Properties of Silicone fluids before and after purification

Abstract

Event Abstract Back to Event Properties of Silicone fluids before and after purification Can B. Hu1* and Mike Lowery1* 1 Abbott Medical Optics, United States Introduction: Silicone is a widely used biomaterial[1]. For ophthalmologic applications such as intraocular lenses (IOLs), many properties such as amount of leachables, clarity, refractive index (RI) and viscosity are all important factors for the IOL design. Freshly synthesized high RI silicone fluid usually needs to go through the filtration[2] process to improve the clarity; however, filtration alone can’t remove the low molecular weight species which may leach out after long term implantation. Purification of silicone fluid would be important to remove the undesired low molecular weight species. In this study, properties of silicone fluid before and after purification by solvent washing process are discussed. Material and Methods: High molecular weight silicone with refractive index of 1.47±0.01 was synthesized by anionic ring-opening polymerization[3]-[5]. After filtration through 0.2 µm PTFE filters, silicone fluid was purified by solvent washing process to remove low molecular weight species. Washing process was repeated multiple times (3X and 5X) to check the effect of purification on properties of refractive index (RI), Abbe number, UV-Vis percent transmission (%T), haze level and viscosity. Results: Table 1 shows RI and Abbe number before and after multiple purification process. Although RI of purified silicone fluid was slightly dropped (0.0015 and 0.0019 respectively with 3 and 5 times purification when compared to the filtered control sample only, nevertheless, the difference is significant with p value <0.05 for both purification processes. Abbe number increased slightly after purification. The haze levels before and after purification was summarized in Table 2. It was found that haze level was increased from 2.6 to 3.9 and 5.2 respectively after 3 times and 5 times purification. Although the haze difference of silicone fluid after purification was statistically significant, however, the difference was difficult to tell by naked eyes. It was found that haze level increased with number of purification process. Table 1 and 2. RI, Abbe number and Haze level of silicone fluid before and after purification. An overlap UV/Vis scan of silicone fluid before and after multiple purification process was shown in Figure 1. As in Figure 1, percent transmission (%T) of UV/Vis of purified silicone fluids were also slightly lower than that of non-purified control sample. This observation is consistent with the results of haze study and confirmed our previous study[2]. Figure 1. UV/Vis scans of silicone before and after purification Results of viscosity measurement of silicone fluid before and after purification were summarized in Table 3. It was found that viscosity increased significantly after purification which indicated that low molecular weight species were removed effectively. Table 3. Viscosity of silicone fluid before and after filtration Conclusions: In this study, we found that purification is a very effective method to remove the low molecular weight species of silicone fluid as indicated by the significantly increased the viscosity of silicone fluid. However, other properties such as refractive index, abbe number, haze level and percent transmission of silicone are also impacted by the purification process as well and worth studying further. Thanks approval from Abbott Medical Optics to presented this work SC2015CT0038