biomaterials<\/a> for drug deliveries.<\/p>\nChemists have relied on two-step polymerisations in one or two separate vessels to synthesise block copolymers. A \u2018two-pot\/two-step\u2019 polymerisation requires isolating the first segment before proceeding with the next reaction, which is cumbersome and costly.<\/p>\n
A \u2018one-pot\/two-step\u2019 approach<\/h3>\n A \u2018one-pot\/two-step\u2019 approach bypasses this isolation step, yet requires a so-called living polymerisation, where, once the first monomer is consumed, the growing chain remains reactive to accept another monomer and as a result, both monomers are fully converted. However, this can lead to unwanted side reactions if the second monomer is not added in time.<\/p>\n
Nikos Hadjichristidis and co-workers devised a \u2018one-pot\/one-step\u2019 approach to produce diblock terpolymers, in which three monomers form two different alternating copolymer segments. \u201cThis is the simplest method,\u201d explained post doctorate fellow Jiaxi Xu, who co-led the study.<\/p>\n
Polymerisations involving three monomers usually produce random terpolymers. Therefore, it was crucial to find a smart catalyst to regulate the monomer sequence during the polymerization, Xu explains.<\/p>\n
Auto-switchable phosphazene-based catalysts<\/h3>\n The researchers discovered that an auto-switchable phosphazene-based catalyst can stimulate the polymerisation of one monomer and inhibit that of others. The ability to switch the catalyst depends on its ability to exchange protons with the growing chain.<\/p>\n
\u201cWhen the first monomer is consumed completely in the alternating copolymerization with the second monomer, the catalyst turns on to promote the alternating copolymerization of the excess of the second monomer with the third one,\u201d Xu said.<\/p>\n
Furthermore, selecting cyclic monomers from the nitrogen-containing N-sulfonyl aziridine, the oxygen-containing epoxide and the anhydride families was essential for the terpolymerization. \u201cWe had previously synthesised block copolymers consisting of one alternating copolymer and a homopolymer using aziridines and anhydrides,\u201d Xu commented. This suggested that three monomers with different reactivity would effectively enable the \u2018one-pot\/one-step\u2019 preparation of diblock dialternating terpolymers.<\/p>\n
The researchers discovered that the catalyst promoted the aziridine\/anhydride alternating copolymerisation before switching to the epoxide\/anhydride alternating copolymerisation, demonstrating its high monomer selectivity and kinetic control.<\/p>\n
The team intends to further tap into aziridine, epoxide and anhydride terpolymers. \u201cThese families contain hundreds of monomers, which will provide extremely diverse diblock dialternating terpolymers for many potential industrial applications,\u201d Hadjichristidis concluded. \u201cThis study also opens new horizons for the terpolymerisation of other monomer families.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":"
Scientists have developed a catalyst that turns three monomer mixtures into diblock dialternating terpolymers in one single step. A catalyst developed at King Abdullah University of Science and Technology (KAUST) could be the key to structural diversity in polymer materials and industrial-scale polymerisations involving multiple monomers. The catalyst transforms a mixture of three monomers into […]<\/p>\n","protected":false},"author":19,"featured_media":17396,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"categories":[766,24429],"tags":[24605,763,833],"acf":[],"yoast_head":"\n
Scientists use innovative approach to create catalyst for polymer diversity<\/title>\n \n \n \n \n \n \n \n \n \n \n \n \n \n\t \n\t \n\t \n \n \n \n \n \n\t \n\t \n\t \n