pH-Responsive Nanomaterial Surface Energy Transfer (NSET) Between a Naphthalene-Based Hyperbranched Copolymer and In Situ Prepared Silver Nanoparticles.

Excitation energy transfer between hyperbranched copolymers and the nanomaterials synthesized within the self-assembled copolymer has been rarely explored so far. The in situ nanoparticle-fabrication and variation in their size, tuned by the pH sensitivity of the self-assembled copolymer can modulate the nanomaterial surface energy transfer (NSET) efficiency. Herein, we report the synthesis of a copolymer of naphthalen-1-yl(4-vinylbenzyl)carbonotrithiolate (NVCT) and acrylic acid via reversible addition-fragmentation chain transfer (RAFT) polymerization technique, where NVCT serves both as the chain transfer agent (CTA) and the polymerizable monomer. The copolymer readily aggregates in water, due to excimer formation between the naphthalene rings on the side chains, which also acts as the capping agent for the silver nanoparticles (AgNPs) formed in situ. They, in turn, act as dark quenchers of the excimer fluorescence from the copolymer framework through structurally driven NSET upon excitation at 280 nm. The pH-resonsive polymer assembly helps in modulating the NSET efficiency from 81% to 54% upon going from extremely acidic to basic pH at highest nanoparticle concentration, as it also altered the size of the AgNPs from 25 ± 1.1 nm to 2 ± 0.01 nm. These properties bear importance in fabricating a pH-responsive drug delivery platform, postulating various biological applications due to the in situ prepared AgNPs.