用可见激光在聚(氨酯-酰亚胺)表面制备周期性亚微米结构

由于含有偶氮苯染料侧基,聚(氨酯-酰亚胺)(PUI)对532nm的光具有较强的吸收.采用该波长的可见偏振脉冲激光(Nd∶YAG激光器的倍频输出),在PUI薄膜表面制备了激光诱导周期性表面微结构(LIPSS).研究了染料引入方式以及染料侧基含量对微结构形成过程的影响,讨论了入射角、激光脉冲数、激光脉宽等激光辐射条件对LIPSS形成过程以及对微结构形貌和周期性的影响.     

UV Laser‐Induced Gas‐Phase Copolymerization of Carbon Disulfide and Ethene

Summary: The laser irradiation at 193 nm of a gaseous mixture of carbon disulfide and ethene induces the copolymerization of both compounds and affords the chemical vapour deposition of a C/S/H polymer, the composition of which indicates the reaction between two to three CS₂ molecules and one C₂H₄ molecule. Polymer structure is interpreted on the basis of X‐ray photoelectron and FT‐IR spectra as consisting of >CS, >CC<,  CH₂ CH₂ , (CC)S_nC_{4 − n},  C (CS) S ,  S (CS) S , and C S S C configurations. The gas‐phase copolymerization of carbon disulfide and ethene represents the first example of such a reaction between carbon disulfide and a common monomer.

Scheme showing the expected reaction of excited CS₂ molecules with other CS₂ molecules to form dimers, which then react with another CS₂ molecule or add to ethene.     

IR Laser‐Induced Degradation of Poly(vinyl acetate): Novel Thermal Reactions in Solid Polymers

Summary: Pulsed‐IR laser‐induced decomposition of poly(vinyl acetate) (PVAC) differs remarkably from its conventional pyrolysis, which results in the formation of acetic acid and non‐polar carbonaceous residue. In contrast, the products in the former case are (i) vinyl acetate (low energy channel), (ii) products of cleavage in the acetate group, and (iii) an ablatively deposited polar polymeric film containing roughly half of the acetoxy groups initially present.

Schematic of the different routes of poly(vinyl acetate) degradation.     

Direct Creation of Highly Conductive Laser‐Induced Graphene Nanocomposites from Polymer Blends

The current state‐of‐the‐art mixing strategies of nanoparticles with insulating polymeric components have only partially utilized the unique electrical conductivity of graphene in nanocomposite systems. Herein, this paper reports a nonmixing method of direct creation of polymer/graphene nanocomposites from polymer blends via laser irradiation. Polycarbonate‐laser‐induced graphene (PC‐LIG) nanocomposite is produced from a PC/polyetherimide (PC/PEI) blend after exposure to commercially available laser scribing with a power of ≈6 W and a speed of ≈2 cm s⁻¹. Extremely high electrical conductivities are obtained for the PC‐LIG nanocomposites, ranging from 26 to 400 S m⁻¹, depending on the vol% of the starting PEI phase in the blend. To the authors' knowledge, these conductivity values are at least one order of magnitude higher than the values that are previously reported for conductive polymer/graphene nanocomposites prepared via mixing strategies. The comprehensive microscopy and spectroscopy characterizations reveal a complete graphitization of the PEI phase with columnar microstructure embedded in the PC phase.     

Cyclotrimerization‐Induced Chiral Supramolecular Structures of 4‐Ethynyltriphenylamine on Au(111) Surface

Cyclotrimerization‐induced chiral supramolecular structures of 4‐ethynyltriphenylamine (ETPA) have been synthesized on the Au(111) surface through alkyne‐based reactions. Whereas the ETPA molecules adsorbed on the Au(111) surface remain inert and form a close‐packed self‐assembled structure at room temperature, the combination of scanning tunneling microscopy observations and theoretical calculations unambiguously reveal that the ETPA molecules cyclotrimerize to form new trimer‐like species—1,3,5‐tris[4‐(diphenylamino)phenyl]benzene (TPAPB)—after annealing at 323 K. Further annealing drives these cyclotrimerized TPAPB molecules to form chiral hexagonal supramolecular structures with an extraordinary self‐healing ability.     

Laser‐induced periodic surface structure on a polymer surface: The effect of a prerubbing treatment on the surface structure

The influence of the mechanical rubbing of a polyimide (PI) film on the laser‐induced periodic structure (LIPS) was demonstrated. The periodicity and amplitude of LIPS were greater when the rubbing direction was parallel to the laser polarization direction. The amplitude became small and the periodicity of LIPS did not show an obvious change when the rubbing direction was perpendicular to the laser polarization direction. The effect of the rubbing pretreatment on LIPS was explained on the basis of the wave‐guide effect of rubbing‐induced microgrooves on LIPS formation. The orientation of PI chains induced by mechanical rubbing was relaxed after laser irradiation, and a new orientation of PI chains was formed during the LIPS formation. When the rubbing direction was perpendicular to the laser polarization direction, the orientation of PI chains remained in the rubbing direction. The laser‐irradiated, perpendicularly rubbed PI surface could be used to verify the effects of surface morphologies and intermolecular interactions on liquid‐crystal alignment. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1273–1280, 2003     

Viability of Human Mesenchymal Stem Cells Seeded on Crosslinked Entropy‐Elastic Gelatin‐Based Hydrogels

Biomimetic polymer network systems with tailorable properties based on biopolymers represent a class of degradable hydrogels that provides sequences for protein adsorption and cell adhesion. Such materials show potential for in vitro MSC proliferation as well as in vivo applications and were obtained by crosslinking different concentrations of gelatin using varying amounts of ethyl lysine diisocyanate in the presence of a surfactant in pH 7.4 PBS solution. Material extracts, which were tested for cytotoxic effects using L929 mouse fibroblasts, were non‐toxic. The hydrogels were seeded with human bone marrow‐derived MSCs and supported viable MSCs for the incubation time of 9 d. Preadsorption of fibronectin on materials improved this biofunctionality.

     

Reactivity Towards Europium(III) of the Radiolysis Products of the Ionic Liquid 1‐Methyl‐3‐butyl‐1H‐imidazolium Bis[(trifluoromethyl)sulfonyl]amide (C4‐mimTf2N) and Effect of Water: A TRLFS (Time‐Resolved Laser‐Induced Fluorescence Spectroscopy) Preliminary Study

The effect of laser irradiation at λ_exc 266 nm onto the fluorescence characteristics of Eu^III in solution of the ionic liquid 1‐methyl‐3‐butyl‐1H‐imidazolium bis[(trifluoromethyl)sulfonyl]amide (C₄‐mimTf₂N) was examined for various amounts of H₂O added. Stable radiolytic products that were generated at very low doses (in the range of 4 kGy) were very reactive with Eu^III and led to the appearance of a new europium luminescent species that was characterized by lifetime, relative intensity, and emission spectrum. Although the lifetime and the intensity depended on the H₂O content, the emission spectrum was not influenced by H₂O. It was shown that large amounts of H₂O, although not preventing radiolysis of C₄‐mimTf₂N, inhibited the complexation with Eu^III.     

Evaluation of 3D Printed Gelatin‐Based Scaffolds with Varying Pore Size for MSC‐Based Adipose Tissue Engineering

Adipose tissue engineering aims to provide solutions to patients who require tissue reconstruction following mastectomies or other soft tissue trauma. Mesenchymal stromal cells (MSCs) robustly differentiate into the adipogenic lineage and are attractive candidates for adipose tissue engineering. This work investigates whether pore size modulates adipogenic differentiation of MSCs toward identifying optimal scaffold pore size and whether pore size modulates spatial infiltration of adipogenically differentiated cells. To assess this, extrusion‐based 3D printing is used to fabricate photo‐crosslinkable gelatin‐based scaffolds with pore sizes in the range of 200–600 µm. The adipogenic differentiation of MSCs seeded onto these scaffolds is evaluated and robust lipid droplet formation is observed across all scaffold groups as early as after day 6 of culture. Expression of adipogenic genes on scaffolds increases significantly over time, compared to TCP controls. Furthermore, it is found that the spatial distribution of cells is dependent on the scaffold pore size, with larger pores leading to a more uniform spatial distribution of adipogenically differentiated cells. Overall, these data provide first insights into the role of scaffold pore size on MSC‐based adipogenic differentiation and contribute toward the rational design of biomaterials for adipose tissue engineering in 3D volumetric spaces.     

Characterization of polysuccinate and hydroxyapatite‐based nanocomposites containing poly(ester‐anhydride) microspheres

Repair and regeneration of bone defects with particular shape may be enhanced by in situ forming biomaterials which can be used in minimal invasive surgery. This study is aimed to prepare novel in situ forming biodegradable nanocomposites based on poly(3‐allyloxy‐1,2‐propylene) succinate (PSAGE) and nanosized hydroxyapatite (HA). These nanocomposite materials contain poly(ester‐anhydride) (PEA) microspheres embedded in a polyester matrix prepared by crosslinking PSAGE with oligo(1,2‐propylene maleate) and methacrylic monomers. Methyl methacrylate and one of hydrophilic oligo(ethylene glycol) methacrylates with different functionality and various length of oligooxyethylene chains were used as polymerizable diluents. Incorporation of microspheres which degrade faster than crosslinked polyester matrices enables formation of porous structure in situ. The obtained materials are liquid before curing and harden in several minutes with moderate exothermic effect. The effect of the composition of nanocomposite materials on selected properties, such as water sorption, mechanical strength, porosity and hydrolytic degradation process, was investigated. Rheological behavior and injectability of liquid formulations were studied. Analysis by energy dispersive spectroscopy confirmed the presence of characteristic features of HA in the nanocomposite materials. The morphology of the cured nanocomposites subjected to hydrolytic degradation was evaluated by scanning electron microscopy. The MTS cytotoxicity assay was carried out for extracts from crosslinked materials using hFOB1.19 cells. It was found that the extracts exhibit a dose‐dependent cytotoxic response. Copyright © 2014 John Wiley & Sons, Ltd.     

Two‐Dimensional Spatial Resolution of Concentration Profiles in Catalytic Reactors by Planar Laser‐Induced Fluorescence: NO Reduction over Diesel Oxidation Catalysts

Planar laser‐induced fluorescence (PLIF) enables noninvasive in situ investigations of catalytic flow reactors. The method is based on the selective detection of two‐dimensional absolute concentration maps of conversion‐relevant species in the surrounding gas phase inside a catalytic channel. Exemplarily, the catalytic reduction of NO with hydrogen (2 NO+5 H₂→2 H₂O+2 NH₃) is investigated over a Pt/Al₂O₃ coated diesel oxidation catalyst by NO PLIF inside an optically accessible channel reactor. Quenching‐corrected 2D concentration maps of the NO fluorescence above the catalytic surface are obtained under both, nonreactive and reactive conditions. The impact of varying feed concentration, temperature, and flow velocities on NO concentration profiles are investigated in steady state. The technique presented has a high potential for a better understanding of interactions of mass transfer and surface kinetics in heterogeneously catalyzed gas‐phase reactions.     

Simultaneous Determination of Levodopa and Its Metabolite in Human Blood by Capillary Electrophoresis with Laser‐induced Fluorescence Detection

A rapid, sensitive and reproducible method is described for the analysis of levodopa and its metabolite dopamine (DA) in human blood. The influence of carbidopa as the inhibitor againist the decarboxylase activity on the metabolism has been also studied. After derivatization in a dark pulsator for 12 h at room temperature, the fluorescein isothiocyanate (FITC) derivative of levodopa and other components were separated by capillary zone electrophoresis (CZE) within 13 min and detected with laser-induced fluorescence (LIF). Under the optimum analysis conditions, the linear range is 3.0×10^－8—4.0×10^－6 mol/L and 1.0×10^－8—2.0×10^－6 mol/L for levodopa and DA, respectively. The detection limits of levodopa and DA were 7.8×10^－9 mol/L (39.0 amol) and 3.1×10^－9 mol/L (15.5 amol), respectively. The method was successfully applied to monitoring the levodopa and DA in human blood after one took tablets orally.     

Preparation of a Novel Polymer‐Modified Si Surface for DNA Immobilization

The design of a novel polymer‐modified overlayer composed of PPAPE and GPMS on a silicon wafer for immobilization of DNA molecules is described. After hydroxylation of Si(100) surfaces, GPMS molecules were self‐assembled onto these surfaces. PPAPE molecules were then covalently attached to the epoxy‐terminated surfaces. The incubation time and concentration of PPAPE was found to effect both layer thickness and water CA. The type of organic solvent and the pH were found to change the nature of the PPAPE‐modified surface for DNA immobilization. It is concluded that PPAPE‐modified surfaces show advantages for DNA immobilization by electrostatic interactions between DNA molecules and positively charged free amino groups of the PPAPE‐modified surfaces at the appropriate pH values.

     

Facile Fabrication of AIE‐Active Fluorescent Polymeric Nanoparticles with Ultra‐Low Critical Micelle Concentration Based on Ce(IV) Redox Polymerization for Biological Imaging Applications

Fluorescent polymeric nanoparticles (FPNs) with aggregation‐induced emission (AIE) property have received increasing attention and possess promising biomedical application potential in the recent years. Many efforts have been devoted to the fabrication methodologies of FPNs and significant advance has been achieved. In this contribution, a novel strategy for the fabrication of AIE‐active amphiphilic copolymers is reported for the first time based on the Ce(IV) redox polymerization. As an example, ene group containing AIE‐active dye (named as Phe‐alc) is directly grafted onto a water soluble polymer polyethylene glycol (PEG) in H₂O/THF system under low temperature. Thus‐obtained amphiphilic fluorescent polymers will self‐assemble into FPNs with ultra‐low critical micelle concentration, ultra‐brightness, and great water dispersibility. Biological evaluation results suggest that the PEG‐poly(Phe‐alc) possess excellent biocompatibility and can be used for tracing their behavior in cells using confocal laser scanning microscope. These features make PEG‐poly(Phe‐alc) FPNs promising candidates for many biomedical applications, such as cell imaging, drug delivery vehicles, and targeted tracing. More importantly, many other functional groups can also be incorporated into these AIE‐active FPNs through the redox polymerization. Therefore, the redox polymerization should be a facile and effective strategy for fabrication of AIE‐active FPNs.

     

A Molecular Toolkit for the Functionalization of Titanium‐Based Biomaterials That Selectively Control Integrin‐Mediated Cell Adhesion

We present a click chemistry‐based molecular toolkit for the biofunctionalization of materials to selectively control integrin‐mediated cell adhesion. To this end, α5β1‐selective RGD peptidomimetics were covalently immobilized on Ti‐based materials, and the capacity to promote the selective binding of α5β1 was evaluated using a solid‐phase integrin binding assay. This functionalization strategy yielded surfaces with a nine‐fold increased affinity for α5β1, in comparison to control samples, and total selectivity against the binding of the closely related integrin αvβ3. Moreover, our methodology allowed the screening of several phosphonic acid containing anchoring units to find the best spacer–anchor moiety required for establishing an efficient binding to titanium and to promote selective integrin binding. The integrin subtype specificity of these biofunctionalized surfaces was further examined in vitro by inducing selective adhesion of genetically modified fibroblasts, which express exclusively the α5β1 integrin. The versatility of our molecular toolkit was proven by shifting the cellular specificity of the materials from α5β1‐ to αvβ3‐expressing fibroblasts by using an αvβ3‐selective peptidomimetic as coating molecule. The results shown here represent the first functionalization of Ti‐based materials with α5β1‐ or αvβ3‐selective peptidomimetics that allow an unprecedented control to discriminate between α5β1‐ and αvβ3‐mediated adhesions. The role of these two integrins in different biological events is still a matter of debate and is frequently discussed in literature. Thus, such bioactive titanium surfaces will be of great relevance for the study of integrin‐mediated cell adhesion and the development of new biomaterials targeting specific cell types.     

Adsorption and Decomposition Mechanism of 1,1‐Diamino‐2,2‐dinitroethylene on Al(111) Surface by Periodic DFT Calculations

The adsorption of 1,1‐diamino‐2,2‐dinitroethylene (FOX‐7) molecule on the Al(111) surface was investigated by the generalized gradient approximation (GGA) of density functional theory (DFT). The calculations employ a supercell (4×4×2) slab model and three‐dimensional periodic boundary conditions. The strong attractive forces between oxygen and aluminum atoms induce the N? O bond breaking of the FOX‐7. Subsequently, the dissociated oxygen atoms and radical fragment of FOX‐7 oxidize the Al surface. The largest adsorption energy is ?940.5 kJ/mol. Most of charge transfer is 3.31e from the Al surface to the fragment of FOX‐7 molecule. We also investigated the adsorption and decomposition mechanism of FOX‐7 molecule on the Al(111) surface. The activation energy for the dissociation steps of P2 con?guration is as large as 428.8 kJ/mol, while activation energies of other con?gurations are much smaller, in range of 2.4 to 147.7 kJ/mol.     

Bottom‐up Assembly of Poly(3‐hexylthiophene) on Carbon Nanotubes: 2D Building Blocks for Nanoscale Circuits

Hierarchical poly(3‐hexylthiophene)(P3HT)/carbon nanotube (CNT) supramolecular structures were fabricated through a bottom‐up CNT induced P3HT crystallization strategy. P3HT nanowires growing perpendicular from CNT surface have uniform width and height. The density and the length of these nanowires can be controlled by tuning the P3HT/CNT mass ratio. The quasi‐isothermal crystallization process monitored by in situ UV–Vis spectroscopy indicates that CNTs can greatly enhance the P3HT crystallization, and the P3HT nanowire formation follows first‐order kinetics. Such bottom‐up strategy provides a general approach to build 2D functional conductive supramolecular structures that will lead to numerous applications in nanoscale electronics.

     

MALDI‐TOF MS Coupled with Collision‐Induced Dissociation (CID) Measurements of Poly(methyl methacrylate)

Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) was chosen for an in‐detail analysis of poly(methyl methacrylate) (PMMA) in order to determine the possible fragmentation mechanism with the help of collision‐induced dissociation (CID). All experiments were performed on a well‐defined PMMA standard and were optimized for sample preparation and measurement conditions of both MS and MS/MS. In order to investigate the fragmentation pathways, two parent peaks—both charged with sodium (m/z = 1 625.9 and 2 226.2 Da, respectively)—were selected, thus permitting the examination of possible cleavages, and reaction pathways. For both chosen peaks, the MALDI‐TOF MS/MS spectra revealed four fragmentation series that could be explained by single or multiple main chain scissions and secondary reactions of the PMMA side groups. According to the molar mass of the fragments, a loss or migration of the side group to the end of the free radical, followed by a β‐scission, was favored. These insights are the first steps toward the construction of a library with fragments and fragmentation pathways, complementary to proteomics libraries, in order to obtain fast and automated identification of substances.