2024-03-29T06:13:20Zhttp://digital.csic.es/dspace-oai/requestoai:digital.csic.es:10261/96022012-11-26T23:00:00Zcom_10261_5063com_10261_5col_10261_5066
Formation and properties of reverse micellar cubic liquid crystals and derived emulsions
Rodríguez-Abreu, Carlos
Shrestha, Lok Kumar
Varade, Dharmesh
Aramaki, Kenji
Maestro, Alicia
López Quintela, Arturo
Solans, Conxita
Reverse micellar
Cubic liquid crystals
Water droplets
Elastic modulus
Viscosity
Polymerizable oils
8 pages, 11 figures.-- PMID: 17910486 [PubMed].-- Supporting information (Suppl. figures S1-S3, 3 pages) available at: http://pubs.acs.org/doi/suppl/10.1021/la701722f/suppl_file/la701722f-file001.pdf
Printed version published Oct 23, 2007
The structure of the reverse micellar cubic (I2) liquid crystal and the adjacent micellar phase in amphiphilic block copolymer/water/oil systems has been studied by small-angle X-ray scattering (SAXS), rheometry, and differential scanning calorimetry (DSC). Upon addition of water to the copolymer/oil mixture, spherical micelles are formed and grow in size until a disorder-order transition takes place, which is related to a sudden increase in the viscosity and shear modulus. The transition is driven by the packing of the spherical micelles into a Fd3m cubic lattice. The single-phase I2 liquid crystals show gel-like behavior and elastic moduli higher than 10^4 Pa, as determined by oscillatory
measurements. Further addition of water induces phase separation, and it is found that reverse water-in-oil emulsions with high internal phase ratio and stabilized by I2 liquid crystals can be prepared in the two-phase region. Contrary
to liquid-liquid emulsions, both the elastic modulus and the viscosity decrease with the fraction of dispersed water, due to a decrease in the crystalline fraction in the sample, although the reverse emulsions remain gel-like even at high volume fractions of the dispersed phase.Atemperature induced order-disorder transition can be detected by calorimetry
and rheometry. Upon heating the I2 liquid crystals, two thermal events associated with small enthalpy values were detected: one endothermic, related to the "melting" of the liquid crystal, and the other exothermic, attributed to phase separation. The melting of the liquid crystal is associated with a sudden drop in viscosity and shear moduli. Results
are relevant for understanding the formation of cubic-phase-based reverse emulsions and for their application as templates for the synthesis of structured materials.
This work was partly supported by Core Research for Evolution Science and Technology (CREST) of
JST Corporation. C.R. thanks Josep Carilla (Institut d’Investigacions Químiques i Ambientals de Barcelona) for his help with
DSC measurements. L.K.S. is thankful to the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan for the Monbukagakusho Scholarship. D.V. thanks JSPS
for financial support. The authors are grateful to Dr. Takaaki Sato (Waseda University) for valuable discussions and comments on SAXS results.
Peer reviewed
2009-01-14T09:24:13Z
2009-01-14T09:24:13Z
2007-10-02
artículo
http://purl.org/coar/resource_type/c_6501
Langmuir 23(22): 11007-11014 (2007)
1520-5827
http://hdl.handle.net/10261/9602
10.1021/la701722f
en
http://dx.doi.org/10.1021/la701722f
none
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American Chemical Society