Quantitative end-group functionalization of PNIPAM from aqueous SET-LRP via in situ reduction of Cu(ii) with NaBH₄

Abstract

Rapid in situ azidation and CuAAC ‘click’ reaction demonstrating very high chain-end functionality.

SET-LRP in biphasic mixtures of fluorinated alcohols with water

“…20 These developments together with the development of SET-LRP of N-isopropylacrylamide catalyzed by Cu(0) generated in situ by the reduction of Cu(II)Br 2 with NaBH 4 in water led to the elaboration of "programmed" biphasic SET-LRP systems that are produced by design. 42,43 SET-LRP of MA catalyzed by non-activated Cu(0) wire/Me 6 -TREN in TFE/water and TFP/water mixtures Previously, we reported the SET-LRP of MA and BA, using Cu(0) generated in situ by the reduction of Cu(II)Br 2 with NaBH 4 , in "programmed" bi(multi)phasic alcohol/water mixtures. 35,41 The selection of an alcohol solvent was determinant for the evolution of the SET-LRP reaction mixture.…”

“…[39][40][41] Most of these systems were developed applying a multicomponent catalytic SET-LRP methodology where Cu(0) is generated "in situ" via the reduction of Cu(II)Br 2 with NaBH 4 although the simplest Cu(0) wire catalytic system was also successfully employed. 5,42,43 Recently our laboratory reported the replacement of Me 6 -TREN, the common ligand in the first generation of "programmed" multiphasic SET-LRP systems, by TREN, which is 80 times less expensive. 40 This attractive alternative provided excellent results when applied to the aqueous polymerization of vinyl chloride [44][45][46] and also to the Cu(0)-catalyzed SET-LRP in organic media.…”

Established and emerging strategies for polymer chain‐end modification

“…The azide functionality is particularly versatile as it can be used for copper‐catalyzed or strain promoted azide‐alkyne cycloaddition “click” coupling with both reactions being widely exploited in polymer chemistry . To expedite azide incorporation at ATRP polymer chain‐ends, several one‐pot strategies have been developed for the in situ azidation of the halide end‐group . For example, Vermonden and coworkers reported a rapid, non‐S N 2 azidation reaction catalyzed by the ATRP copper catalyst that required only a small excess of NaN 3 and enabled the polymerization, functionalization and subsequent “click” conjugation to be performed in one pot .…”

Kupfervermittelte radikalische Polymerisation mit reversibler Deaktivierung in wässrigen Medien

“…This results in dead chains and broadening of the molecular weight distribution. The rate of hydrolysis in Cu-RDRP's has been demonstrated to be effectively independent of copper concentration, [14] indicating that copper mediated hydrolysis is not significant, but is of course dependent on the halide (R-Br is more readily hydrolyzed than R-Cl) and the nature of the monomer used (i.e. the nature of the alkyl halide polymer chain end).…”

“…Furthermore, the end group fidelity was also shown to be high (~95% at conversions approaching 100%) through matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-ToF MS) of samples 'endcapped' by a thio-bromo substitution reaction to eliminate hydrolysis. [14] This technique is one of the few Cu-mediated protocols shown to be effective for polymerizing an acrylamide monomer, however the scope currently only encompasses PNiPAm at relatively low molecular weights (Mn < 5 kDa) with no demonstration of chain extension, despite the high end group fidelity reported.…”