EVOH are materials with broad application in high barrier packaging due to transparency and superior oxygen barrier. However, these materials suffer from significant plasticization in properties due to sorption of moisture, which handicaps their application under high moisture conditions such as those applied in many packaging cases. This paper shows the development of a novel clay based compound developed in our labs, commercially marketed as Soarnol (R) NC7003, which is based on an engineered clay traded as O2Block (R), which exhibits enhanced UV and gas barrier and decreased water permeability and sensitivity.

Ethylene–vinyl alcohol copolymers, polyamides, polyvinyl alcohol and, since more recently, some biopolymers are materials with broad applications in high-barrier packaging due to transparency and superior oxygen barrier. However, these materials suffer from strong plasticization in properties due to sorption of moisture, which handicaps their application under high-moisture conditions such as those applied in many packaging cases. This article shows the development of novel nanocomposites based on an optimized kaolinite grade, commercially marketed as O2Block®, which exhibit enhanced ultraviolet and decreased oxygen permeability, by up to 70%, as well as reduced both water permeability, by up to 50%, and sensitivity.

To test whether undernutrition during foetal to pre-pubertal life would have long lasting effects on testicular histology in adult male offspring, eleven adult Sprague-Dawley pregnant rats were divided into two groups: Control group, n = 4, fed ad libitum, during gestation and lactation (until 25 day post-partum). Underfed group pregnant females (n = 7) were kept in cages where only dams had access to food (standard rat chow, 33.5% of ad libitum intake of Control group pregnant dams). After parturition, litters were adjusted to either 14 (Underfed group) or eight (Control group) pups. Mothers were weighed weekly. At 25 day of age pups were weaned, housed at four animals per cage, fed ad libitum and weighed weekly until euthanized at 100 day of age. Testes were processed for standard histology and morphometrical evaluation. At weaning, mother weight was lower in underfed than in Control group (mean +/- SD): 214.1 +/- 26.2 g vs 361.9 +/- 33.1 g. Body weight at 100 days of age (254 +/- 26.9 g vs 342.4 +/- 10.2 g, p <or= 0.001), testicular weight (1.29 +/- 0.16 g vs 1.45 +/- 0.13 g, p = 0.03), number of Sertoli cells per seminiferous tubule cross section (18.2 +/- 1.2 vs 20.2 +/- 1.3, p <or= 0.01) and per testis (30.5 +/- 4.2 x 10(6) vs 36.0 +/- 5.4 x 10(6)) were lower (p < 0.05) in Underfed than in Control group. This is the first report stating that foetal to pubertal subnutrition is accompanied by changes in testicular structure and lower Sertoli cell numbers in adult life, strongly suggesting lower daily sperm production.

Star polymers consisting of poly(epsilon-caprolactone), (PCL), grafted onto third generation dendrimer, which had hyperbranched and dendron cores, were studied by polarized light microscopy together with reference linear PCL. The degree of polymerization of the PCL arms in the star polymers ranged between 14 and 81. The star polymers exhibited a greater tendency than the linear polymers to form spherulites. It is suggested that the preference of the star polymers for forming spherulites is due to the presence of amorphous material-dendritic cores and PCL cilia-between crystal lamellae that generates the necessary pressure to force the lamellae to diverge at lamellar branch points. The linear growth rate data followed a single crystallization regime. The fold surface free energy was higher for the star polymers than for their linear analogs. It is proposed that the presence of the large and rigid dendritic cores on the fold surfaces of the star polymer crystals increases the fold surface energy.

The dynamics of the amphiphilic semifluorinated F(CF2)12(CH2)12H (F12H12) alkane that undergoes two condensed phase transitions have been investigated by Brillouin light spectroscopy, shear rheometry, small- (SAXS) and wide-angle (WAXS) X-ray scattering, and thermodynamic PVT measurements. The solid (I)-solid (II) transition (Ts) is marked by a stronger temperature dependence of the sound velocity in phase II and by a 2 orders of magnitude drop of the shear modulus. Between the Ts and the melting transition (Tm), the presence of two phonons implies a coexistence of solid (II) and amorphous (liquid) regions in the submicrometer range at thermal equilibrium as revealed by the SAXS pattern of a single reflection superimposed on a very broad amorphous halo. This intriguing finding of a transient, very slow (over 10 h) solid/liquid coexistence within phase II is rationalized by a two-stage mechanism for melting of the smectic phase (II) of F12H12. A refinement of the known packing motifs for the two solid-state structures is proposed.

The selective transport of Au(III) over Cu(II) and Hg(II) using ω-thiocaprolactam as extractant and carrier in solvent extraction and polymer inclusion membrane transport experiments is discussed. Solvent extraction experiments were carried out using the extractant dissolved in chloroform to establish the chemical equilibria involved in the Au(III)-ω-thiocaprolactam separation system. Au(III) is extracted into the organic phase quantitatively (E (%)>99%) at low extractant concentrations from aqueous HCl solutions. Cu(II) extraction kinetics is slow compared to Au(III) extraction, allowing for the efficient separation of both metals. Polymer inclusion membranes (PIMs) are designed as alternatives to the use of high amounts of hazardous and expensive reagents. Several stripping phases were tested. Up to 70% of Au(III) can be recovered from 1M HCl feed aqueous phase solutions. Interference from Cu(II) or Hg(II) is negligible at short times (160min) in competitive ([M(II, III)]0,feed=0.1mM) membrane transport experiments using a cellulose triacetate/NPOE/ω-thiocaprolactam PIM and a potassium iodide–hydrochloric acid aqueous stripping solution. Apparent diffusion coefficients in the membrane for Au(III) and Hg(II) in the system were estimated to be 2.2×10−11 and 3.4×10−15m2s−1, respectively.

The knowledge regarding certain issues in polymer crystallization e.g. the possible existence of short–lived mesophases remains inconclusive due to experimental limitations. Polymers undergo chain ...

Star-branched polymers consisting of poly(ε-caprolactone) (PCL) attached to third generation dendrimer, hyperbranched and dendron cores have been studied together with linear PCL analogues. The degree of polymerisation of the PCL arms of the star-branched polymers ranged from 14 to 81. Single crystals were grown from dilute solution and studied by transmission electron microscopy. Single crystals of linear PCL were multilayer hexagons with flat or slightly curved {110} and {100} faces. These single crystals were larger along [010] than along [100]. Single crystals of star-branched PCL showed the same basic shape, but with many crystallographic and irregular steps on the lateral crystal faces. The width of the micro-faces was typically 100–300 nm. These single crystals were more extended along [100] than along [010]. It is proposed that the high fold surface free energy and the constrained character of the star-branched polymers favour the formation of steps on the growth faces. Globular polycrystalline aggregates were also observed. They originated from a more concentrated polymer phase following phase separation of the solution. In the case of the star-branched polymers, lamellar branching was observed with a 30° angle between the crystals arms.

One complex fact of polymer crystallisation is that polymer crystals have a tendency to rearrange with time. In this paper, poly(ethylene oxybenzoate)s (PEOB) with different degrees of polymerisation ranging from 5 to 30 have been studied by differential scanning calorimetry and polarised microscopy. The samples showed a great tendency for crystal rearrangement during heating to the melting point, even at high heating rates. The relationship between melting point and crystallisation temperature was analyzed and the Hoffman–Weeks method was found to be unsuitable for determining the equilibrium melting point of these polymers. It is proposed that fast crystal rearrangement, which is a characteristic feature of poly(ethylene oxybenzoate), is the reason for the inadequacy of the Hoffman–Weeks method to obtain reliable estimates of the equilibrium melting point. Polarised microscopy showed, remarkably in view of the low molar mass of the polymers, the formation of perfect banded spherulites. Linear growth rate data suggested that the branched polymers crystallised more slowly than their linear analogues, presumably due to differences in the equilibrium melting point.

Star polymers consisting of poly(ε-caprolactone), PCL, attached to third generation dendrimer, hyperbranched and dendron cores have been studied by differential scanning calorimetry and wide-angle X-ray scattering. The degree of polymerisation of the PCL arms of the star polymers ranged from 14 to 81. The crystal unit cell was the same for the star polymers as for their linear PCL analogues. The star polymers showed a lower degree of crystallinity than the linear PCL, suggesting that the dendritic cores imposed restriction on PCL crystallisation. Slow heating of rapidly cooled samples led to crystal rearrangement—a gradual increase in melting point with decreasing heating rate and recrystallisation followed by additional high temperature melting. The tendency for crystal rearrangement was less pronounced in star polymers based on dendrimer or hyperbranched cores, suggesting that the dendritic cores constitute an obstacle to crystal rearrangement. The star polymers showed higher equilibrium melting points than the linear PCL analogues. It is suggested that covalent attachment of the PCL arms to the dendritic core reduced the positional freedom and the entropy of the melt with respect to that of linear PCL.

The concentrations of three stabilizers-a hindered phenol (Irganox 1076), a hindered amine light stabilizer (Tinuvin 770) and a bifunctional stabilizer with chain-breaking hindered phenol and secondary amine and hydroperoxide-decomposing sulphide moieties (Irganox 565)-in crosslinked polydimethylsiloxane were varied using swelling solutions of the stabilizers at different concentrations. The concentration of the stabilizer in the rubber was assessed by UV-Vis spectroscopy of Soxhlet and microwave assisted extracts. Irganox 1076 and Tinuvin 770 were soluble in polydimethylsiloxane to at least 0.2-0.3 wt.%, whereas the solubility of Irganox 565 was considerably lower. The samples were exposed to GHz air plasma and the surface structures of the exposed samples were studied by X-ray photoelectron spectroscopy, and by optical and scanning electron microscopy after uniaxial stretching. The plasma exposure time required for the formation of an oxidised glassy layer increased in a linear fashion with increasing stabilizer concentration, suggesting that the consumption rate was constant in time during the plasma exposure. Tinuvin 770 showed the strongest overall protecting effect whereas Irganox 565 showed the strongest protecting effect per mass fraction of stabilizer. Irganox 1076 was of moderate efficiency. The results suggest that efficient protection towards air plasma is achieved with hindered amine stabilizers or with stabilizers combining chain-breaking and hydroperoxide-decomposing functions. Differential scanning calorimetry showed that Tinuvin 770 and Irganox 565 protected polydimethylsiloxane against thermal oxidation at elevated temperatures. The chemical consumption of these stabilizers followed basically the classical scheme with zero-order kinetics and a rate constant obeying the Arrhenius law. (C) 2002 Elsevier Science Ltd. All rights reserved.