“Click” synthesis of thermally stable au nanoparticles with highly grafted polymer shell and control of their behavior in polymer matrix
(3464–3474) Journal of Polymer Science Part A: Polymer  Chemistry 49 #16 (2011)
Lim et al ofKorea Advanced Institute of Science and Technology and Korea University, South Korea, synthesized thermally stable core–shell gold nanoparticles (Au NPs) with highly grafted polymer shells by combining reversible addition-fragmentation transfer (RAFT) polymerization and click chemistry of copper-catalyzed azide-alkyne cycloaddition (CuAAC).  First, alkyne-terminated poly(4-benzylchloride-b-styrene) (alkyne-PSCl-b-PS) was prepared from the alkyne-terminated RAFT agent.  Then, an alkyne-PSCl-b-PS chain was coupled to azide-functionalized Au NPs via the CuAAC reaction.  PSCl-b-PS chains were successfully grafted onto the Au NP surface with high grafting density.  Finally, azide groups were introduced to PSCl-b-PS chains on the Au NP surface to produce thermally stable Au NPs with crosslinkable polymer shell (Au-PSN3-b-PS 1).  As the control sample, PS-b-PSN3-coated Au NPs (Au-PSN3-b-PS 2) were made by the conventional “grafting to” approach. The grafting density of polymer chains on Au-PSN3-b-PS 1 was found to be much higher than that on Au-PSN3-b-PS 2.  To demonstrate the importance of having the highly packed polymer shell on the nanoparticles, Au-PSN3-b-PS 1 particles were added into the PS and PS-b-poly(2-vinylpyridine) matrix, respectively. Consequently, it was found that Au-PSN3-b-PS 1 nanoparticles were well dispersed in the PS matrix and PS-b-P2VP matrix without any aggregation even after annealing at 220 °C for 2 days. Our simple and powerful approach could be easily extended to design other core–shell inorganic nanoparticles.  (RDC 7/14/2011)

Polymer nanoparticles via intramolecular crosslinking of sulfonyl azide functionalized polymers
(3597-3602) Polymer 52 #16 (2011)
Jiang, Pu, and Wang of Tongji University, China prepared polymeric nanoparticles via intramolecular collapse of single chain of sulfonyl azide functionalized polymers.  Upon heating, the sulfonyl azide functionalized linear copolymers lose nitrogen and form nitrene.  This nitrene reacts with CH bond of the backbone in dilute solution and leads to the efficient intramolecular crosslinking and formation of nanoparticles where the diameter of nanoparticles can be controlled by both the molecular weight and the content of sulfonyl azide groups.  A significant reduction in the hydrodynamic volume is observed on going from the starting random coil of linear chains to the corresponding nanoparticles.  (RDC 7/15/2011)