Copolymerization of Acrylonitrile and Ethene in the Presence of Trifluoroacetic Acid as Complexing Agent

Abstract

The free radical copolymerization of ethene (ET) with acrylonitrile (AN) in the presence of carboxylic acids has been studied. Carboxylic acids and trifluoroacetic acid (TFA) in particular were found to be useful complexing agents for acrylonitrile with regard to the alternating copolymerization with ethene. The complexation via hydrogen bonding could be observed by IR analysis of the stretching frequency of the nitrile group in the monomer. The complex formation resulted in a decrease of the copolymerization parameter r 1 of the complexed and the uncomplexed comonomer acrylonitrile, which was found to decrease with increasing TFA/AN ratio. The degree of alternation could be increased by increasing the TFA/AN or the ET/AN ratio in the initial polymerization mixture. Almost strictly alternating copolymers were obtained with TFA as solvent. The copolymers showed high crystallinity and melting temperatures similar to the strictly alternating copolymer, which has been synthesized in the presence of EtAlCl2 as a Lewis acid.

Brønsted Acid Cocatalysts in Photocatalytic Radical Addition of α-Amino C–H Bonds across Michael Acceptors

“…The first is that TFA is capable of lowering the kinetic barrier for addition of the nucleophilic α-amino radical to the enone, to the point that step III becomes no longer rate-limiting in this process. Although the ability of Lewis acids to accelerate the addition of nucleophilic radicals to Michael acceptors has been of significant recent interest, only a few reports have suggested the ability of Brønsted acids to catalyze similar radical additions . We expect that this observation could have important implications in the design of other radical addition reactions.…”

Mn2(CO)10-Induced Controlled/Living Radical Copolymerization of Methyl Acrylate and 1-Hexene in Fluoroalcohol: High α-Olefin Content Copolymers with Controlled Molecular Weights

“…Recently, Sen et al alleviated some of these problems using the relatively water-tolerant rare-earth metal Lewis acid like Sc(OTf) 3 , Brønsted acid like pyridinium triflate, and solid acidic Al 2 O 3 for the copolymerizations of acrylates and nonpolar olefins while the effectiveness on the copolymerizability was relatively small for some compounds. Although trifluoroacetic acid was employed for the copolymerizations between highly electron-deficient polar monomers, such as α-cyanoacrylate and acrylonitrile, and ethylene, the effects were unknown for the acrylate−α-olefin copolymerizations. ,, Thus, more effective radical copolymerization systems based on metal-free compounds are awaited from various aspects.…”

“…Another recent breakthrough in the controlling radical polymerization is triggered by the use of protic fluoroalcohols for the stereospecific radical polymerizations, in which the acidic and bulky fluoroalcohols coordinate to the carbonyl groups of the monomer units like VAc and methacrylates to induce the syndiospecific propagation via steric repulsion around the growing polymer terminals. Although the fluoroalcohols have not been used for the copolymerizations between acrylic and nonpolar monomers, some protic solvents are known to change the monomer reactivity ratios. ,,, These results suggest that the acidic fluoroalcohols would become novel effective solvents for enhancing the copolymerizations.…”

Effect of Lewis and Brønsted acids on the homopolymerization of acrylates and their copolymerization with 1‐alkenes

“…Besides Lewis acids, a strong organic Brønsted acid has also been used in the copolymerization of acrylonitrile with ethene 21…”