Chiral block copolymers (BCPs*) comprising chiral entities were designed to fabricate helical architectures (i.e., twisted morphologies) from self-assembly. A new helical phase (H*) with P622 symmetry was discovered in the self-assembly of poly(styrene)-b-poly(l-lactide) (PS-PLLA) BCPs*. Hexagonally packed, interdigitated PLLA helical microdomains in a PS matrix were directly visualized by electron tomography. The phase diagram of the PS-PLLA BCPs* was also established. Phase transitions from the H* phase to the stable cylinder and gyroid phases were found after long-time annealing, suggesting that the H* is a long-lived metastable phase. In contrast to racemic poly(styrene)-b-poly(d,l-lactide) BCPs, chiral interaction significantly enhances the incompatibility between achiral PS and chiral PLLA blocks in the PS-PLLA BCPs* and can be estimated through the determination of the interaction parameter.

Nanoporous polymers with gyroid nanochannels can be fabricated from the self-assembly of degradable block copolymer, polystyrene-b-poly(l-lactide) (PS-PLLA), followed by the hydrolysis of PLLA blocks. A well-defined nanohybrid material with SiO2 gyroid nanostructure in a PS matrix can be obtained using the nanoporous PS as a template for sol-gel reaction. After subsequent UV degradation of the PS matrix, a highly porous inorganic gyroid network remains, yielding a single-component material with an exceptionally low refractive index (as low as 1.1).

Three-dimensional hexagonally packed PLLA nanohelices in the PS matrix were formed in the self-assembly of PS-PLLA chiral block copolymer. After hydrolysis of the PLLA blocks, PS with hexagonally packed helical nanochannels can be fabricated and treated as the template for the following sol-gel process. Subsequently, silica precursor mixture was introduced into the PS template by a pore-filling process. Well-defined helical nanocomposites with SiO(2) inorganic nanohelices orderly dispersed in polymeric matrix can be successfully obtained after the sol-gel process. As a result, with the combination of the self-assembly of degradable block copolymers and sol-gel chemistry, we suggest a novel method for the preparation of the helical nanocomposites with ordered texture.

The incidence of distal SINE seemed to be high; however, there were also low rates of death and complications after TEVAR for aortic dissection using stainless steel-based stent grafts. Complicated distal SINE can successfully be resolved by distal endograft implantation. Excessive oversizing of the distal stent graft, as measured by the true lumen area, may be a significant factor causing delayed distal SINE. Precise size selection is crucial for the distal end of the stent, especially for high taper ratio dissection pathology in which the implantation sequence of a distal small-sized stent graft first might be considered to prevent future distal SINE.

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A zero-dimensional steady-state model of low-pressure (2-60 Torr) microwave-generated hydrogen plasmas was developed. The electron energy distribution function (EEDF) was determined using the Boltzmann equation, coupled to species, energy and power balances. The EEDF from the Boltzmann equation permitted computation of the rate constants and average electron temperature required for simultaneous solution to the six species balances, two for neutrals (H, H 2 ) and four for charged (H + , H + 2 , H + 3 and electron) species, and the energy balance. The average electron temperature and species concentrations were then employed in a power balance to check for self-consistency with the input power used to solve the Boltzmann equation. E/N values were appropriately adjusted after each iteration until self-consistency was achieved. The model provides information on the details of the transfer of power from electrons via various processes (ionization, dissociation, vibration, rotation) to the neutral species. The mechanism of energy loss from the neutrals (radiation, convection) is also computed, and thus gas temperature can be estimated. Indeed, for low-pressure (p < 15 Torr) plasmas the model yields accurate absolute gas temperatures as a function of pressure, including the fact that gas temperature rises steeply at pressures in excess of 15 Torr. This results from the fact that at low pressures a very large fraction of the input power is transmitted by the electrons to the molecular vibration modes, such that T vib T trans .

Endovascular stainless steel-based stent graft implantation with vascular bypass to gain a sufficient proximal landing zone is feasible for type B aortic dissection and has low early and midterm mortality and morbidity in both the acute and chronic phases. Although early intervention might result in more favorable aortic remodeling with a higher possibility of complete regression and lower risk of late distal erosion, longer-term follow-up still necessitates continuous careful surveillance of the entire aorta, especially the distal condition.

Nature uses the self-assembly of molecules as a tool for structuring substances. [1,2] Biological architectures are formed by the interplay between secondary forces, such as hydrophobic, hydrogen-bonding, steric, and electrostatic interactions, to achieve different levels of organization, i.e., morphologies at different length scales. Mimicking these motifs found in Nature, helical morphologies at different length scales, ranging from helical chain conformations and helical aggregates to helical agglomerates, are amongst the most fundamental and interesting textures found in organic systems. [2][3][4][5][6][7][8][9] The chirality of organic compounds is thought to be one of the main origins for the formation of helical textures, and is used as a secondary interaction to assemble chiral molecules and macromolecules into hierarchical structures with a helical sense.[4] The self-assembly of block copolymers has been extensively studied because of their fascinating phase behavior. Nanoscale microstructures with distinct microphases can be obtained simply by chemically attaching immiscible polymer chains together as block copolymers.[10] Recently, a well-organized, three dimensionally packed nanohelical phase has been obtained by the self-assembly of chiral block copolymers, polystyrene-b-poly(L-lactide) (PS-PLLA) with PS-rich fractions.[11a] The hexagonally packed nanohelical microstructure of PLLA in the PS matrix exhibits a springlike response upon stimulation. Moreover, the self-assembled nanohelices have been transformed into cylinders by crystallization and shear.The stress-induced formation of cylinders has been found to be thermally reversible through undulation upon annealing, which could potentially enable the manipulation and switching of these helical microstructures.[11b] The morphology of the PLLA helical microstructure in the PS matrix is attributed to a combination of chirality and the immiscibility of the constituent blocks. Intuitively, hierarchical structures with a helical sense for the achiral block might be expected in the phase diagram of block copolymers, namely PS-PLLA with PLLArich fractions. Interestingly, a bulk core-shell cylinder microstructure is formed from the self-assembly of PLLA-rich PS-PLLA. Unlike the core-shell cylinder microstructure observed in ABC triblock copolymers, [12][13][14][15][16] this unique tubular texture of the achiral block is attributed to the chiral effect induced by the chiral block. Consequently, a scrolling mechanism has been proposed to interpret the formation of the core-shell cylinder microstructure, which is assembled from a hierarchical structure with a helical sense. Moreover, tubular nanostructures can be simply obtained by hydrolyzing the degradable PLLA block from the core-shell cylinder microstructure. As a complementary approach for the formation of nanotubes from triblock and tetrablock copolymer systems, [17] the self-assembly of chiral diblock copolymers with a degradable character may also provide an easy and convenient way to fabricate tub...