Biomedical subjects

Costantino Creton

Publications and source records attributed to Costantino Creton.

3 recordsLinked to original sources

PubMed2005

Adhesion between chemically heterogeneous switchable polymeric brushes and an elastomeric adhesive.

We investigated the adhesive properties of binary heterogeneous polymer brushes made from end-functionalized polystyrene (PS) and poly(2-vinylpyridine) (P2VP) chains. The molecular organization of the mixed brush could be varied reversibly by exposure to selective solvents for PS (toluene) and for P2VP (acidic water). This exposure results in reversible switching of adhesive and wetting properties. The manner in which the adhesion switching occurs can be tuned by the composition of mixed brushes. However, the outer surface composition could be enriched more effectively in PS after the toluene treatment than in P2VP after the acidic water treatment. As a result, the mixed brush compositions that showed the largest difference in properties between an exposure to toluene and an exposure to water were the P2VP-rich compositions. Adhesive properties, tested against a soft hydrophobic pressure-sensitive adhesive (PSA) using a probe test, always showed smaller differences between solvent treatments than wetting properties with water, suggesting a much higher sensitivity of the hydrophobic/hydrophilic brushes to polar molecules than to nonpolar molecules.

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PubMed2005

Assessing the effect of latex particle size and distribution on the rheological and adhesive properties of model waterborne acrylic pressure-sensitive adhesives films.

The adhesive and rheological properties of model acrylic pressure-sensitive adhesive (PSA) films prepared from high solid emulsions with different particle sizes and distributions have been investigated with a customized probe tack apparatus. For each emulsion, the monomer composition and gel content were kept constant but different average particle sizes and distributions were used. Adhesive films 100 microm thick were then prepared from these emulsions and their rheological properties in the linear regime and adhesive properties were systematically characterized. Surprisingly, both the rheological and adhesive properties were found to be very dependent on the initial latex particle size distribution. A series of experiments were carried out to assess the adhesive properties of films made from blends of small- and large-particle-size latexes. Using the probe tack test, a maximum in adhesion energy of the dry films was found for 60% of small particles in the blend, a composition clearly different from that giving a minimum viscosity of the latex implying that optimizing for properties may not be equivalent to optimizing for processing in these adhesive applications. Finally, the adhesive properties of two multimodal latexes with different particle size distributions were investigated. Both gave significantly higher adhesion energies and clear evidence of a fibrillar detachment process. This important result suggests that the spatial distribution of gel domains in the dry film and the molecular connectivity between those gel domains also play an important role in controlling its adhesive properties.

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PubMed2003

Effects of geometric confinement on the adhesive debonding of soft elastic solids.

The effect of increasing confinement on soft elastic gel layers has been investigated and a means of analyzing the behavior of such systems has been developed. A probe tack test was used to study the behavior of thin elastic layers during interfacial debonding from a cylindrical glass indenter. For this gel-indenter system, confinement is defined as the ratio of a(0), the radius of the indenter, to h, the thickness of the elastic layer. In order to investigate geometric effects, the adhesion energy of the gel was kept constant while the thickness and modulus of the gels were varied. A fracture mechanics approach, based on the compliance of the layer, has been employed in analyzing the experimental data. It is shown that a fracture mechanics analysis is appropriate for these systems, allowing quantitative results to be obtained, despite very irregular contacts. It has also been shown that the interfacial instabilities observed during debonding maximize the compliance of the elastic layer. Additionally, four dimensionless parameters that dictate the behavior of confined systems have been defined, offering a general guide to understanding and characterizing the mechanical behavior of thin elastic layers.

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