Phase transition in polymer gels induced by visible light

Suzuki, Atsushi; Tanaka, Toyoichi

doi:10.1038/346345a0

Cited by 968 publications

(678 citation statements)

References 12 publications

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“…Discontinuous volume phase transitions are phenomena found in some polymeric gels, which reversibly swell or shrink in volume by as much as several hundred times in response to changes in temperature, pH, ionic strength, electric or magnetic field, or light [1][2][3][4]. Phase transition of a polymeric gel is a result of a competitive balance between repulsive forces (the electrostatic interaction between the polymer charges of the same kind, which can be imposed upon a gel by introducing ionization into the network) that act to expand the polymer network, and attractive forces (van der Waals, hydrophobic interactions and hydrogen bonding) that act to shrink the network.…”

Section: Introductionmentioning

confidence: 99%

Transport of Ions and Electrostatic Interactions in Thermoresponsive Poly(N-Isopropylacrylamide-co-acrylic acid) Hydrogels: Electroanalytical Studies

Zhang

Ciszkowska

2001

J. Phys. Chem. B

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Poly(N-isopropylacrylacrylamide-co-acrylic acid) hydrogels, NIPA-AA, undergo discontinuous reversible volume phase transitions as a response to temperature increase. Those hydrogels are weakly negatively charged and, therefore, are expected to interact electrostatically with charged species dissolved in those systems. To study transport phenomena and electrostatic interactions in NIPA-AA hydrogels, electroanalytical experiments with two positively charged probes, (ferrocenylmethyl)trimethylammonium, FcTMA+, and hexaammineruthenium(III), Ru(NH3)6 3+, cations were performed, and the results compared with those for an uncharged electroactive probe, 1,1‘-ferrocenedimethanol, Fc(MeOH)2. Steady-state voltammetry and chronoamperometry at platinum disk microelectrodes were used to determine diffusion coefficients of those probes. For temperatures below the volume phase transition of a gel, there are not significant differences in the transport behavior of cationic and uncharged probes. After the volume phase transition occurs and the gel collapses, the diffusion coefficients of all probes decrease, the change in diffusion coefficient is more pronounced for cationic probes than for a neutral probe and depends on the charge of the cationic probe. In addition to changes of transport of cationic species in collapsed NIPA-AA hydrogels, changes in their concentration were detected as a result of the volume phase transition.

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Section: Introductionmentioning

confidence: 99%

Transport of Ions and Electrostatic Interactions in Thermoresponsive Poly(N-Isopropylacrylamide-co-acrylic acid) Hydrogels: Electroanalytical Studies

Zhang

Ciszkowska

2001

J. Phys. Chem. B

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“…1,2 Some hydrogels undergo changes in swelling or network structure in response to external stimuli such as pH, 3 temperature, 4,5 light, 6,7 ionic strength 3 and electric field. 8 The development of such materials has recently received considerable interest due to the potential applications in a vast range of areas.…”

Section: Introductionmentioning

confidence: 99%

Thermoresponsive Polymer Micropatterns Fabricated by Dip-Pen Nanolithography for a Highly Controllable Substrate with Potential Cellular Applications

Laing

Suriano²,

Lamprou

et al. 2016

ACS Appl. Mater. Interfaces

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We report a novel approach for patterning thermoresponsive hydrogels based on N,Ndiethylacrylamide (DEAAm) and bifunctional Jeffamine ED-600 by dip-pen nanolithography (DPN). The direct writing of micron-sized thermoresponsive polymer spots was achieved with efficient control over feature size. A Jeffamine-based ink prepared through the combination of organic polymers, such as DEAAm, in an inorganic silica network was used to print thermosensitive arrays on a thiol-silanised silicon oxide substrate. The use of a Jeffamine hydrogel, acting as a carrier matrix, allowed a reduction in the evaporation of ink molecules with high volatility, such as DEAAm, and facilitated the transfer of ink from tip to substrate. The thermoresponsive behaviour of polymer arrays which swell/de-swell in aqueous solution in response to a change in temperature was successfully characterised by atomic force microscopy (AFM) and Raman spectroscopy: a thermally-induced change in height and hydration state was observed, respectively. Finally, we demonstrate that cells can adhere to and interact with these dynamic features and exhibit a change in behaviour when cultured on the substrates above and below the transition temperature of the Jeffamine/DEAAm thermoresponsive hydrogels. This 3 demonstrates the potential of these micropatterned hydrogels to act as a controllable surface for cell growth.

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“…Triggers other than solvent composition, such as temperature, light (14), and magnetic field (15), can, in principle, be used by properly designing the gel composition.…”

Section: Discussionmentioning

confidence: 99%

Gel catalysts that switch on and off

Wang

Kuroda

Enoki

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

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We report development of a polymer gel with a catalytic activity that can be switched on and off when the solvent composition is changed. The gel consists of two species of monomers. The major component, N-isopropylacrylamide, makes the gel swell and shrink in response to a change in composition of ethanol͞water mixtures. The minor component, vinylimidazole, which is capable of catalysis, is copolymerized into the gel network. The reaction rate for catalytic hydrolysis of p-nitrophenyl caprylate was small when the gel was swollen. In contrast, when the gel was shrunken, the reaction rate increased 5 times. The activity changes discontinuously as a function of solvent composition, thus the catalysis can be switched on and off by an infinitesimal change in solvent composition. The kinetics of catalysis by the gel in the shrunken state is well described by the Michaelis-Menten formula, indicating that the absorption of the substrate by the hydrophobic environment created by the N-isopropylacrylamide polymer in the shrunken gel is responsible for enhancement of catalytic activity. In the swollen state, the rate vs. active site concentration is linear, indicating that the substrate absorption is not a primary factor determining the kinetics. Catalytic activity of the gel is studied for substrates with various alkyl chain lengths; of those studied the switching effect is most pronounced for p-nitrophenyl caprylate.N atural enzymes catalyze chemical reactions, and equally importantly, regulate them by reversibly and repeatedly switching on and off the catalytic activities. To mimic this special feature of enzymes, we designed a polymer gel consisting of two species of monomers, each having a specific role. The major component allows the gel to reversibly swell and shrink in response to changes in environmental parameters such as temperature and solvent (1-9). On swelling and shrinking, the local density of the hydrophobic moiety changes and the affinity to substrate molecules is altered accordingly. The minor component capable of catalysis of substrate decomposition is copolymerized with the responsive monomers into the gel network. The catalytic activity of the gel is expected to be switched on and off as the substrate is reversibly bound and released during the cycle of gel swelling and shrinking. Materials and MethodsTo demonstrate the feasibility of the idea, we chose hydrolysis of p-nitrophenyl esters with different alkyl chain lengths as the chemical reaction to examine (Fig. 1a). This reaction is known to be catalyzed by 4(5)-vinylimidazole (10). We, therefore, used it as the minor catalytic monomer component of the gel (Fig. 1b). As the major component, we chose the widely used hydrophobic monomer N-isopropylacrylamide (NIPA). The substrate and gel monomer components were selected because (i) the substrate and one of the hydrolysis products, p-nitrophenol, were easily detected by using UV spectroscopy; (ii) the NIPA gel underwent a discontinuous swelling͞shrinking transition in response to changes in environmen...

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Phase transition in polymer gels induced by visible light

Cited by 968 publications

References 12 publications

Transport of Ions and Electrostatic Interactions in Thermoresponsive Poly(N-Isopropylacrylamide-co-acrylic acid) Hydrogels: Electroanalytical Studies

Transport of Ions and Electrostatic Interactions in Thermoresponsive Poly(N-Isopropylacrylamide-co-acrylic acid) Hydrogels: Electroanalytical Studies

Thermoresponsive Polymer Micropatterns Fabricated by Dip-Pen Nanolithography for a Highly Controllable Substrate with Potential Cellular Applications

Gel catalysts that switch on and off

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