Structural properties and topological defects of swollen polymeric mesophases: Low angle X-ray diffraction and optical microscopic studies

Candau, Françoise; Ballet, François; Debeauvais, F.; Wittmann, J. C.

doi:10.1016/0021-9797(82)90333-2

Cited by 27 publications

(21 citation statements)

References 24 publications

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“…We tend to think that the undulations are probably inherent properties of the structure of the paired disclinations in these materials. We suspect that the paired disclinations with transverse striations previously reported elsewhere [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] are complicated patterns of the isolated and the interacting paired disclinations like those we have described rather than rows of focal conics as previously suggested [l,17]. We have not understood the true cause of the observed undulations of disclination pairs in smectic A lyotropic liquid crystals, but we believe that we have identified the gross features of these defect structures.…”

Section: Resultsmentioning

confidence: 98%

“…Defect structures in liquid crystals provide important clues to understanding the symmetry of perfect crystals and their mechanical properties. Paired disclinations, or « oily streaks », with transverse striations are observed in thermotropic smectic [1][2][3], cholesteric [4][5], lyotropic (smectic) liquid crystals [6][7][8][9][10] and most recently in liquid crystalline polymers [11][12][13] and polymeric liquid crystals [14,15J and in lamellar phases of mixtures which also have a microemulsion phase [16]. The basic structure of the oily streak is a pair of positive disclinations of strength 1/2 [9][10].…”

Section: Introductionmentioning

confidence: 99%

“…The basic structure of the oily streak is a pair of positive disclinations of strength 1/2 [9][10]. This structure suggests a straight, smooth form which does not explain the dark transverse striations always observed in disclination pairs between crossed polarizers [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. In thermotropic smectic A's, the observed striations have been attributed to a row of focal conics [1,3] which form from the.…”

Section: Introductionmentioning

confidence: 99%

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Undulating paired disclinations (oily streaks) in lyotropic liquid crystals

Schneider

Webb

1984

J. Phys. France

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Optical microscopy reveals regular periodic undulations of the lateral position of the axes of paired disclinations or « oily streaks » in thin, fully hydrated lyotropic liquid crystals of dimyristoyl phosphatidylcholine (DMPC) in the Lα (smectic A) phase. These undulations explain the characteristic dark bands that traverse the paired disclinations on observation with crossed polarizers. When paired disclinations are adjacent, their undulation periods become equal and lock in phase. The undulations appear spontaneously in all paired disclinations on formation of homeotropically aligned specimens in the Lα phase

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Section: Resultsmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Undulating paired disclinations (oily streaks) in lyotropic liquid crystals

Schneider

Webb

1984

J. Phys. France

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“…These two phases are originally found in the case of many amphiphilic compounds 58, 59. The textures observed with the polarizing light microscope studies for all of the biphasic and lyotropic solutions in both protic and aprotic polar solvents within the range of dielectric constants 32.6–48.9 for polymers I‐1–I‐3 indicated small and large bâtonnets and different types of polygonal arrays [often referred to as mosaic textures60 (Figs. 1–4)], all of which were indicative of their lamellar phase.…”

Section: Resultsmentioning

confidence: 99%

Intravascular ultrasound and quantitative coronary angiography assessment of late in‐stent restenosis: In vivo human correlation and methodological implications

Prati¹,

Pawłowski

Sommariva³

et al. 2002

Cathet Cardio Intervent

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Quantitative coronary angiography (QCA) is routinely used for assessment of strategies aimed at reducing in-stent restenosis. Yet QCA enables only the measurement of luminal variation of stented segments and, unlike intravascular ultrasound (IVUS), provides only an indirect estimation of late in-stent neointimal formation, which has a key role in the process of in-stent restenosis. The aims of the present study were to correlate the IVUS measurement of in-stent intimal hyperplasia (IH) with QCA indexes of restenosis, to find out whether QCA is an adequate surrogate of IVUS, and, using either QCA and IVUS data, to define the sample sizes needed to demonstrate the effectiveness of strategies to reduce in-stent restenosis. The database of the European Imaging Laboratory was used to screen 154 stents implanted between 1997 and 2001 and studied by IVUS at 6 +/- 1 months of follow-up. All cases underwent serial QCA assessment (preintervention, postintervention, and follow-up). Only 131 cases with single stent implantation in native coronary arteries were included in the study. Stent restenosis, defined as percent diameter stenosis (DS) > 50%, was present at QCA in 69 out of 131 cases (53%). Linear regression analyses were performed to correlate the amount of IH, calculated by IVUS as the average of all cross-section areas (CSA; mean % IH CSA) and QCA indexes of restenosis (late loss and % DS). A positive significant correlation was found between IVUS mean % IH CSA and QCA % DS (r = 0.74; P < 0.0001) and between IVUS mean % IH CSA and QCA late loss (r = 0.72; P < 0.0001). Based on IVUS measurements of mean % IH CSA, a total sample size of 74 stents would be required in a two-arm comparison to have 0.80 power to detect at 0.05 significant level a 30% difference between two compared groups. Alternatively, adopting the QCA late loss, 230 stents would be required. QCA measurements of late in-stent restenosis are well correlated with IVUS calculation of in-stent neointimal formation. IVUS assessment of IH allows smaller sample sizes than QCA to document significant reductions of in-stent restenosis. Therefore, the use of IVUS should be encouraged in comparison studies aimed at revealing significant neointimal differences in small sample size populations.

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“…On cooling from the isotropic phase, each compound/mixture exhibited various types of mosaic textures and spherical birefringent particles having a more or less regular cloverleaf shape (figure 3). All of them were indicative of smectic LC phases [17][18][19][20]. The viologen 2 and all of its mixtures with 1, but not the viologen 1 itself, retained these LC phases down to RT, since their crystallization exotherms were below RT.…”

Section: Methodsmentioning

confidence: 99%

Ambient temperature thermotropic liquid crystalline viologen bis(triflimide) salts

et al. 2003

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Two dicationic salts with bis(triflimide) as counterions exhibited crystal-to-smectic liquid crystalline phase transitions (T m~4 1 and 37 ‡C) and smectic-to-isotropic liquid phase transitions (T i~1 12, 136 ‡C). They had a broad liquid crystalline phase range (71-99 ‡C) and an excellent range of thermal stability (360-364 ‡C). Their mixtures of various compositions also displayed liquid crystalline properties from r.t. to an extended range of temperatures. They exhibited fluorescence in 1, 2-dimethoxyethane and methanol.

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Structural properties and topological defects of swollen polymeric mesophases: Low angle X-ray diffraction and optical microscopic studies

Cited by 27 publications

References 24 publications

Undulating paired disclinations (oily streaks) in lyotropic liquid crystals

Undulating paired disclinations (oily streaks) in lyotropic liquid crystals

Intravascular ultrasound and quantitative coronary angiography assessment of late in‐stent restenosis: In vivo human correlation and methodological implications

Ambient temperature thermotropic liquid crystalline viologen bis(triflimide) salts

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