Nanostructures Based on Bulk Phase Separation

Selective polymerization of the phase within the spherical domains 

Using a similar strategy with an (A)m-(B) -(C)p type triblock copolymer, but with an additional feature of being able to transform (or degrade) the core block, 

The formation of cylindrical domains of one block in a matrix of another, in diblock copolymers, has also been exploited for the generation of nanochannels in thin film membranes [40, 41]. Using diblock copolymers of PtBA-b-PCEMA, but this time with a larger volume fraction (ca. 74 vol%) of the photo-crosslinkable PCEMA block, Liu et al, prepared thin polymer films containing a densely packed array of nanocylinders (diameter 22 nm) [40]. As expected, in these cases the PCEMA block forms the continuous phase with nanocylinders of the hydrolyzable PtBA blocks forming a densely packed array. Typically, thick films (or disks of ca. 

It must be recognized that these channels are not empty but have poly(acrylic acid) (PAA) chains tethered to their inner walls. However, since the relative volume occupied by these chains is significantly lower than the parent PtBA, these channels are rendered substantially porous. A very interesting feature of these porous membranes is the chemical valving effect , wherein the relative permeability of the membranes was shown to vary by almost two orders of magnitude as a function of pH, with the lowest permeability being witnessed at a pH of 3 [41]. The explana- 

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