Phosphazene/triisobutylaluminum-promoted anionic ring-opening polymerization of 1,2-epoxybutane initiated by secondary carbamates

Abstract

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.Phosphazene/triisobutylaluminum-promoted anionic ring-opening polymerization of 1,2-epoxybutane initiated by secondary carbamates L Hassouna, Nicolas Illy, P Guégan To cite this version:L Hassouna, Nicolas Illy, P Guégan. Phosphazene/triisobutylaluminum-promoted anionic ringopening polymerization of 1,2-epoxybutane initiated by secondary carbamates . Polymer Chemistry, Royal Society of Chemistry -RSC, 2017, 8 (27) (runs 7, 9, 11 and 12), SEC traces (runs 7, 9 and 11) and MALDI-ToF spectra (runs 9 and 10). Additional experiment protocols with kinetic plots, MALDI-ToF spectra and SEC traces at various reaction times. Attempts to use carbamate-phosphazene base as initiating systems for the polymerization of 1,2-epoxybutane were unsuccessful. As a matter of fact, carbamate deprotonation by phosphazene bases led to their fast decomposition generating alkoxide anions which initiate the polymerization rather than carbamate anions. Conversely, in the presence of triisobutylaluminum -a Lewis acid-the in situ generation of an anionic initiator X -obtained by the deprotonation of with tBuP4 phosphazene base was tested as possible way to initiate the polymerization of 1,2-epoxybutane. A particular attention was given to the detection of eventual transfer or side-reactions according to the carbamate:triisobutylaluminum:phosphazene base ratio, to the solvent dielectric constant and to the number of P=N-units in the phosphazene base. Reaction performed with the stoichiometric ratio (1:1:1) of carbamate:triisobutylaluminum:tBuP2, gave the best results. Under these conditions, the initiation of the polymerization by the carbamate anion was quantitative; no transfer reactions have been observed and the polymerization proceeded in a controlled manner to afford amide end-capped poly(butylene oxide) with narrow molar mass distribution and expected molar masses. IntroductionThe controlled synthesis of complex macromolecular architectures remains one of the most appealing topics in polymer chemistry. In particular, metal-free polymerization techniques provide new opportunities in the field, such as extending the range of functional groups that can be used as polymerization initiators. In this context, phosphazene bases are a very powerful and versatile tool. 1 These "superbases" are able to deprotonate low acidic molecules, generating extremely reactive anions which can be used as initiator for anionic polymerizations: e.g. monofunctional alcohols 2 (methanol, 3 solketal, 4 4-phenyl-2-butanol, 2-methyl...

Anionic ring‐opening polymerization of N‐glycidylphthalimide: Combination of phosphazene base and activated monomer mechanism

“…Another major peak series can be attributed to polyglycidylphthalimide chains with methyl and hydroxyl end groups (P4), which indicates the occurrence of a transfer reaction to the aluminum derivative resulting in hydride initiation. 25 Peaks corresponding to isobutyl endgroups are observed at 0.61, 0.77 and 1.15 ppm in 1 H NMR spectra. The molar fraction of macromolecular chains resulting from transfer reactions to aluminum derivative (%ISO, Table 1) was roughly calculated by 1 H NMR using the endgroup aromatic protons and the CH3 end-group protons resulting from transfer reactions.…”

Modification of proline‐based 2,5‐diketopiperazines by anionic ring‐opening polymerization

“…N ‐modified DKPs were used as initiator for reversible addition‐fragmentation polymerization (RAFT) polymerization and as monomer in acyclic diene metathesis (ADMET) polymerization to develop polymers integrating natural and structurally constrained moieties. Amide and carbamate moieties have been shown to be deprotonated with phosphazene bases to initiate the polymerization of epoxide monomers . Based on these results, our group published the first N‐modification of symmetric cyclic dipeptides through controlled anionic ring‐opening polymerization paving the way toward the synthesis of various peptide‐based functional polymers readily applicable in the biomedical field …”

“…Amide and carbamate moieties have been shown to be deprotonated with phosphazene bases 18 to initiate the polymerization of epoxide monomers. [19][20][21][22] Based on these results, our group published the first N-modification of symmetric cyclic dipeptides through controlled anionic ring-opening polymerization 23 paving the way toward the synthesis of various peptide-based functional polymers readily applicable in the biomedical field. 24,25 In this article, we have extended our previous results 23 to the N-functionalization of proline-based cyclic dipeptide by anionic ring-opening polymerization (AROP).…”

Anionic Polymerization of Styrene and 1,3-Butadiene in the Presence of Phosphazene Superbases

“…In this case, high molecular weight (297,000 g/mol) with high polydispersity (Ð > 1.9) ( Figure S1 ) was obtained in 20 min, suggesting that the basicity of t -BuP 4 ( p K a , ACN = 42.6) leads to fast but uncontrollable polymerization of styrene ( Figure 1 , Black line). The big radius of the phosphazeniun lithium cation (~5 Å) [ 43 , 44 ] increases the interionic distance from the propagating anionic sites, generating extremely reactive carbanions, due to the delocalization of the positive charge over 17 positions in t -BuP 4 . We assume that during the polymerization either two active populations (aggregated non-active and active initiating species) coexist or the active species partially deactivated by the t -BuP 4 and thus the produced polymers exhibit extremely high molecular weight and broad polydispersity.…”