Piero Narducci

Hydrogels of poly(vinyl alcohol) and collagen as new bioartificial materials Part I Physical and morphological characterization

Poly(vinyl alcohol) was used to make hydrogels containing various amounts of collagen. These “bioartificial materials”, made of synthetic and biological polymers, were studied to investigate the effect of the presence of the collagen on the structural properties of the hydrogels. A comparison between thermal and morphological properties of collagen-containing hydrogels and hydrogels of pure poly(vinyl alcohol) was made.

Evaluation of biodegradability of poly(ε-caprolactone)/poly(ethylene terephthalate) blends

The results of an investigation aimed at evaluation of the biodegradability of blends of poly(e-caprolactone) (PCL) with poly(ethylene terephthalate) (PET) as the major component are reported. Specimens of the blends, as melt extruded films and/or powders, were submitted to degradation tests under different environmental conditions including full-scale composting, soil burial, bench-scale accelerated aerobic degradation, and exposure to axenic cultures and esterolytic enzymes. Indications have been gained that blending in the melt gives rise to insertion of PCL segments in the PET chain. Copolymers thus attained acted as macromolecular compatibilizers, allowing for a complete miscibility of PCL and PET. The biodegradation detected on the blend samples was, however, well below the values expected from chemical composition and behavior of individual homopolymers under the same environmental conditions. The presence of PET as the major component in PET/PCL blends apparently reduces the propensity of PCL to be degraded, at least in the investigated composition range. The degradation data collected under different environmental conditions indicate that the full-scale composting system is the most efficient among the tested degradation procedures.

Thermal and Spectroscopic Characterization of Interactions between 2-Nonyl-1,3-Dioxolane and Stratum Corneum Components

The effect of 2-nonyl-1,3-dioxolane (SEPA™) on the structure of human stratum corneum was investigated by FT-IR spectroscopy at variable temperature, differential scanning calorimetry and scanning electron microscopy. A significant influence of SEPA™ treatment on position and intensity of IR absorption bands and DSC thermal transitions of SC lipids was detected. An appreciable loosening of SC cell packing was also observed by SEM analysis. These modifications are reversed after SEPA™ is removed from the site of application. The results clearly demonstrate that SEPA™ is able to modify the structure of the lipid matrix in which corneocytes are embedded, thus suggesting a possible use of SEPA™ to increase the permeability of the stratum corneum to lipophilic drugs.

Preparation of activated carbons from heavy-oil fly ashes

The use of heavy oil fly ash with high ash content (45 wt.%) as a precursor for the preparation of activated carbons has been investigated. The raw fly ash and the fly ash with lower ash content, obtained by a HCl/HF washing treatment, have been pyrolyzed at 900 degrees C and then activated with CO(2) in the temperature range of 800-900 degrees C for different times. The activated carbons have been characterised as regards the surface area and the pore volume. The evolution of the porosity has been related to the burn-off degree.

Physical and biological properties of dehydro-thermally cross-linked collagen-poly(vinyl alcohol) blends

Dehydro-thermal treatments for 3, 24 and 72 h were used to crosslink blends of collagen and poly(vinyl alcohol) with various compositions. This crosslinking method increases the biological stabilityin vitro of collagen, as was established by an enzymatic test. When the poly(vinyl alcohol) content is not more than 20% the resistance of collagen to enzymatic digestion is not affected by the presence of the synthetic component. A higher content of poly(vinyl alcohol) produces a steric hindrance screening that enhances the resistance of collagen to the collagenase. Dehydro-thermal treatment performed for 24 and 72 h increases the crystallinity of poly(vinyl alcohol), thus reducing the solubility of this component of the blend. Calorimetric analysis was carried out by differential scanning calorimetry to investigate the structure and the thermal stability of the blends. Dehydro-thermal treatments carried out for 24 and 72 h induce high degrees of crosslinking in collagen and high crystallinity in poly(vinyl alcohol). The two components of the blend seem to create independent structures and the blend can show interpenetrating-network-like behaviour.

Oxygen and water vapor barrier properties of MMT nanocomposites from low density polyethylene or EPM with grafted succinic groups.

LDPE, EPM and their derivatives containing a moderate amount (0.08-1.8 by mol) of diethylsuccinate or succinic anhydryde groups were used as matrices in blending with different amount of organophilic montmorillonites and the resulting composite morphology and structure (by XRD, SEM, TEM microscopy, DSC analysis and selective solvent extraction) were studied with reference to the polar groups/MMT ratio. Exfoliated, intercalated and mixed morphologies were achieved. High concentrations of polar groups grafted to the polyolefin and montmorillonite loading not larger than 5% wt were favourable for obtaining high exfoliation degree. Particularly in the exfoliated MMT composite LDPE had lower crystallinity degree, while EPM showed increased glass transition temperature and reduced solubility in hot toluene. Moreover, oxygen and water vapor barrier property improvement was observed in films where MMT exhibits either exfoliated or intercalated morphologies. Strong interactions with the montmorillonite particle surface through the polar groups grafted to the polyolefin seems to be the basic effect responsible for the morphology and peculiar properties. A model based on the reduced mobility of the polymer located near the particle surface or inside the MMT gallery (confined phase) was proposed to explain the observed oxygen permeability reduction, the T(g) increase and solubility of poly(ethylene-ran-propylene)/MMT nanocomposites.

Composites Between Alumina and an Ester‐Ether‐Ester Bioresorbable Copolymer

Composites between alumina and the biore-sorbable (poly(e-caprolactone)-block-poly(oxyethylene)-block-poly(e-caprolactone) copolymer were obtained by reacting e-caprolactone with preformed poly(ethylene glycol), in the presence of ceramic alumina powder, at 185°C under vacuum. The mechanical properties, tested by compression and flexural strengths and Youngs modulus, show that the copolymer interacts poorly with the alumina grains. Both scanning electron and atomic force microscopy show a scare wettability between alumina and copolymer, as well as the aggregation of alumina micro-particles into clusters of big size. Both mechanical and morphological tests seem to indicate a stronger interaction between the alumina micro-particles than between the alumina surface and the reaction mixture during the polymerization, as well as a compacting effet by alumina on the forming copolymer. The FT-IR spectra of the composites show both copolymer and alumina absorption bands. The FT-IR analysis on the fractions of an extraction which CHCl 3 indicates the presence of traces of poly(e-caprolactone), stably linked to alumina. The polymerization of e-caprolactone with alumina alone in the same conditions gives poly(e-caprolactone), mainly free and in minor part linked to the alumina surface. Two polymerization mechanisms, simultaneously occuring, are proposed. The most relevant result of this work is the lack of chemical inertness of alumina towards e-caprolactone, which leads to reconsider also the use of alumina as a biochemically inert material.