Bottle brush copolymers

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... 

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,...

ATRP has been successfully carried out in bulk, in solution [27,28], as well as in aqueous solution [157], emulsion [169], miniemulsion [170], and suspension [135,171], and in other media (e.g., liquid or supercritical CO2 [109] or ionic liquids) [172,173]. Typical temperature range for a polymerization is from sub-ambient temperature to +130 °C. Molecular weights for linear and graft copolymers range from 200 < Mn < 500,000 (however the molecular weight of bottle-brush copolymers and particle tethered copolymers can reach well into the millions), and polydispersities are low, 1.05 < < 1.3,... 

Subsequently, Wolf and coworkers [49] investigated the effect of copolymer architecture on the interfacial tension reduction for the PDMS/PEO blend utilizing PDMS-h-PEO diblocks, PDMS-b-PEO-b-PDMS triblocks, and bottle-brush copolymers consisting of PDMS backbone and PEO brushes. The study showed that for the range of molecular weights investigated, the total number of PDMS... 

Scheme 22 Procedure for preparation of bottle brush copolymers and AFM image of a brush macromolecule with a backbone DP = 4000 and branch DP = 20.

Scheme 23 Densely grafted bottle brush copolymers formed by a grafting onto click reaction. Reprinted from Gao, H. Matyjaszewski, K. J. Am. Chem. Soc. 2007, 129, 6633-6639, ° with permission from the ACS.

Macromonomers provide an easy access to a large number of functional copolymers and controlled topologies, such as comb-like, star-like, bottle brush, and graft copolymers. These types exhibit exceptional solution or solid state properties compared to their linear homologues. 

Fig. 4 Molecular structure of diblock copolymers and side-chain modified lipopolymers whose pressure-area isotherms are presented in Figs. 6 and 7, respectively. Diblock copolymers are poly(2-n-nonyl)-poly(2-methyl or 2-ethyl-2-oxazoline) (NxEy and NxMj,), where x and y denote the block sizes of the hydrophobic nonyl and hydrophilic oxazoline blocks. Side-chain modified lipopolymers, which contain short oligo-EG sidechains in each monomer of the lipopolymer to create a bottle-brush-like structure, are di-octadecanoyl-glycerol 2-(3 -methoxymonoethylene glycol)propyl-2-oxazoline (DiCigMEGOxn) and di-octadecanoyl-glycerol 2-(3 -methoxytiiethyleneglycol)propyl-2-oxazoline (DiCisTEGOxn) (adapted from [7,8])...

Zheng, X., et al. 2015. Antifouling property of monothiol-terminated bottle-brush poly (methylacrylic acid)-graft-poly(2-methyl-2-oxazoline) copolymer on gold surfaces. Journal... 

Schlaad et al. reported in greater detail on the solid-state phase behavior of linear and bottle-brush shaped polystyrene-block-poly(Z-L-lysine) in a wide range of molecular weight, composition, and architectures [76]. According to earlier reports on rod-coil block copolymers with polypeptides, mainly (undulated) lamellar morphologies were observed (see Figure 21). 

Figure21 Generalized phase diagram including morphologies found in polystyrene-block-poly(Z-L-lysine), linear block copolymers, O bottle-brush shaped block copolymers, and schematic presentation of the undulated lamellar morphology. (Reprinted from H. Schlaad, H. Kukula, B. Smarsly, M. Antonietti, and T. Pakula. Polymer 43 5321,2002. Copyright [2002], with permission from Elsevier Science.)...

Fig. 2. Selected architectures of block copolymers (a) diblock (b) triblock (c) comb copolymer consisting of flexible chains (d) rod-coil diblock copolymer consisting of a rodlike block and a coil-like block (e) hairyrods, i.e., comb-block copolymers consisting of rodlike backbone and coil-like side chains and (f) LC coil with a side-chain liquid crystalline (LC) block and a flexible block. Many other variations have been introduced, such as multiblock copolymers, block copolymers consisting of several rodlike blocks, or star-shaped block copolymers. Comb-coil block copolymers with dense packing of side chains are also denoted as molecular bottle brushes, as is illustrated in (g) by a simulated structure of an isolated molecule dissolved in a solvent. (Courtesy of Mika Saariaho.)...

Gus kova OA, Pavlov AS, Khalatur PG, Khokhlov AR (2007) Molecular bottle brushes in a solution of semiflexible polyelectrolytes and block copolymers with an oppositely charged block a molecular dynamics simulation. J Phys Chem B 111 8360-8368. doi 10.1021/... 

Fig. 32 (a) Perfect phase separation of side chains in a binary (A, B) copolymer bottle bmsh with alternating grafting sequence ABAB... of side chains along the backbone into a Janus cylinder structure implies formation of an AB-interface phase (shaded) between the A-rich part (bottom) and the B-rich part (top) of the cylindrical brush. The local orientation of the interface can be characterized by a unit vector oriented normal to it (arrows), (b) At nonzero but low temperatures, phase separation will occur locally, but entropy will lead to long wavelength fluctuations of the... 

Well-defined carbon stractures were also prepared from densely grafted bottle bmsh molecules with PAN di-(AB) and triblock-( ABC) copolymer SCs. Thin films of the SC brushes were prepared by drop casting aqueous solutions onto dean silicon wafer substrates. After thermal treatment, the SC brash precursors were converted into nanostractured carbon. AFM images of the resulting films revealed a sirrface with characteristic round protrusions and roughness of 4.0 nm. 

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