TY - JOUR
T1 - Structural behavior and interactions of dendrimer within lyotropic liquid crystals, monitored by EPR spectroscopy and rheology
AU - Bitan-Cherbakovsky, Liron
AU - Libster, Dima
AU - Ottaviani, Maria Francesca
AU - Aserin, Abraham
AU - Garti, Nissim
PY - 2012/3/1
Y1 - 2012/3/1
N2 - Micro- and macrostructural behaviors of three different lyotropic liquid crystals (LLCs) loaded with a dendrimer, namely second generation poly(propylene imine) (PPI-G2), were studied by means of rheology and electron paramagnetic resonance (EPR). The three mesophases were Lα, Q224, and HII composed of glycerol monooleate (GMO) and water-PPI-G2 solution (and d-α-tocopherol (vitamin E) in the case of HII). We characterized the impact of PPI-G2 interactions with the components of the host mesophases on their structural characteristics on different length scales. The incorporation of PPI-G2 within the Lα and HII systems induced the formation of more elastic hexagonal systems with a "solidlike" behavior, while in the Q224 system a different trend with a "liquidlike" behavior was observed. As a result, the dendrimer induced a remarkable change in both the structural and viscoelastic properties of the systems. Hence, the microenvironment in the interface region within the systems was monitored by computer-aided EPR using 5-doxylstearic acid (5-DSA) as a pH-dependent probe. The microviscosity (τ) and order (S) of systems were found to be sensitive to the PPI-G2 presence: when PPI-G2 concentration increased, τ and S increased in both the Lα and Q224 systems. In the HII systems two trends were observed, reflecting a decrease in τ and S up to 10 wt % PPI-G2 and subsequently their increase at higher dendrimer concentrations. It was assessed that PPI-G2 interacted strongly with the GMO hydroxyl groups in the L α phase, with the water molecules in the Q224 systems. In the HII mesophase strong interactions with both the water and GMO hydroxyl molecules were detected.
AB - Micro- and macrostructural behaviors of three different lyotropic liquid crystals (LLCs) loaded with a dendrimer, namely second generation poly(propylene imine) (PPI-G2), were studied by means of rheology and electron paramagnetic resonance (EPR). The three mesophases were Lα, Q224, and HII composed of glycerol monooleate (GMO) and water-PPI-G2 solution (and d-α-tocopherol (vitamin E) in the case of HII). We characterized the impact of PPI-G2 interactions with the components of the host mesophases on their structural characteristics on different length scales. The incorporation of PPI-G2 within the Lα and HII systems induced the formation of more elastic hexagonal systems with a "solidlike" behavior, while in the Q224 system a different trend with a "liquidlike" behavior was observed. As a result, the dendrimer induced a remarkable change in both the structural and viscoelastic properties of the systems. Hence, the microenvironment in the interface region within the systems was monitored by computer-aided EPR using 5-doxylstearic acid (5-DSA) as a pH-dependent probe. The microviscosity (τ) and order (S) of systems were found to be sensitive to the PPI-G2 presence: when PPI-G2 concentration increased, τ and S increased in both the Lα and Q224 systems. In the HII systems two trends were observed, reflecting a decrease in τ and S up to 10 wt % PPI-G2 and subsequently their increase at higher dendrimer concentrations. It was assessed that PPI-G2 interacted strongly with the GMO hydroxyl groups in the L α phase, with the water molecules in the Q224 systems. In the HII mesophase strong interactions with both the water and GMO hydroxyl molecules were detected.
UR - http://www.scopus.com/inward/record.url?scp=84857732878&partnerID=8YFLogxK
U2 - 10.1021/jp212008a
DO - 10.1021/jp212008a
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AN - SCOPUS:84857732878
SN - 1520-6106
VL - 116
SP - 2420
EP - 2429
JO - Journal of Physical Chemistry B
JF - Journal of Physical Chemistry B
IS - 8
ER -