RESUMEN
The eligibility of tetraquinoxaline cavitands (QxCav) as molecular grippers relies on their unique conformational mobility between a closed (vase) and an open (kite) form, triggered in solution by conventional stimuli like pH, temperature and ion concentration. In the present paper, the mechanochemical conformational switching of ad hoc functionalized QxCav covalently embedded in an elastomeric polydimethylsiloxane and in a more rigid polyurethane matrix is investigated. The rigid polymer matrix is more effective in converting mechanical force into a conformational switch at the molecular level, provided that all four quinoxaline wings are covalently connected to the polymer.
RESUMEN
The data reported in this paper are complementary to the characterization of 4-(phenylazo)-benzoyl-2,2,6,6-tetramethylpiperidine-1-oxyl radical (AzO-TEMPO) and of the 4-(2-thienylazo)-benzoyl-2,2,6,6-tetramethylpiperidine-1-oxyl radical (ThiO-TEMPO) before and after their grafting to two polyethylene matrices (a copolymer ethylene/α-olefin (co-EO) and a high density polyethylene (HDPE)). Particularly the data reported in this paper confirm the structure (FT-IR analysis), the thermal (TGA and EPR) and the photo-physical (UV-vis) properties of the RO-TEMPO derivatives before and after their grafting. Herein, the FT-IR spectrum and TGA thermogram of ThiO-TEMPO were compared with those of AzO-TEMPO. Moreover, the superimposition of UV-vis spectra collected during the irradiation under 366 or 254 nm emitting lamp of AzO-TEMPO and ThiO-TEMPO in acetonitrile solution are reported. Finally, a complete DSC characterization of the functionalized POs is shown. DOI of original article: ãhttp://dx.doi.org/10.1016/j.polymer.2015.11.018ã [1].
RESUMEN
Unique alternating copolymers based on vinyl acetate (VAc) and tert-butyl-2-trifluoromethacrylate (MAF-TBE, a nonhomopolymerizable monomer under radical conditions) have been synthesized by nitroxide-mediated polymerization (NMP) using a SG1-based BlocBuilder alkoxyamine (MAMA-SG1) at moderate temperature (at 40 °C) in dimethyl sulfoxide. First-order kinetics and linear evolutions of the molecular weight (up to 17100 g mol-1), maintaining low dispersity values (D ≤ 1.33), confirmed the controlled nature of the copolymerization. Interestingly, none of the starting monomers could undergo homopolymerization under the NMP condition initiated by MAMA-SG1. The resulting alternating copolymers were characterized by 1H, 13C, 19F, and 31P NMR spectroscopies and size exclusion chromatography (SEC). The poly(VAc-alt-MAF-TBE) copolymer is amorphous and exhibited a single glass transition temperature of 59 °C. This is the first report of nitroxide-mediated (co)polymerization of VAc leading to well-defined copolymers with satisfactory yields. The results presented in this study established a new route via NMP toward the synthesis of strictly 1:1 alternating fluorocopolymers that can display diverse functionalities.
