Atom transfer radical polymerization ring-opening polymerizations

CHE2 Chen, J., Liu, M., Gong, H., Huang, Y., and Chen, C., Synthesis and self-assembly of thermoresponsive PEG-Z>-PNIPAM-Z>-PCL ABC triblock copolymer through the combination of atom transfer radical polymerization, ring-opening polymerization, and chck chemistry, J. Phys. Chem. B, 115, 14947, 2011. 

Xie M, Han H, Ding L et al (2009) Promotion of atom transfer radical polymerization and ring-opening metathesis polymerization in ionic liquids. J Macromol Sci R, Part C Polym... 

In contrast, here a bifunctional initiator is employed and the polymerization order of the two blocks is inverted In a first step, the styrene block is synthesized by atom transfer radical polymerization (ATRP) followed by the addition of lactide via the recently developed organocatalytic ring-opening polymerization, as depicted in Fig. 3.1 [4, 5]. This synthesis route reduces the involved steps and enables a simplified and time-efficient preparation of copolymers with different block compositions. Importantly, both polymerization techniques offer precise and robust control over the copolymer composition, which is an essential requirement to reliably target the double-gyroid s narrow location in phase space [6]. 

Figure 8 Main mechanistic transformation reactions in living and/or controlled polymerization methods. ATRP, atom transfer radical polymerization RAFT, reversible addition-fragmentation chain transfer NMRP, nitroxide-mediated free radical polymerization CROP, cationic ring-opening polymerization AROP, anionic ring-opening poiymerization.

Keywords atom transfer radical polymerization living polymerization polypeptides ring-opening polymerization rod-coil diblock copolymers... 

Frontal polyurethane polymerization [13-15], frontal atom transfer radical polymerization [16], and frontal ring-opening metathesis polymerization (ROMP) [17] all suffer from short pot lives that is, bulk polymerization occurs in less than an hour. In some cases, the only way to avoid even faster bulk polymerization is to cool the reagents. For example, with frontal ring-opening metathesis polymerization of dicyclopentadiene with a Grubbs catalyst, the starting materials had to be frozen to prevent rapid bulk polymerization [17]. 

De Clerq, B., Verpoort, F., A new class of ruthenium complexes containing Schiff base ligands as promising catalysts for atom transfer radical polymerization and ring opening metathesis polymerization, J. Mol. Catal. A Chem. 2002,180 67-76. 

Abraham, S., Ha, C.-S., and Kim, I. (2006) Self-assembly of star-shaped polystyrene-WocA -polypeptide copolymers synthesized by the combination of atom transfer radical polymerization and ring-opening living polymerization of a-amino acid-N-carboxyanhydrides. Journal of Polymer Science Part A Polymer Chemistry,... 

Becer CR, Paulus RM, Hoppener S et al. (2008) Synthesis of poly(2-ethyl-2-oxazoline)-h-poly(styrene) copolymers via a dual initiator route combining cationic ring opening polymerization and atom transfer radical polymerization. Macromolecules 41 5210-5215... 

Lenoir S, Riva R, Lou X, Detrembleur C, Jerome R, Lecomte P (2004) Ring-opening polymerization of a-chloro- -caprolactone and chemical modification of poly(a-chloro- -caprolactone) by atom transfer radical processes. Macromolecules 37 4055 061... 

Heise, Palmans, de Geus, Villarroya and their collaborators (17,41,42) have been working on a chemoenzymatic cascade synthesis to prepare block copolymers. They combine enzymatic ring-opening polymerization (eROP) and atom transfer radical polymerization (ATRP). The synthesis of block copolymers was successful in two consecutive steps, i.e., eROP followed by ATRP. In the one-pot approach, block copolymers could be obtained by sequential addition of the ATRP catalyst, but side reactions were observed when all components were present from at the onset of reactions. A successful one-pot synthesis was achieved by conducting the reaction in supercritical carbon dioxide. 

An approach similar to the previous divergent grafting-from method also served to synthesize dendrigraft poly(L-lysine) by ring-opening polymerization [111], styrene homopolymers and styrene-methacrylate copolymers by a combination of stable free-radical polymerization and atom transfer radical polymerization (ATRP) [112], and copolymers of 2-hydroxyethyl methacrylate with styrene or ferf-butyl methacrylate by ATRP [113]. 

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