Polymer Janus

Along this line of using amphiphilic features of particles to drive assembly using a hydrophobic effect, there has been a recent surge of interest in the fabrication and behavior of anisotropic patchy or Janus-type colloidal particles as a promising route to innovative nanocomposite materials [40, 41]. Whereas a thorough review lies outside our scope, we would like to highlight a few examples. Muller and coworkers prepared disc-like polymer Janus particles from assem-... 

Muller and coworkers prepared disc-like polymer Janus particles from assembled films of the triblock copolymer SBM and, after hydrolysis of the ester groups into methacrylic acid units, used these as Pickering stabilizer in the soap-free emulsion polymerization of styrene and butyl acrylate [111]. Armes and coworkers described the synthesis of PMMA/siUca nanocomposite particles in aqueous alcoholic media using silica nanoparticles as stabilizer [112], extending this method to operate in water with a glycerol-modified silica sol [113, 114]. Sacanna showed that methacryloxypropyltrimethoxysilane [115] in the presence of nanosized silica led to spontaneous emulsification in water, which upon a two-step polymerization procedure afforded armored particles with an outer shell of PMMA [116]. Bon and coworkers demonstrated the preparation of armored hybrid polymer latex particles via emulsion polymerization of methyl methacrylate and ethyl methacrylate stabilized by unmodified silica nanoparticles (Ludox TM O) [117]. Performance of an additional conventional seeded emulsion polymerization step provided a straightforward route to more complex multilayered nanocomposite polymer colloids (see Fig. 14). 

Berger S, Synytska A, Ionov L, Eichhom K-J, Stamm M (2008) Stimuli-responsive bicomponent polymer janus particles by grafting from / grafting to approaches. Macromolecules 41(24) 9669-9676... 

Hong S, Leroueil PR, Janus EK, et al. (2006). Interaction of polycationic polymers with supported lipid bilayers and cells nanoscale hole formation and enhanced membrane permeability. Bioconjug. Chem. 17 728-34. 

Erhardt R (2001) Janus-Micellen Amphiphile oberflachenkompartimentierte Polymer-micellen mit vernetztem Kern. Shaker, Aachen... 

T. Nisisako and T. Torii, Formation of biphasic Janus droplets in a micro-fabricated channel for the synthesis of shape-controlled polymer microparticles. Advanced Materials, 19, 1489—l-, (2007). 

The synthesis of polyelectrolytes with well-defined architectures, however, has imposed many challenges to the polymer chemists. Many polymerization techniques are not tolerable to the ionic functional groups. In most cases, preparation of polyelectrolytes involves the protection and deprotection of the ionic groups in the monomer. For polyelectrolytes with different architectures, various synthetic strategies are required. Recently, we have synthesized various complex architectures containing polyelectrolytes with different nonlinear topologies, such as combshaped [22], hyperbranched [23-25], Janus-type [26], stars [27, 28] and brushes [29-31],... 

Recently, Perro et al. [55] reviewed the developments in the field of Janus particles over the last 15 years, describing various strategies to obtain Janus-type particles using polymer precursors. One strategy is based on the self-assembly of ABC terpolymers in bulk [56, 57] or in solution [58], Another uses the electrostatic interactions of AB and CD diblock copolymers, which lead to inter-polyelectrolyte complexes [59], A different synthetic concept is to obtain Janus particles made of inorganic materials, e.g., acorn-like particles made of PdSx-CogSg [60] or... 

Walther A, Matussek K, Muller AHE (2008) Engineering nanostructured polymer blends with controlled nanoparticle location using Janus particles. Acs Nano 2(6) 1167-1178... 

The incorporation of Janus recognition moieties 5 and 6 on a tartrate scaffold in the form of double-Janus tectons 39 and 40 permits the design of infinite 2-dimensional polymeric assemblies (Fig. 27) [84]. The assembly of 39 and 40 with single-Janus tectons 5 and 6, respectively, would then result in a truncated 2-dimensional assembly, a double H-bonded ribbon. More recently, 1-dimensional main-chain H-bonded polymers have been reported based on... 

Fig. 27. Two-dimensional supramolecular network of H-bonded cross-linked main-chain polymers incorporating Janus recognition groups 5 and 6...

Crini G, Bertini S, Torri G, Naggi A, Sforzini D, Vecchi C, Janus L, Lekchiri Y, Morcellet M. (1998). Sorption of aromatic compounds in water using insoluble cyclodextrin polymers. Journal of Applied Polymer Science 68 1973-1978. 

Crini G, Janus L, Morcellet M, Torri G, Morin N. (1999). Sorption properties toward substituted phenolic derivatives in water using macroporous polyamines containing beta-cyclodextrin. Journal of Applied Polymer Science 73 2903-2910. 

Figure 8.6 U V-vis-NIR spectra of solutions of Janus Green B azo dye in NMP (A), and aqueous acidic solution (B), and resonance Raman spectra of Janus Green B azo dye in the solid state obtained at the indicated exciting radiations. The dye molecular structure is also shown. (Reprinted with permission from Macromolecules, Aniline Polymerization into Montmorillonite Clay A Spectroscopic Investigation of the Intercalated Conducting Polymer by G. M. do Nascimento, V. R. L. Constantino, R. Landers and M. L. A. Temperini, 37, 25. Copyright (2004) American Chemical Society)...

In addition, Liu and Chen prepared a MWCNT-based macroinitiator through an addition reaction between the ATRP initiator 1-bromoethylben-zene or the macroinitiator of bromine-terminated PS, and CNTs with CuBr/ PMDETA as the catalyst system at 80 °C for 24 h. Further ATRP of styrene or NIP A Am on the functionalized CNTs afforded PS-grafted CNTs or V-shaped amphiphilic polymer PS-PNIPAAm-grafted CNTs which showed Janus... 

Figure 5.21 TEM images of poly(w-butyl methacrylate)-grafted MWCNTs with azido groups (MWCNT-Az-PnBMA) (a), MWCNTs grafted with both poly( -butyl methacrylate) and poly(ethylene glycol) brushes (MWNT-PnBMA-PEG) (b, c). (d) Cartoon for the local phase separation and assembly of amphiphilic polymer brushes into Janus polymer structures on CNTs as shown in (c) (marked by arrows), (e) Photograph of MWCNT-PnBMA-PEG dispersed in a mixed solvent of water (upper layer) and chloroform (bottom layer). Reprint with permission from Zhang et al...

Keywords Coacervate Co-assembly Janus Micelle Polyelectrolyte Polymer Scattering Segregation Self-assembly Self-consistent field calculations... 

In this contribution, we describe our recent experimental and theoretical findings on complex coacervate core micelles. We have investigated the co-assembly of several types of oppositely charged ionic-hydrophilic block copolymers into mixed micelles. In particular, we have focused on chain mixing/segregation in the micellar corona as a function of monomer type and (the ratio between the) chain length of the polymer blocks in the corona. Our aim has been to employ co-assembly in such systems as a route towards formation of reversible Janus micelles. These are micelles with a corona that exhibits two distinguishable sides (hemispheres in the case... 

Now that we have established the requirements for the formation of reversible Janus micelles, we turn our attention to the choice of ionic-hydrophilic block copolymers. The ionic blocks have to be oppositely charged to ensure co-assembly in aqueous solutions, whereas the neutral blocks have to be water-soluble. Furthermore, the unlike water-soluble polymer blocks need to segregate, not mix within the micellar corona. Since the classical works of Flory and Huggins, extended by Scott to describe binary polymer solutions [58], it is well known that two unlike polymers... 

We have shown that a combination of four simple building blocks (i.e. monomers) and exclusively non-covalent interaction forces, achieved via the co-assembly of fully water-soluble double hydrophilic block copolymers, results in mixed micelles in aqueous solutions. The chemically unlike polymer chains in the micellar corona may give rise to various coronal microstructures, ranging from mixed to segregated, in either the radial or lateral direction, or in both. Hence, co-assembly of charged block copolymers can result in the spontaneous formation of reversible Janus micelles. 

Fig. 12 Selfassembly and light induced disassembly of the Janus-like hyperbranched polymer formed by hyperbranched polyglycerol with a p-CD apex and an hyperbranched poly(3-ethyl-3-oxetanemethanol) with azobenzene apex. Reproduced with permission from ref, 66, Copyright 2013 American Chemical Society.

---