Di-tert-butyl cyclo­hex-2-ene-1,4-diyl dicarbonate

In the title mol­ecule, C16H26O6, the central cyclo­hexene ring is in a half-chair conformation. The carbonyl groups are in a trans arrangement with respect to each other and the dihedral angle between the mean planes of the carbonate groups is 10.8 (2)°

2,5-Dimethyl­hexane-2,5-diyl bis­(4-nitro­phen­yl) dicarbonate

The title structure, C22H24N2O10, contains two independent centrosymmetric mol­ecules. The only significant difference between the mol­ecules is the dihedral angle between the unique carbonate group (–O—CO2–) and the benzene ring, the values being 77.35 (8) and 66.42 (8)°. The crystal structure is stabilized by weak inter­molecular C—H⋯O hydrogen bonds

trans-Cyclo­hexane-1,4-diyl bis­(4-nitro­phen­yl) dicarbonate

In the title crystal structure, C20H18N2O10, there are two independent mol­ecules, both of which lie on crystallographic inversion centres. In one mol­ecule the 4-nitro­phenyl dicarbonate groups are substituted in equatorial (A eq) positions of the chair-form cyclo­hexane ring while in the other mol­ecule the substitution is axial (B ax). The dihedral angles between the atoms of the symmetry-unique carbonate group (O=CO2—) and benzene ring for each mol­ecule are 47.3 (1)° for A eq and 11.7 (2)° for B ax. In B ax, this facilitates the formation of a weak intra­molecular C—H⋯O hydrogen bond, while the packing is stabilized by weak inter­molecular C—H⋯O inter­actions

Cylindrical Micelles with "patchy" Coronas from the Crystallization-Driven Self-Assembly of ABC Triblock Terpolymers with a Crystallizable Central Polyferrocenyldimethylsilane Segment

Solution self-assembly of a series of linear ABC triblock terpolymers with a central crystallizable poly­(ferrocenyldimethylsilane) (PFS) core-forming “B” block and terminal polystyrene (PS) and poly­(methyl methacrylate) (PMMA) “A” and “C” blocks has been investigated. Three PS-<i>b</i>-PFS-<i>b</i>-PMMA triblock terpolymers with different block ratios (<b>1</b>, 3.6:1.0:4.7; <b>2</b>, 7.0:1.0:6.9; and <b>3</b>, 1.1:1.0:1.4) but with similar degrees of polymerization for the central PFS block were prepared through a combination of living anionic and atom-transfer radical polymerization techniques, together with azide/alkyne “click” chemistry. Cylindrical micelles with a crystalline PFS core were formed in solvents selective for the terminal PS and PMMA blocks. In ethyl acetate, a slightly more selective solvent for the PS block, cylinders with significant microphase separation within the corona in the dry state were observed on the basis of TEM analysis. The use of acetone, which is slightly more selective for the PMMA block than the PS block, led to more distinct microphase separation to generate a “patchy” coronal morphology. Living crystallization-driven self-assembly studies in acetone allowed the formation of uniform cylindrical micelles and block comicelles of controlled length with “patchy” coronal segments by seeded growth methods

trans-Cyclo­hex-2-ene-1,4-diyl bis­(4-nitro­phen­yl) dicarbonate

Although the title mol­ecule, C20H16N2O10, does not possess mol­ecular inversion symmetry, it lies on a crystallographic inversion centre which imposes disorder on the central cyclo­hexene ring. In addition, the cyclo­hexene ring has non-symmetry-related disorder over two sites, with the ratio of the major and minor components being 0.54:0.46. The overall effect is to produce four disorder components for the atoms of the cyclo­hexene ring. The side chain is perfectly ordered and the dihedral angle between the atoms of the carbonate group (O=CO2—) and the benzene ring is 72.99 (6)°

Bis(4-nitro­phen­yl) 1,3-phenyl­ene­dimethyl­ene dicarbonate

In the title mol­ecule, C22H16N2O10, the dihedral angles between the benzene rings of the 4-nitro­phenyl groups and the central benzene ring are 32.7 (1) and 34.7 (1)°, while the dihedral angle between the two benzene rings of the 4-nitro­phenyl groups is 3.6 (2)°. In the crystal structure, weak inter­molecular C—H⋯O hydrogen bonds link mol­ecules into centrosymmetric dimers

Uniform patchy and hollow rectangular platelet micelles from crystallizable polymer blends

Growing patterned rectangular objects The growth of patterned objects usually requires a template to aid the positioning of multiple materials. Qiu et al. used the seeded growth of a crystallizable block copolymer and a homopolymer to produce highly uniform rectangular structures (see the Perspective by Ballauff). Chemical etching, or dissolution, of uncross-linked regions of the rectangular structures produced perforated platelet micelles. The sequential addition of different blends and cross-linking/dissolution strategies allowed the formation of well-defined hollow rectangular micelles, which can be functionalized in a variety of ways. Science , this issue p. 697 ; see also p. 656 </jats:p

NMR Study of the Dissolution of Core-Crystalline Micelles

Short fragments of the core-crystalline micelles formed by a sample of poly­(ferrocenyl­dimethylsilane)-<i>block</i>-poly­(isoprene) (PFS-<i>b</i>-PI) block copolymer (BCP) underwent self-seeding in decane when heated above its dissolution temperature. Variable temperature (VT) ¹H NMR and diffusion-ordered pulsed-gradient spin–echo (DOSY) NMR were used to monitor the behavior of micelles that dissolved as a function of increasing temperature. We examined a sample of micelle fragments of PFS₆₅-<i>b</i>-PI₆₃₇ characterized by <i>L</i>_n = 39 nm and <i>L</i>_w/<i>L</i>_n = 1.13. The PI corona had high mobility and gave a ¹H NMR signal in both micellar and unimer forms. In contrast, the PFS component could only be detected for the dissolved unimer. We found from ¹H NMR that essentially all the BCP molecules were incorporated into the micelles at temperatures up to and including 50 °C, at the limit of NMR detection. Both PFS and PI resonances could be detected between 70 and 100 °C, and the integration ratio of the PFS-to-PI peaks increased with temperature. DOSY NMR measured the self-diffusion coefficients (<i>D</i>_s) of the micelle fragments and unimer at these temperatures. The hydrodynamic radii (<i>R</i>_h) for these species were calculated from <i>D</i>_s using the Stokes–Einstein equation. The PFS signals gave <i>R</i>_h values in the range of 5–6 nm at temperatures between 80 and 100 °C, consistent with unimer diffusion. PI signals were fitted by an exponential decay at 25 °C with <i>R</i>_h = 38 nm characteristic of the micelle fragments and at 90, 95, and 100 °C with <i>R</i>_h ≈ 6 nm, corresponding to unimer. At intermediate temperatures (70–85 °C), PI signals were fitted to a sum of two exponential terms, consistent with a fast diffusing species and a slow diffusing species. Interestingly, we noticed that the size of the micelle fragments at elevated temperatures (80 and 85 °C) was sensitive to sample history; samples heated directly to the elevated temperatures were found to be shorter than those heated stepwise

Monodisperse Cylindrical Micelles and Block Comicelles of Controlled Length in Aqueous Media

Cylindrical block copolymer micelles have shown considerable promise in various fields of biomedical research. However, unlike spherical micelles and vesicles, control over their dimensions in biologically relevant solvents has posed a key challenge that potentially limits in depth studies and their optimization for applications. Here, we report the preparation of cylindrical micelles of length in the wide range of 70 nm to 1.10 μm in aqueous media with narrow length distributions (length polydispersities <1.10). In our approach, an amphiphilic linear-brush block copolymer, with high potential for functionalization, was synthesized based on poly­(ferrocenyldimethylsilane)-<i>b</i>-poly­(allyl glycidyl ether) (PFS-<i>b</i>-PAGE) decorated with triethylene glycol (TEG), abbreviated as PFS-<i>b</i>-(PEO-<i>g</i>-TEG). PFS-<i>b</i>-(PEO-<i>g</i>-TEG) cylindrical micelles of controlled length with low polydispersities were prepared in <i>N</i>,<i>N</i>-dimethylformamide using small seed initiators via living crystallization-driven self-assembly. Successful dispersion of these micelles into aqueous media was achieved by dialysis against deionized water. Furthermore, B–A–B amphiphilic triblock comicelles with PFS-<i>b</i>-poly­(2-vinylpyridine) (P2VP) as hydrophobic “B” blocks and hydrophilic PFS-<i>b</i>-(PEO-<i>g</i>-TEG) “A” segments were prepared and their hierarchical self-assembly in aqueous media studied. It was found that superstructures formed are dependent on the length of the hydrophobic blocks. Quaternization of P2VP was shown to cause the disassembly of the superstructures, resulting in the first examples of water-soluble cylindrical multiblock comicelles. We also demonstrate the ability of the triblock comicelles with quaternized terminal segments to complex DNA and, thus, to potentially function as gene vectors