Synthesis and Characterization of ω-Halogenated Poly(dimethyl siloxane)

Poly (dimethyl siloxane) (PDMS) has received special attention due to its unique properties such as high surface tension، high gas permeability، high hydrophobicity، high chain flexibility at room temperature، good biocompatibility and very low glass transition temperature. One of the simplest methods to impart these properties in copolymers is to use PDMS as a macroinitiator in the controlled radical polymerization. In the present study، hydroxyl-ω PDMS was characterized by FTIR، 1H NMR and GPC analyses. The results showed that there is an impurity present in the commercial hydroxyl-ω PDMS. Functionalization reactions were used to investigate the reactivity of the impurities. Hydroxyl-terminated PDMS was brominated via 2-bromopropionyl bromide and α-bromoisobutyryl bromide. Brominated PDMS، used as a macroinitiator in the atom transfer radical polymerization، was then iodinated by sodium iodide in anhydrous acetone as a solvent to prepare iodinated PDMS. Bromination and iodination were verified by FTIR، 1H NMR and GPC analyses. GPC results showed that a high molecular weight impurity present in the sample can be removed after functionalization and purification of PDMS though there may be still impurities remain in the purified product. 1H NMR spectrum of the brominated and iodinated PDMS showed that the peaks related to the impurity do not show any change in intensity and chemical shift in comparison with those appeared in the 1H NMR spectrum of the hydroxyl-ω PDMS، indicating that impure species are not reactive in chemical modifications. In other words، these impurity species do not have any hydroxyl reactive functional group.