Nanophase separation

It is quite well known that the formation of nanophases plays an important role in adhesive technology although this fact was ignored for many years due to the difficulties relating to the imaging of such small structures. Nanometer-scale interdiffusion layers account for polymer/polymer adhesion. This is illustrated in Fig. 13.6 for the sandwiched films of the thermoplastic elastomer SEES and isotactic polypropylene, annealed at 160°C for several hours. The interdiffusion layer is approximately 100 nm wide. This interfacial nanodesign is the key to improved adhesion of polypropylene materials. 

Several dendritic and hyperbranched polymers are available on a commercial, semi-commercial or pilot scale  

Nanometer-scale molecules of hyperbranched polymers and dendrimers can be dissolved and assembled in various polymer matrices as well as on polymer surfaces and polymer/polymer, polymer/filler and polymer/fiber interfaces. 

The syntheses, properties and applications of hyperbranched polyesters have been investigated in great detail [22]. The addition of hyperbranched polyesters was reported to double the interlaminar fracture resistance of epoxy-based composites and to reduce the internal stress level by as much as 80% in the pres- 

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Robertson and Yeager used Py and Ru(bpy)3 probes for the purpose of locating the locations of Cs+ and 1 ions in the nanophase-separated morphology. It is known that these probes take residence in the intermediate polarity hydrophobic—hydrophilic interfacial regions. The studies concluded that Cs+ ions were located in the aqueous regions, but I ions were in the interfacial regions. 

M. Maaloum, P. Muller, M.P. Krafft, Lateral and vertical nanophase separation in Langmuir-Blodgett films of phospholipids and semifluorinated alkanes, Langmuir 20 (2004) 2261-2264. 

The signiflcant recent advances in both colloidal and polymer chemistries have enabled the successful fabrication of complex, defect-free tianoslruclures following a bottom-up approach [353]. Two recent related examples are mentioned to stress the point. Recently, triblock copolymer with divalent counter-ions in mixed solvents led to the formation of particles with tunable internal structure mimicking lipid anphiphiles for potential use in drug delivery. The mechanism of formation involves either nanophase separation within the triblock copolymer nanoparticle upon addition of water or microemulsion formation similar to that in lipid systems... 

Fig. 13.7 The TEM image of the nanophase-separated structural epoxy adhesive containing nitrile rubber/phenolic polyurethane liquid rubber blends (cure with dicyandiamide at 180°C).

Note that in a subsequent study a similar result of micro-/nanophase separation has been observed in block copolymers of PNIPAAM and Ai-isopropylmetAa-crylamide (PNIPMAM). This small-angle neutron scattering (SANS) study used a scattering analysis with a new form factor model taking into account a nanophase separated internal morphology [50]. 

The simple and cheap EPR method presented here not only directly mirrors the nanophase separation in the CW EPR spectra without the use of any model but even allows the characterization of the nano-inhomogeneity on the functional level of a chemical reaction. 

Her current research interests include studies of miscibility and physical aging in blends, nanophase separation in polymers with long side-chains, polymer dynamics, liquid crystalline polymers, composites, and systems containing nanoparticles. A common feature of these studies is the use of scattering techniques, especially neutron scattering, to study the local structure, conformation, and dynamics in polymers. She has written various reviews and book chapters in this area and has served on selection panels to allocate beam time at neutron facilities. 

Watanabe S, Fujiwara R, Hada M, Okazaki Y, lyoda T. 2007. Site specific recogni tion of nanophase separated surfaces of amphiphilic block copolymers by hydro philic and hydrophobic gold nanoparticles. Angew Chem Int Ed Engl 46 1120 1123. 

S. Hsu, C. Chen, C. Chao, C. Chen, J. Chiu, Cell migration on nanophase-separated poly(carbonate urethane)s, J. Med. Biol. Eng. 27 (1)... 

Fig.l a Smectic LC ordering as a nanophase separation process. The picture shows smectic layering when for only one out of five backbone positions a side chain is attached [20]. b Cartoon model of a LC/amorphous diblock copolymer... 

Noro A, Ishihara K, Matsushita Y (2011) Nanophase-separated supramolecular assemblies of two functionalized polymers via acid-base complexation. Macromolecules 44 (16) 6241-6244... 

Bolognesi, A., Galeotti, F., Giovanella, U., Bertini, F., Yunus, S. Nanophase separation in polystyrene-polyfluorene block copolymers thin films prepared through the breath figure procedure. Langmuir 25, 5333-5338 (2009)... 

Polyethylene is recognized as a semicrystalline polymer, where the prefix semi indicates that the material is not perfectly crystaUine (such as low molar mass compounds, e.g. dimethoxy biphenyl, which forms amazing crystals from supersaturated solutions) but rather is a nanophase-separated material that consists... 

The combination of thermal annealing and crosslinking, which can be done here at 250 °C by the trimerization of the terminal ethynyl groups, results in a morphological transformation. An eventual nanophase separation between the hydrophilic and hydrophobic domains forms well-connected hydrophilic nanochannels. These show a dramatically enhanced proton conduction. 

By solution casting, tough and ductile membranes could be obtained. A nanophase separated morphology in the membranes accounts for an enhanced proton conductivity at reduced relative humidity [111]. 

Both the 4,4 -biphenol and hydroquinone based membranes show high proton conduchvity with moderate water uptake and good mechanical properties. The block copolymers have nanophase separated morphologies [46]. 

Radzilowski, L.H., and S.I. Stupp. 1994. Nanophase separation in monodisperse rod-coil diblock polymers. Macromolecules 27 7747. 

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