P A Hassan
Articles written in Pramana – Journal of Physics
Volume 63 Issue 2 August 2004 pp 277-283
Sphere-to-rod transition of triblock copolymer micelles at room temperature
R Ganguly V K Aswal P A Hassan I K Gopalakrishnan J V Yakhmi
A room temperature sphere-to-rod transition of the polyethylene oxide-polypropylene oxide-polyethylene oxide-based triblock copolymer, (PEO)20(PPO)70 (PEO)20 micelles have been observed in aqueous medium under the influence of ethanol and sodium chloride. Addition of 5–10% ethanol induces a high temperature sphere-to-rod transition of the micelles, which is brought to room temperature upon addition of NaCl. The inference about the change in the shape of the micelles has been drawn from small-angle neutron scattering (SANS) and viscosity studies.
Volume 63 Issue 2 August 2004 pp 351-355
Effect of substitution on aniline in inducing growth of anionic micelles
Gunjan Garg V K Aswal S K Kulshreshtha P A Hassan
Small-angle neutron scattering (SANS) measurements were carried out on sodium dodecyl sulfate (SDS) micelles in the presence of three different hydrophobic salts, i.e. aniline hydrochloride,
Volume 71 Issue 5 November 2008 pp 991-995 Small Angle Neutron Scattering
Jayita Bhattacharjee Gunjan Verma V K Aswal P A Hassan
Self-assembling behaviour of block copolymers and their ability to evade the immune system through polyethylene oxide stealth makes it an attractive candidate for drug encapsulation. Micelles formed by polyethylene oxide–polypropylene oxide–polyethylene oxide triblock copolymers (PEO–PPO–PEO), pluronic P123, have been employed for encapsulating the anti-cancer drug doxorubicin hydrochloride. The binding affinity of doxorubicin within the micelle carrier is enhanced through complex formation of drug and anionic surfactant, aerosol OT (AOT). Electrostatic binding of doxorubicin with negatively charged surfactants leads to the formation of hydrophobic drug–surfactant complexes. Surfactant-induced partitioning of the anti-cancer drug into nonpolar solvents such as chloroform is investigated. SANS measurements were performed on pluronic P123 mi-celles in the presence of drug–surfactant complex. No significant changes in the structure of the micelles are observed upon drug encapsulation. This demonstrates that surfactant–drug complexes can be encapsulated in block copolymer micelles without disrupting the structure of aggregates.
Volume 71 Issue 5 November 2008 pp 997-1002 Small Angle Neutron Scattering
Tuning intermicellar potential of Triton X-100– anthranilic acid mixed micelles
Gunjan Verma V K Aswal S K Kulshreshtha C Manohar P A Hassan Eric W Kaler
Structural parameters of micelles formed by Triton X-100 in the presence of solubilized anthranilic acid at different pH values was investigated using light scattering and small angle neutron scattering. Analysis of the SANS data indicate that micelles are oblate ellipsoidal in nature with little variation in the dimensions, in the investigated pH range (from 0.5 to 6.0). The interaction potential of the micelles shows a minimum closer to the isoelectric point of anthranilic acid. A similar variation is observed in the cloud point of the micelles with pH. The observed variation in the interaction potential with pH of the micellar solution can be explained in terms of the reversal of charge on anthranilic acid due to shift in the acid–base equilibrium. The variation in interaction potential and cloud point with pH is modelled using Coulombic repulsion of charged molecules at the micelle interface.
Volume 71 Issue 5 November 2008 pp 1003-1008 Small Angle Neutron Scattering
Structural investigation of viscoelastic micellar water/CTAB/NaNO3 solutions
K Kuperkar L Abezgauz D Danino G Verma P A Hassan V K Aswal D Varade P Bahadur
A highly viscoelastic worm-like micellar solution is formed in hexa-decyltrimethylammonium bromide (CTAB) in the presence of sodium nitrate (NaNO3). A gradual increase in micellar length with increasing NaNO3 was assumed from the rheological measurements where the zero-shear viscosity ($\eta_{0}$) versus NaNO3 concentration curve exhibits a maximum. However, upon increase in temperature, the viscosity decreases. Changes in the structural parameters of the micelles with addition of NaNO3 were inferred from small angle neutron scattering measurements (SANS). The intensity of scattered neutrons in the low 𝑞 region was found to increase with increasing NaNO3 concentration. This suggests an increase in the size of the micelles and/or decrease of intermicellar interaction with increasing salt concentration. Analysis of the SANS data using prolate ellipsoidal structure and Yukawa form of interaction potential between mi-celles indicate that addition of NaNO3 leads to a decrease in the surface charge of the ellipsoidal micelles which induces micellar growth. Cryo-TEM measurements support the presence of thread-like micelles in CTAB and NaNO3.
Volume 97, 2023
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