Synthesis and Study of Hybrid Organic – Inorganic Polyhedral Oligomeric Silsesquioxanes (poss) Based Polymers

Hybrid organic-inorganic materials represent a new class of materials having scientific and technological potential. In this thesis, Polyhedral Oligomeric Silsesquioxanes (POSS) are used as an inorganic building block which has been tethered to an organic polymer. POSS are silica precusors, having a well defined silsesquioxane cental core surrounded by an organic periphery which makes them compatible with monomers and possibly polymers. The objectives of this study are to (1) study the basic structures of POSS homopolymers, (2) to incorporate POSS building blocks by a bottomup approach into polymer chains and study the resulting morphologies, and (3) to study the thin film behavior of POSS block copolymers. PMA and styryl POSS homopolymers of different peripheries were synthesized by ATRP and mass spectrometry studies were carried out by MALDI-TOF and ESI. PMA POSS chains undergo a number of fragmentations while styrly POSS chains have a relatively robust backbone. Poly(ethylene-butylene-b-MAPOSS), AB type copolymers and poly(MAPOSS-b-styrene-b-MAPOSS), ABA type copolymers were synthesized by a combination of anionic and ATRP polymerization. Spheres, inverse cylinders, lamellar and crystalline lamellar morphologies were observed for the poly(ethylene-butylene-b- MAPOSS) copolymers. In the poly(MAPOSS-b-styrene-b-MAPOSS) copolymers, cylindrical, lamellar and perforated lamellar morphologies were obtained. Beyond the interaction parameter (χ), total degree of polymerization (N) and volume fraction (f), the conformational asymmetry (ε) also plays an important role in determining the morphology of these block copolymer. Crystallization of the POSS phase and better thermal properties were observed in the both block copolymers. Thin film studies of poly(MAPOSS-b-styrene-b-MAPOSS) copolymers showed that the microdomains can be oriented either parallel or perpendicular to the substrate depending upon the film thickness, morphology and relative volume fractions of the connecting blocks. By removal of the organic phase, ordered mesoporous low dielectric constant silica films were obtained. These hybrid block copolymers are a potential candidate for nanopatterning applications

Case report: Antenatal MRI diagnosis of cloacal dysgenesis syndrome

Cloacal dysgenesis sequence (CDS) is a lethal malformation with a highly variable presentation. CDS is characterized by direct communication between the gastrointestinal, urinary, and genital structures, resulting in a single perineal opening. Prenatal diagnosis of a cloacal anomaly is often difficult because of the highly variable imaging features. Here, we report a case in which a diagnosis of CDS was made with fetal MRI on the basis of a meconium-containing, bilobed, abdominopelvic cystic mass communicating with the ureters and the colon

Metabolic bone disease as a presenting manifestation of primary Sjögren's syndrome: Three cases and review of literature

Primary Sjögren's syndrome (pSS) is a chronic autoimmune disease characterized by a progressive lymphocytic infiltration of the exocrine glands with varying degrees of systemic involvement. Chronic inflammation compromises the glands’ function that leads to dry symptoms in the mouth/eyes. Renal involvement is a well recognized extraglandular manifestation of pSS. Metabolic bone disease (MBD), however, rarely occurs as the primary manifestation of a renal tubule disorder due to pSS. To the best of our knowledge there are only 6 reported cases of metabolic bone disease as the primary manifestation of pSS to date. Four of these had distal renal tubular acidosis (RTA), and 2 had a combined picture of distal and proximal tubular dysfunction. We herein present our experience of 3 cases who presented to us with a clinical picture suggestive of MBD. While investigating these patients, we found evidence of RTA, which was found to be secondary to pSS