154 research outputs found
Polymer/montmorillonite nanocomposites with improved thermal properties: Part II. Thermal stability of montmorillonite nanocomposites based on different polymeric matrixes.
In previous part of this work factors influencing the thermal stability of
polymer nanocomposite materials were indicated, such as chemical constitution of
organic modifier, filler content, nanocomposites’ structure and the processing-
dependent degree of homogenization of nanofiller, were presented. In this part
the basic changes in thermal behaviour of different polymeric matrixes (e.g.
polyolefins, polyamides, poly(vinyl chloride) and styrene-containing polymers)
upon addition of montmorillonite have been described. Brief description of the
kinetics of the decomposition process in inert and oxidative environment, as
well as analysis of volatile and condensed products of degradation, have also
been present
Rehydration of CTMA modified DNA powders observed by NMR
The rehydration of salmon sperm deoxyribonucleic acid (DNA) and cetyltrimethylammonium chloride complexes was observed using hydration kinetics, sorption isotherm, and high power proton relaxometry (at 30 MHz). The hydration kinetics shows (i) a very tightly bound water not removed by incubation over silica gel ( = 0.061 ± 0.004), (ii) a tightly bound water saturating at = 0.039 ± 0.011, with the hydration time = (1.04 ± 0.21) h, a loosely bound water fraction (iii) with the hydration time = (19.1 ± 3.2) h and the contribution progressively increasing with the air humidity. For the hydration at = 100%, after = (152.6 ± 2.5) h of incubation the swelling process begins. The swelling time was = (12.5 ± 5.4) h, and the swelling amplitude = 0.140 ± 0.016. The sorption isotherm is sigmoidal in form and is fitted by the Dent model with the mass of water saturating primary binding sites Δ M/ = 0.102 ± 0.021. Proton free induction decay is a superposition of the immobilized proton signal (Gaussian, with * ≈ 30 μs) and two liquid signal components coming from tightly bound (* ≈ 100 μs) and loosely bound water fraction with the amplitude proportional to the mass of water added (* ≈ 1000 μs)
Photoinduced Gratings in Functionalized Azo-Carbazole Compounds in Picosecond Regime
We report results of diffraction grating inscription on thin films prepared from epoxy resin doped with azo-carbazole based dyes. Diffraction gratings were recorded at the wavelength 532 nm and monitored through intensity of first order of diffraction (632 nm). Atomic force microscope scans of the gratings show that a surface relief grating also appeared
Effect of different polyethers on surface and thermal properties of poly(urethane-siloxane) copolymers modified with side-chain siloxane
Dielectric relaxation mechanisms in polyoxymethylene/polyurethane/layered silicates hybrid nanocomposites
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PEGylated systems in pharmaceutics
This review addresses the use of poly(ethylene glycol) (PEG) and PEG conjugation for the design of novel dosage forms and the modification of biomolecules. The peculiarities of PEGylated nanoparticles, liposomes, proteins, enzymes, and small drug and polyelectrolyte molecules and their influence on systemic drug delivery, including overcoming of various biological barriers and adhesion to mucosal tissues (mucoadhesion), are considered
Polymer/montmorillonite nanocomposites with improved thermal properties: Part I. Factors influencing thermal stability and mechanisms of thermal stability improvement.
The results of recent research indicate that the introduction of layered
silicate – montmorillonite – into polymer matrix results in increase of thermal
stability of a number of polymer nanocomposites. Due to characteristic structure
of layers in polymer matrix and nanoscopic dimensions of filler particles,
several effects have been observed that can explain the changes in thermal
properties. The level of surface activity may be directly influenced by the
mechanical interfacial adhesion or thermal stability of organic compound used to
modify montmorillonite. Thus, increasing the thermal stability of
montmorillonite and resultant nanocomposites is one of the key points in the
successful technical application of polymer–clay nanocomposites on the
industrial scale. Basing on most recent research, this work presents a detailed
examination of factors influencing thermal stability, including the role of
chemical constitution of organic modifier, composition and structure of
nanocomposites, and mechanisms of improvement of thermal stability in polymer/
montmorillonite nanocomp
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