Structure–properties investigations in hydrophilic nanocomposites based on polyurethane/poly(2–hydroxyethyl methacrylate) semi‐interpenetrating polymer networks and nanofiller densil for biomedical application

Nanocomposites based on sequential semi–interpenetrating polymer networks (semi–IPNs) of crosslinked polyurethane and linear poly(2‐hydroxyethyl methacrylate) filled with 1–15 wt % of nanofiller densil were prepared and investigated. Nanofiller densil used in an attempt to control the microphase separation of the polymer matrix by polymer–filler interactions. The morphology (SAXS, AFM), mechanical properties (stress–strain), thermal transitions (DSC) and polymer dynamics (DRS, TSDC) of the nanocomposites were investigated. Special attention has been paid to the raising of the hydration properties and the dynamics of water molecules in the nanocomposites in the perspective of biomedical applications. Nanoparticles were found to aggregate partially for higher than 3 and 5 wt % filler loading in semi–IPNs with 17 and 37 wt % PHEMA, respectively. The results show that the good hydration properties of the semi–IPN matrix are preserved in the nanocomposites, which in combination with results of thermal and dielectric techniques revealed also the existence of polymer–polymer and polymer–filler interactions. These interactions results also in the improvement of physical and mechanical properties of the nanocomposites in compare with the neat matrix. The improvement of mechanical properties in combination with hydrophilicity and biocompatibility of nanocomposites are promising for use these materials for biomedical application namely as surgical films for wound treatment and as material for producing the medical devises. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43122.     

Synthesis and characterization of new polymethacrylate bearing cyclopropane ring as side group

A cyclopropanation reaction of allylmethacrylate (1) with ethyldiazoacetate (2) lead to the formation of 2-(2-methyl-acryloyloxymethyl)-cyclopropanecarboxylic acid ethyl ester (3) as a mixture of cis/trans isomers in molar ratio 2:1. The cis isomer could be selectively hydrolyzed by use of Pig liver esterase (PLE). An isolated cis-2-(2-methyl-acryloyloxymethyl)-cyclopropanecarboxylic acid (4) exhibited optical activity. The monomer 3 was easily polymerized using AIBN and benzopinacol as free radical initiators at 65 and 130 °C, respectively. ¹H NMR and FT-IR analyses confirmed the presence of the chemically stable cyclopropane ring in both monomer and polymers. The obtained polymers were also characterized by GPC and DSC measurements. A depolymerization behaviour was observed heating the polymers at 200-250 °C. The regeneration of starting cis/trans isomers of 3 can be taken as a proof of the high thermal stability of the cyclopropane ring.     

Effect of Hypergravity on the Level of Heat Shock Proteins 70 and 90 in Pea Seedlings

Exposure to hypergravity induces significant changes in gene expression of plants which are indicative of stress conditions. A substantial part of the general stress response is up-regulation of heat shock proteins (Hsp) which function as molecular chaperones. The objective of this research was to test the possible changes in the Hsp70 and Hsp90 level in response to short-term hypergravity exposure. In this study 5-day-old etiolated pea seedlings were exposed to centrifuge-induced hypergravity (3–14 g) for 15 min and 1 h and a part of the seedlings was sampled at 1.5 and 24 h after the exposures. Western blot analysis showed time-dependent changes in Hsp70 and Hsp90 levels: an increase under hypergravity and a tendency towards recovery of the normal content during re-adaptation. The quantity and time of their expression was correlated with the g-force level. These data suggest that short-term hypergravity acts as a stress which could increase the risk of protein denaturation and aggregation. Molecular chaperons induced during the stress may have an essential role in counteracting this risk.     

Mathematical modeling and numerical analysis of elastic body with thin inclusion

This article studies elastic multi-component structure consisting of matrix body with thin inclusion. Mathematical model dwells on membrane shell theory for thin inclusion, while classical elasticity theory is used for matrix medium under the assumption of perfect bonding on the media interface. We prove the existence and uniqueness of the weak problem solution. In order to implement finite element scheme, a coupled model is developed. Simulations are performed for the plane coupled problem. Eventually we compare the solutions obtained with the classical approach results and estimate a posteriori errors for different meshes to assess the model. Bridging theory with practice, the model’s applicability to engineering problems is demonstrated finally.     

Solvation effects on spectral and photophysical properties of phenalenone dyes in polyurethane polymers

Spectral and photophysical properties of several phenalenone dyes were investigated in the dependence on a type of the polyurethane polymer matrix. The increase in polarity of the solid-state medium was shown to shift absorption and luminescence spectra to the low energy side. Effects of the substituents in the phenalenone chromophore on a Stokes shift value were studied. Photophysical properties of phenalenones were found out to be significantly dependent on the polymerization method of polymer matrices. Considerable growth in photostability of organic dyes was observed when the dyes were bonded covalently with a polymer chain.     

Graphene growth on Ni(111) by transformation of a surface carbide

A novel growth mechanism of graphene on Ni(111) has been discovered that occurs at temperatures below 460 °C. At these conditions, a surface-confined nickel-carbide phase coexists with single layer graphene. The graphene grows by in-plane transformation of the carbide along a one-dimensional phase-boundary, which is distinctively different from known growth processes on other transition metals and on Ni above 460 °C, where carbon atoms attach to "free" edges of graphene islands.     

Peculiarities of interactions between 6-aminophenalenone dye and polyurethane matrix

Possibility for chemical interactions of 6-aminophenalenone dye with the components of reaction mixture at the polyurethane formation was shown by means of X-ray wide angle scattering, EPR and visible spectroscopy methods. This was also confirmed by IR-spectroscopy, identifying the products of the model reaction between 6-aminophenalenone and hexamethylene diisocyanate. Observed large Stokes shift gives prospects to use efficiently the polyurethane matrix with 6-aminophenalenone as an active element in dye lasers.     

Microstructure changes of polyurethane by inclusion of chemically modified carbon nanotubes at low filler contents

The surface of multi-walled carbon nanotubes (MWCNTs) was modified to introduce acidic groups in either covalent or van der Waals interaction bonding environments to establish cross-linking sites with a host polymer. Nanocomposites based on a polyurethane matrix (PU) containing chemically functionalised multi-walled carbon nanotubes (MWCNTs) have been shown to alter its mechanical performance depending on the nature of the surface functional groups on MWCNTs, which correlates to the type of bonding interaction of the surface group and also the dispersibility of MWCNTs and their influence on the domain structure of polyurethane. The stress at break for nanocomposites containing 0.25 wt% of acid-oxidised MWCNTs (MWCNT-ox), bearing covalently attached carboxylic, lactone and phenolic groups, was twice that of the native PU and Young’s Modulus for the nanocomposites increased by four times. Whereas when hemin, which contains carboxylic functionality, was immobilised to the surface of pure MWCNTs, the improvement in Young’s Modulus was only around twice that of pure PU. Differences in the disaggregation of MWCNTs into PU were observed between the samples as well as variation of the native domain structure of PU. The results also infer that the purification of MWCNTs from acid-oxidative lattice fragments (fulvic acids) is vital prior to conducting surface chemistry and polymerisation in order to ensure maximum mechanical performance enhancement in their reinforcement of the host polymer.