Atom transfer radical polymerization block copolymers

Block copolymers were synthesized by a combination of fipase-catalyzed polymerization and atom transfer radical polymerization (ATRE). " " At first, the polymerization of 10-hydroxydecanoic acid was carried out by using lipase CA as catalyst. The terminal hydroxy group was modified by the reaction with a-bromopropionyl bromide, followed by ATRP of styrene using CuCE2,2 -bipyridine as catalyst system to give the polyester-polystyrene block copolymer. Trichloromethyl-terminated poly(e-CL), which was synthesized by lipase CA-catalyzed polymerization with 2,2,2-trichloroethanol initiator, was used as initiator for ATRP of styrene. 

Synthesis of Block Copolymers by Atom Transfer Radical Polymerization, ATRP... 

In this review, synthesis of block copolymer brushes will be Hmited to the grafting-from method. Hussemann and coworkers [35] were one of the first groups to report copolymer brushes. They prepared the brushes on siUcate substrates using surface-initiated TEMPO-mediated radical polymerization. However, the copolymer brushes were not diblock copolymer brushes in a strict definition. The first block was PS, while the second block was a 1 1 random copolymer of styrene/MMA. Another early report was that of Maty-jaszewski and coworkers [36] who reported the synthesis of poly(styrene-h-ferf-butyl acrylate) brushes by atom transfer radical polymerization (ATRP). 

Matyjaszewski K, Miller PJ, ShuklaN, Immarapom B, Gelman A, LuokalaBB, Siclovan TM, Kickelbick G, Valiant T, Hoffmann H, Pakula T (1999) Polymers at interfaces using atom transfer radical polymerization in the controlled growth of homopolymers and block copolymers from silicon surfaces in the absence of untethered sacrificial initiator Macromolecules 32 8716-8724... 

Controlled free-radical polymerization methods, like atom-transfer radical polymerization (ATRP), can yield polymer chains that have a very narrow molecular-weight distribution and allow the synthesis of block copolymers. In a collaboration between Matyjaszewski and DeSimone (Xia et al., 1999), ATRP was performed in C02 for the first time. PFOMA-/)-PMMA, PFOMA-fr-PDMAEMA [DMAEMA = 2-(dimethylamino)ethyl methacrylate], and PMMA-/)-PFOA-/)-PM M A copolymers were synthesized in C02 using Cu(0), CuCl, a functionalized bipyridine ligand, and an alkyl halide initiator. The ATRP method was also conducted as a dispersion polymerization of MMA in C02 with PFOA as the stabilizer, generating a kine-... 

Hedrick, J. L., et al. (1998), Dendrimer-like star block and amphiphilic copolymers by combination of ring-opening and atom transfer radical polymerization, Macromolecules, 31,8691-8705. 

A block copolymer consisting of a SCLCP-block of monomer XXVII with a laterally-attached mesogenic unit, and butyl-acrylate, was synthesized using a combination of ROMP and atom transfer radical polymerization (ATRP) (Fig. 16) [81]. 

Recently diblock copolymers of PEG and ionic segments were prepared by atom-transfer radical polymerization of methacrylic aminoester using a monofunctionalized PEG macroinitiator and then subsequent quaternization. Like others [60] these polymers form so called polyion complex micelles by electrostatic interaction with oppositely charged molecules (e.g. drugs, oligonucleotides), where the PEG block acts as a steric stabilizer [67]. 

Controlled free-radical polymerization (CFRP) has been used successfully to produce block, graft, and other controlled architecture copolymers within the last decade for a variety of free radically polymerizable monomers. The main techniques include reversible addition fragmentation and transfer (RAFT) polymerization, stable free-radical polymerization (SFRP) mediated by nitroxide/alkoxyamine based radicals, atom transfer radical polymerization (ATRP), diphenyl ethylene (DPE) mediated polymerization, and novel precipitation/emulsion polymerization based methods like free-radical retrograde precipitation polymerization (FRRPP). ... 

The PDEA-PEG block copolymer was synthesized by a typical atom-transfer radical polymerization (ATRP) using PEG as the macroinitiator (Scheme 10.4). This block copolymer formed micelles with diameters less than lOOnm, which is ideal for endocytosis. The dissolution of the micelles at low pH was monitored using A-phenyl-2-naphthylamine (PNA) as a florescent probe which has a low fluorescent activity in hydrophilic environments. The PDEA-PEG micelle was loaded with PNA. Its flnorescence was monitored as a fnnction of the solution pH. Eigure 10.18 suggests that the micelles dissolved at a pH about 6.0, which implies that the nanoparticles can... 

Cai, Y Armes, S. P. Synthesis of well-defined Y-shaped zwitterionic block copolymers via atom-transfer radical polymerization. Macromolecules 2005, 38, 271-279. 

Fig. 15 Solid phase strategy towards peptide-containing block copolymers by polymerization from the supported peptide via atom transfer radical polymerization [66]...

Peeters et al. combined the enantioselective eROP of 4-methyl-e-caprolactone (4-MeCL) with controlled atom transfer radical polymerization (ATRP) of methyl methacrylate (Scheme 11.17) [58]. It was found that the addition of Ni(PPh3)4 inhibited Novozym 435 and at the same time catalyzed the ATRP reaction. On the other hand, Novozym 435 did not interfere with the ATRP of methyl methacrylate. As a result the sequence of the reaction was important first the enantioselective eROP of 4-MeCL was conducted at low temperature to have a high enantioselectivity until the conversion was around 50%. Then, Ni(PPh3)4 and MM A were added and the temperature was raised to 80 °C to start up the ATRP reaction of MM A. After precipitation of the polymer to remove the unreacted (R)-4-MeCL, the chiral block copolymer (Mn= llkgmoT1 and 17 kg mol 1) was... 

Numerous examples of block copolymers formed in supercritical C02 via the bifunctional initiator approach have been reported [54], Perhaps the most common approach is to incorporate eROP with free-radical polymerization-the general scheme for this methodology is shown in Figure 13.3. Howdle et al. [55] was the first to report the synthesis of a block copolymer by the bifunctional initiator approach in supercritical C02 and showed the simultaneous eROP of e-caprolactone with controlled free radical polymerization of methyl methacrylate by atom transfer radical polymerization (ATRP)-at this time simultaneous eROP and ATRP had not been reported in any media. The bifunctional initiator incorporated both a primary hydroxyl group (as an initiation site for eROP of e-caprolactone) and a bromine moiety (for initiation of ATRP). Howdle showed that... 

Figure 13.3 Overview showing the use of bifunctional initiators for block-copolymer synthesis. Two examples using either reversible addition fragmentation chain transfer polymerization or atom transfer radical polymerization combined with eROP are shown.

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