Effect of temperature on surface pressure–area isotherms and surface dilational moduli of poly(N-isopropyl acrylamide) monolayers spread at air–water interface

Yokoi, K.; Kawaguchi, Masami

doi:10.1016/j.colsurfa.2014.06.028

Cited by 8 publications

(5 citation statements)

References 15 publications

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“…At 35 °C, however, hysteresis levels slightly change with the increase of cycle number. That is, surface pressures in the second compression isotherm are slightly lower than those in the first one, which are quite different from those at 20 °C but similar to the decreasing trends typically observed in the PNIPAM and PS -b -PNIPAM systems . This means that most of the immersed POEGA blocks with less hydrophilicity are more likely to return to the interface.…”

Section: Resultsmentioning

confidence: 59%

“…Environmentally responsive polymers are a new class of functional materials well-developed in recent years, which can present obvious changes in their physical or chemical properties with the slight stimulation of environment pH and/or temperature. − Some thermoresponsive copolymers in aqueous solutions present the so-called lower critical solution temperature (LCST) behavior. Their conformation transitions around LCST are attributed to the influences of the hydrogen bonds between specific groups and water molecules and the hydrophobic interactions. − Correspondingly, responsive polymers have also been extensively studied at the air/water interface. − …”

Section: Introductionmentioning

confidence: 99%

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Surface Micelle Structures and Monolayer Compression Moduli of Double Hydrophilic Block Copolymer

et al. 2020

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At the air/water interface, amphiphilic block copolymers are well-known to form typical surface micelles composed of hydrophobic block cores and hydrophilic block coronas. However, the micelle/aggregate structures of the double hydrophilic block copolymers (DHBCs) need to be explored because of the lack of hydrophobic blocks. Influences of subphase pH and temperature on the interfacial aggregation behavior of a thermoresponsive DHBC of poly(N-isopropylacrylamide)-block-poly[oligo(ethylene glycol) acrylate] (PNIPAM-b-POEGA) and the structures of its Langmuir− Blodgett (LB) films were studied with the Langmuir monolayer technique and atomic force microscopy, respectively. All initial LB films of PNIPAM-b-POEGA show circular micelles with a sunflowerlike structure composed of a small PNIPAM backbone core, a short amide group shell, and several large POEGA petals, the structure of which is proposed in the DHBCs for the first time. Two kinds of novel methods based on the methylene group number in a core or the core diameter were successfully used to evaluate the micelle structure. With the increase of subphase pH, the isotherms move toward the larger mean molecular areas due to the gradually increased stretching degrees of POEGA blocks at the air/water interface. With the rise in temperature, the limiting molecular areas of the isotherms initially increase and then decrease above the lower critical solution temperature. As compared to those of other copolymers, the maximum monolayer compression moduli of PNIPAM-b-POEGA are very low, which indicates that the DHBC monolayers are highly compressible. Furthermore, at low temperature, hysteresis levels in the continuous compression−expansion cycles decrease stage by stage, whereas those at high temperature change slightly.

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Section: Resultsmentioning

confidence: 59%

Section: Introductionmentioning

confidence: 99%

Surface Micelle Structures and Monolayer Compression Moduli of Double Hydrophilic Block Copolymer

et al. 2020

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“…The critical temperature of PNIPAM is close to the body temperature of human beings, and hence, it has potential applications in drug release and drug carriers. , Graziano pointed out that the coil- to -globule collapse of PNIPAM above the Θ-point temperature is a first-order entropy-driven phase transition . In recent years, the aggregation behaviors of block copolymers containing PNIPAM at the air/water interface have attracted much attention. − Liu et al explored the interfacial conformation properties of PS- b -PNIPAM and found that the dependencies of surface pressure on temperature and compression rate were strongly influenced by the loop or trail conformations of PNIPAM blocks; however, it has no dependency when they took the train conformation …”

Section: Introductionmentioning

confidence: 99%

Effects of Subphase pH and Temperature on the Aggregation Behavior of Poly(lauryl acrylate)-block-poly(N-isopropylacrylamide) at the Air/Water Interface

et al. 2019

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Effects of subphase pH and temperature on the aggregation behavior of a thermosensitive amphiphilic diblock copolymer poly(lauryl acrylate)-block-poly(N-isopropylacrylamide) (PLA-b-PNIPAM) at the air/water interface and the morphologies of its Langmuir–Blodgett (LB) films were characterized with the Langmuir film balance technique and atomic force microscopy, respectively. The surface pressure–molecular area isotherms shift positively with the increase of subphase pH, and there exist two quasi-plateaus under acidic condition but only one under neutral or alkaline conditions. The lower and upper plateaus under acidic condition are attributed to immersion into water for the protonated amide groups and the rest of PNIPAM blocks, respectively. The plateau pressures gradually decrease with the elevation of temperature due to promotion of protonation and solubility of PNIPAM blocks. On the contrary, those under neutral and alkaline conditions gradually increase but exhibit a lower critical solution temperature behavior which is consistent with that of PNIPAM-containing polymers in aqueous solutions. The initial LB films of PLA-b-PNIPAM transferred from different subphases exhibit tiny isolated circular micelles which coalesce and transform into large dense ones upon compression. Furthermore, PLA cores usually coalesce with the elevation of temperature due to the increased molecular thermal mobility as a result of their low glass transition temperature.

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“…Experiment includes: 1) The formation of continuous water curtain through half arc outlet; 2) As in practical application, the wider the continuous water curtain is, the better smoke control results will be get, so, the change of formation of continuous water curtain will be observed by changing the surface tension of the water, which can be changed by adding a certain amount of detergent into the water. [7]), the total water flow remains steady during testing. Table 1 below shows the test results, Fig.…”

Section: Experiments Researchmentioning

confidence: 94%

“…The model size of the water tank is 200 mm ×80 mm× 130mm (length × width × height), and the whole calculation domain is 600 mm ×166 mm ×800mm (length × width ×height). Boundary condition is to set the mass-flow-inlet of 0.0734 kg/s and the outlet boundary is defined as pressure-out, choose the VOF model, using the pressure-based solver, the water temperature is 20°C, and the surface roughness constant is 0.5, the water surface tension is 0.07 N/m [5][6][7]. Simulation results are shown in velocity contours (Fig.…”

Section: Simulation Studiesmentioning

confidence: 99%

Theoretical and Experimental Study on the Water Curtain Shape and Mechanical Relationship of the Smoke Control System

Gong¹,

Jiang²,

Qiu³

et al. 2016

Proceedings of the International Symposium on Mechanical Engineering and Material Science

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First, we conduct the research on the mechanical mechanism of smoke control system to form a continuous water curtain and analysis the mechanical model of continuous water curtain and micro-unit; then simulate the continuous water curtain's shape of smoke prevention system by using Fluent software and the results are compared with the theoretical analysis; Finally, adopting the experimental verification of continuous water curtain shape and analyzing shape change of continuous water curtain in different water surface tension. Studies have shown that:1) the water curtain boundary track is curved, but the water curtain was similar to the shape of inverted trapezoid.2) under conditions of lowering the surface tension of water (test conditions), and continuous water curtain area growth rate with an average value is 0.26%, the width of growth rate with an average value is 17.32%, the length of the growth rate with an average value is-5.19%; Results indicates that the decrease of surface tension will cause the width of water curtain increase, the length is reduced ,but it has less effect to the area of water curtain.

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Effect of temperature on surface pressure–area isotherms and surface dilational moduli of poly(N-isopropyl acrylamide) monolayers spread at air–water interface

Cited by 8 publications

References 15 publications

Surface Micelle Structures and Monolayer Compression Moduli of Double Hydrophilic Block Copolymer

Surface Micelle Structures and Monolayer Compression Moduli of Double Hydrophilic Block Copolymer

Effects of Subphase pH and Temperature on the Aggregation Behavior of Poly(lauryl acrylate)-block-poly(N-isopropylacrylamide) at the Air/Water Interface

Theoretical and Experimental Study on the Water Curtain Shape and Mechanical Relationship of the Smoke Control System

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