Estimation of the Free form Particle size distribution of Polymer Particles Embedded in a Solid Polymer Matrix

F. OTERO; G. FRONTINI; E. R. SOULÉ; G. E. ELIÇABE

Lima, Perú

Congreso; XI Simposio Latinoamericano de poímeros y IX congreso ibroamericano de polímeros (SLAP 2008); 2008

<!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman";} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> In this work we present the results obtained from the size characterization of polymer particles embedded in a solid polymer matrix using Static Light Scattering (SLS). The analyzed samples are the result of the solution polymerization of polyisobutylene (PIB) in isobornyl methacrylate (IBoMA). As the system reacts, phase separation, induced by polymerization, occurs. As a result, spherical sub-micron sized particles rich in PIB are formed. At the end of the polymerization process the particles become trapped in a solid polymer matrix rich in Poly-IBoMA. The size, concentration, and refractive index, make the resulting particle system scatter light under the Rayleigh-Debye-Gans (RDG) regime with interparticle interference. The samples are measured with the Flat Cell Static Light Scattering (FCSLS) apparatus described in reference [1], in which the reaction takes place. The resulting SLS spectra are analyzed using the Percus-Yevick approximation to model the interference effects. The local monodisperse approximation [2] is used to consider polydispersity in the particle sizes. The resulting light scattering model is used to solve a free form particle size distribution estimation problem from which a completely unrestricted distribution that fits the experimental data is obtained. Unlike a previous work in which the same experimental data are analyzed using a two parameters fix form distribution [3], no assumptions are made about the shape of the particle size distribution. Preliminary results are shown in the figures presented here. In the first a Scanning Electron Microscopy (SEM) of one of the analyzed samples shows the spherical polymer particles that we want to characterize. The other figure shows on the left the measured light scattering spectrum together with the model fit. On the right, the estimated Particle Radii Distribution (PRD) (full line) and the distribution obtained from the previous SEM (full circles) are shown for the same sample. The estimated results agree well with the measurements from SEM. This work, against the opinion of other authors [4], shows the feasibility of measuring still particles using a one dimensional array of light detectors.