel column (Reprinted with permission from [27], Copyright 1998 Wiley-VCH). Conditions Column 48.5 cm (24 cm active) x 75 pm i.d., stationary phase 4.1% T, 9.7% C, 0.7% S poly(2-acrylamido-2-methyl-l-propanesulfonic acid-co-N-isopropyl acrylamide-co-methylene bisacrylamide) mobile phase 20 80 acetonitrile and 2.5 mol/L phosphate buffer pH 6.8 16 kV.

Information from a molecular probe experiment is usually presented in the form of a retention diagram, that is, a plot of log Vg against 1/T(K). A sample curve for a semi-crystalline polymer is shown in Figure 2. The slope reversals are indicative of phase transitions. Such transitions had been noted (28) as early as 1965 for polyethylene (PE) and polypropylene (PP), but the first comprehensive study of polymer structure using IGC was done in 1968 by Smidsrod and Guillet (1) on poly(N-isopropyl acrylamide) (poly-(NIPAM)). 

A similar approach was followed by Couet et al. [69] who fimctionahzed peptide Ghadiri rings on 3 sites with ATRP initiators, which were subsequently used for the polymerization of N-isopropyl acrylamide. These hybrid polymer peptide structures were capable of forming peptide nanotubes, which were homogeneously covered by the attached polymer. 

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