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

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 pm to 1200 mu m with an apparent density value similar to 1.18 +/- 0.03 g/cm(3), a solid structure and a saponification grade alpha similar to 0.8. In turn, Ms-T shows a size distribution between 400 and 1900 mu m, porous structure, a lower density value rho similar to 0.87 +/- 0.03 g/cm(3) and alpha similar to 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. [GRAPHICS] .