Synthesis and mechanical behavior of poly (vinyl alcohol) / poly (vinyl acetate) microspheres

Abstract

In this work, the effect of an organic solvent (tert-butanol) during the polymerization of vinyl acetate (VAc) on the structural and elastic properties of poly(vinyl alcohol)/poly(vinyl acetate) microspheres fabricated by the suspension polymerization method was investigated. As a result, two types of microspheres were obtained: without tert-butanol (Ms-P) and with tert-butanol (Ms-T), the later was added during the polymerization. For the experimental conditions used in this work, both types of Ms had spherical shape. Also, Ms-P exhibits a size distribution ranging from 10 µm to 1200 µm with an apparent density value ~1.18 ± 0.03 g/cm3, a solid structure and a saponification grade α ~ 0.8. In turn, Ms-T shows a size distribution between 400 and 1900 µm, porous structure, a lower density value ρ ~ 0.87 ± 0.03 g/cm3 and α ~ 0.5. The mechanical tests performed on Ms-P and Ms-T in three different conditions (dry, suspended in distilled water and saline solution) showed Young’s modulus (E) values of 569 ± 162 MPa (dried), 8 ± 9 MPa (distilled water), 11 ± 9 MPa (saline solution) for Ms-P measured up to 30% of deformation. For Ms-T, 242 ± 63 MPa (dried), 0.52 ± 0.08 MPa (distilled water), 0.9 ± 0.5 MPa (saline solution) values were obtained. Thus, we have found that the E values for Ms-T are more than one order of magnitude lower than for Ms-P. Also, it was observed that keeping Ms in an aqueous medium helps decrease the E value. This work shows that the ability to control the structural and elastic properties in Ms employing addition to an organic solvent gives the possibility of tuning its behavior for possible use in the treatment of embolization and chemoembolization.