Poly(<i>N</i>-isopropylacrylamide) at the Air/Water Interface

Ju, Zhang; Pelton, Robert

doi:10.1021/la950548x

Cited by 54 publications

(56 citation statements)

References 6 publications

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“…The preparation and characterization of PNIPAM homopolymer (L-6B) was reported previously. 19 NI-PAM (Kodak Co.) was recrystallized twice from toluene/hexane. AM (Aldrich) and initiator ammonium persulfate (Aldrich) were used as received.…”

Section: Experimental Preparation Of the Polymersmentioning

confidence: 99%

“…24 The composition of the copolymers were determined through integration of the methyl proton peak area (A), the methylene proton peak area (B), and the methyne proton peak area (C). The NIPAM mole fraction in a copolymer was 0.5A/ BϩC and the AM content was (1 Ϫ 0.5A/B ϩ C) The copolymer compositions are summarized in Table I.…”

Section: H-nmr Composition Analysismentioning

confidence: 99%

“…In previous work we have reported the dynamic surface tension behavior of aqueous PNI-PAM homopolymers 19,20 as a function of molecular weight and temperature. Interestingly, the equilibrium surface tension did not show a discontinuity at the LCST when plotted as a function of temperature, 19 suggesting that polymer adsorbed at the air/water interface did not undergo a phase transition.…”

Section: Introductionmentioning

confidence: 99%

“…Interestingly, the equilibrium surface tension did not show a discontinuity at the LCST when plotted as a function of temperature, 19 suggesting that polymer adsorbed at the air/water interface did not undergo a phase transition. Another interesting feature was that when a new interface was formed at a temperature above the LCST the resulting surface tension was low.…”

Section: Introductionmentioning

confidence: 99%

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The surface tension of aqueous poly(N-isopropylacrylamide-co-acrylamide)

Pelton

1999

J. Polym. Sci. A Polym. Chem.

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Section: Experimental Preparation Of the Polymersmentioning

confidence: 99%

Section: H-nmr Composition Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The surface tension of aqueous poly(N-isopropylacrylamide-co-acrylamide)

Pelton

1999

J. Polym. Sci. A Polym. Chem.

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“…34 It is well documented that both PNIPAM chains 35 and microgels 28 spontaneously adsorb onto oil-water interfaces because of the amphiphilicity of PNIPAM, which includes both hydrophobic isopropyl and hydrophilic amide groups. 36 For S/N 8 particles, also at 10 -3 g/mL, the heptane-water interfacial tension does not significantly decrease even after 6000 sec.…”

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confidence: 99%

Fundamental Study of Emulsions Stabilized by Soft and Rigid Particles

Harbottle

Pensini

et al. 2015

Langmuir

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Two distinct uniform hybrid particles, with similar hydrodynamic diameters and comparable zeta potentials, were prepared by copolymerizing N-isopropyl acrylamide (NIPAM) and styrene.These particles differed in their styrene to NIPAM (S/N) ratios of 1 and 8, and were referred to as S/N 1 and S/N 8. Particle S/N 1 exhibited typical behavior of soft particles, i.e., the particles shrank in bulk aqueous solutions when the temperature was increased. As a result, S/N 1 particles were interfacially active. In contrast, particle S/N 8 appeared to be rigid in response to temperature changes. In this case, the particles showed negligible interfacial activity. Interfacial shear rheology tests revealed the increased rigidity of the particle-stabilized film formed at the heptane-water interface by S/N 1 than S/N 8 particles. As a result, S/N 1 particles were shown to be better emulsion stabilizers and emulsify a larger amount of heptane compared to S/N 8 particles. The current investigation confirmed a better performance of emulsion stabilization by soft particles (S/N 1) than by rigid particles (S/N 8), reinforcing the importance of controlling softness or deformability of particles for the purpose of stabilizing emulsions.

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Temperature‐Sensitive Hydrogel‐Particle Films from Evaporating Drops

Still

Yunker

Hanson

et al. 2015

Adv Materials Inter

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that was initially suspended. This highly nonuniform deposition is known as the coffee-ring effect; it is produced when the drop edges are pinned during evaporation and subsequent radial capillary fl ows from the drop center carry suspended solutes to the drop perimeter. [5][6][7] The coffeering effect, however, can be ameliorated in aqueous systems of large (>10 µm) suspended spheres, [ 8 ] in suspensions of ellipsoidal particles with strong capillary interactions, [ 9 ] via electrowetting, [ 10 ] in systems with strong attractive forces between particles and substrate, [ 11 ] and in the presence of surfactants that lead to strong Marangoni fl ows, [ 12,13 ] among other techniques. [14][15][16] In these cases, the drying drop system provides experimenters with an opportunity to make uniform thin particle coatings and fi lms.The present contribution builds on investigations of Horigome and Suzuki, which demonstrated that drying aqueous suspensions of PNIPAM particles on polystyrene substrates did not yield typical coffee-ring deposition. [ 17 ] Rather, the hydrogel particles tend to act as amphiphilic moieties, populating the air-water interface fairly uniformly during evaporation. [ 18 ] This behavior, also observed for linear PNIPAM polymers, [ 19,20 ] induces a predominantly uniform deposition of hydrogel particles on the substrate. In our work, we employ micrometersize (diameter d = 1-4 µm) PNIPAM microgel particles with comonomer 2-aminoethylmethacrylate hydrochloride (AEMA) in the suspension. Importantly, the AEMA comonomer introduces primary amine groups onto the microgel particle surfaces that can be used for subsequent cross-linking. Much smaller (<100 nm) PNIPAM particles are feasible, [ 21 ] but systematic studies on the introduction of amine groups still have to be performed. On the other end of the spectrum, we can prepare functionalized particles with amine groups up to approximately 10 µm with the referenced methods. Even larger particles are achievable using microfl uidic techniques.After the water has evaporated, a mostly uniform microgel particle fi lm remains on the substrate. It is kept untouched for another 24 h to ensure cross-linking of neighboring particles by glutaraldehyde that is also mixed into the original droplet suspension. The resultant hydrogel-particle fi lm is temperature-sensitive because the hydrogel particles that compose it are temperature-sensitive. Thus, fi lm size, shape, porosity, and even optical properties are readily varied with temperature control.Our novel responsive fi lms can be utilized as membranes that differ from fi lm structures that have been previously A simple method to prepare temperature-sensitive fi lms composed of micrometer-sized colloidal hydrogel particles using evaporating drops of colloidal suspensions is demonstrated. The fi lms range in thickness from a monolayer to approximately fi fty particle diameters depending on initial particle volume fraction. Sessile droplets of hydrogel-particle suspensions are evaporated on silicon wafers. The fi lm i...

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Poly(N-isopropylacrylamide) at the Air/Water Interface

Cited by 54 publications

References 6 publications

The surface tension of aqueous poly(N-isopropylacrylamide-co-acrylamide)

The surface tension of aqueous poly(N-isopropylacrylamide-co-acrylamide)

Fundamental Study of Emulsions Stabilized by Soft and Rigid Particles

Temperature‐Sensitive Hydrogel‐Particle Films from Evaporating Drops

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