Strong molecular alignment in anisotropic fluid media

Bain, Angus J.; Chandna, P.; Butcher, G. W.

doi:10.1016/0009-2614(96)00841-x

Cited by 19 publications

(31 citation statements)

References 16 publications

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“…Quintella et al 18 obtained polarization maps of the first four perpendicular lobes of both frontal and lateral views, for several thin free liquid jets, reporting and explaining their lobed structure. Bain et al 19 used polarized single-photon counting to study depolarization kinetics with picosecond resolution.…”

Section: Introductionmentioning

confidence: 99%

Intermolecular Alignment Dependence of Ethylene Glycol Flow on the Chemical Nature of the Solid Surface (Borosilicate and SnO2)

Quintella¹,

Gonçalves²,

Pepe³

et al. 2001

J. Braz. Chem. Soc.

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Este trabalho estuda o fluxo de etileno glicol (MEG) sobre duas superfícies sólidas com constituições químicas diferentes: borossilicato e dióxido de estanho (SnO 2 ). O alinhamento intermolecular, determinado como polarização e anisotropia, mostrou dependência da natureza química do sólido. A razão entre as tensões interfaciais dinâmicas foi 1.09 ± 0.07, devendo ser maior para MEG/borossilicato do que para MEG/SnO 2 . A razão da capilaridade foi 0.92 ± 0.06, sendo menor para MEG/borossilicato. Medidas estáticas do ângulo de contato mostraram valores menores para borossilicato do que para SnO 2 . Os mapas de polarização e anisotropia apresentaram valores mais altos para MEG/SnO 2 , o que pode ser explicado pela alta tensão interfacial do MEG/borossilicato. Estes resultados são compatíveis com interações de volume mais fortes em MEG/SnO 2 e com contribuições de superfície mais fortes em MEG/borossilicato. Isto pode ser atribuído ao borossilicato ser mais eletronegativo, favorecendo mais as pontes de hidrogênio com o MEG.This work studied ethylene glycol (MEG) flowing on two different solid surfaces, borosilicate and thin dioxide (SnO 2 ). Intermolecular alignment, determined as polarization and anisotropy, showed dependence on the solid chemical nature. The ratio between dynamic surface tensions was found 1.09 ± 0.07, being stronger for MEG/borosilicate than for MEG/SnO 2 . The capillary ratio found was 0.92 ± 0.06, being smaller for MEG/borosilicate. Static contact angle measurements gave lower values for borosilicate than for SnO 2 . Both polarization and anisotropy maps presented higher values for MEG/SnO 2 , which can be explained by MEG/borosilicate higher interfacial interaction. The results obtained are compatible with stronger bulk phenomena for MEG/SnO 2 and with stronger interfacial phenomena for MEG/borosilicate. This may be due to borosilicate being more electronegative, yielding more efficiently hydrogen bonds with MEG.

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Section: Introductionmentioning

confidence: 99%

Intermolecular Alignment Dependence of Ethylene Glycol Flow on the Chemical Nature of the Solid Surface (Borosilicate and SnO2)

Quintella¹,

Gonçalves²,

Pepe³

et al. 2001

J. Braz. Chem. Soc.

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“…Free thin liquid jets in air were mapped with respect to their nonhomogeneous intermolecular orientation in the central region [10,11]. Fluorescence depolarization kinetics was obtained with picosecond resolution within certain regions, indicating a strong anisotropy in θ and φ rotational diffusion dynamics [12]. Previous results have shown that for thin channels the flow consists mainly of superposed boundary layers where interfacial chemical interactions become predominant over bulk flow [13].…”

Section: Introductionmentioning

confidence: 99%

Detection of chemical alterations at internal walls of microchannel flow cells by nondestructive fluorescence depolarization

Quintella¹,

Lima²,

Mammana³

et al. 2004

Journal of Colloid and Interface Science

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A recent trend is the production of workable microchannel flow cells (MF cells). The nondestructive methods used to assess their reliability are based mainly on output monitoring and do not evaluate internal chemical interactions. We investigate a nondestructive method for evaluating changes in the chemical composition of the inner walls based on evaluation of the extent of alignment of a fluorescent probe in a liquid flowing within MF cells. Two MF cells were built with a 10-microm inner spacing. Their inner walls had four parallel SnO(2) strips, 2.00 mm wide, separated by 0.50-mm-wide glass strips. One cell had strips parallel to the flow and the other perpendicular. Flow-induced intermolecular alignment of rhodamine B in monoethylene glycol was scanned with 28-microm precision by fluorescence depolarization, using polarized-laser-induced fluorescence within induced flows (PLF-FI). No changes of polarization were seen when the flow was stopped. Under flowing conditions, polarization was always 4% lower in the glass region as compared to SnO(2). Glass had a higher solid-liquid interfacial tension (determined by contact angle measurements), thus being more wettable and increasing the drag, which propagates into the liquid flow, decreasing polarization. PLF-FI can thus identify regions with different chemical constitutions.

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“…,Q DQ RUGHUHG PHGLXP LW LV FUXFLDO WR DFKLHYH D IXOO UHVROXWLRQ RI WKH RULHQWDWLRQDO ERWK DQG φ) dynamics as the imposition of order gives rise to a marked departure from conventional (isotropic) molecular relaxation [1][2][3][4][5] . Molecular order has to date been probed using a range of optical processes including Raman scattering 6 , laser induced fluorescence [7][8][9] and surface second harmonic generation 10 .…”

Section: Introductionmentioning

confidence: 99%

“…Picosecond fluorescence anisotropy studies of molecular probes have been shown to yield useful information on molecular order, orientational dynamics and photophysical processes in both molecular and biomolecular systems 1,11 . Recent work in our group has shown that it is possible to obtain information on the order and full angular motion of a fluorescent probe in an ordered environment using single pulse variable photoselection and picosecond polarised fluorescence [2][3][4] . Here the variation of the excitation (linear) polarisation gives rise to the creation of varying degrees of (non-equilibrium) cylindrically symmetric and asymmetric probe alignment.…”

Section: Introductionmentioning

confidence: 99%

“…Defining the measurement direction perpendicular to the Z axis as X, the probe fluorescence anisotropy R(t) at time t following the application of an ultrashort pulse sequence (or single pulse) is given by (2) where (ss) denotes the equilibrium or steady state value of the probe alignment. The cylindrically symmetric and asymmetric alignment rates τ 20 and τ 22 DUH UHODWHG WR WKH DQG φ diffusion rates in the laboratory frame …”

Section: Introductionmentioning

confidence: 99%

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Single and three pulse photoselection of dye probes in nematic liquid crystals

et al. 2002

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We present results of single and three pulse photoselection studies of the dynamics of a fluorescent probe (Oxazine 4) in the nematic phase of the liquid crystal 4-n-pentyl-4'-cyanobiphenyl (5CB). The combination of these techniques with time resolved fluorescence anisotropy measurements allows the unambiguous determination of the full angular motion of the probe together with the ground and excited state degrees of equilibrium (steady state) alignment. The restricted JHRPHWU\ LPSRVHG E\ WKH QHPDWLF KRVW LV VHHQ WR LPSDUW D PDUNHG DQLVRWURS\ LQ DQG φ GLIIXVLRQ ! ~4 ).

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Strong molecular alignment in anisotropic fluid media

Cited by 19 publications

References 16 publications

Intermolecular Alignment Dependence of Ethylene Glycol Flow on the Chemical Nature of the Solid Surface (Borosilicate and SnO2)

Intermolecular Alignment Dependence of Ethylene Glycol Flow on the Chemical Nature of the Solid Surface (Borosilicate and SnO2)

Detection of chemical alterations at internal walls of microchannel flow cells by nondestructive fluorescence depolarization

Single and three pulse photoselection of dye probes in nematic liquid crystals

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