Nucleation-Controlled Polymerization of Nanoparticles into Supramolecular Structures

Jing Wang †, Hongwei Xia §, Yanfeng Zhang ‡, Hua Lu ‡, Ranjan Kamat †, Andrey V. Dobrynin †,Jianjun Cheng ‡, and Yao Lin *†§

†Polymer Program, Institute of Materials Science and§Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269, United States

‡ Department of Materials Science and Engineering,University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States

J. Am. Chem. Soc., Article ASAP

DOI: 10.1021/ja402757e

Publication Date (Web): May 22, 2013

Copyright © 2013 American Chemical Society

Controlled assembly of inorganic nanoparticles (NPs) into structurally defined supramolecular polymers will create nanomaterials with new collective properties. However, supramolecular polymerization of isotropic NPs remains a challenge because of the lack of anisotropic interactions in these monomers to undergo directional associations for the cooperative growth of supramolecular chains. Herein we report self-assembly behavior of poly(l-glutamic acid)-grafted gold NPs in solution and describe how combined attractive and repulsive interactions influence the shape and size of the resulting supramolecular assemblies. The study shows that the chain growth of supramolecular polymers can be achieved from the NP monomers and the process occurs in two distinct stages, with a slow nucleation step followed by a faster chain propagation step. The resulting supramolecular structures depend on both the grafting density of the poly(l-glutamic acid) on the NPs and the size of the NPs.