Behavior of PNIPAM Microgels in Different Organic Solvents

Komarova, Galina A.; Kozhunova, Elena Yu.

doi:10.3390/molecules27238549

Cited by 6 publications

(1 citation statement)

References 55 publications

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“…Moreover, using functionalized acrylamides as monomers, it is possible to produce hydrophilic [ 3 ], or hydrophobic gels [ 4 ], thermosensitive (“smart”) materials [ 5 ], polyelectrolytes bearing positive [ 6 ] or negative charges [ 7 ], etc. The hydrophilic gels swell strongly (>20.000%) in water [ 8 ], and the more hydrophobic polymers also swell in nonaqueous solvents [ 9 ]. Similar to other synthetic hydrogels, their large water retention capacity makes them useful in drug release [ 10 ], water absorption [ 11 ] and decontamination [ 12 ], sensors [ 13 ], actuators [ 14 ], etc.…”

Section: Introductionmentioning

confidence: 99%

Functional Materials Made by Combining Hydrogels (Cross-Linked Polyacrylamides) and Conducting Polymers (Polyanilines)—A Critical Review

Barbero

2023

Polymers

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Hydrogels made of cross-linked polyacrlyamides (cPAM) and conducting materials made of polyanilines (PANIs) are both the most widely used materials in each category. This is due to their accessible monomers, easy synthesis and excellent properties. Therefore, the combination of these materials produces composites which show enhanced properties and also synergy between the cPAM properties (e.g., elasticity) and those of PANIs (e.g., conductivity). The most common way to produce the composites is to form the gel by radical polymerization (usually by redox initiators) then incorporate the PANIs into the network by oxidative polymerization of anilines. It is often claimed that the product is a semi-interpenetrated network (s-IPN) made of linear PANIs penetrating the cPAM network. However, there is evidence that the nanopores of the hydrogel become filled with PANIs nanoparticles, producing a composite. On the other hand, swelling the cPAM in true solutions of PANIs macromolecules renders s-IPN with different properties. Technological applications of the composites have been developed, such as photothermal (PTA)/electromechanical actuators, supercapacitors, movement/pressure sensors, etc. PTA devices rely on the absorption of electromagnetic radiation (light, microwaves, radiofrequency) by PANIs, which heats up the composite, triggering the phase transition of a thermosensitive cPAM. Therefore, the synergy of properties of both polymers is beneficial.

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Section: Introductionmentioning

confidence: 99%

Functional Materials Made by Combining Hydrogels (Cross-Linked Polyacrylamides) and Conducting Polymers (Polyanilines)—A Critical Review

Barbero

2023

Polymers

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Exploring pNIPAM lyogels: Experimental study on swelling equilibria in various organic solvents and mixtures, supported by COSMO-RS analysis

Eckert,

Müller,

Luinstra

et al. 2024

Fluid Phase Equilibria

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Effect of particle stiffness on microgel self-assembly and suspension phase behavior over a broad temperature range

Misra,

Kawale,

Behera

et al. 2024

Physics of Fluids

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We synthesized thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) colloidal microgel particles of different stiffnesses by controlling the concentration of a polar crosslinker in a precipitation polymerization synthesis method. When suspended in an aqueous medium, the particles collapsed by expelling water as the temperature was raised toward the volume phase transition temperature (VPTT) of ≈ 34 °C. We noted that the sizes of the stiffer particles, synthesized with higher crosslinker concentration, collapsed less abruptly. Using Fourier transform infrared spectroscopy, we observed enhanced particle dehydration with increasing temperature and decreasing particle stiffness. Oscillatory rheology experiments on dense aqueous PNIPAM suspensions, prepared at a fixed particle effective volume fraction ϕeff = 1.5 at 25°C, revealed that suspensions constituted by the stiffest particles are the most elastic over a broad temperature range. Above the VPTT, suspensions of particles of intermediate stiffnesses exhibited two-step yielding, a typical signature of fragile gel formation. Zeta potential measurements showed that PNIPAM particles of lower stiffnesses are rendered electrostatically unstable in aqueous suspension. Combining cryogenic scanning electron microscopy and rheology, we noted a glass–glass transition when the temperature of a dense suspension of stiff PNIPAM particles was raised across the VPTT. In contrast, suspensions of particles of the lowest stiffnesses showed a gel-viscoelastic liquid–gel transition during an identical temperature ramp experiment. Our study reveals that temperature-induced phase transformations in dense PNIPAM suspensions depend sensitively on the stiffness of the constituent particles and can be explained by considering amphiphilicity-driven morphological changes in the suspension microstructures.

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Behavior of PNIPAM Microgels in Different Organic Solvents

Cited by 6 publications

References 55 publications

Functional Materials Made by Combining Hydrogels (Cross-Linked Polyacrylamides) and Conducting Polymers (Polyanilines)—A Critical Review

Functional Materials Made by Combining Hydrogels (Cross-Linked Polyacrylamides) and Conducting Polymers (Polyanilines)—A Critical Review

Exploring pNIPAM lyogels: Experimental study on swelling equilibria in various organic solvents and mixtures, supported by COSMO-RS analysis

Effect of particle stiffness on microgel self-assembly and suspension phase behavior over a broad temperature range

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