Atom-transfer radical polymerization methacrylate synthesis

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-... 

Zeng F, Shen Y, Zhu S, Pelton R. (2000) Synthesis and Characterization of Comb-Branched Polyelectrolytes. 1. Preparation of Cationic Macromonomer of 2-(Dimethylamino)ethyl Methacrylate by Atom Transfer Radical Polymerization. Macromolecules 33 1628-1635. 

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... 

A controlled free radical polymerization technique was also used, namely, atom transfer radical polymerization (ATRP), to synthesize ATE on the basis of ABA triblock copolymers (Fig. 11.3b) (Cui et al., 2004). The triblock copolymer was designed to have a rubbery midblock of poly(n-butyl acrylate) (PnBA) and two end blocks of poly 6-[4-(4-methoxyphenylazo)phenoxy]hexyl methacrylate) (PAzoMA) that is azo-SCLCP. For synthesis, a dibromo initiator, namely, l,l -biphenyl-4,4 -bis(2-bromoisobutyrate), can first be used to prepare the dibromo PnBA macroinitiator, which is then used to polymerize the azobenzene methacrylate monomer to yield the two end blocks of PAzoMA. This ATE is different from azo-SCLCP-grafted SBS. It is a thermoplastic elastomer, in which... 

Huang, J. Cusick, B. Pietrasik, J. Wang, L. Kowalewski, T. Lin, Q. Matyjaszewski, K. Synthesis and in situ atomic force microscopy characterization of temperature-responsive hydrogels based on poly(2-(dimethylamino)ethyl methacrylate) prepared by atom transfer radical polymerization. Langmuir 2007, 23 (1), 241-249. 

Using an original approach, Zhang and coworkers recently reported the synthesis of PMMA latex particles stabilized by MMT platelets tethered with poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) brushes (Fig. 33) [290]. The PDMAEMA polyelectrolyte brush was synthesized by atom transfer radical polymerization using a cationic initiator previously introduced in the clay galleries. The PDMAEMA-functionaUzed clay platelets were further used to stabilize the emulsion polymerization of MMA initiated by the remaining free radical initiator present on the clay surface. 

Figure 4.2 Synthesis of the compatibilizer (P2) and schematic illustration of non-covalent functionalisation of MWNTs by P2. Reproduced with permission from Mandal and Nandi." EBIBT- 3-[l-ethyl-2(2-bromoisobutyrate)] thiophene DMAEMA- 2-(dimethylamino ethyl methacrylate) HMTETA- 1,1,4,7,10,10-hexamethyltriethylenetetra-mine ATRP- atom transfer radical polymerization.

Among these reactions, the Cu(l)-catalyzed azide-alkyne cycloaddition (CuAAC) is the most widely used. This reaction has been implemented for the preparation of segmented block copolymers from polymerizable monomers by different mechanisms. For example, Opsteen and van Hest [22] successfully prepared poly(ethylene oxide)-b-poly(methyl methacrylate) (PEO-b-PMMA) and PEO-b-PSt by using azide and alkyne end-functionalized homopolymers as the click reaction components (Scheme 11.2). Here, PEO, PSt, and PMMA homopolymers were obtained via living anionic ring-opening polymerization (AROP), atom transfer radical polymerization (ATRP), and postmodification reactions. Several research groups have demonstrated the combination of different polymerization techniques via CuAAC click chemistry, in the synthesis of poly(e-caprolactone)-b-poly(vinyl alcohol) (PCL-b-PVA)... 

H) Atom transfer radical polymerization Numerous reports have been published regarding the synthesis of star polymers using multifunctional initiators capable of initiating the atom transfer radical polymerization (ATRP) of certain monomers, mainly styrene, methacrylates, and acrylates. The living character of the growing chain ends provides the possibility for the synthesis of star-block copolymers. 

Pantoustier, N., Moins, S., Wautier, M., Deg, P., and Dubois, P., Solvent-free synthesis and purification of poly(2-dimethylamino)ethyl methacrylate) by atom transfer radical polymerization,... 

Z.H. Luo, T.Y. He, Synthesis and characterization of poly (dimethylsiloxane)-block-poly (2,2,3,3,4,4,4-heptafluorobutyl methacrylate) diblock copolymers with low surface energy prepared by atom transfer radical polymerization, React. Funct. Pol. 68 (5) (2008) 931-942. 

Lobb EJ, Ma I, BiUingham NC, Ames SP, Lewis AL. Facile synthesis of well-defined, biocompatible phosphoiylcholine-based methacrylate copolymers via atom transfer radical polymerization at 20°C. J Am Chem Soc 2001 123(32) 7913. ... 

Liu, Y., Wang, L., and Pan, C. (1999). Synthesis of block copoly(styrene-b-p-nitrophenyl methacrylate) and its derivatives by atom transfer radical polymerization. Macromolecules, 32(25) 8301-8305. 

Even with the successes of these methods, synthesis of selective membrane skins with minimal (< 50 nm) thicknesses is still difficult. Balachandra et at [47] described the use of room-temperature atom transfer radical polymerization (ATRP) from a substrate to synthesize two types of ultrathin ( 50 nm) polymer skins crosslinked poly(ethylene glycol dimethacrylate) (PEGDMA) and linear poly(2-hydroxyethyl methacrylate) (PHEMA). 

Parnell, A. J., Martin, S. J., Dang, C. C., Geoghegan, M., Jones, R. A. L., Crook, C. J., et al. (2009). Synthesis, characterization and sweUing behaviour of poly(methacrylic acid) brushes synthesized using atom transfer radical polymerization. Polymer, 50, 1005-1014. 

Liquid crystalline amphiphilic diblock copolymers poly(ethylene oxide)-h/oc -ll-[4-(4-butylphenyl-azo)phenoxy]-undecyl methacrylate, PEOn,-h-PMA(Az) , as shown in Fig. 16, prepared by atom transfer radical polymerization [61], were composed of hydrophilic PEOn, sequences and hydrophobic PMA(Az) , with azobenzene moieties such as mesogen connected by a flexible spacer. The synthesis of such amphiphilic liquid crystal block copolymers has been recently reported [62]. In diblock copolymers PEO ,-h-PMA(Az)n, m and n indicate the degree of polymerization of PEO and PMA(Az) components, respectively. Differential scanning calorimetry (DSC) of PEO ,-f>-PMA(Az)n gives a clear picture of the thermal properties of these liquid crystaUine polymers, as shown in Fig. 17, for PEOn4-h-PMA(Az)2o [58, 61]. 

Lim, K.T., Lee, M.Y., Moon, M.J. et al. (2002) Synthesis and properties of semifluorinated block copolymers containing poly(ethylene oxide) and poly(fluorooctyl methacrylate) via atom transfer radical polymerization. Polymer, 43,7043-7049. 

---