Cloud points in aqueous solutions of poly(N-isopropylacrylamide) synthesized by aqueous redox polymerization

Ise, Tomoyo; Nagaoka, Kouta; Osa, Masashi; Yoshizaki, Takenao

doi:10.1038/pj.2010.121

Cited by 12 publications

(14 citation statements)

References 23 publications

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“…However, the value of the cloud‐point could be influenced by neighboring hydrophilic/hydrophobic groups. [ 11,14 ] Generally, hydrophobic groups lower the cloud‐point while hydrophilic groups shift the cloud‐point toward higher temperature. [ 15 ] In Figure 3, one can observe that, whatever the value of X TEMPO + , the swelling factors values are slightly decreasing as temperature increases and dramatically drop down between 70 and 80 °C.…”

Section: Resultsmentioning

confidence: 99%

Temperature and Redox‐Responsive Hydrogels Based on Nitroxide Radicals and Oligoethyleneglycol Methacrylate

Khodeir

Antoun

Ruymbeke

2020

Macro Chemistry & Physics

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A temperature and redox‐responsive polymer hydrogel is constructed by randomly incorporating 2,2,6,6‐tetramethyl‐1‐piperidinyloxy‐methacrylate (TEMPO) stable nitroxide radicals and oligoethyleneglycol methacrylate (OEGMA) groups in a polymer network. TEMPO can be reversibly oxidized into an oxoammonium cation (TEMPO+) providing the redox‐responsive properties while the lower critical solubility temperature (LCST) of OEGMA results in temperature‐responsive properties. Since a rather low amount of di(ethylene glycol) dimethacrylate (OEGMA2) is used to chemically crosslink the polymer network, the accordingly formed hydrogels obtained after swelling with water consist of microgel particles with entangled polymer chains that are not chemically crosslinked. By varying the amount of TEMPO in the polymer network, it is demonstrated that the radical form of TEMPO aggregates into hydrophobic domains acting as physical crosslinking nodes in the hydrogels and further increasing the cohesion between microgel particles. Increasing the temperature results in two opposite effects on the solubility of TEMPO and OEGMA units. The oxidation of TEMPO into TEMPO+ also results in a deep change in the hydrogel properties since TEMPO+ units are essentially hydrophilic and do not aggregate into physical crosslinking nodes.

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Section: Resultsmentioning

confidence: 99%

Temperature and Redox‐Responsive Hydrogels Based on Nitroxide Radicals and Oligoethyleneglycol Methacrylate

Khodeir

Antoun

Ruymbeke

2020

Macro Chemistry & Physics

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“…The PNIPA sample R5 was prepared by aqueous redox polymerization using a redox catalyst consisting of ammonium persulfate, (NH 4 ) 2 S 2 O 8 (Nacalai Tesque, Inc., Kyoto, Japan), as the oxidant and sodium metabisulfite, Na 2 S 2 O 5 (Nacalai Tesque Inc.), as the reductant, according to the procedure reported by Wooten et al 17 The procedure used for the polymerization and purification of the sample was the same as that described in our previous paper, 5 except the present sample was not fractionated. We note that almost all of the initiating chain ends of the sample R5 are considered to be anionic sulfonate groups.…”

Section: Experimental Procedures Materialsmentioning

confidence: 99%

“…Recently, we performed a series of experimental studies on the phase behavior of aqueous poly(N-isopropylacrylamide) (PNIPA) solutions, [1][2][3][4][5] which exhibited lower critical solution temperature miscibility near human body temperature that was caused by the breakdown of hydrogen bonds between polymers and the surrounding water molecules. During the course of these studies, [1][2][3][4][5] we observed that the phase behavior was not as simple as it is generally considered to be and that cloud-point curves were affected considerably by the nature of the PNIPA chain-end groups, as well as by the degree of branching.…”

Section: Introductionmentioning

confidence: 99%

A fluorescence probe study on the effects of surfactants on cloud points in aqueous poly(N-isopropylacrylamide) solutions

Osa

Itoda

Suzuki

et al. 2014

Polym J

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Fluorescence probe methods were used to investigate micelle formation of poly(N-isopropylacrylamide) (PNIPA) with two types of surfactants, anionic sodium n-dodecyl sulfate (SDS) and cationic n-dodecyltrimethylammonium chloride (DTAC), in aqueous solutions using pyrene or 1-pyrenecarboxaldehyde as a fluorescence probe. Two PNIPA samples, one having a hydrophobic chain-end group and the other having a negatively charged hydrophilic chain-end group, were used to investigate the effects of the chain-end group on the formation of the micelles. The critical aggregation concentration, at which surfactant molecules begin to bind to PNIPA chains to form micelles, was observed to be much lower for PNIPA solutions containing SDS than for solutions containing DTAC. This is consistent with previous results showing that the cloud point in PNIPA solutions containing SDS begins to increase from its value in surfactant-free solutions at a much lower concentration of added surfactant than that in solutions containing DTAC. It was also observed that there is a discrepancy in the emission spectra of solutions containing SDS between the two PNIPA samples but not for solutions containing DTAC, indicating that the chain-end groups of PNIPA may affect the microenvironmental polarity in the micelles composed of PNIPA and the surfactants.

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“…Equation is often used for describing the free‐radical generation by the persulfate/metabisulfite redox pair . However, a variety of reports in the literature have proposed the bisulfate anions as reductant in the redox reaction, which is in equilibrium with metabisulfite anion in aqueous medium, as described by Equation . The end‐group studies also support the idea that the reducing part of the redox pair is the bisulfite anion, Equation , rather than the metabisulfite anion in Equation .…”

Section: Introductionmentioning

confidence: 99%

“…However, a variety of reports in the literature have proposed the bisulfate anions as reductant in the redox reaction, which is in equilibrium with metabisulfite anion in aqueous medium, as described by Equation . The end‐group studies also support the idea that the reducing part of the redox pair is the bisulfite anion, Equation , rather than the metabisulfite anion in Equation .

{normalS}_{2} {normalO}_{normal8}^{2 -} + {normalS}_{2} {normalO}_{normal5}^{2 -} \overset{k_{r}}{\to} {SO}_{normal4}^{• -} + {SO}_{normal4}^{2 -} + {normalS}_{2} {normalO}_{normal5}^{• -}

{normalS}_{2} {normalO}_{normal5}^{2 -} + {normalH}_{2} O \leftrightarrow 2 {HSO}_{3}^{-}

{normalS}_{2} {normalO}_{normal8}^{2 -} + {HSO}_{normal3}^{-} \overset{k_{r}}{\to} {HSO}_{normal3}^{•} + {SO}_{normal4}^{• -} + {SO}_{normal4}^{2 -}

{HSO}_{normal3}^{-} + {SO}_{normal4}^{• -} \overset{}{\to} {SO}_{normal4}^{2 -} + {HSO}_{normal3}^{•}

Reactions and are expected to dominate under bisulfite in excess over persulfate and with a polymerization temperature of around 40 °C, thus producing polymers with mainly sulfonate end‐groups.…”

Section: Introductionmentioning

confidence: 99%

Scale Inhibitor and Dispersant Based on Poly(Acrylic Acid) Obtained by Redox‐Initiated Polymerization

Gutierrez

Montenegro²,

Minari

et al. 2019

Macro Reaction Engineering

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DispersantLow molar mass poly(acrylic acid) (PAA) is generally obtained by free radical polymerization of acrylic acid (AA) in aqueous solution, using thermal initiators and some chain transfer agent. However, under such conditions it is rather difficult to efficiently produce molar masses as low as those required for obtaining an effective dispersant. In this work, the semibatch polymerization of AA at 45 °C is considered, using potassium persulfate (KPS) and sodium metabisulfite (KPS/NaMBS), or alternatively KPS and sodium hypophosphite (KPS/NaHP) as redox initiators to produce PAA of controlled low molar masses. These initiation systems allow the production of PAA with M n as low as 2.0 kDa, relatively narrow molar mass distribution (1.5 < M w /M n < 3.0), and low branching degree. Most of the investigated polymerizations reach almost complete conversions (>95%); and it is verified that both reductants, NaMBS and NaHP, also behave as chain transfer agents. Finally, the investigated process with redox couples allowed the production of PAA with acceptable dispersant and antiscaling properties.

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Cloud points in aqueous solutions of poly(N-isopropylacrylamide) synthesized by aqueous redox polymerization

Cited by 12 publications

References 23 publications

Temperature and Redox‐Responsive Hydrogels Based on Nitroxide Radicals and Oligoethyleneglycol Methacrylate

Temperature and Redox‐Responsive Hydrogels Based on Nitroxide Radicals and Oligoethyleneglycol Methacrylate

A fluorescence probe study on the effects of surfactants on cloud points in aqueous poly(N-isopropylacrylamide) solutions

Scale Inhibitor and Dispersant Based on Poly(Acrylic Acid) Obtained by Redox‐Initiated Polymerization

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