MICELLIZATION STUDIES OF DODECYL BENZENESULFONIC ACID AND ITS INTERACTION WITH POLYVINYLPYRROLIDONE

Dodecyl benzenesulfonic acid (DBSA) surfactant was used in the present study to find the effect of concentration on its electrical conductance in solution from 293-323K above and below the critical micelle concentration (CMC). The micellization parameters i.e. degree of counter ion binding (β), aggregation number (n) and number of counter ion micelle(m) were measured. The interaction of DBSA with polyvinylpyrrolidone (PVP) was also studied at 293K throughconductance and surface tension measure ments. A number of important parameters i.e. critical aggregation concentration (CAC), Gibb‘s free energy (△G) and binding ratio (R) were determined and the effect of NaCl on the CAC and polymer saturation point (PSP) was also investigated.     

MOLECULAR ENGINEERING STUDIES ON NONTHROMBOGENIC BIOMATERIALS--A NOVEL CLASS OF NONTHROMBOGENIC BIOMATERIALS WITH ZWITTERIONIC STRUCTURE OF CARBOXYBETAINES

N,N-dimethyl-N-methacryloyloxyethyl-N-carboxyethyl ammonium (DMMCA) was graft-copolymerized onto the surface of segmented poly(ether urethane) (SPEU) and PE film. The carboxybetaine structure on SPEU and PE film surfaces was confirmed by ATR-FTIR, XPS and water contact angle measurements. Through the experiments with platelet adhesion and protein adhesion assay in vitro, the two materials studied, including poly-DMMCA gel, all show excellent nonthrombogenicity. This confirms once again that the zwitterionic molecular structure on the surfaces of materials is essential for improving their nonthrombogenicity and biocompatibility.     

FTIR STUDIES ON THE MODEL POLYURETHANE HARD SEGMENTS BASED ON A NEW WATERBORNE CHAIN EXTENDER DIMETHYLOL BUTANOIC ACID （DMBA）

Three model polyurethane hard segments based on dimethylol butanoic acid (DMBA) and 1,6-hexane diisocyanate (HDI), toluene diisocyanate (TDI) and 4,4‘-diphenylmethane diisocyanate (MDI) were prepared by the solution method.Fourier Infrared (FTIR) spectroscopy was employed to study the H-bonds in these model polyurethanes. The model polyurethane hard segment prepared from HDI and 1,4-butanodiol (BDO) was used for comparison. It was found that the incorporation of the pendent carboxyl through DMBA into the model hard segments weakens the original NH…O=C H-bond but gives more H-bond patterns based on the two H-bond donors, urethane NH and carboxylic OH. The carboxylic dimer is one of the main H-bond types and is stronger than another main H-bond type NH…O=C. In addition, the H-bond in aromatic model hard segments is stronger than that of aliphatic hard segments. The appearance of the free C:O and the fact that almost all N-H is H-bonded suggest that there possibly exist either the third H-bond acceptor or the H-bond formed by one acceptor with two donors.     

STUDIES ON COMBUSTION BEHAVIOR OF NR/MMT NANO-COMPOSITES BY CONE CALORIMETER

The NR/modified montmorillonite(EMT)nano-composites were prepared by mechanical mixing and reacting in situ with glycidyl methacrylate.Under 30 kW.m~(-2)of heat flux,the combustion behavior of the nano-composites was studied with cone calorimetry,and PHRR,THR,EHC,TSR and MLR were tested.The results showed that the nano- composite had improved mechanical properties and flame retardance properties,and to some extent,the nano-composite had smoke suppress effect.Compared with pure NR,the PHRR,EHC and SPR of the nano-composite reduced by 34%,21% and 16.8%,respectively.     

Organotin(IV) complexes of Schiff bases derived by condensation of heterocyclic ketones and sulfa drugs

Abstract —Reaction of bis(triorganotin)oxide with Schiff bases derived by condensation of heterocyclic ketones, 2-acetylfuran and 2-acetylthiophene, with various sulfadrugs (sulfaguanidine, sulfathiazole, sulfisoxazole and sulfadiazine) leads to the formation of a new series of organotin(IV) complexes. An attempt has been made to probe their structures on the basis of elemental analysis, conductance measurements, molecular weight determination, UV, IR and NMR (1H, 13C and 119Sn) spectral studies. The results of antimicrobial effects of some representative complexes on different species of pathogenic fungi and bacteria have also been recorded and discussed.     

Synthesis and Characterization of Multi-layered Core/Shell Particles by Sequential Emulsion Polymerization

A series of core/shell particles were prepared by sequential emulsion polymerization. The core/shell particles consisting of poly(methyl methacrylate) core grafted with using rubbery layer [poly(butyl acrylate)co-(styrene)] and then glassy layer [poly(methyl methacrylate)-co-(ethyl acrylate)] were prepared. The conditions which led to controlled particle size and morphology were discussed. A highly cross-linked structure was formed in both the cores and the shells by using a cross-linking agent, which could prevent the migration of hydrophobic shells to the inside of the particles. The core/shell particles were characterized by Fourier-transform infrared spectroscopy, solid state ¹³C-NMR. Thermogravimetric analysis (TGA) and differential scanning calorimeter (DSC) were used to determine the thermal stability and glass transition temperature of the core/shell particles, respectively. Results of the particle size analysis indicate that particle sizes were decreased when there is a rubbery layer as outer layer (0.44 μm) whereas it increases when there is a glassy layer as outer layer (324 μm). Scanning electron microscopy (SEM) also confirms the multi-layers formation in the polymer.     

STUDIES ON THE PORE FORMATION MECHANISM OF β-CRYSTALLINE POLYPROPYLENE UNDER STRETCHING

The pore formation mechanism of β-crystalline polypropylene under stretching was investigated. The porosity of the samples increases rapidly with stretching, having a maximum at draw ratios around 2 and then decreases monotonically.An abrupt formation process of initial micropores at very low draw ratios was evidenced by in situ SAXS measurements. At the same time the phase transition from β-crystal to a-crystal proceeds slowly in the whole deformation process up to large draw ratios around 5. Comparative studies of a- and β-crystalline polypropylene samples before stretching indicate that in addition to difference in crystal forms the a- and β-crystalline polypropylene samples exhibit quite different morphological features. There are a lot of interfaces in β-crystalline polypropylene samples, which may have a lower density value and can be easily etched by argon ions and penetrated by small molecules. It was concluded from these experimental facts that the pore formation and crystal transition are two independent phenomena during the deformation of β-crystalline polypropylene samples, and phase transition from β-crystal to a-crystal could hardly be the origin of pore formation. A defect initiation mechanism was proposed to understand the pore formation behavior of β-crystalline polypropylenes.