RAFT polymers

This raft polymer cannot be obtained in a pure state ance large amounts of pure polystyrene also are present. The previous reaction in which methyl methacrylate was grafted onto a substituted polystyrene was much more clearcut in that the only possible product was the graft copolymer. 

Zard SZ (2008) The radical chemistry of thiocarbonylthio compounds an overview. Handb RAFT Polym 151-187... 

Mertoglu M, Gamier S, Laschewsky A, Skrabania K, Storsberg J. Stimuli responsive amphiphilic block copolymers for aqueous media synthesised via reversible addition fragmentation chain transfer polymerisation (RAFT). Polymer 2005 46(18) 7726-40. 

An, Z.S. Tang, W. Wu, M.H. Jiao, Z. Stucky, G.D. Heterofunctional polymers and core-shell nanoparticles via cascade aminolysis/Michael addition and alkyne-azide click reaction of RAFT polymers. Chem. Commun. 2008,48 (48), 6501-6503. 

Scheme 21.5 Reliable strategies to introduce or remove end groups from RAFT polymers. Note that the efficiency of the radical end group removal pathways depend on the individual RAFT agent, as well as the leaving group ability of the polymer. The provided...

Within the realm of modular polymer conjugation, the development of transformations that exploit the presence of the RAFT end group in atom-economic fashion has opened the possibiHties for the direct conjugation of RAFT polymers... 

Schilli, C. M. Mueller, A. H. E. Rizzardo, E. etal. RAFT Polymers Novel Precursors tor Polymer-Protein Conjugates, Matyjaszewski, K Ed. ACS Symposium Series Washington DC, 2003 Vol. 854 p. 603. 

Molecularly imprinted polymers (MIPs) that are capable of sensing specific organophosphorus compounds, such as pinacolyl methylphosphonate (PMP), by luminescence have been synthesized and characterized. The polymers have been synthesized using conventional free radical polymerization and using Reversible Addition Fragmentation Transfer (RAFT) polymerization. The RAFT polymers exhibited many advantages over conventional free radical processes but are more difficult to make porous. 

Figure 14. Scanning electron micrograph of a large particle of the RAFT polymer using toluene as the solvent (left 1000 X right 3000 X). (Reproduced with permission from reference 20. Copyright 2007 Elsevier.)...

One of the major applications of living polymerization is the synthesis of block copolymers via sequential addition of monomers. In this approach, monomer A is rst polymerized quantitatively by the RAFT process, followed by direct addition of a second monomer for chain extension, or alternatively, the RAFT polymer of A from the rst step is puri ed and used as a macro-CTA to... 

Figure 11.44 Eind-group modi cation of RAFT polymers and recovery of CTA by mixing the polymeric chains with an excess source of radicals. (Adapted from Perrier and Takolpuckdee, 2005.)...

Scheme P12.9.2 Conversion of the trithioccabonate end group of a RAFT polymer into colorless and stable thioether in a one-pot process combining (1) aminolysis of the trithiocarbonate function and (2) Michael addition of the formed thiol to an cr. -unsaturated carbonyl derivative.

Scheme P12.13.2 Formation of 2-arm, 3-arm, and 4-arm star polymers with PSt arms via HDA cycloadditions of RAFT polymers with dienes. (After Inglis et al., 2008. With permission from American Chemical Society.)...

Employing a similar approach as above, thiol-terminated RAFT polymers have also been reacted with a variety of low and high molecular weight acrylate species for ef cient end functionalization (Spruell et al., 2009) and immobilized onto ene-decorated microspheres of poly(divinyl benzene) (Goldmann et al., 2009). Considering the abundance of commercially available activated alkene substrates amenable to nucleophihc addition (e.g., acrylates and maleimides) and the simplicity-cum-robusrness of the aforesaid approach, the RAFT/thiol-ene combination can be expected to remain as a valuable tool for macromolecular synthesis (Sumerlin and Vogt, 2010). 

A block copolymer of poly(A-isopropylacrylamide) (PNI-PAAm) and PLA may combine the thermosensitive property of PNIPAAm and the biodegradable property of PLA. Polymeric micelles from such polymers can improve protein release properties. Temperature change can alter the hydro-philicity and conformation of PNIPAAm, which may affect the physicochemical properties of microspheres of the polymer. Amphiphilic block copolymers of P(NIPAAm-Z -LA) have been prepared by ROP of LA in toluene using Sn(Oct)2 as a catalyst and hydroxyl-terminated PNIPAAm, as depicted in Figure 4.6 [62]. Such copolymers have recently been synthesized by ROP of lactide using the two hydroxyl groups of 5, 5 -bis(2-hydroxyethyl-2 -butyrate)trithiocarbonate (BHBT). PLA-Z -PNIPAAm-Z -PLA was prepared by reversible addition-fragmentation chain transfer (RAFT) polymer-... 

Schilli CM, Muller AHE, Rizzardo E, Thang SH (2003) RAFT polymers novel precursors for... 

Moad, G., et al. (2000). Living free radical pol5nnerization with reversible addition-fragmentation chain transfer (the life of RAFT). Polym. Int., 49(9) 993-1001. 

As a numerical value for c, we assume value 53, derived in research [4] on the base of Eq. (12), at immediate experimental measurement of monomer and low-molecular RAFT-agent conversions. Since chain transfer reaction in RAFT-polym-erization is usually characterized by low value of activation energy, compared to activation energy of chain growth, it is supposed that constant C j doesn t depend or slightly depends on temperature. We will propose as an assumption that Ctt, doesn t depend on temperamre [ 10]. 

OEH 13] Oehlenschlaeger K.K., Mueller J.O., Heine N.B. et al, Light-Induced Modular Ligation of Conventional RAFT Polymers , Angewandte Chemie International Edition, vol. 52, pp. 762-766, 2013. 

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