Fluorescence Studies of Hydrophobic Association of Fluorocarbon-Modified Poly(<i>N</i>-isopropylacrylamide)

Li, Mei; Jiang, Ming; Zhang, Yunxiang; Fang, Qin

doi:10.1021/ma960966o

Cited by 98 publications

(123 citation statements)

References 37 publications

(127 reference statements)

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“…Nevertheless, the LCST is dependent on the solvent composition, [5][6][7] amounts of salt and surfactants, [8][9][10] as well as on the structure of the polymers, which can be varied by copolymerization. [11][12][13] A decrease of the LCST by several degrees has been reported for dodecyl (C12)-modified PNIPAAM (molar ratio 1.5%). [14] This was attributed to the hydrophobic microdomains, which tend to reduce the overall solubility of the polymer.…”

Section: Introductionmentioning

confidence: 86%

Lower Critical Solution Temperature Properties of N‐Isopropylacrylamide‐Based Pseudopolyrotaxanes by Complexation with Cucurbituril[6]

Choi¹,

Ritter²

2007

Macromol. Rapid Commun.

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Pseudopolyrotaxanes 4a and 5a are synthesized by two paths: a) directly from the pseudorotaxane, and b) by complexing with cucurbituril (CB[6]) in water at room temperature after the polymerization. Free radical copolymerization with CB[6] (un)complexed monomer and N‐isopropylacrylamide (NIPAAM) is carried out using a redox initiator in aqueous media at room temperature. The properties of pesudorotaxanes (4a and 5a) and polymers (4 and 5) are investigated by TGA, DSC, and turbidity measurements. The lower critical solution temperatures of the NIPAAM‐containing copolymers and CB[6] are significantly higher than those of pure NIPAAM copolymers. The pseudopolyrotaxanes 4a and 5a have a higher thermal stability, as a result of threading of the CB[6] rings onto the polymer side groups.magnified image

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Section: Introductionmentioning

confidence: 86%

Lower Critical Solution Temperature Properties of N‐Isopropylacrylamide‐Based Pseudopolyrotaxanes by Complexation with Cucurbituril[6]

Choi¹,

Ritter²

2007

Macromol. Rapid Commun.

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“…[27][28][29] In the present study, however, pyrene is not a suitable probe for studying the self-association behavior of perfluoroalkyl groups because of poor affinity of pyrene to fluorocarbon moieties. 30 To improve its affinity for perfluoroalkyl microdomains, we employed a derivative of pyrene substituted with a perfluoroalkyl moiety (PyR F 8 in Chart 1). This perfluoroalkyl-substituted pyrene exhibits steadystate fluorescence spectra with a common feature of vibronic bands of pyrene molecules, and the relative intensities of the vibronic bands depend on solvent.…”

Section: Self-association In Benzene (A) Light Scatteringmentioning

confidence: 99%

Synthesis and Characterization of Self-Associative Perfluoroalkyl-End-Capped Polystyrene

Yusa

Yamamoto

Hashidzume

et al. 2002

Polym J

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ABSTRACT:Polystyrene bearing a perfluoroalkyl group at one polymer chain end was synthesized by a "living" radical polymerization of styrene in the presence of 4-perfluoro(n-tetradecanoylamino)-2,2,6,6-tetramethylpiperidinyl-1-oxy. The "living" polymerization was evidenced by the fact that chain extension occurred upon addition of styrene to a prepolymer at an elevated temperature, i.e., the number-average molecular weight increased linearly with monomer conversion while the molecular weight distribution remained narrow independent of the conversion. The presence of the perfluoroalkyl group in the polymer was confirmed from IR and NMR ( 1 H and 13 C) spectra. A preliminary study of the associative behavior of perfluoroalkyl-end-capped polystyrene, using light scattering, spin-lattice relaxation time in 19 F NMR, and fluorescence probe techniques, indicated that self-association of terminal perfluoroalkyl groups occurred in benzene at polymer concentrations higher than ca. 30 g L −1 when weight-average molecular weight is as low as 5500.KEY WORDS 2,2,6,6-Tetramethylpiperidinyl-1-oxy (TEMPO) / Controlled Radical Polymerization / Self-Association / Perfluoroalkyl Group / Diblock copolymers form micelle-like aggregates as a result of the association of a less soluble block when the copolymers are dissolved in a solvent that is good for only one of the blocks. 1-4 For example, amphiphilic diblock copolymers form micelles in aqueous media, hydrophobic blocks constituting a core and the hydrophilic blocks forming a corona. In analogy with amphiphilic diblock copolymers, watersoluble polymers possessing a large hydrophobic substituent at one chain end form micelle-like aggregates in water. This type of end-modified polymers has been synthesized by free-radical polymerization of hydrophilic monomers using hydrophobically modified azo initiators. For example, Winnik et al. [5][6][7] synthesized poly(N-isopropylacrylamide) (PNIPAM) substituted with a dioctadecyl group at its chain end and revealed that the hydrophobe-end-modified PNI-PAM formed multipolymer micelles at temperatures below its lower critical solution temperature in water. In our previous work, we synthesized poly(sodium 2-(acrylamido)-2-methylpropanesulfonate) end-capped with a cholesterol moiety and showed that the polymer underwent multipolymeric micellization in water. 8 A complexity of free radical polymerization initiated by hydrophobically modified azo initiators is that chain termination occurs via recombination or disproportionation, yielding polymers with hydrophobic groups at † To whom correspondence should be addressed.

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“…But from Figure 3, the volume-phase transition was observed in the increasing and decreasing processes, and the critical temperature was the same as reported in the literature. [3][4][5][6][7] It's interesting to note that these two experimental lines were not overlapped exactly. The transition from globule to coil was retarded to that of coil to globule transition, obviously.…”

Section: The Dependence Of the Intrinsic Viscosity With Temperaturementioning

confidence: 99%

“…2 There are a great number of articles about the solution properties of poly(N-isopropylacrylamide) in water. [3][4][5][6][7] The main interesting research was concentrated on the coil-to-globule transition when the temperature was higher than its lower critical solution temperature (LCST) at about 32°C by the fluorescence spectrum, and so forth. The nature of the coil-to-globule transition was revealed as the hydrophilic interaction changed to hydrophobic interaction.…”

Section: Introductionmentioning

confidence: 99%

Investigation of solution properties of poly(N-isopropylacrylamide) in water with its thermohistory

Yang¹,

Yan²,

Cheng³

2000

J. Polym. Sci. B Polym. Phys.

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Fluorescence Studies of Hydrophobic Association of Fluorocarbon-Modified Poly(N-isopropylacrylamide)

Cited by 98 publications

References 37 publications

Lower Critical Solution Temperature Properties of N‐Isopropylacrylamide‐Based Pseudopolyrotaxanes by Complexation with Cucurbituril[6]

Lower Critical Solution Temperature Properties of N‐Isopropylacrylamide‐Based Pseudopolyrotaxanes by Complexation with Cucurbituril[6]

Synthesis and Characterization of Self-Associative Perfluoroalkyl-End-Capped Polystyrene

Investigation of solution properties of poly(N-isopropylacrylamide) in water with its thermohistory

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