Diethylene Glycol Groups Research Articles

Structure of alumina-silica nanoparticles grafted with alkylphosphonic acids in poly(ethylacrylate) nanocomposites

Alumina-coated silica nanoparticles (NPs) grafted with phosphonic acids of different hydrophobicity were used as filler in poly(ethylacrylate) nanocomposites. Phosphonic acids bearing short alkyl chains or a diethylene glycol group have been grafted at densities up to 3.2 P/nm2 on NPs (20 nm) dispersed in water. Nanocomposites at particle fractions up to 10 vol% have been formulated by casting from the colloidal mixtures of modified NPs and nanolatex in water. The dispersion of the NPs in the polymer matrix has been studied by TEM combined with small-angle scattering, evidencing aggregation of NPs. TEM shows micrometer-scale inhomogeneities depending on the surface/polymer matrix compatibility. For the local interparticle correlations, a quantitative analysis of the intensity based on the mapping onto the effective structure factor of polydisperse hard spheres is developed. This mapping allows the model-free determination of the internal volume fraction of aggregates, termed compacity κ, to between 10% and 30%, compatible with the TEM analysis. κ is found to increase for the higher particle volume fractions, to decrease with grafting density, and to be mostly independent of the nature and mass of the graft. Preliminary evidence for an improved compatibility of grafted with respect to bare NPs is found, as opposed to their aqueous precursor suspensions where some pre-aggregation is induced by grafting.

Physical Evaluation of Explanted Vascular Prostheses

The authors attempt to describe a comprehensive study of physical ageing in vivo on the properties of explanted prostheses. Infrared spectroscopy (FTIR) technique has been used to compare the molecular conformation of various polyethylene terephthalate (PET) yarns extracted from the different areas of the prostheses (with different lifetimes) collected after ageing. The FTIR found results showed an increased PET crystallinity related to the development of microcrystallites in the amorphous areas of PET chains. Nevertheless, these small crystallites are not perfectly orientated according to the fiber axis. In addition, we can deduced that the ruptures in macromolecular chain can occur in the diethylene glycol groups existing in the zones amorphous and can be induced the crystallization process.

Optimization of the polycondensation stage of poly(ethylene terephthalate) reactors

A general kinetic scheme for the polycondensation step of the PET formation has been used to establish the mole balance equations of various functional groups in batch reactors. An objective function has been defined which aims to attain a desired degree of polymerization in the shortest time, has a specified level of diethylene glycol group content, and minimizes the other side products. Using the control vector iteration procedure, an optimum temperature profile has been calculated. The computations suggest that a high temperature should be used initially which must be lowered as the time of reaction increases for limiting the formation of side products.