A group of mesomorphic polyacetylenes with different lengths of alkyl spacer −{HCC[(CH 2 ) m −OCO−Biph−OC7H15]} n − [1(m), m = 2, 3, 4, 9] and orientations of ester bridge −{HCC[(CH2)3−CO 2 −Biph−OC7H15]} n − [2(3)] are synthesized, and the effects of the structural variables on the properties of the polymers are investigated. The liquid crystalline acetylene monomers n-{[(4‘-heptoxy-4-biphenylyl)oxy]carbonyl}-1-alkynes 3(m) and 5-{[(4‘-heptoxy-4-biphenylyl)carbonyl]oxy}-1-pentyne 4(3) are prepared by consecutive etherification and esterification reactions. The T m and T i values of 3(m) decrease with an increase in the spacer length (m). While 3(3) shows a monotropic SmA phase, its counterpart with a different ester orientation 4(3) exhibits an enantiotropic SmB phase. The monomers are polymerized by transition-metal halides and carbonyls, and the polymerizations catalyzed by WCl6−Ph4Sn under optimal conditions produce polymers with high molecular weights (up to 1.2 × 105) in high yields (up to 92%). The structures and properties of the polymers are characterized and evaluated by IR, UV, TGA, DSC, POM, and XRD analyses. With the increase in the spacer length, the thermal stability of the polymers increases, their T g and T i decrease, and the packing arrangements in their mesophases change from mixed mono- and bilayer structures to a homogeneous monolayer structure. Compared to 1(3), 2(3) shows a blue-shifted absorption spectrum (Δλ max >30 nm), a higher T g and T i (ΔT ∼40 °C), and a better packed SmAd structure.

Pyrolysis of hyperbranched poly[1,1‘-ferrocenylene(methyl)silyne] (5) yields mesoporous, conductive, and magnetic ceramics (6). Sintering at high temperatures (1000−1200 °C) under nitrogen and argon converts 5 to 6N and 6A, respectively, in ∼48−62% yields. The ceramization yields of 5 are higher than that (∼36%) of its linear counterpart poly[1,1‘-ferrocenylene(dimethyl)silylene] (1), revealing that the hyperbranched polymer is superior to the linear one as a ceramic precursor. The ceramic products 6 are characterized by SEM, XPS, EDX, XRD, and SQUID. It is found that the ceramics are electrically conductive and possess a mesoporous architecture constructed of tortuously interconnected nanoclusters. The iron contents of 6 estimated by EDX are 36−43%, much higher than that (11%) of the ceramic 2 prepared from the linear precursor 1. The nanocrystals in 6N are mainly α-Fe2O3 whereas those in 6A are mainly Fe3Si. When magnetized by an external field at room temperature, 6A exhibits a high-saturation magnetization (M s ∼ 49 emu/g) and near-zero remanence and coercivity; that is, 6A is an excellent soft ferromagnetic material with an extremely low hysteresis loss.

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Poly(3-hydroxybutyrate) (PHB) was plasticized with dioctyl (o-)phthalate, dioctyl sebacate, and acetyl tributyl citrate (ATBC). The thermal properties, mechanical properties, and melt flow ability were studied with differential scanning calorimetry, thermogravimetric analysis, a universal material testing machine, and a melt flow indexer. ATBC was revealed to be an efficient plasticizer, reducing the glass-transition temperature and increasing the thermoplasticization ability of PHB. We also blended poly(3-hydroxybutyrate-co-hydroxyhexanoate) (PHBHHx) and poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3/4HB)] with PHB, ATBC, and antioxidant 1010 to overcome the brittleness of PHB and improve the melt flow stability of the materials. PHBHHx did little to improve the thermal processing but increased the fluidity of PHB, and P(3/4HB) toned the toughness of PHB. The addition of antioxidant 1010 enhanced the thermal stabilization of PHB.

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Diyne polycyclotrimerizations initiated by transition-metal catalysts afforded hyperbranched polyphenylenes, which exhibited low viscosity, outstanding thermal stability, and small optical dispersion. Under optimized reaction conditions, polycyclotrimerizations of 1,8-nonadiyne (1) and 1,9-decadiyne (2) catalyzed by TaCl 5-Ph4Sn produced hyperbranched poly(1,2,4-benzenetriyl-1,5-pentanediyl) (3) and poly-(1,2,4-benzenetriyl-1,6-hexanediyl) (4), 1-5 respectively, in high yields (up to 93%). The polymers were completely soluble and film-forming, and possessed high molecular weights (Mw up to ∼1.4 × 10 6 ) but low intrinsic viscosities ([η] down to 0.13 dL/g). Their structures and properties were analyzed and evaluated by IR, UV, NMR, SEC, TGA, DSC, spectrofluorometry, light scattering, and spectroellipsometry. The structural characterizations confirmed the expected hyperbranched molecular architectures of 3 and 4 (comprising of 1,2,4-benzene rings and R,ω-alkyl spacers) and revealed the regioselective feature of the diyne polycyclotrimerizations. Polymers 3 and 4 underwent glass transitions at 43 and 23 °C, respectively, and lost almost no weights when heated to ∼500 °C. Polymer 3 emitted UV light upon excitation, whereas 4 was practically nonluminescent. The thin films of 3 were highly transparent (g99.5% transmittance) and displayed an optical dispersion as low as 0.009 in the visible spectral region, much superior to those of the commercially important "organic glasses" such as poly(methyl methacrylate) and polycarbonates.

Vertebrobasilar dolichoectasia (VBD) is a rare disease characterized by significant expansion, elongation, and tortuosity of the vertebrobasilar arteries. Current data regarding VBD are very limited. Here we systematically review VBD incidence, etiology, characteristics, clinical manifestations, treatment strategies, and prognosis. The exact incidence rate of VBD remains unclear, but is estimated to be 1.3% of the population. The occurrence of VBD is thought to be due to the cooperation of multiple factors, including congenital factors, infections and immune status, and degenerative diseases. The VBD clinical manifestations are complex with ischemic stroke as the most common, followed by progressive compression of cranial nerves and the brain stem, cerebral hemorrhage, and hydrocephalus. Treatment of VBD remains difficult. Currently, there are no precise and effective treatments, and available treatments mainly target the complications of VBD. With the development of stent technology, however, it may become an effective treatment for VBD.

A series of hyperbranched poly(ferrocenylenesilyne)s, [(η 5 -C5H4) 18)]}, was prepared in good isolation yields (up to 77 wt %) by one-pot coupling reactions of dilithioferrocene with trichlorosilanes. While the polymers with small R groups [1(1) and 1(V)] were partially soluble, those with long alkyl chains [1(m) with m g 8] were completely soluble and readily film forming. The polymers exhibited diagnostic solution properties of hyperbranched macromolecules; for example, 1(18) had a high absolute molecular weight (M w ) 5 × 10 5 Da) but a low intrinsic viscosity ([η] ) 0.02 dL/g). Spectroscopic analyses revealed that the polymers possessed rigid skeleton structures with extended conjugations, with their absorption spectra tailed into the infrared region (>700 nm). With an increase in the alkyl chain length, the polymer changed from glassy to rubbery state. The polymers lost little of their weights when heated to ∼400 °C but ceramized when pyrolyzed at higher temperatures, with ceramization yield increasing with a decrease in the alkyl chain length. Sintering 1(1) and 1(V) in 700-1200 °C produced ceramics in ∼50% yields. Higher temperature pyrolyses favored the formation of ceramics with bigger inorganic nanoclusters and better magnetic performances. The ceramic prepared from the calcination of 1(1) at 1200 °C contained large iron silicide nanocrystals and exhibited high magnetizability (up to ∼51 emu/g) but near-zero remanence and coercivity. This ceramic is thus an outstanding soft ferromagnet with a high magnetic susceptibility and practically nil hysteresis loss.