Morphology and electrochemical properties of amphiphilic viologen functionalized multiwalled carbon nanotube hybrids in Langmuir-Blodgett films

Amphiphilic viologens were electrostatically adsorbed on the surface of multiwalled carbon nanotubes (MWCNT) to form viologen-MWCNT hybrids, in which the content of viologens was about 5-10% in weight. Although both viologens and MWCNT hardly dispersed in the water-insoluble organic solvents, the as-prepared viologen-MWCNT hybrids were well dispersed in them with a strong long-term stability, the features of which provided a possibility to prepare their insoluble monolayers at the air-water interface. The surface pressure-area isotherms of these hybrids revealed that they could form stable monolayers, which were transferred on the substrate surfaces by the Langmuir-Blodgett (LB) method. Morphologies of the LB films were characterized by using scanning electron microscopy and atomic force microscopy, the images of which revealed the formation of network two- or three-dimensional films of the functionalized MWCNT. Cyclic voltammograms of the LB films revealed one or two couples of one electron transfer process corresponding to the viologen-MWCNT hybrids with the cathodic and anodic potentials closely related to the alkyl chains of the viologens.     

Fabrication of Langmuir-Blodgett films using amphiphilic peptides

To introduce self-organization ability of transmembrane proteins into Langmuir (L) and Langmuir-Blodgett (LB) techniques, we focused on "amphiphilic peptide" (AP) which is composed of two distinct hydrophilic and hydrophobic domains. Three types of APs of different average hydropathies were used to prepare the AP/lipid mixed L and LB films. According to the circular dichroism spectra, the secondary structures of APs were not uniform but were a mixture of alpha-helix, beta-strand and random coil. The fraction of alpha-helix was higher for lower hydropathy AP. The interaction between AP and lipid in the L film and the structure of the LB film were also depended on the APs used.     

两亲嵌段共聚物PS-b-PAA自组装薄膜的表面形貌与结晶性能研究

采用溶液浸渍-提拉法制备了两亲性嵌段共聚物PS-b-PAA自组装薄膜,并利用图像分析仪和X射线衍射仪研究了聚合物薄膜的表面形貌和结晶性能.研究结果表明,PS-b-PAA的溶液浓度和嵌段长度通过影响溶液中形成的反胶束数目和粒径进而造成溶剂挥发过程中反胶柬在扩散动力学上的差异,最终得到不同形貌的嵌段共聚物薄膜.结晶性能研究结果表明,室温下PS-b-PAA在玻璃基板表面的结晶是一种受膜厚影响、动力学控制的受限结晶过程.当溶液浓度达到0.1g/mL时,可制备出致密的结晶性嵌段共聚物薄膜.     

丙烯腈-丙烯酸共聚物超细纤维的制备及其pH响应性能的研究

以N,N-二甲基甲酰胺(DMF)为溶剂,通过气流-静电纺丝法制备了具有pH响应性能的丙烯腈-丙烯酸共聚物(Poly(AN-co-AA))超细纤维。利用扫描电镜(SEM)对超细纤维形貌进行表征,研究了聚合单体中丙烯酸(AA)的含量、纺丝溶液中L-苯丙氨酸(L-Phe)的含量和浸泡时间对Poly(AN-co-AA)超细纤维形貌的影响,并从缓冲溶液的pH值及其与纤维直径变化的可逆性等方面研究了Poly(AN-co-AA)超细纤维的pH响应性能,确定了制备具有pH响应性能的Poly(AN-co-AA)超细纤维的最佳工艺参数。     

蓝光材料双亲共聚芴的合成、表征与性能

通过Suzuki缩聚方法,将单体2,7-二溴-9,9'-二-(3,6-二氧烷基)芴和9,9'-二辛基芴-2,7-二-(三亚甲基硼酸酯)合成了一种新型的蓝光材料-双亲芴基共聚物.采用1H NMR、13C NMR和元素分析对共聚芴结构进行了表征;通过GPC、DSC和TGA测试,共聚芴有较高的分子量和较窄的分子量分布,同时还有很好的热稳定性.对共聚芴的紫外吸收光谱分析表明,在甲苯溶液和薄膜中的波长分别为389nm和393nm;对共聚芴的荧光发射光谱分析表明,在甲苯溶液和薄膜中的波长分别为415nm和437nm.     

Morphology of polycrystalline ZnO and its physical properties

Five commercial polycrystalline ZnO samples with different morphologies (nodular and needle-like) have been studied. Nodular ZnO crystallites reveal lower polydispersity, higher ultraviolet luminescence (380 nm), low green luminescence (500 nm), a small ESR signal with g=1.96 and a density close to the theoretical value for ZnO with the wurtzite structure. Needle-like ZnO crystallites have a higher polydispersity, higher green luminescence, higher ESR signal with g=1.96 and lower values of density. The observed differences in the physical properties are associated with the presence of oxygen vacancies in needle-like particles and probably also interstitial zinc atoms in nodular particles.     

Morphology and properties of ASA/PET blends

This study examines the morphology and mechanical properties of acrylate styrene acrylonitrile (ASA) and polyethylene terephthalate (PET) blends. The morphology of the 60/40 and 40/60 ASA/PET blends reveals a dispersed phase morphology verging on co-continuity, whilst the 50/50 blend appears to be completely co-continuous. Processing temperature has no effect on blend modulus or tensile strength and there is no statistically significant difference in mechanical performance between the three blend ratios. Charpy impact resistance decreases with increasing processing temperature. The fracture surface reveals a similar mushroom fibril morphology found for the ASA/polybutylene terephthalate (PBT) system, but is less extensive. Thermal analysis shows a marked drop in glass transition temperature for the blends compared to the component polymers.     

Morphology and physical-chemical properties of baked nanoporous frustules

We investigated the morphology and physical-chemical properties of baked and unbaked nanoporous frustules. Scanning electron microscopy (SEM) observations showed that the nanoporous structures of frustules unchanged at 400 degrees C even after baking for 6 h. During baking at 800 degrees C, the frustule structures changed dramatically. On the other hand, Fourier transform infrared spectroscopy (FTIR) of bulk frustule samples indicated that physical-chemical properties of the frustules had clearly changed after baking at not only 800 degrees C but also 400 degrees C. These results showed that the reconstruction of the structures had occurred inside the frustules, even though the morphology of the frustules had not apparently changed at 400 degrees C. In order to characterize the exact shape of the frustules, living diatom cells were grown on a functionalized mica surface, and then baked without any chemical treatment for SEM study. This 'direct baking' technique is effective for comparing minute structures of the frustules, because completed combination of every part of the frustules can be observed.     

Electronic and structural properties of BaTe

We present the results of a theoretical study of the structural and electronic properties of BaTe, using first principle pseudopotential plane wave (PP-PW) and full potential linear augmented plane wave (FP-LAPW) methods. In both approaches the generalized gradient approximation (GGA) was used for the exchange-correlation potential. In the case of PP-PW we repeated the calculation using local density approximation (LDA). Our calculated values for the structural parameters, metallization and structural transition pressures are in reasonable agreement with experimental results. Although the calculated band gap within GGA shows substantial improvement over LDA, it is still lower than the measured ones. There is a speculation that at least part of this discrepancy is due to the discontinuity inherent in the exchange-correlation potential. The partial contribution from each atom to the total density of states is calculated. It is seen that the lower valence bands are mainly formed by s orbitals of Te, while the upper valence bands are formed by the p orbitals of Te. Empty states of the conduction bands are mainly formed by d orbitals of Ba.     

Synthesis and properties of amphiphilic block polymer functionalized multi-walled carbon nanotubes and nanocomposites

The grafting of poly(ethylene glycol)-block-polyacrylonitrile (PEG-b-PAN) amphiphilic block polymer onto multi-walled carbon nanotubes (MWCNTs) was achieved by combination of coupling reaction and redox radical polymerization. The chemical structure and yield of the resulting grafted polymer were characterized and confirmed by FT-IR and TGA. Transmission electron microscopy (TEM) images clearly indicated that the nanotubes were coated with a polymer layer. The concentrated DMF dispersions of MWCNT-g-(PEG-b-PAN) nanocomposite were stable for months, the viscoelasticity being monitored by rheometer. MWCNT-g-(PEG-b-PAN) hybrid nanocomposite membranes were fabricated by phase inversion in a wet process. The results showed that high concentration of MWCNTs could be dispersed in the polymer matrix. The morphology and surface hydrophilicity characteristics of the membrane could be controlled by the composition of MWCNT-g-(PEG-b-PAN) nanocomposite membrane.     

Random amphiphilic copolymeric sub-micro particles as a carrier shielding from enzymatic attack for peptides and proteins delivery

The development of peptide drugs and therapeutic proteins is limited by their rapid clearance in liver and other body tissues by proteolytic enzymes, and consequently peptides and proteins are difficult to administer except by injection. There is a growing effort to circumvent these problems by designing strategies to deliver these drugs to specific site of the body. Among them, this peptide carrier presents several advantages for protein therapy including stability in physiological buffer and lack of toxicity. Here, we have been developing a novel bioadhesive polymer matrix that protects entrapped proteins and peptides from degradation by serine protease. Poly(2-lactobionamidoethyl methacrylate-ran-3-acrylamidophenylboronic acid-ran-methoxypolyethylene glycol methacrylate) glycopolymers were synthesized and could self-assemble into the sub-micro particles. The loading capability of insulin, as a drug model, and the insulin release from the particles were assessed. The inhibitory effect of the particles toward trypsin, elastase, and chymotrypsin was evaluated in vitro. Insulin was effectively encapsulated, up to 10%, and could be stained release in vitro. These glycopolymers displayed a strong inhibitory effect toward these exopeptidases. Therefore, novel glycopolymers with excellent inhibitory activity against proteolytic enzymes and reasonable mucoadhesivity might be a useful tool in overcoming the enzymatic barrier to the mucosal delivery (e.g. nasal and buccal) of therapeutic peptides or proteins.     

Morphologies and optical properties of nanostructures self-assembled from asymmetrical, amphiphilic perylene derivatives

Two asymmetrical, amphiphilic perylene derivatives, N-Decyl-perylene-3,4:9,10-tetracaboxylic-3,4-di(methoxyethoxyethyl)ester-9,10-imide (D1E2) and N-(1-Decylundecyl)-perylene-3,4:9,10-tetracaboxylic-3,4-di(methoxyethoxyethyl)ester-9,10-imide (D2E2), have been synthesized and characterized. These compounds contain one long hydrophobic chain on one end and two hydrophilic ethoxy chains on the other end. Self-assembly of these molecules in a variety of solvents has been demonstrated. Scanning electron microscopy images showed that these compounds self-assembled to various nanostructures in different solvents. The most well-defined structure was flexible nanoribbons obtained from D1E2 precipitation in methanol. The UV–vis absorption and fluorescence spectra of these compounds in solution and solid form are also reported. The self-assembled nanostructures have potential applications in optoelectronics.     

Morphology and size dependent optical properties of CdS nanostructures

CdS nanoparticles with different sizes ranging from 2.5 nm to 300 nm and nanorods with aspect ratio -32 were synthesized by simple solvothermal process with a view to explore the effect of size and shape on the optical properties of these nanoforms. Solvent, temperature and the Cd source played important role in determining the morphologies and sizes of the nanocrystals. Comparative study of the optical properties of these nanoforms showed systematic changes in the optical absorption spectra with the reduction in particle size. Nanorods showed bulk like properties. Photoluminescence and Raman studies were carried out to explore the size and morphology dependent optical properties of the CdS nanoforms.     

Spectroscopic properties of an amphiphilic styryl pyridinium dye in Langmuir-Blodgett films

Surface pressure-molecular area and surface potential-molecular area isotherms of the recently synthesized amphiphilic dye 1 indicate that it forms monolayers on distilled water. A shift of the fluorescence maximum from 505 up to 570 nm was measured upon increasing the surface pressure applied during the Langmuir-Blodgett transfer from 7 up to 20 mN/m, and a slight red shift in the absorption. The increase of the surface pressure also produces a new blue-shifted band only present in the p-polarized component of the absorption spectra under oblique incidence of light. The results were interpreted as reorientation and association of the chromophores in the monolayer, according to the extended dipole model.     

Morphology and mechanical properties of polyacrylonitrile/attapulgite nanocomposite

The major objective of this work is to understand the effects of attapulgite (AT) on the mechanical properties of polyacrylonitrile (PAN)/AT nanocomposite film. The well dispersed but irregularly distributed AT nanoparticles in the matrix was observed by scanning electron microscopy (SEM) and UV–vis spectra. The mechanical properties were investigated by means of tensile tests and dynamic mechanical analyses (DMA). The results showed that the incorporation of AT significantly improved the tensile strength and modulus of the PAN matrix. The fracture morphologies analysis has further suggested that small amount of AT nanorods may slide and orient along the tensile direction, resulting in homogenous stress transfer, thus increase the toughness of the PAN. However, the nanorods network formed in high AT content sample probably hindered the deformation of the matrix and generated the stress concentration points, leading to the remarkable increase of embrittlement of the samples. Following this concept, the volume of the constrained polymer chains was also calculated with DMA data and showed the good correlation with conclusion drawn in the tensile tests.     

Incorporation of designed extended chromophores into amphiphilic 4-helix bundle peptides for nonlinear optical biomolecular materials

Multipigment ensembles that feature (porphinato)metal components and appropriate ethyne- and oligoyne-based chromophore-to-chromophore connectivity can manifest large optical polarizabilities and hyperpolarizabilities by design. Their vectorial orientation and local environment are controlled upon incorporation into designed amphiphilic 4-helix bundle peptides via axial histidyl ligation without disturbing the peptide's helical secondary structure. The chromophore/peptide stoichiometry can be tuned by varying the peptide's oligomeric state. The chromophore/peptide complexes are thermally stable, making them ideal candidates for the fabrication of nonlinear optical biomolecular materials.