Synthesis and Characterization of Novel Copolymers with Different Topological Structures and TEMPO Radical Distributions

Abstract

A series of novel linear and hyperbranched copolymers with different topological structures and 2,2,6,6-tetramethyl­piperidine-1-oxyl (TEMPO) radical distributions were synthesized, and their paramagnetic property was systematically investigated. Based on the ring-opening polymerization (ROP) mechanism of GTEMPO, glycidol (Gly) or ethylene oxide (EO) monomers, the linear Poly­(EO-co-GTEMPO) and hyperbranched Poly­(Gly-co-GTEMPO) copolymers were obtained from a bifunctional 2,2-dimethyl-1,3-propanediol initiator and a tetrafunctional pentaerythritol initiator, respectively. Alternatively, from the multifunctional macroinitiator of hyperbranched polyglycerol (HPG), the hyperbranched HPG-g-Poly­(Gly-co-GTEMPO) and HPG-g-PGTEMPO copolymers were also targeted. The copolymers were characterized by GPC, DSC, and UV–vis analysis. The paramagnetic property of the copolymers was studied and compared by EPR analysis at different concentrations of copolymers and temperatures. The results displayed that the concentrations of copolymers majorly manipulated the signal intensity of EPR spectra, and the temperature majorly modulated the shape of EPR spectra. Essentially, the TEMPO radical distributions in copolymers played an important role: the higher regional density tended to give the EPR spectra with intense, broad peaks, while the lower one led to the regular, well-pronounced EPR spectra. The difference was rationalized to different intramolecular spin–spin exchange and dipole–dipole interaction modulated by the topological structures and the corresponding TEMPO radical distributions.

Controlling open‐shell loading in norbornene‐based radical polymers modulates the solid‐state charge transport exponentially

“…That is, for a nitroxide radical, the spin is predominantly located on the oxygen, and the neighboring nitrogen of which has a spin number of unity. This corresponds to a splitting pattern of three peaks . This is evidenced by the three sharp peaks observed for the small molecule TEMPO‐OH (Supporting Information Fig.…”

“…When the radicals are close in proximity and restricted in motion, due to being tethered along a polymer backbone, the result is a high amount of spin interaction among radicals. A high degree of spin‐exchange results in broadening of the three prominent nitroxide peaks, which, in the case of PTNB, converge to form a single Lorentzian curve (as seen in Supporting Information Fig. S5) …”

A versatile approach for the preparation of end‐functional polymers and block copolymers by stable radical exchange reactions

“…After pioneering work of Georges et al . who used 2,2,6,6‐tetramethylpiperidine‐1‐oxyl radical (TEMPO) for controlling styrene polymerization, significant progress has been achieved to demonstrate the ability of TEMPO to control polymerization of styrene and styrene derivatives and for the production of different complex macromolecular architectures, such as block copolymers, polymer brushes, star‐shaped polystyrenes, and hyperbranched copolymers …”

“…After pioneering work of Georges et al 7 who used 2,2,6,6tetramethylpiperidine-1-oxyl radical (TEMPO) for controlling styrene polymerization, significant progress has been achieved to demonstrate the ability of TEMPO to control polymerization of styrene and styrene derivatives 5,8 and for the production of different complex macromolecular architectures, such as block copolymers, 9 polymer brushes, [10][11][12][13] star-shaped polystyrenes, 14 and hyperbranched copolymers. 15 Synthesis of block copolymers are of a special interest since intermediary properties reflected by the individual segments could be obtained. Block copolymers have specific applications in a wide range of areas such as drug delivery, 16,17 holography, 18 solar cells, 19 and stimuli responsive materials 20 and their uses in other multidisciplinary platforms are rapidly expanding.…”

Synthesis of Novel Nitroxide Radical Polymer Materials for Imaging and Energy Storage Applications

“…Wang et al prepared a variety of topological structures with radical-containing regions by copolymerizing TGE with ethylene oxide (EO) or glycidol (Gly) from different initiators. 180 The authors synthesized linear oxiranyl-3-pyrrolin-1-oxyl. 181 Unfortunately, attempts to polymerize the former remained unsuccessful.…”