Block copolymers (BCPs) self-assemble into ordered arrays of nanoscopic domains, the nature of which depends on the constituents of the BCPs and their molecular architecture.[1] BCPs have been exploited as precursors for nanoporous materials [2] and as templates for the rational design of nanoscopic architectures with periods from below 10 nm up to the 100-nm-range in thin-film configurations.[3] Whereas molds containing arrays of aligned cylindrical nanochannels with hard confining walls, such as self-ordered anodic aluminum oxide (AAO), [4] have been used to fabricate one-dimensional nanostructures from a plethora of materials, [5] the self-assembly of BCPs in cylindrical confinement has only recently emerged as an access to nanorods exhibiting ordered nanoscopic fine structures.[6] Sol-gels containing precursors for inorganic scaffold materials and BCPs as structuredirecting soft templates were infiltrated into AAO. Subsequent gelation and calcination yielded nanorods consisting of various inorganic oxides and amorphous carbon exhibiting ordered mesoporous fine structures. [7] However, direct infiltration of microphase-separated BCP melts into AAO [8] has received much less attention, mainly because of a lack of obvious applications of the solid BCP nanorods thus obtained. Only recently, BCP nanorods have been converted into mesoporous polymeric nanorods by degrading sacrificial blocks [9] and by selective swelling.[10]BCPs confined to AAO with pore diameters about one order of magnitude larger than their characteristic bulk periods have been reported to retain bulk-like morphologies, such as cylinders oriented along the pore axes and concentric-cylindrical lamellae.Nanoscopic domain structures substantially different from those obtained in the absence of geometric constraints form if BCPs self-assemble within cylindrical pores having diameters of the same order of magnitude than their characteristic periods. [11][12][13] Wu et al. synthesized silica nanorods containing helical and circular-cylindrical ''stacked-doughnuts'' mesopore structures by gelation and calcination of sol-gels containing poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) and tetraethyl orthosilicate infiltrated into AAO with pore diameters below 70 nm, [11] and prepared metal replicas of helical mesopores by electrochemical deposition.[14] However, only little effort has been directed to the experimental study of BCP melts selfassembling under strong cylindrical confinement, [12] even though the formation of a broad variety of unprecedented confinementinduced nanoscopic domain structures has been predicted. [15] Thus, only a small range of the potentially accessible morphologies has been realized, and their exploitation for the generation of functional nanostructures has not yet been addressed.Here, we report the fabrication of hierarchical one-dimensional semiconductor nanostructures containing structural motifs, such as helices and stacked doughnuts, that mimic unconventional, confinement-induced nanoscopic...

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Summary:We report on the formation of polymer nanofibers and nanotubes by melt infiltration of block copolymers (BCPs) containing poly (norbornene) blocks bearing polar and non-polar moieties synthesized via ring opening metathesis polymerization (ROMP) into Al 2 O 3 porous templates. The effect of pore size of the Al 2 O 3 template and polymer chain length on the formed structure i.e. fibers or hallow tubes is investigated. SEM analysis revealed that a smaller pore size ($ 180 nm) of the Al 2 O 3 template with a BCP of lower molecular weight (< 15 kg/mol) results in complete filling of the pores to yield fibers in contrast to bigger pore size (400 nm) or higher molecular weights (> 25 kg/mol) furnishing hollow tubes.

The frontispiece shows a TEM image of block copolymer nanorods exhibiting nanoscopic domain structures visualized by selective staining. The insets represent the methodology for producing semiconductor nanostructures reported by Yong Wang, Martin Steinhart, and co-workers on p. 2763. The fi rst panel shows block copolymer nanorods, the second, the nanorods after conversion of the nanoscopic domain structure into a mesopore structure, and the third, the complex 1D semiconductor nanostructures obtained by ALD using the mesopores as templates.