scholarly journals Rheological Investigation of Self-emulsification Process

2009 ◽  
Vol 12 (1) ◽  
pp. 17 ◽  
Author(s):  
Shailesh V Biradar ◽  
Ravindra S Dhumal ◽  
Anant Paradkar
Keyword(s):  
Liquid Crystalline ◽  
Bound Water ◽  
Tween 80 ◽  
Cubic Phase ◽  
Scanning Calorimetry ◽  
Polarizing Microscopy ◽  
Rheological Analysis ◽  
Mesophase Formation ◽  
High Level ◽  
Emulsification Process

PURPOSE Aim of this study is to investigate the mechanism of self-emulsification through rheological analysis of intermediate liquid crystalline (LC) phase formed during self-emulsification process. METHODS Binary system of tween 80 (T80) and imwitor 742 (I742) was used and different SES were prepared with I742 at 10, 30, 50, 70 and 90% w/w concentration levels. Self-emulsification was monitored by visual observations and droplet size measurement. Mesophases obtained by 50% v/v hydration of SES were utilized for polarizing microscopy, differential scanning calorimetry and rheological studies. RESULTS Good emulsification with nano sized droplets was observed for SES 30% as compared to micron sized droplets for other SES. In polarizing microscopy, formation of intermediate LC phase was observed in all SES. Lamellar phase was evident in 30% SES while other SES exhibited micellar cubic phase. Presence of high level of structurally bound water in thermal analysis confirmed mesophase formation in all SES. In frequency sweep, decrease in elastic modulus, and an increase in phase degree and loss tangent was observed for 30% SES. Exactly opposite trend was seen in other SES. Thus, rheological studies concluded presence of weak and fragile mesophase structure in 30% SES while LC phase structure with little structural buildup was observed in other SES. This weak mesosphere structure in SES 30% presented no or very little resistance against strain induced deformation. Therefore, during emulsification, weak mesophase in SES 30% ruptured with ease and released jet of nanosize droplets compared to coarse droplets for other SES. CONCLUSION This study signifies the effect of viscoelastic properties of intermediate LC phase on self-emulsification performance.

scholarly journals Rheological Investigation of Self-emulsification Process: Effect of Co-surfactant

2009 ◽  
Vol 12 (2) ◽  
pp. 164 ◽  
Author(s):  
Shailesh V Biradar ◽  
Ravindra S Dhumal ◽  
Ananat R. Paradkar
Keyword(s):  
Liquid Crystalline ◽  
Aqueous Media ◽  
Tween 80 ◽  
Hydrocarbon Chain ◽  
Cubic Phase ◽  
Scanning Calorimetry ◽  
Polarizing Microscopy ◽  
Dsc Studies ◽  
High Turbidity ◽  
Almost All

PURPOSE The aim of study is to investigate role of co-surfactant in self-emulsification through rheological analysis of intermediate liquid crystalline (LC) phase formed during self-emulsification. METHODS To mixture of Captex® 200P (C200) and tween 80 (T80) (SES Plain), either medium hydrocarbon chain co-surfactant (Capmul® MCM (CMCM): SES C) or long hydrocarbon chain co-surfactant (Peceol® (P): SES P) was added separately at different concentration levels. Self-emulsification was monitored by visual observations, turbidimetric and droplet size measurement. Mesophases were obtained by 30% v/v aqueous hydration of SES and characterized by polarizing microscopy, differential scanning calorimetry (DSC) and rheological studies. RESULTS SES Plain exhibited ‘bad’ emulsification owing to instantaneous gel formation in aqueous media. Almost all SES C have shown ‘good’ emulsification with transparent appearance, very low turbidity value and nano size droplets. All SES P presented ‘moderate’ emulsification with milky appearance, high turbidity value and coarse droplets. Polarizing microscopy revealed formation of lamellar phase in SES Plain and in all SES P while almost all SES C exhibited formation of micellar cubic phase. In DSC studies, higher extent of LC phase formation was observed in SES C as compared to SES P. Rheological study clearly demonstrated presence of elastic and partially recoverable mesophase in SES Plain, which was transformed into a viscous and non-recovering mesophase with addition of CMCM while there was no change in rheological status of SES Plain after addition of P. The weak and viscous LC phase in SES C must have not presented any resistance to strain induced deformation. Therefore, it might have ruptured easily and quickly, releasing jet of nanosize droplets whereas elastic mesophase in SES P might have ruptured with little resistance resulting in coarse droplets. CONCLUSION The ability of co-surfactant to promote self-emulsification was attributed to their influence on viscoelastic properties of intermediate LC phase.

Synthesis, Characterization and Adsorption Performance of Semi-crystalline/Liquid Crystalline Polyether Chelating Resins

e-Polymers ◽  
2009 ◽  
Vol 9 (1) ◽  
Author(s):  
Shuangqing Zhang ◽  
Chaocan Zhang ◽  
Changhai He ◽  
Jun Xu
Keyword(s):  
Adsorption Capacity ◽  
Chemical Structure ◽  
Liquid Crystalline ◽  
Selective Adsorption ◽  
Scanning Calorimetry ◽  
Polarizing Microscopy ◽  
Adsorption Ability ◽  
H Nmr ◽  
Chelating Resins ◽  
Crystal Polymer

AbstractA series of polyether chelating resins with pendent biphenyl mesogenic groups were synthesized, and the chemical structure of monomers and polymers were confirmed by IR and 1H NMR detection. The thermal properties of resins were investigated by the Differential Scanning Calorimetry (DSC) and Polarizing Microscopy (POM), and the results showed that only the product of polyepichlorohydrin grafted with 4-cyano-4’-hydrobiphenyl, i.e., HPCN resin, was a kind of nematic liquid crystal polymer with typical schlieren texture (70-130 0C) and other resins were semi-crystalline. The results of adsorption experiments showed that all five resins exhibited a higher adsorption capacity (>1.0 mmol/g) for Cu (II) and Hg (II) and medium adsorption ability for Cd (II), Zn (II), Pb (II) and Co (II), however, a poor adsorption capacity (<0.3 mmol/g) for Mg (II), indicating that this type of polyether resins have a better selective adsorption for above metal ions. In addition, the adsorption capacity of HPnCP resins was generally higher than that of HPd and HPCN owing to the existence of terminal pyrrole coordination groups in HPnCP resins.

scholarly journals Liquid Crystalline Compounds in the Thiophene Series, Part 6+ Synthesis and Characterization of Azomethines and Vinylenes with Two Mesogenic Groups and Different Alkylene Spacer Lengths

1993 ◽  
Vol 48 (6) ◽  
pp. 826-843 ◽  
Author(s):  
Gerhard Koßmehl ◽  
Frank Dirk Hoppe ◽  
Barbara Hirsch
Keyword(s):  
Aromatic Amines ◽  
Liquid Crystalline ◽  
Synthesis And Characterization ◽  
Scanning Calorimetry ◽  
Polarizing Microscopy ◽  
Alkyl Chains ◽  
Liquid Crystalline Phases ◽  
Smectic Mesophase ◽  
Methylene Groups

Compounds which have two mesogenic groups with and without terminal alkyl chains containing thiophene systems, were prepared from α.ω-bis(5-formyl-2-thienyl)alkanes (3a-3n) and various aromatic amines or 2-fluorenyl-Wittig-salt (10). The liquid crystalline properties of these compounds were characterized by differential scanning calorimetry (DSC) and polarizing microscopy. Only the series of α.ω-bis{5-[N-(4′-butyloxybiphenyl-4-yl)imino]formyl-2-thienyl}alkanes (7a-71) showed enantiotropic smectic and nematic mesophases. The series of E,E-α.ω-bis[5-(2-fluorenylvinyl)-2-thienyl]alkanes (8a-81) showed enantiotropic nematic mesophases for the compounds with 4 and 6 methylene groups, monotropic nematic mesophases for the compounds with 7—12 methylene groups and no liquid crystalline phases for compounds with 3, 5, 16 methylene groups in the connecting alkylene chain. In contrast to the compounds 8a-81, E-l-(5-butyl-2-thienyl)-2-(2-fluorenyl)ethylene has a smectic mesophase.

Donor/Acceptor Interaction-assisted Mesophase Formation in Liquid Crystals Containing Azobenzenes and Their Polymers

2008 ◽  
Vol 63 (5) ◽  
pp. 571-576 ◽  
Author(s):  
Chinnusamy Saravanan ◽  
Mohan Deepa ◽  
Palaninathan Kannan ◽  
Sengodan Senthil
Keyword(s):  
Liquid Crystalline ◽  
Low Molecular Weight ◽  
Scanning Calorimetry ◽  
Acceptor Interaction ◽  
Correlation Studies ◽  
Mesophase Formation ◽  
Low Molecular Weight Compounds ◽  
Donor Acceptor ◽  
The Individual ◽  
Better Than

Azobenzene-based monomers and their polymers containing donor or acceptor groups at terminal positions have been synthesized. The liquid crystalline (LC) mesophase stability of one type of polymer and mixtures of donor or acceptor substituted polymers have been investigated. Mesophase formation and stability of the mixtures were studied using differential scanning calorimetry (DSC) and a hot-stage optical polarizing microscope (HOPM). The mesophase stability of the mixtures was better than those of the individual components. Binary mixture studies of acceptor monomers (a) and donor monomers (d) show that the pure low molecular weight compounds did not form any molecular aggregates and failed to show LC properties, whereas the mixture of donor substituted azobenzene and acceptor substituted azobenzene exhibits LC property. In the case of polymers, the individual acceptors (A) or donors (D) exhibit LC property, and their mixture stabilizes the crystallinity of the mesophase. The results of correlation studies of various proportions of mixtures of a/d and A/D with regard to LC properties and their mesophase stabilities are presented

scholarly journals Liquid-crystalline heterodimesogens and ABA-heterotrimesogens comprising a bent 3,5-diphenyl-1,2,4-oxadiazole central unit

2012 ◽  
Vol 8 ◽  
pp. 472-485 ◽  
Author(s):  
Govindaswamy Shanker ◽  
Marko Prehm ◽  
Carsten Tschierske
Keyword(s):  
Liquid Crystalline ◽  
Optical Observations ◽  
Central Unit ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Polarizing Microscopy ◽  
X Ray ◽  
Nematic Phases ◽  
Lower Temperature ◽  
Optical Polarizing Microscopy

Three new types of terminally connected ABA-heterotrimesogens and heterodimesogens, composed of a bent 3,5-diphenyl-1,2,4-oxadiazole central unit and one or two rod-shaped 4-cyanobiphenyl cores or one 2-phenyl-1,3,4-thiadiazole core, connected by flexible spacers, have been synthesized, and their mesomorphic behavior was studied by optical polarizing microscopy (PM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). All dimesogens exhibit broad ranges of cybotactic nematic phases (NcybA and NcybC), in some cases accompanied by additional mesophases (CybA or SmC) at lower temperature. The combination of the 3,5-diphenyl-1,2,4-oxadiazole unit with one cyanobiphenyl core leads to the removal of tilted smectic and cybotactic nematic phases (SmC, NcybC), which are replaced by the nontilted CybA phases and nematic phases composed of SmA-type clusters (NcybA). The orthogonal cybotactic nematic phases of bent-core mesogens are of special interest for achieving biaxial nematic phases of the orthorhombic type. The orthogonal (NcybA) and skewed (NcybC) cybotactic nematic phases were distinguished by XRD and optical observations.

scholarly journals Induced Wide Nematic Phase by Seven-Ring Supramolecular H-Bonded Systems: Experimental and Computational Evaluation

Molecules ◽  
2020 ◽  
Vol 25 (7) ◽  
pp. 1694 ◽  
Author(s):  
Latifah Abdullah Alshabanah ◽  
Laila A. Al-Mutabagani ◽  
Hoda A. Ahmed ◽  
Mohamed Hagar
Keyword(s):  
Nematic Phase ◽  
Density Functional ◽  
Liquid Crystalline ◽  
Uv Spectroscopy ◽  
Energy Difference ◽  
Scanning Calorimetry ◽  
Computational Evaluation ◽  
Mesophase Formation ◽  
Temperature Ranges ◽  
Effective Role

New seven-ring systems of dipyridine derivative liquid crystalline 2:1 supramolecular H-bonded complexes were formed between 4-n-alkoxyphenylazo benzoic acids and 4-(2-(pyridin-4-yl)diazenyl)phenyl nicotinate. Mesomorphic behaviors of the prepared complexes were investigated using a combination of differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). Fermi bands attributed to the presence of intermolecular H-bond interactions were confirmed by FT–IR spectroscopy. All prepared complexes possessed an enantiotropic nematic phase with a broad temperature nematogenic range. Phases were confirmed by miscibility with a standard nematic (N) compound. A comparison was constructed to investigate the influence of the incorporation of the azophenyl moiety on the mesomeric behavior of corresponding five-membered complexes. It was found that the present complexes observed induced a wide nematic phase with relatively higher temperature ranges than the five aromatic systems. Density functional theory (DFT) suggested the nonlinear geometry of the formed complex. The results of the DFT explained the nematic mesophase formation. Moreover, the π–π stacking of the aromatic moiety in the phenylazo acid plays an effective role in the mesomorphic thermal stability. The energy difference between the frontier molecular orbitals, HOMO (highest occupied) and LUMO (lowest occupied), and the molecular electrostatic potential (MEP) of the prepared complexes were estimated by DFT calculations. The results were used to illustrate the observed nematic phase for all H-bonded supramolecular complexes. Finally, photophysical studies were discussed which were carried out by UV spectroscopy connected to a hot stage.

scholarly journals New azobenzene liquid crystal with dihydropyrazole heterocycle and photoisomerization studies

2020 ◽  
Vol 7 (7) ◽  
pp. 200474
Author(s):  
Xiaoxuan Wang ◽  
Zhaoxia Li ◽  
Haiying Zhao ◽  
Shufeng Chen
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystalline ◽  
Ester Group ◽  
Azo Compounds ◽  
Scanning Calorimetry ◽  
Polarizing Microscopy ◽  
Mesogenic Unit ◽  
Crystal Properties ◽  
Azobenzene Derivatives ◽  
Long Chain

New azobenzene derivatives with dihydropyrazole heterocycle have been prepared and characterized. According to thermal polarizing microscopy and differential scanning calorimetry studies, the compounds consisting of four linearly linked rings and a long alkoxy chain on the azobenzene side ( 3a-8 and 3a-14 ) displayed no liquid crystal properties. When the length of mesogenic unit increased to five rings, except for compound 5a-8 , all compounds from 5a-10 to 5a-16 containing a long chain of 10–16 carbon atoms on the side of ester group displayed liquid crystalline properties, and the mesogenic domain gradually narrowed with increase of the chain length. However, in the case of the molecule with long alkoxy chains on both sides, only 5c-16 with a long chain of 16 carbon atoms exhibited liquid crystal behaviour. In addition, these azo compounds underwent isomerization from E to Z under ultraviolet irradiation and then thermal back relaxation slowly in the dark, which can be recycled many times.

Electron microscopy of crystalline structure in thermotropic random copolymers

1991 ◽  
Vol 49 ◽  
pp. 1054-1055
Author(s):  
Afzana Anwer ◽  
S. Eilidh Bedford ◽  
Richard J. Spontak ◽  
Alan H. Windle
Keyword(s):  
Electron Microscopy ◽  
Crystalline Structure ◽  
Liquid Crystalline ◽  
Elevated Temperatures ◽  
Random Copolymers ◽  
Molecular Characteristics ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Identical Monomer ◽  
Periodic Layer

Random copolyesters composed of wholly aromatic monomers such as p-oxybenzoate (B) and 2,6-oxynaphthoate (N) are known to exhibit liquid crystalline characteristics at elevated temperatures and over a broad composition range. Previous studies employing techniques such as X-ray diffractometry (XRD) and differential scanning calorimetry (DSC) have conclusively proven that these thermotropic copolymers can possess a significant crystalline fraction, depending on molecular characteristics and processing history, despite the fact that the copolymer chains possess random intramolecular sequencing. Consequently, the nature of the crystalline structure that develops when these materials are processed in their mesophases and subsequently annealed has recently received considerable attention. A model that has been consistent with all experimental observations involves the Non-Periodic Layer (NPL) crystallite, which occurs when identical monomer sequences enter into register between adjacent chains. The objective of this work is to employ electron microscopy to identify and characterize these crystallites.

Triply-periodic nanostructures in surfactant, block copolymer, and biomembrane systems, and simulation of TEMs

1993 ◽  
Vol 51 ◽  
pp. 884-885
Author(s):  
David M. Anderson ◽  
Tomas Landh
Keyword(s):  
Liquid Crystalline ◽  
Diblock Copolymers ◽  
Cubic Phase ◽  
List Type ◽  
Interpenetrating Networks ◽  
Triply Periodic ◽  
Wide Range ◽  
Bicontinuous Cubic ◽  
Phase Liquid ◽  
Dividing Surface

First discovered in surfactant-water liquid crystalline systems, so-called ‘bicontinuous cubic phases’ have the property that hydropnilic and lipophilic microdomains form interpenetrating networks conforming to cubic lattices on the scale of nanometers. Later these same structures were found in star diblock copolymers, where the simultaneous continuity of elastomeric and glassy domains gives rise to unique physical properties. Today it is well-established that the symmetry and topology of such a morphology are accurately described by one of several triply-periodic minimal surfaces, and that the interface between hydrophilic and hydrophobic, or immiscible polymer, domains is described by a triply-periodic surface of constant, nonzero mean curvature. One example of such a dividing surface is shown in figure 5.The study of these structures has become of increasing importance in the past five years for two reasons:1)Bicontinuous cubic phase liquid crystals are now being polymerized to create microporous materials with monodispersed pores and readily functionalizable porewalls; figure 3 shows a TEM from a polymerized surfactant / methylmethacrylate / water cubic phase; and2)Compelling evidence has been found that these same morphologies describe biomembrane systems in a wide range of cells.

Electron microscopy and diffraction of crystalline dendrimers and macrocycles

1993 ◽  
Vol 51 ◽  
pp. 1218-1219
Author(s):  
C. J. Buchko ◽  
P. M. Wilson ◽  
Z. Xu ◽  
J. Zhang ◽  
S. Lee ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Liquid Crystalline ◽  
Structural Information ◽  
High Resolution Electron Microscopy ◽  
Scanning Calorimetry ◽  
Tertiary Butyl ◽  
Phenyl Acetylene ◽  
Selected Area Electron Diffraction ◽  
Liquid Crystalline Phases ◽  
Resolution Electron

The synthesis of well-defined organic molecules with unique geometries opens new opportunities for understanding and controlling the organization of condensed matter. Here, we study dendrimers and macrocycles which are synthesized from rigid phenyl-acetylene spacer units, Both units are solubilized by the presence of tertiary butyl groups located at the periphery of the molecule. These hydrocarbon materials form crystalline and liquid crystalline phases which have been studied by differential scanning calorimetry, hot stage optical microscopy, and wide-angle x-ray scattering (WAXS).The precisely defined architecture of these molecules makes it possible to investigate systematic variations in chemical architecture on the nature of microstructural organization. Here we report on the transmission electron microscopy (TEM), selected area electron diffraction (SAED), and high resolution electron microscopy (HREM) studies of crystalline thin films formed by deposition of these materials onto carbon substrates from dilute solution. Electron microscopy is very attractive for gaining structural information on new molecules due to the scarcity of material to grow single crystals suitable for conventional crystallography.

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