Hullathy Subban Ganapathy

Characterization of micellar film morphologies of semifluorinated block copolymers by AFM

The micellar morphologies of well-defined amphiphilic block copolymers composed of 1H,1H-dihydroperfluorooctyl methacrylate (FOMA) and ethylene oxide (EO) blocks with different chain lengths were effectively investigated by using tapping mode-atomic force microscopy (TM-AFM). By spin-casting chloroform solutions, well-ordered spherical micellar films could be obtained for poly(FOMA(10k)-b-EO(10k)) and poly(FOMA(20k)-b-EO(20k)) copolymers. The atomic force microscopy (AFM) height and phase image analysis indicated that dark regions of the micelles corresponded to PEO blocks and the light regions were for PFOMA blocks. The spherical micelles with PEO corona and PFOMA core were also identified by transmission electron microscopy (TEM) and X-ray photoelectron spectrometer (XPS) analysis. The core diameters of the block-copolymer aggregates were 20 nm for poly(FOMA(10k)-b-EO(10k)) and 30 nm for poly(FOMA(20k)-b-EO(20k)) by TM-AFM, whereas slightly lower values of 17 and 26 nm were obtained from TEM. A detailed study on the inverted morphological change observed in the micelles films after annealing above glass transition temperature (T(g)) was also presented.

Inclusion complex formation of water- Soluble drug, captopril, and peracetylated-β-cyclodextrin in supercritical CO2 for controlled release applications

The inclusion complex of CO2-soluble peracetylated-β-cyclodextrin (PAc-β- CD), heptakis(2,3,6-tri-O-acetyl)-β-cyclodextrin, and highly water-soluble drug captopril, was prepared by a chemical solvent-free method using supercritical carbon dioxide. The captopril-PAc-β-CD inclusion complex was further confirmed by DSC and XRD studies. In- vitro release of captopril from an oily suspension confirmed that the dissolution rate of captopril was much retarded from the inclusion complex as a result of the hydrophobic properties of PAc-β-CD.

A Novel Method to Prepare Nano-Structured Semi-Conducting Polythiophenes by Supercritical Process

Rapid Expansion of Supercritical carbon dioxide Solutions (RESS) containing CO2-soluble, fluorinated ester substituted polythiophene: poly[2-(3-thienyl)acetyl ,3,4,4,5,5,6,6- 7,7,8,8,8,tridecafluoro-1-octanate] (PSFTE) through a small heated micro-orifice (150 .m) produces nanoparticles in the size range of 50 - 300 nm. Pre-expansion temperatures and pressures were found to have marked impact on particle size and morphology. While the particle size increased with more agglomeration with increase in temperature, smaller and spherical particles were produced with increase in pressure owing to the higher solubility of PSFTE in CO2 at high pressures.

Supercritical Carbon Dioxide Assisted Impregnation of Molsidomine into Poly(DL-Lactide-co-Glycolide) for Sustained Release Applications

Supercritical carbon dioxide (scCO2) was used as a processing medium for the fabrication of drug encapsulated poly(DL-lactide-co-glycolide) (PLGA) monoliths for their potential application in the controlled release of water soluble drugs. Exposure of PLGA to scCO2 leads to effective plasticization and liquefaction due to the high solubility and interaction of the scCO2 in the copolymer. By exploiting this property, it was demonstrated that prolonged release formulations of molsidomine, a peripheral nitrovasodilator used to treat angina pectoris, can be prepared by chemical solvent-free, scCO2 assisted drug impregnation method. The in-vitro dissolution studies revealed that the release rates of drug from the porous polymer monoliths containing different amount of the drug samples were significantly retarded due to encapsulation of molsidomine into the PLGA matrix.

Polymerization of methyl methacrylate in supercritical carbon dioxide with PDMS based stabilizers : A study on the effect of stabilizer anchor groups

The effect of different type of polydimethysiloxane (PDMS) based stabilizers on the dispersion polymerization of MMA in supercritical carbon dioxide (scCO 2 ) has been investigated in terms of their anchor group architecture. PDMS chain was used in each case as a CO 2 -philic portion of the stabilizer and five different PMMA-philic endgroups were investigated: an alcohol, an acetate group, a methacrylate unit, and two block copolymers containing acrylate groups. A trifunctional block copolymer, PDMS-b-(PMMA(l.lK)-co-PMA(0.5K) was found to be very effective stabilizer due to the efficient stabilizer anchor-soluble balance (ASB) which produced excellent yield, high molecular weight, and uniform particles of micron sized PMMA.

Hydrophobically Modified Amphiphilic Cylodextrins as Novel Carriers for Controlled Delivery of Water-Soluble Drugs

Hydrophobically modified derivative of a γ-cyclodextrin, functionalized with perfluoro alkyl ester group, was prepared and investigated for its potential use as a sustained release carrier for water-soluble drug molsidomine, a peripheral nitrovasodilator used in the treatment of angina pectoris. The molecular encapsulation of molsidomine by the amphiphilic cyclodextrin, octakis(6-O-perfluorobutanoyl)-γ-cyclodextrin (γ-CyD-F), was confirmed by DSC and XRD studies. The in-vitro release of molsidomine from peanut oil suspensions into aqueous phase was found to be significantly retarded by the complexation with γ-CyD-F, mainly due to the hydrophobic properties of the γ-CyD-F.