Alejandro Presa Soto

Pointed-Oval-Shaped Micelles from Crystalline-Coil Block Copolymers by Crystallization-Driven Living Self-Assembly†

Self-assembly of block copolymers in block-selective solvents can lead to a variety of different morphologies with shapeand composition-dependent potential applications in areas as diverse as drug delivery and nanolithography. Amorphous block copolymers usually give rise to spherical micelles in selective solvents, but since the mid 1990s various strategies that promote the formation of other morphologies including cylinders 4] or cylinder networks, disks, helices, Janus micelles, toroids, nanotubes, and other complex forms have been developed. Previous work on the solution self-assembly of diblock copolymers has shown that the presence of crystalline coreforming blocks such as poly(ferrocenyldimethylsilane) (PFS), polyethylene, polyacrylonitrile, polycaprolactone, and poly(ethylene oxide) promote the formation of morphologies with low interfacial curvature such as cylinders and platelets. Moreover, recent studies of PFS block copolymers have revealed that on addition of further unimer, epitaxial growth from the exposed crystalline cores of the ends of cylindrical micelles or the edges of platelets is possible to generate hierarchical micelle architectures such as block co-micelles and scarf structures, respectively. This crystallizationdriven living self-assembly process has enabled the preparation of well-defined self-assembled structures with spatially defined attachment of nanoparticles and oxide surface coatings. Here we report that by using this crystallization-driven living self-assembly approach, the formation of unusual nanoscopic architectures such as pointed ovals and hierarchical pointed-oval-based co-micelle architectures is also possible. We used two types of asymmetric, narrow polydispersity crystalline-coil, PFS core-forming diblock copolymers: firstly, PFS34–P2VP272 (P2VP = poly(2-vinylpyridine)) [17, 19] to generate cylindrical micelles, especially short “seed” micelles, and, second, PFS54–PP290 [18,19] (PP = poly[bis(trifluoroethoxy)phosphazene]; Scheme 1 and Supporting Information Table S1).

Polymeric materials based on main group elements: the recent development of ambient temperature and controlled routes to polyphosphazenes

This Perspective discusses the development of new routes to polyphosphazenes, [R(2)P[double bond, length as m-dash]N](n), that occur at ambient temperature and, in some cases, allow molecular weight control and access to narrow molecular weight distributions and block copolymers. For example, the room temperature silyl-carborane initiated ring-opening polymerisation of (NPCl(2))(3) is described together with chain growth condensation polymerisations of phosphoranimines Cl(3)P[double bond, length as m-dash]NSiMe(3) and BrMePhP[double bond, length as m-dash]NSiMe(3). Recent works on donor-stabilised cationic phosphoranimines are also discussed.

Functionalization of Poly(ferrocenyldimethylsilane) via Lithiation of the Cyclopentadienyl Rings

The metallation of the cyclopentadienyl (Cp) ligands of poly(ferrocenyldimethylsilane) (PFDMS) can be performed by reaction with the Schlossers base pair t-BuLi/KOt-Bu in THF. Subsequent treatment with a series of electrophiles affords a range of Cp-substituted polymers with up to an average of 1.8 new substituents per repeating unit. NMR studies on polymers containing trimethylsilyl groups and deuterium on the Cp rings are indicative of high regioselectivity with selective metallation at the β-carbon.