Nitroxide‐mediated homopolymerization and copolymerization of 2‐vinylpyridine with styrene

Abstract

Homopolymerization and copolymerization of 2-vinylpyridine (2VP) with styrene (S) at 125°C in the presence of 2,2,6,6-tetramethyl piperidin-1-yloxyl (TEMPO) radicals have been studied. The homopolymerization was carried out with 2,2Ј-azobis-(isobutyronitrile) (AIBN) as a thermal initiator or without AIBN in the initial reaction mixture. In the copolymerization initiated with AIBN, the molar fraction of 2VP in the feed, F 2VP , varied in the range of 0.1-0.9; F 2VP ϭ 0.65 was found to be the azeotropic composition. The linear semilogarithmic time-conversion plots demonstrated a pseudoliving nature of the polymerizations under study. The molecular weight-conversion dependences indicated the participation of side reactions, diminishing the number of TEMPO-terminated polymer chains. The synthesized homopolymers and copolymers were characterized using size-exclusion chromatography (SEC), nitrogen analysis, and NMR spectroscopy.

Hydrogen bonding promoting the controlled radical polymerization of 2-vinyl pyridine: supramonomer for better control

“…Computer simulation for optimized geometries of 2VP and 2VP-HFIP with 15 The equilibrium constant (K) of the complex between 2VP and HFIP was calculated to be 6.31 L·mol -1 based on eqs (1) to (3), where ∆δ was the difference in the observed double bond proton chemical shift of 2VP between the absence and the presence of a certain amount of HFIP, ∆δ 0 was the difference in 20 the chemical shift of double bond proton between the absence of HFIP and that saturated with HFIP, and [2VP] 0 and [HFIP] 0 represent the initial concentration of the corresponding component, respectively. K = 6.31 L·mol -1 and the hydrogen bonding length of approximate 1.751 Å ( Figure S3, ESI †) 25 quantificationally confirmed a strong hydrogen bonding between 2VP and HFIP, 33 constructing the 2VP-HFIP supramonomer; Compare to the naked 2VP monomer, the formed 2VP-HFIP supramonomer would express different polymerization behavior due to electron induction as well as steric effects. 30 The polymerization behavior of Cu(0)-catalyzed 2VP was carefully explored with equiv 2VP and HFIP under different temperatures (25, 40 and 60 o C).…”

“…In 20 N-methyl-2-pyrrolidone (NMP) and N,N-dimethylformamide (DMF), the polymerizations were also poorly controlled by manifesting uncontrollable molecular weights and high M w /M n values (M w /M n >1.90) ( Table 1, entries 4&5). Whereas, with fluoroalcohols as solvents under identical conditions (entries 6-11, 25 Table 1), the polymerization conveyed reasonably controlled features with controllable molecular weights and relatively narrow molecular weight distributions, especially with HFIP as solvent. From above results, the good control over molecular weight with fluoroalcohol as solvent could be attributed to the hydrogen bonding interaction between 2VP and fluoroalcohol, similar with 35 those in 4VP polymerization.…”

Synthesis and quaternization of nitroxide-terminated poly(4-vinylpyridine-co-acrylonitrile) macroinitiators and related diblock copolymers

“…This can be due to easier irreversible deactivation of long copolymer chains containing terminal nitroxyl groups (Scheme 2) [11,17].…”

“…Instead of the conjuction of thermal initiator with nitroxide, an alkoxyamine-based unimolecular initiator carrying both a latent initiating group and nitroxide in the 1:1 mole ratio can be used [10,15]. Some monomers and monomer pairs (styrene, styrene maleimide or styrene Nsubstituted maleimide derivative) polymerize in the quasiliving manner even without any added initiator, only in the presence of nitroxide [5,16,17]. The mediating role of the nitroxide consists in reversible termination of growing polymer chains under formation of thermally unstable N-alkoxyamine bonds.…”

“…Vinylpyridine polymers and their ionic derivatives rank among promising materials such as polyelectrolytes, polymeric reagents, membranes and in electrical applications [18]. So far, the NMRP studies of vinylpyridine monomers have been devoted mainly to their homopolymerization and copolymerization with styrene [11,17,19,20]. Yet the incorporation of other monomer units in polymer chains could modulate the properties of resulting products.…”