Grafting of Poly(methyl methacrylate) with Different Sulfur-Containing End Groups on Gold Nanoparticles and Their Interfacial Assembly into Superlattice Films

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.

2D superlattices via interfacial self-assembly of polymer-grafted Au nanoparticles

“…However, when the concentration exceeded a certain range, such as 200 mg mL −1 , a multilayered structure was formed due to the excessive number of NPs and the drastically increased viscosity. In addition, the spreading of the NP dispersion is also related to the grafting density of polymer ligands, which was recently confirmed by Liu et al 114 It was found that a minimum grafting density of 0.51 chains per nm 2 is needed for the effective spreading of ordered self-assembled NPs into large-area 2D NP superlattices. The influence of grafting density on the superlattice structure was recently studied by Kim and coworkers.…”

“…The interparticle distance is basically dependent on the grafting density and chain length of the polymer ligands. As presented by Liu et al , 114 the interparticle distance is positively related to the grafting density. However, as mentioned above, when the grafting density is not sufficient, it is difficult to obtain large-area 2D NP superlattices.…”

γ-Functional Iminiumthiolactones for the Single and Double Modification of Peptides

“…In a single modification, the heterocyclic carbonyl undergoes chemo- and regioselective amidation, while in the additional presence of a Michael acceptor (e.g., maleimide), a double modification takes place (ring opening, followed by a thiol–X reaction). , The unique reactivity of TLs can be introduced through the commercially available homocysteine thiolactone (HCTL), which can be easily modified through the amine in the α-position (Figure ). Hence, it has been extensively used for postpolymerization modifications, − toward sequence-defined and functional polymers, − surfaces, , hydrogels, , and bioconjugate materials. − …”

“…13,14 The unique reactivity of TLs can be introduced through the commercially available homocysteine thiolactone (HCTL), which can be easily modified through the amine in the αposition (Figure 1). Hence, it has been extensively used for postpolymerization modifications, 15−17 toward sequence-defined and functional polymers, 18−20 surfaces, 21,22 hydrogels, 23,24 and bioconjugate materials. 25−27 In one of our previous studies, we demonstrated how selected amino acids and the dipeptide carnosine could be attached to a TL derivative, forming polypeptides/polyelectrolytes in a facile one-pot procedure.…”