Dipole moments of poly(methylmethacrylate)-poly(4-vinylpyridine) block copolymers

Nugay, Nihan; Küçükyavuz, Zühal

doi:10.1016/0014-3057(94)00139-1

Cited by 2 publications

(2 citation statements)

References 14 publications

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“…Indeed, when two different molecules with dipole moments μ 0,T1 and μ 0,T2 are present in solution, the Guggenheim method gives (cf. ref ) We also note that the standard Guggenheim presentation of (ε − n 2 ), measured in solution, as a function of solute concentration, which was used in ref , gives a correct 〈μ 0 2 〉 value only for strongly nonpolar solvents. For slightly polar solvents, where the solvent dielectric constant (ε 0 ) is not equal to the refractive index squared ( n 0 2 ), the 〈μ 0 2 〉 value obtained with the standard method is overestimated by a factor of (1 − (ε 0 − n 0 2 )/(ε 0 + 2)) -1 ; see ref .…”

Section: Resultsmentioning

confidence: 93%

Strong Two-Photon Absorption in Push−Pull Phthalocyanines: Role of Resonance Enhancement and Permanent Dipole Moment Change upon Excitation

et al. 2008

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We study near-IR two-photon absorption (2PA) spectra of nonsymmetric push-pull metal-free phthalocyanines, which are present in solution at room temperature as a mixture of two spectrally nonequivalent tautomers T1 and T2. Large 2PA cross sections, σ 2 ) (1-3) × 10 3 GM, are obtained in the excitation wavelength region λ ex ) 815-850 nm and are explained by ( 1) a new charge transfer state appearing in the one-photon absorption (1PA) spectrum of these compounds at 420-430 nm and (2) a strong resonance enhancement within the quasi-three-level system when the Q-state(s) serve as the real intermediate state(s). In the Q-region, λ ex ) 1100-1500 nm, 2PA and 1PA transitions coincide, and the 2PA strength of any pure electronic or vibronic band is quantitatively described in terms of a two-level approximation.

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Section: Resultsmentioning

confidence: 93%

Strong Two-Photon Absorption in Push−Pull Phthalocyanines: Role of Resonance Enhancement and Permanent Dipole Moment Change upon Excitation

et al. 2008

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“…2-Vinylpyridine was added dropwise and was allowed to react for 1 h. The presence of LiCl slowed down the reaction but it prevented the complexation of lithium counterions with the penultimate pyridine moiety. Complexation would increase the reactivity of the growing anion and cause it to attack the ester function of tert -butyl acrylate . An aliquot of the reaction mixture was withdrawn from the reactor and terminated by methanol and then tert -butyl acrylate was added dropwise and allowed to react for 45 min.…”

Section: Methodsmentioning

confidence: 99%

Polyelectrolyte Poly(tert-butyl acrylate)-block-poly(2-vinylpyridine) Micelles in Aqueous Media

et al. 1996

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Poly(tert-butyl acrylate)-block-poly(2-vinylpyridine), PBA-b-PVP, was prepared by living anionic polymerization. Polymolecular spherical micelles with compact hydrophobic PBA cores and protonated PVP shells in acid water were prepared by a dialysis from organic-aqueous mixtures and are stable if the pH is less than pH 4.8. The stretching of the PVP blocks in shells depends on pH and ionic strength of the solution and decreases significantly in a narrow pH region below 4.8. Small hydrophobic molecules, such as benzene, may be solubilized into micellar core swelling the core and releasing the segmental mobility of core-forming blocks. Two fluorimetric techniques for determination of pyrene partitioning between micelles and the aqueous phase were used. The first method is based on measurements of the ratio of intensities of the first and third vibrational bands, I1/I3, in the emission spectra of pyrene solubilized in a micellar solution as a function of micellar concentration. The second method is based on the quenching of fluorescence from solubilized pyrene by thallium salts. The two experimental techniques yield close values of the apparent partition coefficient, Kapp ) 1.3 × 10 5 and 1.1 × 10 5 , respectively.

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Dipole moments of poly(methylmethacrylate)-poly(4-vinylpyridine) block copolymers

Cited by 2 publications

References 14 publications

Strong Two-Photon Absorption in Push−Pull Phthalocyanines: Role of Resonance Enhancement and Permanent Dipole Moment Change upon Excitation

Strong Two-Photon Absorption in Push−Pull Phthalocyanines: Role of Resonance Enhancement and Permanent Dipole Moment Change upon Excitation

Polyelectrolyte Poly(tert-butyl acrylate)-block-poly(2-vinylpyridine) Micelles in Aqueous Media

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