A versatile living polymerization method for aromatic amides

Abstract

Polycondensation polymers typically follow step growth kinetics assuming all functional groups are equally likely to react with one another. If the reaction rates with the chain end can be selectively accelerated, living polymers can be obtained. Here, we report on two chlorophosphonium iodide reagents that have been synthesized from triphenylphosphine and tri(o-methoxyphenyl)phosphine. The former activates aromatic carboxylic acids as acid chlorides in the presence of secondary aromatic amines and the latter even in the presence of primary aromatic amines. These reagents allow p-aminobenzoic acid derivatives to form solution stable activated monomers that polymerize in a living fashion in the presence of amine initiators. Other aryl amino acids and even dimers of aryl amino acids can be polymerized in a living fashion when slowly added to the phosphonium salt in the presence of an amine initiator. Diblock copolymers as well as a triblock terpolymer of aryl amino acids could be prepared even in the presence of electrophilic functional groups. preventing classical step-growth kinetics. The polymers obtained by this elegant method showed narrow dispersity and the possibility to form block copolymers. Poly(aromatic amides) are amongst the best investigated polymers in this context. However, low temperatures, the use of strong bases and several known side reactions 14 limit this technique as far as the average molar mass of the polymers is concerned (Mn=22 kDa). 15 As strong nucleophiles are required throughout the polymerization, the method is limited to monomers devoid of electrophilic functional groups. In particular, this technique could not yet be applied to the growing field of aromatic amide foldamers which aims at mimicking the function of biological macromolecules with similarly sized synthetic oligo and polyamides.

Group 16 conjugated polymers based on furan, thiophene, selenophene, and tellurophene

“…[16][17][18] The other is dictated by reactivity differences rather than an associative intermediate, 19,20 where the dissociated catalyst preferentially reacts with the C-Br bond at the polymer terminus instead of the counterpart on a organometallic monomer, reminiscent of the living synthesis of polyamide. 17,21 In this review, we will summarize the recent progress of Kumada, Negishi, Murahashi, Suzuki-Miyaura, and direct arylation polymerizations, representing the best routes to welldefined, high molecular weight (MW) CPs containing furan, thiophene, selenophene, and tellurophene.…”

Cavity-containing aromatic oligoamide foldamers and macrocycles: progress and future perspectives

“…Kilbinger and coworkers were successful in the synthesis of a variety of polyamides through controlled, living polymerization. 21 This versatile method afforded a plethora of polyamides (including diblock copolymers and triblock tripolymers) with impressively narrow dispersity (Fig. 4).…”

Hierarchical self-assembly of aromatic peptide conjugates into supramolecular polymers: it takes two to tango

“… 27 Such cooperative effects can originate from internal ( e.g. activation/deactivation 28,29 and folding 30,31 ) or external ( e.g. template-assisted polymerization 32 ) forces that modulate reactivity throughout the polymerization process.…”