Living Radical Polymerization via Organic Superbase Catalysis

Abstract

Organic superbases reacted with alkyl iodides (R-I) to reversibly generate the corresponding alkyl radicals (R • ). Via this reaction, organic superbases were utilized as new and highly efficient organic catalysts in living radical polymerization. The superbase catalysts included guanidines, aminophosphines and phosphazenes. Low-polydispersity polymers (M w /M n = 1.1-1.4) were obtained up to high conversions (e.g., 80%) in reasonably short times (3-12 h) at mild temperatures (60-80 °C) for methyl methacrylate, styrene and several functional methacrylates. The high polymerization rate and good monomer versatility are attractive features of these superbase catalysts.

Bromoalkyl ATRP initiator activation by inorganic salts: experiments and computations

“…In this case the catalyst may be phenol or other oxygencontaining antioxidants, 32 an amine, [33][34][35][36] hexamethylphosphoramide 37 or a soluble iodide salts with a variety of organic cations such as ammoniums, phosphoniums, sulfoniums, imidazoliums, 38,39 substituted quinoliniums, 40 and choline derivatives, 41 and even with crown ether-complexed alkali and alkaline earth metals (Na, K, Cs, Mg, Ca). 42,43 Notably, these systems used only alkyl iodides as initiators.…”

Schiff base as a novel kind of catalyst for reversible complexation‐mediated radical polymerization of methyl methacrylate

“…The extents of reaction at different times are shown in Table 2. The reaction extent of CP‐I was about 97% after 2 h in the presence of NDBE, which is higher than those of amines, organic salts, and superbases . In addition, the rate of producing R• from R‐I was also much higher, indicating high activity of NDBE.…”

“…The reaction extent of CP-I was about 97% after 2 h in the presence of NDBE, which is higher than those of amines, 31 organic salts, 34 and superbases. 32 In addition, the rate of producing R• from R-I was also much higher, indicating high activity of NDBE. The 1 H NMR result of radical capture experiment of NDSE is shown in Figure S7.…”

“…As the complex of iodine radical is not stable, it can recombine with another iodine radical to produce the complexes of iodine molecule and catalyst (catalyst/I 2 ). Polymer• react with catalyst/I• or catalyst/I 2 to generate Polymer‐I and catalyst, so these complexes are deactivators . Also similar to ATRP, an equilibrium would be established based on persistent radical effect (PRE) in the initial reaction period, leading to limited biradical termination during polymerization process due to the buildup of the deactivator concentration .…”

“…Organic salts (including tetrabutylammonium iodine (BNI) and ethylmethylimidazolium iodide) were a class of high effective organic catalysts for RCMP, and high‐molecular‐weight polymers (up to M n = 140,000 g mol −1 ) with narrow distribution were obtained. Other reported RCMP catalysts include organic superbases (such as guanidine with conjugated three‐nitrogen framework), alkaline earth metal iodides (such as NaI), choline iodide analogues (including choline iodide and butyrylcholine iodide), and azide anion (such as NaN 3 ) . At the same time, photocontrolled LRP has been achieved using iodine as capping agent .…”