PVA hydrogels behave as non-ideal mixture of water and polymers when increasing their crosslinking degree.

Background: Magnetic fields can interact with liquid matter in a homogeneous and instantaneous way, without physical contact, independently of its temperature, pressure, and agitation degree, and without modifying recipes nor heat and mass transfer conditions. In addition, magnetic fields may affect the mechanisms of generation and termination of free radicals. This paper is devoted to the elucidation of the appropriate conditions needed to develop magnetic field effects for controlling the kinetics of polymerization of water soluble monomers. Methods: Thermal- and photochemically-initiated polymerizations were investigated at different initiator and monomer concentrations, temperatures, viscosities, and magnetic field intensities. Results: Significant magnetic field impact on the polymerization kinetics was only observed in photochemically-initiated polymerizations carried out in viscous media and performed at relatively low magnetic field intensity. Magnetic field effects were absent in polymerizations in low viscosity media and thermally-initiated polymerizations performed at low and high magnetic field intensities. The effects were explained in terms of the radical pair mechanism for intersystem crossing of spin states. Conclusion: Polymerization kinetics of water soluble monomers can be potentially controlled using magnetic fields only under very specific reaction conditions.

Magnetite superparamagnetic nanoparticles (MNP) are becoming one of the firsts nanocommodity products. MNP find a number of applications and they are been produced at relatively large scale. The co-precipitation method presents many technical and economical advantages among alternative processes. However, the relationships between physical and chemical reaction conditions during the co-precipitation process and the resulting properties of obtained MNP are not yet fully understood. The novelty of this contribution is the establishment of the cross-dependency effects of the main physical and chemical parameters of the co-precipitation reaction on the properties of resulting MNP. The conditions were varied by following an experimental design. The crystallite size, particle size and magnetization of the MNP and the Z-potential and size of their aggregates were selected as main response properties. A set of equations in the form of 4D surface responses in the space of co-precipitation process variables was obtained and analyzed in terms of the resulting properties. The set of equations is useful to predict, optimize and tailor very precisely the properties of resulting MNP as a function of reaction conditions.

The development of new cosmetic products, skin contact medical devices, skin medicaments, wound care devices, tattooing and piercing has experienced an impressive growth in recent years. In parallel, new restrictions to in vivo experimentation in animals and humans have been widely implemented by regulatory authorities. New knowledge about alternative materials for in vitro skin-related experimentation is required to overcome these severe limitations. This paper presents a set of three 4-D surface response equations describing the mechanical properties of skin-like gelatin membranes intended for use as an alternative biomaterial for in vitro skin-related experimentation. The membranes were obtained by a sol-gel method. The novelty of this contribution is the establishment of the cross-dependency effects of key synthesis conditions on the final mechanical properties of gelatin membranes. The results of this work are useful to produce gelatin membranes with tailored mechanical properties mimicking different types of human skins. In particular, membranes with Young’s modulus of 1 MPa and maximum tensile strength of 0.85 MPa were obtained.

The effect of magnetic field (MF) on the radical copolymerization of a series of water‐soluble and ionic monomers is presented including acrylamide (AM), acrylic acid (AA), its ionized form acrylate (A⁻), and diallyldimethylammonium chloride (DADMAC). The following combinations have been studied: AM/AA, AM/A⁻, AM/DADMAC, and AA/DADMAC. In addition to the MF, strong electrostatic interactions are present for the majority of monomer combinations and conditions. Although the monomer consumption rate (R_p) increased up to 65% applying a MF of 0.1 Tesla, the composition of the resulting copolymers was not affected under such conditions. Despite this increase of R_p by MF, the electrostatic repulsion between ionic monomers and charged growing radicals dominates R_p and governs the copolymer composition with and without MF. The order of the experimentally obtained reactivity ratios reflects the extent of electrostatic interaction: r_AM/AA (1.41) < r (3.10) < r_AA/DADMAC (4.25) < r_AM/DADMAC (6.95) and r_AA/AM (2.20) > r_DADMAC/AA (0.25) > r (0.17) > r_DADMAC/AM (0.03). Overall, weak MF offers to reduce the production time without modifying the product composition. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 373–383, 2009