Polymeric cylinders from self-assembly

Polymeric Cylinders from Self-Assembly as a Template... 

Polymeric cylinders from self-assembly as template... 

One of the potential applications of these ABC triblock copolymers was explored by Hillmyer and coworkers in 2005 [118]. They have prepared nanoporous membranes of polystyrene with controlled pore wall functionality from the selective degradation of ordered ABC triblock copolymers. By using a combination of controlled ring-opening and free-radical polymerizations, a triblock copolymer polylactide-/j-poly(A,/V-dimethylacrylamide)-ib-polystyrene (PLA-h-PDMA-h-PS) has been prepared. Following the self-assembly in bulk, cylinders of PLA are dispersed into a matrix of PS and the central PDMA block localized at the PS-PLA interface. After a selective etching of the PLA cylinders, a nanoporous PS monolith is formed with pore walls coated with hydrophilic PDMA. 

Polymeric cylinders, as analogs of CPBs, are prepared by the self-assembly of block copolymers. They process a rather rigid (crosslinked or crystalline) cylindrical microdomain as the backbone from which side chains are tethered. These... 

In addition, the self-assembly of block copolymers has provided a promising alternative for the synthesis of analogs of molecular bmshes, in which a cross-linked or crystalline cylindrical (micro)domain instead of a linear polymer backbone acts as the backbone. These assemblies have the characteristic worm-like morphology at a similar nanosize scale as molecular bmshes. In this chapter, the polymeric cylinders assembled from block copolymers are briefly discussed as a complement of molecular bmshes (Section 6.06.2.6). Different synthetic strategies and polymerization techniques are reviewed to illustrate specific advantages and limitations. Particular attention is paid to syntheses employing CRP techniques, as these have proven especially useful in the preparation of well-defined functional molecular bmshes (Figure 1). 

Direct self-assembly (DSA) pays attention to pattern formation in materials smaller than 20 nm in size. DSA does not require special equipment for patterning, which is different from immersion lithography and nanoimprint. Pattern formation is performed by microphase separation in the DSA process. DSA patterning is quite different from conventional patterning. Diblock polymers composed of hydrophilic and hydrophobic polymer units are applied for DSA materials. Diblock polymers of the A-B type, where the A block is reciprocal to the B-block, accelerate to concentrate in the same block. A diblock polymer produces self-assembly and microphase separation by formation of a sphere, cylinder, and lamellar, which are controlled by product P of the % parameter (Flory interaction parameter) and degree of polymerization N siP = Z ab)- Classical structures of phases are shown in Figure 3.20. 

It was shown that high molar mass, polydisperse acrylic PnBA/PMMA diblock and triblock copolymers prepared by SGl-mediated polymerization were shown to self-assemble into various nanostmctures despite substantial molecular dis-order. ° Lamellae are observed around 55-65 vol.% PMMA, while perfectly symmetrical copolymers adopt a curved interface concave toward PMMA and form cylinders or cylindrical micelles with poor lattice order. This was assigned to unbalanced polydispersity between the two blocks arising from the lack of control over polymerization of PMMA under the synthesis conditions used. 

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