Water-annealing regulated protein-based magnetic nanofiber materials: tuning silk structure and properties to enhance cell response under magnetic fields

In this study, flexible silk fibroin protein and biocompatible barium hexaferrite (BaM) nanoparticles were combined and electrospun into nanofibers, and their physical properties could be tuned through the mixing ratios and a water annealing process. Structural analysis indicates that the protein structure of the materials is fully controllable by the annealing process. The mechanical properties of the electrospun composites can be significantly improved by annealing, while the magnetic properties of barium hexaferrite are maintained in the composite. Notably, in the absence of a magnetic field, cell growth increased slightly with increasing BaM content. Application of an external magnetic field during in vitro cell biocompatibility study of the materials demonstrated significantly larger cell growth. We propose a mechanism to explain the effects of water annealing and magnetic field on cell growth. This study indicates that these composite electrospun fibers may be widely used in the biomedical field for controllable cell response through applying different external magnetic fields.     

Actuating Shape Memory Polymer for Thermoresponsive Soft Robotic Gripper and Programmable Materials

For soft robotics and programmable metamaterials, novel approaches are required enabling the design of highly integrated thermoresponsive actuating systems. In the concept presented here, the necessary functional component was obtained by polymer syntheses. First, poly(1,10-decylene adipate) diol (PDA) with a number average molecular weight M_n of 3290 g·mol⁻¹ was synthesized from 1,10-decanediol and adipic acid. Afterward, the PDA was brought to reaction with 4,4′-diphenylmethane diisocyanate and 1,4-butanediol. The resulting polyester urethane (PEU) was processed to the filament, and samples were additively manufactured by fused-filament fabrication. After thermomechanical treatment, the PEU reliably actuated under stress-free conditions by expanding on cooling and shrinking on heating with a maximum thermoreversible strain of 16.1%. Actuation stabilized at 12.2%, as verified in a measurement comprising 100 heating-cooling cycles. By adding an actuator element to a gripper system, a hen’s egg could be picked up, safely transported and deposited. Finally, one actuator element each was built into two types of unit cells for programmable materials, thus enabling the design of temperature-dependent behavior. The approaches are expected to open up new opportunities, e.g., in the fields of soft robotics and shape morphing.     

Characterization of the channel walls roughness in photonic crystal fibers

We present electron microscope (FEI NanoSEM) and atomic force microscopy measurements of surface roughness in nanochannels in photonic crystal fibers (PCF). A method was invented to cleave the PCF along the axis without damaging the surface structure in the nanochannels allowing us to characterize the morphology of the nanochannels in the PCF. A multi-wall carbon nanotube mounted onto commercial AFM probes and super sharp silicon non-contact mode AFM probes were used to characterize the wall roughness in the nanochannels. The roughness is shown to have a Gaussian distribution, and has an amplitude smaller than 0.5 nm. The height–height correlation function is an exponential correlation function with an autocorrelation length of 13 nm, and 27 nm corresponding with scan sizes of 200×100 nm², and 1600×200 nm², respectively.     

TBPB-TBPO引发不饱和聚酯树脂固化的动力学

采用差示扫描量热法(DSC)对不饱和聚酯(UP)树脂复配引发体系进行固化动力学研究,复配引发剂为过氧化苯甲酸叔丁酯(TBPB)-过氧化辛酸酯(TBPO)。采用高斯(Gaussian)分峰法对DSC曲线上的固化放热峰进行双峰拟合,并通过Ozawa方程对拟合结果进行固化动力学参数分析。研究表明:Gaussian双峰拟合后得到的结果与实验数据非常吻合,固化动力学参数更贴近实际固化过程。     

Wastes from Wood Extraction Used in Composite Materials: Behavior after Accelerated Weathering

New materials were obtained by incorporating in polypropylene (PP) matrix 60% wood wastes resulting after extraction with supercritical carbon dioxide, water, and ethanol. Structural, mechanical, thermal, and rheological characterizations, as well as moisture uptake of the composites, were evaluated before and after accelerated weathering. It was found that the extraction method influenced the composite properties due to the hydrophilic-hydrophobic balance. The addition of extracted fibers results in an increase in hardness and tensile properties and a decrease of impact strength as compared to PP.     

Effect of dopant structure on refractive index and glass transition temperature of polymeric fiber‐optic materials

Graded‐index plastic optical fibers, composed of doped polymers, have advantages over conventional glass optical fibers, but need to be developed further for practical application. Here, a variety of aromatic sulfide dopants were synthesized, and their effects on the refractive indexes and glass transition temperatures (T_g) of poly(methyl methacrylate) and methyl 2‐chloroacrylate/2,2,2‐trichloroethyl methacrylate copolymers were studied. While polymers containing large dopants exhibited relatively high refractive indices, their T_g values were low, making these materials unsuitable for graded‐index plastic optical fiber applications. Six dopants yielded polymers that exhibited higher T_g values than the conventionally used (diphenyl sulfide)‐doped polymer. The dopant dibenzothiophene, in particular, yielded polymers with the highest refractive indexes and T_g values, and polymers containing (phenylthio)benzene dopants also performed well. Copyright © 2013 John Wiley & Sons, Ltd.     

Study the electrical conductivity of crosslinked polyester doped with different metal salts

Three crosslinked polymers were prepared via condensation polymerization between triethanolamine and glycerol [(25:75%), (50:50%) and (0:100%) (G:TEA)] with maleic anhydride which produced polymers I, II and III consequently. All the prepared polymers were doped with metal salts (CuCl₂, NiCl₂ and FeCl₂). D.C. conductivity was measured in the temperature range of (298–373 K), the result showed that the electrical conductivity increased several orders of magnitude with increasing temperature, the activation energy decreased with increasing conductivity. A.C. measurement is used to calculate the dielectric constant for the polymers in both pure and doped state.     

Multi‐Colored Fibers by Self‐Assembly of DNA,Histone Proteins,and Cationic Conjugated Polymers

The development of biomolecular fiber materials with imaging ability has become more and more useful for biological applications. In this work, cationic conjugated polymers (CCPs) were used to construct inherent fluorescent microfibers with natural biological macromolecules (DNA and histone proteins) through the interfacial polyelectrolyte complexation (IPC) procedure. Isothermal titration microcalorimetry results show that the driving forces for fiber formation are electrostatic and hydrophobic interactions, as well as the release of counterions and bound water molecules. Color‐encoded IPC fibers were also obtained based on the co‐assembly of DNA, histone proteins, and blue‐, green‐, or red‐ (RGB‐) emissive CCPs by tuning the fluorescence resonance energy‐transfer among the CCPs at a single excitation wavelength. The fibers could encapsulate GFP‐coded Escherichia coli BL21, and the expression of GFP proteins was successfully regulated by the external environment of the fibers. These multi‐colored fibers show a great potential in biomedical applications, such as biosensor, delivery, and release of biological molecules and tissue engineering.     

Cooperative,Reversible Self‐Assembly of Covalently Pre‐Linked Proteins into Giant Fibrous Structures

We demonstrate a simple bioconjugate polymer system that undergoes reversible self‐assembling into extended fibrous structures, reminiscent of those observed in living systems. It is comprised of green fluorescent protein (GFP) molecules linked into linear oligomeric strands through click step growth polymerization with dialkyne poly(ethylene oxide) (PEO). Confocal microscopy, atomic force microscopy, and dynamic light scattering revealed that such strands form high persistence length fibers, with lengths reaching tens of micrometers, and uniform, sub‐100 nm widths. We ascribe this remarkable and robust form of self‐assembly to the cooperativity arising from the known tendency of GFP molecules to dimerize through localized hydrophobic patches and from their covalent pre‐linking with flexible PEO. Dissipative particle dynamics simulations of a coarse‐grained model of the system revealed its tendency to form elongated fibrous aggregates, suggesting the general nature of this mode of self‐assembly.     

N‐Alkylacylamides in Thin Films Display Infrared Spectra of 310‐, α‐, and π‐Helices with Visible Static and Dynamic Growth Phases

A peptide model is a physical system containing a CONH group, the simplest being HCONHCH₃, N‐methylformamide (NMF). We have discovered that NMF and N‐methylacetamide (NMA), which form hydrogen‐bonded oligomers in thin films on a planar AgX fiber, display infrared (IR) spectra with peaks like those of polypeptide helices. Structures can be assigned by their amide I maxima near 1672 (3₁₀), 1655 (3₁₀), 1653 (α), 1655 (π), and 1635 cm^?1 (π), which are the first IR data for the π‐helix. Sharp peaks are an outcome of immobilization of polar species on the polar surface of silver halides. We report the first use of expanded thin‐film IR spectroscopy, in which plots of every spectrum over the amide I–II range show pauses or slow stages in the increase or decrease of absorption. These are identified as static phases followed by dynamic phases, with the incremental gain or loss of a helix turn. A general theory can be stated for such processes. Density functional calculations show that the NMA α‐helix pentamer (crystal structure geometry) is transformed into a π‐helix‐like form. For the first time, an entire sequence (3₁₀‐helix, α‐helix, π‐helix, quasiplanar species) of spectra has been recorded for NMA.