Synthesis and characterization of fluorescently labeled core cross-linked star polymers Part A Polymer chemistry

A series of fluorescently labeled core cross-linked star (CCS) polymers were synthesized via the \"arm-first\" approach, employing atom transfer radical polymerization (ATRP) to control the resulting architecture. The initiator p-toluenesulfonyl chloride (TsCl) was used to synthesize \"living\" poly(methyl methacrylate) (PMMA) macroinitiator, which was subsequently cross-linked to generate the CCS polymers. Divinylbenzene (DVB) was used as the cross-linker and 7-[4-(trifluoromethyl)coumarin] methacrylamide (F₁, λex = 343 nm) was added as a fluorescent labeling monomer. A range of PMMA/DVB/F₁ based CCS polymers were synthesized with the core domain made selectively fluorescent by using varying amounts of monomer F₁. The core functionalized stars were characterized using gel permeation chromatography (GPC) equipped with multi-angle laser light scattering (MALLS), refractive index (RI), and UV-visible detectors. The fluorescence quantum yield (ΦF) and the amount of fluorescent monomer incorporated into the core were quantified by UV-visible and fluorescence spectrophotometry. It was recognized that the overall molecular weights of the stars produced, along with their core molecular weight, decreased as the mol % of monomer F₁ was increased relative to cross-linker. Visual confirmation of F₁ incorporation was obtained by fluorescence microscopy of thin polymer films cast on glass substrates.