The atom‐transfer radical polymerization (ATRP) of acrylates in 1‐butyl‐3‐methylimidazolium hexafluorophosphate was investigated. The solubility of the acrylates in the ionic liquid depends on the substituent. The homogeneous polymerization of methyl acrylate gives polymers with M̄n close to the calculated value and relatively narrow polydispersity. In heterogeneous polymerizations of higher acrylates, with the catalyst present in the ionic liquid phase, deviations from ideal behavior are observed although the polymerization of butyl acrylate approaches the conditions of a controlled polymerization.
Polymerization of epichlorohydrin (ECH) in the presence of diols, catalyzed by Lewis or protic acids, proceeds by activated monomer mechanism (AMM), i.e., by subsequent additions of protonated monomer molecules to the terminal hydroxyl groups of the growing chain. As opposed to the typical active chain end mechanism, side reactions, including cyclization, are strongly suppressed in the polymerization by AMM and well‐defined linear product are obtained. It follows from kinetic considerations, that in order to achieve the high contribution of AMM, the reaction should be carried out at low instantaneous concentration of monomer, and this can be accomplished by slowly adding ECH to the reaction mixture. Using this approach, polyepichlorophydrin diols have been prepared in the M̄n ∼ 2500 products with DPn = [M]0/[I]0 can be obtained practically free of cyclic by‐products with the yields approaching quantitative. Polyepichlorohydrin diols obtained by AM polymerization are strictly bifunctional, regular head‐to‐tail polymers containing mainly (≥ 95%) secondary hydroxyl and groups.
Atom transfer radical polymerization (ATRP) of acrylates in ionic liquid, 1-butyl-3-methylimidazolium hexaflurophospate, with the CuBr/CuBr 2 /amine catalytic system was investigated. Sequential polymerization was performed by synthesizing AB block copolymers. Polymerization of butyl acrylate (monomer that is only partly soluble in an ionic liquid forming a two-phase system) proceeded to practically quantitative conversion. If the second monomer (methyl acrylate) is added at this stage, polymerization proceeds, and block copolymer formed is essentially free of homopolymer according to size exclusion chromatographic analysis. The number-average molecular weight of the copolymer is slightly higher than calculated, but the molecular weight distribution is low (M w /M n ϭ 1.12). If, however, methyl acrylate (monomer that is soluble in an ionic liquid) is polymerized at the first stage, then butyl acrylate in the second-stage situation is different. Block copolymer free of homopolymer of the first block (with M w /M n ϭ 1.13) may be obtained only if the conversion of methyl acrylate at the stage when second monomer is added is not higher than 70%. Matrix-assisted laser desorption/ionization time-of-flight analysis confirmed that irreversible deactivation of growing macromolecules is significant for methyl acrylate polymerization at a monomer conversion above 70%, whereas it is still not significant for butyl acrylate even at practically quantitative conversion. These results show that ATRP of butyl acrylate in ionic liquid followed by addition of a second acrylate monomer allows the clean synthesis of block copolymers by one-pot sequential polymerization even if the first stage is carried out to complete conversion of butyl acrylate.
SUMMARY: Poly(oxyethylene)s terminated at both ends with 2-bromopropionate end-groups were prepared and characterized by means of MALDI TOF mass spectrometry. It was shown, that atom transfer radical polymerization (ATRP) of methyl methacrylate with a poly(oxyethylene) macroinitiator in bulk proceeds with low initiation efficiency while polymerization of tert-butyl acrylate proceeds with practically quantitative initiation, leading to ABA block copolymers. Originally formed tert-butyl acrylate blocks contain terminal bromine, as expected for the ATRP mechanism. MALDI TOF analysis indicates, however, that in the later stages of polymerization side reactions lead to elimination of terminal bromine.
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