Polyisoprene grafted silica nanoparticles for designed interfaces in rubber nanocomposites
Event:187th Technical Meeting Location: Greenville, SC Date: April 27, 2015 Author: Brian C. Benicewicz, Mohammad Mohammadkhani Paper Number:
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Polyisoprene has been recognized as an important class of rubber materials and has been widely used in the automotive and medical industries. We have been conducting polymerizations of isoprene onto the surface of nanoparticles (NPs) using the RAFT polymerization technique. Here we report the surface-initiated RAFT polymerization of isoprene on 15 nm silica NPs surfaces. The first step in this process is to prepare RAFT agent anchored nanoparticles. Since the polymerization of isoprene is conducted at elevated temperatures (above 100 oC), a high temperature stable RAFT agent was needed. A trithiocarbonate RAFT agent, 4-cyano-4-(dodecylsulfanylthiocarbonyl)sulfanylpentanoic acid (CDSS), was anchored onto silica NPs. The amount of CDSS covalently bound to the nanoparticles surface (0.17 to 0.61 chains/nm2) was determined quantitatively by comparing the absorbance (at 299 nm) for the CDSS modified particles to a standard UV-vis absorption curve prepared from known amounts of free CDSS. Surface-initiated polymerization from modified NPs surfaces was performed at 120 °C in THF in sealed tubes. GPC analysis revealed molecular weights of grafted polyisoprene ranging from 7 to 54 kg/mol with polydispersities of 1.1 to 1.6. Hydrogenation of polyisoprene grafted NPs was also conducted and resulted in co-poly (ethylene-propylene) grafted NPs. We are investigating the dispersion and miscibility of these polymer grafted NPs in various matrices.