More on the Analysis of Dilute Solution Data: Polystyrenes Prepared Anionically in Tetrahydrofuran

Yamamoto, Akihiko; Fujii, Masanori; Tanaka, Genzo; Yamakawa, Hiromi

doi:10.1295/polymj.2.799

Cited by 95 publications

(62 citation statements)

References 29 publications

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“…A rough comparison between PEO and certain other polymers with comparable molecular weight illustrates this point: PEO [Z] values are about three-fold larger than those for poly a(methyl styrene) (PaMS) in benzene 13 or toluene 14 and about twice as large as those observed for polystyrene in benzene. 15 The extensive swelling was also observed from the value of unusually large radius of gyration (R g ) for PEO. For example R g values for a representative molecular weight of 500,000 were 452 Å for PEO in water at 308C 9 while the corresponding values for PaMS in toluene at 258C were 301.…”

Section: Viscosity Measurementsmentioning

confidence: 90%

Aggregate formation in poly(ethylene oxide) solutions

Khan

2006

J of Applied Polymer Sci

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Static light scattering and viscosity measurements were performed on different molecular weight poly (ethylene oxide) to see the formation of aggregates in its dilute solutions. Viscosity measurements were carried out for PEO samples in water and methanol at 20-458C and in chloroform at 20-308C. Using Huggin's equation, the viscosity plots showed distinct upward curvature indicating the presence of aggregates in both PEO/H 2 O and PEO/CH 3 OH solutions The [Z] values for PEO/H 2 O and PEO/CH 3 OH system were 2-4 times as large as observed for other linear flexible polymers in good solvents thus showing extensive coil swelling/aggregation. This is also apparent from the exponent a values of the Mark-Houwink-Sakurada equation. Light Scattering results using Zimm method showed that aggregation occurred in low molecular weight samples; however, in higher molecular weight samples there was a little evidence for aggregation both in water and methanol.

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Section: Viscosity Measurementsmentioning

confidence: 90%

Aggregate formation in poly(ethylene oxide) solutions

Khan

2006

J of Applied Polymer Sci

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“…Assume that 2-m polymer particles are prepared from a dispersion system that contains 10 g monomer and 1 g PVP K90 stabilizer in the reaction medium. A study using small-angle neutron scattering (SANS) 31 indicated that the radius of gyration of a typical random coil polymer chain (e.g., polystyrene in cyclohexane) with a molecular weight on the order of 10 5 is about 100 Å. Thus, it is reasonable to assume that the radius of gyration of a PVP K90 molecule, which has a molecular weight of 3.6 ϫ 10 5 , is roughly 100 Å in alcohol/water medium.…”

Section: Effect Of Concentration and Molecular Weight Of Stabilizermentioning

confidence: 99%

Dispersion polymerization of n‐butyl acrylate

Wang

Dimonie

Sudol

et al. 2002

J of Applied Polymer Sci

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ABSTRACT:The dispersion polymerization of n-butyl acrylate (BA) was investigated using alcohol/water mixtures as the dispersion medium, 4,4Ј-azobis-(4-cyanopentanoic acid) as the initiator, and polyvinylpyrrolidone (PVP) as the stabilizer. The effects of polymerization parameters, such as the alcohol/water ratio in the medium and the type and concentration of the polymeric stabilizer, on the resulting particle size and size distribution were studied. The final particle size and the stability of the dispersion system were found to be greatly influenced by the type of alcohol used in the mixture; that is, methanol or ethanol, even though the apparent solubility parameters are almost the same for the two types of mixtures. Poly(butyl acrylate) particles with controlled size and size distribution (monodisperse), and gel content were successfully prepared in a 90/10 methanol/water medium. It was found that the particle size decreased with increasing initiator concentration. This is the opposite of what was previously reported in the dispersion polymerizations of styrene and methyl methacrylate.

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“…Also, we were unable to obtain the radius of gyration (R g ) of the polymer aggregate by SLS probably because R g for the aggregate is smaller than the lower limit of detection on our light scattering instrument. Yamamoto et al 20 reported that R g of polystyrene in benzene at 25 • C is calculated from…”

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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More on the Analysis of Dilute Solution Data: Polystyrenes Prepared Anionically in Tetrahydrofuran

Cited by 95 publications

References 29 publications

Aggregate formation in poly(ethylene oxide) solutions

Aggregate formation in poly(ethylene oxide) solutions

Dispersion polymerization of n‐butyl acrylate

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

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