Grafting of Poly(methyl methacrylate) with Different Sulfur-Containing End Groups on Gold Nanoparticles and Their Interfacial Assembly into Superlattice Films
Simeng Liu, Han Guoqiang, Mengmeng Zhang, Bijin Xiong, Jiangping Xu, Jintao Zhu
Abstract
Grafting polymer ligands on gold nanoparticles (AuNPs) by gold–sulfur (Au–S) bond is a facile way commonly employed to fabricate gold–polymer hybrid NPs (AuNP@polymer). By using the reversible addition–fragmentation chain transfer (RAFT) radical polymerization, it is convenient to present sulfur-containing end groups to polymer ligands, such as dithioester and trithioester groups, which can be usually transferred to thiol/thiolactone/disulfide groups by aminolysis reaction. However, these groups show different bonding effects to AuNPs. Especially for the thiolactone-terminated polymer, the weak bonding between thiolactone and AuNPs results in unstable AuNP@polymer conjugates, which further affects their assembly behavior. Here in this work, the effects of the end group on the surface-grafting of AuNPs were investigated by using poly(methyl methacrylate) (PMMA) ligands containing thiolactone/dithioester/disulfide/thiol end groups. By tuning the solvent property and the concentration of PMMA ligands, the thiolactone-terminated PMMA can be successfully grafted on the AuNPs, which has been regarded as a great challenge due to the weak bonding between gold and thiolactone. The grafting density of thiolactone-terminated PMMA can reach 0.5 chains/nm 2, which is similar to that of disulfide/thiol-terminated PMMA. Moreover, the grafting density shows critical influence on the interfacial assembly behavior of AuNP@PMMA conjugates. By optimizing the assembly parameters, a superlattice film of AuNP@PMMA conjugates could be constructed, which may have promising applications in memory devices and sensors.