γ-Alumina Modification with Long Chain Carboxylic Acid Surface Nanocrystals for Biocompatible Polysulfone Nanocomposites

Abstract

High performance polysulfone/γ-alumina biocom-patible nanocomposites are reported for the first time and the effects of γ-alumina surface modification are explored. We show that some fatty acids chemisorb over the surface of γ-alumina forming nanosized self-assembled structures. These structures present thermal transitions at high temperatures, 100 °C higher than the melting temperatures of the pure acids, and are further shifted about 50 °C in the presence of polysulfone. The chemistry involved in the chemisorption is mild and green meeting the stringent bio sanitary protocols for biocompatible devices. It has been found that the self-assembled structures increase mechanical strength by about 20% despite the foreseeable lack of strong particle−matrix interactions, which manifests as small variations in both the glass transition temperature and the Young's modulus. Electron microscopy observation of fractured surfaces has revealed that some acids induce an extended region of influence around the nanoparticles and this fact has been used to explain the enhancement of mechanical strength.

Surface Modification of Alumina Nanoparticles: A Dispersion Study in Organic Media

“…17 High performance polysulfone/alumina biocompatible NCs are reported and the effects of alumina surface modification are explored by Anaya and co-workers. 18 They show that some fatty acids (palmitic, stearic, oleic and erucic acids) chemisorb over the surface of alumina forming nano-sized self-assembled structures. These structures present thermal transitions at high temperatures, 100 °C higher than the melting point of the pure acids, and are further shifted about 50 °C in the presence of polysulfone.…”

“…These structures present thermal transitions at high temperatures, 100 °C higher than the melting point of the pure acids, and are further shifted about 50 °C in the presence of polysulfone. 18 Llorente and co-workers have investigated the wear and mechanical behavior, along with the thermal stability, of polysulfone/modified alumina. Alumina NPs have been modified with polysulfone (PSU) chains of two different molecular weights.…”

The effect of polymer grafting in the dispersibility of alumina/polysulfone nanocomposites

“…However, different morphologies were obtained in the case of nanocomposites with PSU grafted alumina ( Figure 5(c)-(d)), where particles appear to be uniformly dispersed and surrounded by plastically deformed polymer in a cavity around 1 micron of size, in a similar way that found it in our previous work using fatty modified alumina as nanoreinforcement in a PSU matrix. 5 However in this case, connectivity with the matrix for both grafted nanoparticle is observed, and even more for the large grafted nanoparticle (PSU16k_Al 2 O 3 ). An enhancement in the interfacial adhesion it seems achieved during melt mixing and maintained after cooling.…”

“…Previous attempts to improve the mechanical behavior of PSU were based on the chemisorption of some fatty acids over the surface of -alumina. 5 It was found that the acids formed nanosized self-assembled structures which were the main reason for the improvement of mechanical properties of PSU, despite of absence of favorable nanoparticle-matrix interaction. In the present work we introduce two beneficial effects to the dispersion state: i) a favorable enthalpic interaction with a favorable thermodynamic (Flory-Huggins) interaction parameter, , 35 because segments of both components, matrix and polymer grafts, do no present disparity; and ii) polymer grafted-nanoparticle introduces both steric repulsive forces to keep the nanoparticle separated and strong adhesion between nanoparticles and polymer matrix by entanglements between the chains of either.…”

“…[1][2][3][4] However, in some cases, polysulfones and their derivatives can show relatively poor mechanical and wear resistance, so different types of inorganic nanofillers have been incorporated into this polymer, [5][6][7][8] with the aim of expanding its applications through the enhancement of mechanical strength 9,10 without the loss of desirable physical properties. [11][12][13] These characteristics have demonstrated to be very strongly dependent on the dispersion state of the nanoparticles in the polymer matrix.…”