Fluorescent dye-labeled TIPNO type regulator for nitroxide mediated reversible-deactivation radical polymerization

The TIPNO-type mediator containing fluorescent probe was used to initiate nitroxide mediated reversible-deactivation radical polymerization of styrene. Benzothioxanthene and pyrene were the fluorescent markers. One probe, benzothioxanthene, was attached to the initiating fragment of the polymer chain and the second probe, pyrene, was part of the propagating end of the polymer chain. Mainly UV absorption as well as partly fluorescence spectroscopy was applied to quantify the marked initiating chain ends and marked active alkoxyamine-terminated chain ends. Calculated theoretical molar masses are based on the assumption that all the initiating and propagating chain ends of the polymers bear fluorescent probes. Comparison of these data with the molar masses from GPC gave us the fraction of the marked active polymer chain ends and the fraction of polymers that were formed by thermal initiation. This represents a unique method for evaluation of the extent of livingness of polymerization process. At lower mediator concentration, the extent of marked initiating chain ends and the extent of marked propagating chain ends decreased with rising conversion and at 40% conversion only 50% of the polymer initiating and propagating chain ends contained labels. For the higher mediator concentration, marked initiating fragments of polymer chains were 95% and marked propagating chain ends were 93% at 40% conversion. The prepared polymers are characterized by a narrow distribution of molar masses for all conversion scales. (C) 2015 Elsevier B.V. All rights reserved.