Copolymer brush

Fig. 10 Synthesis of the macroinitiator precursor (I), the macroinitiator (II) and macro-molecular gradient brush copolymer (III). (Reproduced with permission from [55])...

Figure 1 Macromolecular architectures linear macromolecular chains (homopolymer, block-copolymer and statistical copolymer [14]), brushed-polymer (= linear chains attached to a polymer-chain brush-polymer, brush-copolymers [14]), star polymer [4], mikto-star-polymer [16], arborescent graft polymer (=repeated grafting of linear chains on a macromolecule [17,18]), dendrimer (= maximally branched, regular polymer [15])...

Figure 4.22 Schematic drawings of various block copolymers. These long-chain molecules synthetic molecules consist of chemically distinct poiymeric "biocks" (denoted by lines of (Afferent thicknesses in the figure), chemically grafl. (Left to right ) Linear diblock copolymer molecule (AB) linear triblock (ABC) star copolymer brush copolymer. If the blocks are mutually immiscible, under suitable conditions die molecules spontaneously dump together forming an array of mesophases.

The field of densely grafted copolymers has received considerable attention in recent years. The materials (also called bottle-brush copolymers) contain a grafted chain at each repeat unit of the polymer backbone. As a result, the macromolecules adopt a more elongated conformation. Examples of brush copolymers have been provided within the context of ATRP [307-309]. Synthesis of the macroinitiator was achieved through one of two approaches. One method used conventional radical polymerization of 2-(2-bromopropionyloxy)ethyl acrylate in the presence of CBr4 to produce a macroinitiator with Mn=27,300, and a high polydispersity of Mw/Mn=2.3 (Scheme 46A) The alternative involved the ATRP of 2-trimethylsilyloxyethyl methacrylate followed by esterification of the protected alcohol with 2-bromopropionyl bromide. While synthetically more challenging, the latter method provided a macroinitiator of well-defined structure... 

Scheme 46 A,B. Synthesis of densely grafted brush copolymers via A a conventional radical polymerization followed by ATRP B wholly by ATRP [307]...

Figure 337 Schematic illustration of various types of stabilizer molecules (a) non-ionic surfactants Cb) random cal polymers (c) linear block copolymer, (d) comb or brush" copolymer, (e) grafted polymer chains (0 globular molecules...

Degradable brush PHEMA-PDMAEMA-based copolymers were prepared by a combination of ATRP and click chemistty. Click chemistry introduced by Sharpless et al. is one of the most widely used approaches to prepare well-controlled macromolecules and biomolecules. " An azido-modified ATRP initiator was used to prepare PDMAEMA. PHEMA prepared by ATRP was modified with carbonyldiimidazole (CDI)-activated PDMAEMA. The click reaction between two polymers yielded brush polymers of varying molecular weights (Scheme 3.11). A brush copolymer of PDMAEMA of 50 kDa showed high p-galactosidase expression in Cos-7 cells, compared to analogues of other molecular weights. ... 

Figure 17 Preparation of well-defined heterografted brush copolymers by a combination of enzymatic ROPofc-caprolactone (CL) and ROP of i-lactide (LLA) (a) or ATRP of methyl methaciylate (MMA) and />butyl methacrylate (BMA) (b). Reprinted from Hans, M. KeuI, H. Heise, A. Moller, M. Macromolecules 2007, 40 (25), 8872-8880 Hans, M. Xiao, Y. KeuI, H. ef al. Macromol Chem. Phys. 2009,210 (9), 736-746, with permission from ACS. ...

Figure 25 Assembly of DNA-brush copolymers into micelles with spherical or cylindrical morphologies. Amphiphile structures are represented as cones for each respective motphology, with the hydrophobic domain highlighted in red. TEM images of (a) 25-nm spherical micelles assembled from initial DNA-brush copolymers (b) cylindrical morphology formed following DNAzyme addition to spheres (c) spherical micelles (green) formed after the addition of hi to cylinders. Reproduced with permission from Chien, M.-P. Rush, A. M. Thompson, M. P. etal. Angew. Chem. Int. Ed. 2010,49, 5076-5080. 2...

Boyes, S.G. Akgun, B. Brittain, W.J. Foster, M.D. Synthesis, characterization, and properties of polyelectro-1)46 block copol3fmer brushes prepared by atom transfer radical pol3fmerization and their use in the synthesis of metal nanoparticles. Macromolecules 2003, 36, 9539. Neugebauer, D. Zhang, Y. Pakula, T. Matyjaszewski, K. Heterografted PEO-Pn BA brush copolymers. Polymer 2003, 44, 6863. 

In addition to the side chain conformation, chemically different side chains attached to the same main chain may also have a pronounced impact on the main chain conformation, particularly if the respective side chains are incompatible. Demixing of the side chain is hampered by the fact that the chemically different side chains are bound to the same main chain, leading to highly frustrated single chain structures. In order to experimentally address this point, the phase separation within statistical cylindrical brush copolymers comprising PMMA and poly-2-vinylpyridinium (PVP) side chains was investigated [93, 94]. The samples were prepared by radical copolymerization of methacryloyl end-functionalized PMMA M = 3,700 g/mol) and PVP M = 5,100 g/mol) macromonomers. Copolymer brushes with two different compositions were synthesized and characterized as shown in Table 1. Subsequent quatemization of the PVP side chains with ethylbromide was conducted in order to enhance incompatibiUty. 

Gorochovceva N, Naderi A, Dedinaite A et al (2005) Chitosan-N-poly(ethylene glycol) brush copolymers synthesis and adsorption on silica surface. Eur Polym J 41 2653-2662... 

PEG3-PLA Brush copolymer Scheme 2 (Adapted from Gref, 1994). 

Poly(ester-Anhydrides) and Poly(ether-anhydrides). 4,4 -alkane-and oxa-alkanedioxydibenzoic acids were used for the s5mthesis of polyanhydrides. These polyanhydrides melted at a temperature range of 98-176°C and had Mw up to 12,900. Di- and triblock copolymers of poly(caprolactone) (PCL), poly(lactic acid) (PLA), and poly(hydroxybutyrate) (PHB) have been prepared from carboxylic acid terminated low M prepolymers copolymerized with SA prepolymers by melt condensation (49). Similarly, di-, tri-, and brush copolymers of poly(ethylene glycol) (PEG) with poly(sebacic anhydride) (PSA) have been prepared by melt copolymerization of carboxylic acid terminated PEG (50). 

The other example of brush copolymers is based on the grafting through approach where macromonomers with vinyl terminal are synthesized rst and polymerization is carried out through the terminal double bonds to produce densely grafted macromolecules. The grafting through approach in combination with ATRP has also been applied in the copolymerization of PMMA macromonomers with n-butyl acrylate (Roos et al., 1999,2000). 

Figure 11.29 Synthesis of densely grafted ( bottle-brush ) copolymers using ATRP and grafting from process. Note PSt = polystyrene PBA = poly(/i-butyl acrylate). (Adapted from Matyjaszewski and Xia,...

The precursor polymer blend can be made out of (1) linear block copolymers, (2) AB block copolymers, (3) ABA block copolymers, (4) ABC block copolymers, (5) multiblock copolymers, (6) symmetrical and asymmetrical star block copolymers, (7) blends of polymers, (8) graft copolymers, (9) multibranched copolymers, (10) hyperbranched or dendritic block copolymers, and (11) novel brush copolymers. 

Most work on REMP was done with COE (8) or cyclooctadiene (COD) (9) but functionalized monomers can also be used. A dendronized macro-monomer 10 (Figure 1.4) has been used under REMP conditions, leading to the formation of cyclic nanostructures with a diameter of 35-40 nm [40]. Recently, a REMP-derived cyclic macro-initiator derived from monomer 11 was used to prepare cyclic brush copolymers by combining REMP with triazabicyclodecene-catalyzed ring-opening polymerization of a cyclic ester [41]. Furthermore, REMP processes were developed for the synthesis of functional cyclic polymers, cyclic polymer brushes, and cyclic gels [42, 43]. 

Linear amphiphilic block copolymers have been assembled in a selective solvent with a great diversity of kinetically frozen micelles. When a perfect control of nanostructure size and shape was required, brush copolymers were found to be the preferred templates to prepare cylindrical nanoparticles. Wooley et al. 

Scheme 2.10 Synthesis of core-shell brush copolymers by random ROMP and NMP.

Figure 5.9 Three strategies for synthesizing molecular brush copolymers.

Figure 5.12 Schematical representation of the grafting-through polymerization approach to synthesize molecular brush copolymers depicting that the block brush...

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