Polymer brushes, cylindrical

When a linear polymer is grafted with a large number of much shorter side chains, cylindrical polymer brushes are formed [33, 108-111]. They are also denoted as bottlebrushes or molecular brushes. Although most cylindrical polymer brushes contain linear side chains, dendritic or even hyperbranched space demanding grafts can also render cylindrical shapes, which leads to the so-called dendronized [112-116] andhypergrafted[117, 118] polymers, respectively. In this review, we will focus on cylindrical brushes with linear side chains. Due to their anisotropic nature in topology, they have attracted more and more research interest in their synthesis, bulk, or solution properties, as well as applications. 

Three main strategies have been successfully developed for the synthesis of cylindrical polymer brushes grafting through, grafting to, and grafting from. Scheme 8 shows the processes for each preparation strategy. 

Scheme 12 Schematic illustration for the synthesis of a wire-like assembly of magnetic/ semiconducting NPs inside a core-shell cylindrical polymer brush...

We have used core-shell cylindrical polymer brushes with PAA core and PnBA shell as templates for the growth of different inorganic NWs and nanohybrids, such as CdS [160], CdSe [164], and Fe203 [161] (see Scheme 12). 

Block copolymer self-assembly is a very promising alternative to make cylindrical polymer brushes. These brushes can replace the function and roles of molecular bmshes in many fields however, if the response of the main chain is necessary or in the case of multiblock copolymer side chains, they will fail to satisfy the application. 

Cylindrical polymer brushes composed of a poly(DPA) main chain and poly(oxyethylene) side chains have been prepared by the so-called graft-from method. For example, l-(p-trimethylsilylphenyl)-2-(m-methylphenyl)acetylene is at first polymerized into a high-MW polymer (M = 2x 10 ), then the m-methyl group is converted into the chloromethyl... 

Xu Y, Yuan J, Fang B, et al Hybrids of magnetic nanoparticles with double-hydrophilic core/sheU cylindrical polymer brushes and their alignment in a magnetic field, Adv Punct Mato 20 4182-4189, 2010b. 

Scheme 8 Synthesis of a silica nanowire using the polymer brush template approach, (a) ATRP multi-initiator poly[2-(2-bromoisobutyryloxy)ethyl methacrylate] (PBEM) with degree of polymerization of 3,200 (b) cylindrical polymer brush (CPB) with side chains of 20 APTS units (c) core-shell CPB with an additional 57 OEGMA units (d) soluble organo-sUica hybrid nanowires with a crosslinked silsesquioxane network in the core (e) inorganic silica nanowires after pyrolysis. Reprinted with permissitm liom Yuan et al. [40]...

Cylindrical Polymer Brushes Synthesis and Application as Templates for Organic-Inorganic Nanostructures... 

Whereas the LbL assembly typically uses (inorganic) sacrificial templates to prepare capsules, the simation is somewhat opposite for another type of polymeric nanostrucmres, named cylindrical polymer brushes (CPBs). In the last decade, these... 

The synthesis of cylindrical polymer brushes with amphiphilic poly(acrylic acid)-block-poly(n-butyl acrylate) (PAA-b-PnBA) diblock copolymer side chains is shown in Fig. 13.14. The procedure includes several steps (i) synthesis of a well-defined macroinitiator, PBIEM, by esterification of poly(2-hydroxyethyl methacrylate) (PHEMA), which was synthesized via ATRP of 2-hydroxyethyl methacrylate (HEMA) or anionic polymerization of silyl-protected HEMA (ii) ATRP of t-butyl acrylate (tB A) initiated by the pendant a-bromoester groups of PBIEM, yielding cylindrical brushes with PtBA homopolymer side chains (iii) sequential ATRP of n-butyl acrylate (nBA) forming the cylindrical bmshes with diblock copolymer [poly(t-butyl acrylate)-block-poly(n-butyl acrylate) (PtBA-b-PnBA)] side chains and (iv) hydrolysis of the PtBA block to produce the hydrophilic poly(acrylic acid) (PAA) block forming the core of an amphiphilic core-shell cylinder brash [106]. By using this technique, other well-defined core-shell cylindrical polymer brashes with polystyrene (PS), PS-b-PAA or PAA-b-PS, as side chains have been successfully synthesized. 

F. 13.15 Schematic illustration for the synthesis of a wire-like assembly of magnetic nanoparticles inside a cylindrical polymer brush a polymer brush with PAA core and PnBA shell b neutrahzed polymer brush with poly(sodium acrylate) core (Na" ions are not shown) c polychelate of the brush with Fe " or Fe ions and d hybrid nanocylinder of the bmsh and magnetie nanoparticles. Reproduced from [108] with permission fioni John Wiley and Sons... 

Zhang M, Drechsler M, Mirller AHE (2004) Template-controlled S5mthesis of wire-like cadmium sulfide nanoparticle assemblies within core-shell cylindrical polymer brushes. Chem Mater 16 537-543... 

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