A disulfide bond containing polypeptide, PolyK₆-R₈, was designed and prepared by oxidative polymerization between terminal cysteinyl thiol groups of CHK₆HC and CR₈C. The molar ratio between CHK₆HC and CR₈C within obtained PolyK₆-R₈ was 9:1, and PolyK₆-R₈ could combine DNA compactly when weight ratio reached 5. Through in vitro investigation, it was found that PolyK₆-R₈ was an efficient gene vector with low cytotoxicity for delivering DNA in both COS-7 and HeLa cells. Cellular uptake of DNA mediated by PolyK₆-R₈/DNA complexes was promoted after incubation for 4 h. Moreover, by examining the histological sections of hindlimb ischemia rats through immunohistochemistry, PolyK₆-R₈/VEGF complexes were proved to be effective in both VEGF protein expression and succeeding vessel formation. The results indicated that polypeptide-based PolyK₆-R₈ is a promising gene vector for the limb ischemia treatment.

Microbial polyhydroxyalkanoates (PHAs) are a family of biopolyesters produced by many wild type and engineered bacteria. PHAs have diverse structures accompanied by flexible thermal and mechanical properties. Combined with their in vitro biodegradation, cell and tissue compatibility, PHAs have been studied for medical applications, especially medical implants applications, including heart valve tissue engineering, vascular tissue engineering, bone tissue engineering, cartilage tissue engineering, nerve conduit tissue engineering as well as esophagus tissue engineering. Most studies have been conducted in the authors’ lab in the past 20+ years. Recently, mechanism on PHA promoted tissue regeneration was revealed to relate to cell responses to PHA biodegradation products and cell-material interactions mediated by microRNA. Very importantly, PHA implants were found not to cause carcinogenesis during long-term implantation. Thus, PHAs should have a bright future in biomedical areas.

A facile technique is herein reported to fabricate three-dimensional (3D) polymeric porous scaffolds with interior surfaces of a topographic microstructure favorable for cell adhesion. As demonstration, a well-known biodegradable polymer poly(lactide-co-glycolide) (PLGA) was employed as matrix. Under the porogen-leaching strategy, the large and soft porogens of paraffin were modified by colliding with small and hard salt particles, which generated micropits on the surfaces of paraffin spheres. The eventual PLGA scaffolds after leaching the modified porogens had thus interior surfaces of microscale roughness imprinted by those micropits. The microrough scaffolds were confirmed to benefit adhesion of bone marrow stromal cells (BMSCs) of rats and meanwhile not to hamper the proliferation and osteogenic differentiation of the cells. The insight and technique might be helpful for biomaterial designing in tissue engineering and regenerative medicine.

The preparation of large area coverage of films with uniaxially aligned poly(3-hexylthiophene) (P3HT) nanofibers by using zone-casting approach is reported. The length and the orientation of the nanofibers are defined by the solubility of the solvent, the P3HT molecular weight and the substrate temperature. The length of the oriented nanofibers could be increased from 1 μm to more than 10 μm by adding poor solvent into the P3HT solution. It is found that for P3HT of relatively low molecular weight, a solvent with relatively low solubility has to be chosen to get the oriented film. While for the high molecular weight P3HT, the solvent with a relatively high solubility has to be used. The well-aligned film could be obtained because of the solute concentration gradient in the region where the critical concentration is reached during the zone-casting process. Particularly, the solvent evaporation rate and crystallization rate must be chosen properly to satisfy the stationary conditions above, which were controlled by an appropriate choice of solvent and substrate temperature. The film prepared by zone-casting approach had microcrystalline P3HT domains with more inter-chain order than spin-coating film. Meanwhile, the P3HT π-π stacking direction was parallel to the alignment direction of the nanofibers.

A series of half-sandwich group IV metal complexes with tridentate monoanionic phenoxy-imine arylsulfide [O−NS] ligand [2-Bu^t4-Me-6-((2-(SC₆H₅)C₆H₄N=CHC₆H₂O)]⁻ (La) and dianionic phenoxy-amine arylsulfide [O⁻N⁻S] ligand [2-Bu^t4-Me-6-((2-(SC₆H₅)C₆H₄N-CH₂C₆H₂O)]²⁻ (Lb) have been synthesized and characterized. Lb was obtained easily in high yield by reduction of ligand La with excess LiAlH4 in cool diethyl ether. Half-sandwich Group IV metal complexes CpTi[O−NS]Cl₂ (1a), CpZr[O⁻NS]Cl₂ (1b), CpTi[O−N−S]Cl (2a), CpZr[O⁻N⁻S]Cl (2b) and Cp^*Zr[O−N−S]Cl (2c) were synthesized by the reactions of La and Lb with CpTiCl₃, CpZrCl₃ and Cp^*ZrCl₃, and characterized by IR, ¹H-NMR, ¹³C-NMR and elemental analysis. In addition, an X-ray structure analysis was performed on ligand Lb. The title Group IV half-sandwich bearing tridentate [O,N,S] ligands show good catalytic activities for ethylene polymerization in the presence of methylaluminoxane (MAO) as co-catalyst up to 1.58 × 10⁷ g-PE·mol-Zr⁻¹·h⁻¹. The good catalytic activities can be maintained even at high temperatures such as 100℃ exhibiting the excellent thermal stability for these half-sandwich metal pre-catalysts.

A series of nickel halides bearing 2,4-di-t-butyl-6-(quinolin-8-yliminomethyl) phenolate ligands was synthesized and characterized by IR spectroscopy and elemental analysis. Molecular structures of C1 (R = H, X = Br) and C2 (R = H, X = Cl) were further confirmed by single-crystal X-ray crystallographic studies, and revealed a distorted square planar geometry at nickel. Upon activation with diethylaluminum chloride (Et₂AlCl), all nickel pre-catalysts displayed good catalytic activity [up to 9.3 × 10⁵ g mol⁻¹(Ni) h⁻¹] for ethylene oligomerization with major dimerization. In the presence of methylaluminoxane (MAO), the nickel complex C1 was capable of ethylene polymerization under 3 MPa, and produced polyethylene products with narrow polydispersity (1.16−1.73) and molecular weights in the range of 2.6−4.95 kg/mol.

The in vivo behaviors of doxorubicin (DOX)-loaded dextran-poly(3-acrylamidophenylboronic acid) (Dextran- PAPBA) nanoparticles (NPs) were studied. The DOX-loaded NPs had a narrowly distributed diameter of ca. 74 nm and mainly accumulated in liver of tumor-bearing mice after intravenous injection as demonstrated by in vivo real-time near infrared fluorescent imaging. The DOX contents in various tissues were quantified and consisted well with the results of fluorescent imaging. The biodistribution pattern of DOX-loaded NPs encourages us to investigate their liver tumor treatment by using an orthotopically implanted liver tumor model, revealing that the DOX-loaded NPs formulation had better antitumor effect than free DOX.

Novel blue light-emitting poly(aryl ether)s comprising of bipolar oligofluorene pendants as chromophores have been designed and synthesized, in which pyrimidine and arylamine moieties are utilized as the electron acceptor and electron donor, respectively. Through varying π bridge length from monofluorene to bifluorene and end-cappers from hydrogen to carbazole and diphenylamine, the emission color of the resulting polymers covers from deep blue to greenish blue, and their HOMO and LUMO levels can be modulated to facilitate charge injection to improve the device performance. Polymer lightemitting diodes (PLEDs) are fabricated with the device structure of ITO/poly(3,4-ethylenedioxythiophene):poly(styrene sulfonic acid) (PEDOT:PSS) (50 nm)/polymer (80 nm)/Ca (10 nm)/Al (200 nm). Among these polymers, P2Cz5F-Py with bifluorene bridge and carbazole end-capper shows excellent trade-off between the efficiency and emission wavelength, having a peak luminous efficiency as high as 1.26 cd/A and Commission Internationale de L’Eclairage (CIE) coordinates of (0.17, 0.17).

Crystal patterns in ultrathin films of six poly(ethylene oxide) fractions with molecular weights from 25000 to 932000 g/mol were characterized within crystallization temperature range from 20℃ to 60℃. Labyrinthine, dendritic and faceted crystal patterns were observed in different temperature ranges, and then labyrinthine-to-dendritic and dendritic-to-faceted transition temperatures TL-D and TD-F were quantitatively identified. Their molecular weight dependences are T_L-D(M_w) = T_L-D(∞) − K_L-D/M_w, where T_L-D(∞) = 38.2℃ and K_L-D = 253000℃·g/mol and T_D-F(M_w) = T_D-F(∞) − K_D-F/M_w, where T_D-F(∞) = 54.7℃ and K_D-F = 27000℃·g/mol. Quasi two-dimensional blob models were proposed to provide empirical explanations of the molecular weight dependences. The labyrinthine-to-dendritic transition is attributed to a molecular diffusion process change from a local-diffusion to diffusion-limited-aggregation (DLA) and a polymer chain with M_w ≈ 253000 g/mol within a blob can join crystals independently. The dendritic-to-faceted transition is attributed to a turnover of the pattern formation mechanism from DLA to crystallization control, and a polymer chain with a M_w ≈ 27000 g/mol as an independent blob crosses to a depletion zone to join crystals. These molecular weight dependences reveal a macromolecular effect on the crystal pattern formation and selection of crystalline polymers.

Rheological properties of wheat gliadins in 50% (V/V) aqueous propanol were carried out as a function of gliadin concentration c and temperature. The solutions at 20 g L⁻¹ to 200 g L⁻¹ behave as Newtonian fluids with an flow activation energy of 23.5−27.3 kJ mol⁻¹. Intrinsic viscosity [η] and Huggins constant kH are determined according to Huggins plot at c ≤ 120 g L⁻¹. The results reveal that gliadins are not spherical shaped and the molecular size tends to increase with temperature due to improved solvation.

Five novel donor-acceptor (D-A) conjugated cooligomers (F4B-hP, F5B-hP, F5B2[1,2]-hP, F5B2[1,3]-hP and F7B2[1,2]-hP) were synthesized. The absorption spectra of the cooligomers cover a wide range from 300 nm to 630 nm. The cooligomers could form films featured by alternating D-A lamellar nanostructures with the periods relative to the molecular lengths after thermal annealing or solvent vapor annealing. Single molecule solar cells were fabricated, and F5B-hP exhibited the best device performance. When the film of F5B-hP was thermally annealed, a power conversion efficiency (PCE) of 1.56% was realized. With solvent vapor annealing, the PCE could be further improved to 1.72% with a short-circuit current (J_SC) of 5.76 mA/cm2, an open-circuit voltage (V_OC) of 0.87 V and a fill factor (FF) of 0.34.

Structure of PAN fibers during pre-oxidation and carbonization was studied using two dimensional small angle X-ray scattering/wide angle X-ray diffraction (2D SAXS/WAXD). The SAXS results show that during pre-oxidation between 180℃ and 275℃, the volume content of microvoids increases with the temperature increasing, which may be one of reasons for the decrease of tensile strength of pre-oxidized fibers. 253℃ was the critical transition temperature, the length, diameter, aspect ratio and orientation distribution of microvoids increased with temperature before this temperature and decreased after this temperature. After the high temperature carbonization, lots of spindly microvoids formed. WAXD patterns demonstrate that the crystallite size of PAN fibers first increased before 230℃ and then decreased with the increase of temperature during the pre-oxidation. The diffraction peak of PAN fibers at 2^θ ≈ 17° almost disappeared at the end of preoxidation while the diffraction peak of aromatic structure at 2^θ ≈ 25° appeared at 253℃. During carbonization, the peak intensity at 2^θ ≈ 25° increased apparently due to the formation of graphite structure. The results obtained give a deep understanding of the microstructure development in the PAN fibers during pre-oxidation and carbonization, which is important for the preparation of high performance carbon fibers.

A novel amphiphilic copolymer poly(ethylene glycol)-block-poly(N,N-dimethylamino-2-ethylmethacrylate)-block-poly[6-(4-methoxy-azobenzene-4'-oxy) hexyl methacrylate] (PEG-b-PDMAEMA-b-PMMAzo) was prepared by ATRP polymerization. The self-assembly and responsive behaviors were investigated by SEM, TEM, LLS and UV-Vis spectra. The results indicated that the copolymers can self-assemble into spherical structures in aqueous media. The aggregate size can be tuned by pH and temperature. The trans-cis isomerization behavior of the formed aggregates was also examined. Upon irradiation with a linear polarized light, the elongation degree of the aggregates was increased with the irradiation time.