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The diagnosis of liquid and solid biopsies by different instruments makes the clinic loading difficult in many aspects. Given the compositions of magnetic particles (MPs) with diverse characterizations and the innovative acoustic type of vibration sample magnetometer (VSM), the versatile, accessible magnetic diagnosis platform was proposed to meet clinical demands, such as low loading for multiple biopsies. In liquid biopsies of alpha-fetoprotein (AFP) standard solutions and subject serums, molecular concentration was analyzed from saturation magnetization by the soft type of Fe3O4 MPs with AFP bioprobe coating. In the phantom mixture simulated as bounded MPs in tissue, the bounded MPs was evaluated from the area of the hysteresis loop by hard type of cobalt MPs without bio-probes coating. Not only a calibration curve was founded for many hepatic cell carcinoma stages, but also microscale images verified the Ms increase due to magnetic protein clusters, etc. Hence, its wide populations in clinics could be expected.

The structure and properties of graphene oxide aerogels (GOA), prepared by a modified Hummer’s method followed by a freezing-drying process in addition to a pre-oxidized procedure, were studied through FTIR, Raman, SEM and XDR techniques. FTIR results indicated the existence of -C-O, -C-OH and -C=O function groups on the GOA surface. Therefore, the D band intensity of GOA sample exhibited remarkable increasing in the Raman spectra compared with of graphite; it may be due to change the order-structure of graphite to disorder-structure of GOA. The diffractive peak for the graphite at 2θ of 26.5° vanishes instead the one around 10.0° occurred in the XRD pattern for the GOA supported that the structure and d-spacing changed seriously from graphite to GOA. The SEM images revealed that the micro-structure of graphene layer of GOA was wrinkler and softer than that of graphite, however, the former involved fewer lamellar layer appearance with wrinkles on the edges of the graphene. All the characterized evaluation confirmed that the graphite powder has been transformed into a GOA structure through the modified Hummers’ method.

This study determined the characteristics of the time-dependent effective relaxation time τeff and magnetization M when biofunctionalized magnetic nanoparticles (BMNPs) associated with biomarkers in a liquid immunoassay. Carcinoembryonic antigen (CEA) was used as the biomarker. BMNP is an anti-CEA that was coated onto dextran-coated Fe3O4 and labeled as Fe3O4-anti-CEA. The phase lag θ of M with respect to the applied field H was measured using a sensitive homemade alternative-current susceptometer, and θ was measured using lock-in detection. The results were used to estimate τeff using the relationship tan θ(t) = ωτeff(t), where 2πf = ω and f is the excitation frequency. Δτeff increased with ΦCEA, where Δτeff was the increment of τeff after Fe3O4-anti-CEA associated with CEA, and ΦCEA was the concentration of CEA. Additionally, M enhanced when ΦCEA increased. We attributed these enhancements to magnetic dipole–dipole interactions among MNPs that contributed extra M and in turn enhanced τeff. Magnetic clusters after the association were verified using a transmission electron microscope. This study established the relationship between Δτeff/τeff,0 and ΦCEA, where τeff,0 = τeff (ΦCEA = 0), allowing the assay of an unknown amount of CEA molecules.

In this work, a highly balanced ac susceptometer was designed and implemented for magnetic immunoassays for sensing human C-reactive proteins (CRP). It is known that CRPs are used mainly as a biomarker for inflammation or acute diseases. Monitoring CRP values in blood can help medical doctors understand disease progression or the effectiveness of treatments. We characterize magnetic properties of the ac susceptometer as the human CRPs are associated with Fe3O4-antiCRP. In the design, the pickup coil and the excitation coil are positioned side-by-side with their coil axis parallel and separated at a distance of ∼1.5 cm. The pick-up coil consists of two coils wound in opposite direction with a compensation coil to improve balance. We use the Fe3O4-antiCRP-CRP magnetic clusters as the bio-target and study the effects of magnetic clustering on the changes of magnetization. The magnetic clusters are CRPs conjugated onto the Fe3O4-antiCRP and can be observed directly with SEM. The Fe3O4-antiCRP is the anti-C-reactive protein (antiCRP) coated onto dextran-coated magnetic nanoparticles (MNPs), also called the bio-functionalized magnetic nanoparticles (BMNs).

Poly(3-hexylthiophene) (P3HT) is one of the most widely studied conjugated polymers for applications in polymer-based photovoltaics and thin-film transistors. The regioregularity index (RR) represented by the mole percentage of the head-to-tail (HT) dyad in the polymer molecule has been considered as a key factor governing both the kinetics and thermodynamics of the self-assembly of P3HT. In this study, we reveal that the configurational sequence beyond dyad plays an equally important role by demonstrating that two P3HT samples bearing almost identical RR value and average molecular weight displayed very different self-assembly kinetics. Counterintuitively, the semidilute xylene solution of the P3HT with slightly smaller RR value exhibited a much faster gelation. In the bulk state, this sample also showed faster crystallization kinetics and higher melting point. Characterization of the configurational structure by nuclear magnetic resonance (NMR) spectroscopy showed that the P3HT with the smaller RR value contained a higher population of HT-HT triad sequence. Therefore, knowledge of this system parameter, which has been omitted prevalently, is essential for the delicate control of the morphological formation of P3HT for enhancing its photophysical properties.

We compared the crystallization rate of poly(3-hexylthiophene) (P3HT) in the film cast from the gel (called "gel-cast film") with that in the film cast from the liquid solution (called "solution-cast film") to understand the effect of solution structure on the structural development in the subsequently cast film of conjugated polymer. P3HT was found to form a homogeneous liquid solution with xylene at elevated temperature. When the freshly prepared semidilute solution was allowed to age at room temperature, the solution transformed into a gel in which a significant amount of nanowhiskers formed. The nanowhiskers in the gel were effectively transferred to the corresponding cast film, while the film cast from the freshly prepared solution only contained a small amount of such a morphological entity. The in situ small-angle X-ray scattering (SAXS) measurement and thermal analysis revealed that both the cold and melt crystallization of P3HT in the gel-cast film were much slower than those in the solution-cast counterpart. The retardation of crystallization rate in the gel-cast film was attributed to the abundance of the nanowhiskers. In this case, the crystallization of P3HT occurred predominantly within the individual nanowhiskers and the mesh regions in the networks of the whiskers, where their limited sizes in at least one dimension imposed a strong spatial constraint to the crystal growth and chain motion for crystallization.

In this work, we investigate the morphology and microstructure of the aggregates, and the gelation behaviour of Poly(3-hexylthiophene) (P3HT) conjugated polymer in xylene solution as functions of P3HT concentration and aging time by the means of ageing time test, wide angle X-ray diffraction (WAXD), scanning electron microscopy (SEM), UV-visible absorption (UV-vis) and photoluminescence (PL) spectra. The result reveals that the gelation time of P3HT/xylene solution decreases markedly with increasing P3HT concentration. The photophysical properties of the P3HT aggregates in P3HT/xylene solution increase as P3HT concentration and ageing time are raised. It indicates that the well soluble P3HT polymer chains in xylene solution present microphase separation and self-assemble into stiff sheetlike structure, which associates by rodlike nanowhiskers of P3HT polymers during aging. Upon prolonged aging, the sheetlike structure of P3HT aggregates to from the three-dimension network that improves the electronic particle mobility in the organic solar cell.

A composite film composed of platinum nanoparticles (PtNPs) and vapor grown carbon fibers (VGCFs) was coated on FTO glass acted as a counter electrode (CE) for high performance dye-sensitized solar cell (DSSC) via a facially thermal approach. The PtNP/VGCF hybrid film was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetry (TGA), X-ray diffraction (XRD), Raman, and X-ray photoelectroscopy (XPS). In addition, cyclic voltammetry (CV), Tafel polarization, and electrochemical impedance spectroscopy (EIS) were measured to correlate electrocatalytic activity to photovoltaic performance of DSSCs based on these PtNP/VGCF hybrid counter electrodes (CEs). Results indicated that PtNPs can enhance the thermal stability of VGCFs and were uniformly distributed over VGCFs with high porosity to provide large exposed surface area for redox reactions occurring within the films. VGCFs were found to benefit Pt reduction during annealing at 450 °C. A DSSC comprising the hybrid CE with a weight ratio of PtNPs to VGCFs of 3:7 (PV37) illustrated a higher solar-to-electricity efficiency of 7.77% in comparison to 7.31% for a conventional Pt CE or 3.79% for a pure VGCF CE. Electrochemical analyses demonstrated that PV37 CE featured the strongest electrocatalytic ability for the reduction of I3− to I− and the lowest Nernst diffusion resistance, confirming the highest power conversion efficiency among the samples evaluated.

A chemical bath deposition (CBD) method was applied to grow zinc oxide nanorod arrays on transparent conductive oxides acting as templates for the synthesis of TiO2/ZnO nanostructures (TiO2/ZNR) followed by HCl etching, and then these nanostructures were assembled as anodes in dye-sensitized solar cells. The ZnO nanorods, predominantly grew with good crystallinity along c-axis, exhibit wurtzite structure with smooth surface. Etching of the TiO2/ZNR by HCl changes the most preferential crystal plane of ZnO from (002) to (100) and significantly increases the atomic ratio of Ti/Zn. Optical absorption measurements indicate a band gap energy of 3.1 eV for ZNR and TiO2/ZNR. Increasing the spin coating time (SCT) of TiO2on ZNR increases the PL intensity. The seed layer number (SLN) of ZnO exerts moderate influence on the photo-to-electricity conversion and an optimum SLN was observed for this study.

In this work, we established the relationship between the thermally induced microstructure development and the photoluminescence efficiency (Ep) of the poly(9,9-dioctylfluorene) (PF8) fibers prepared from the semidilute PF8/chloroform solutions by direct electrospinning. The as-spun (AS) fibers were found to be composed of an amorphous phase and a significant fraction of mesomorphic β-phase, which may promote the Ep of PF8. The temperature-dependent wide-angle X-ray scattering (WAXS) measurement revealed that the PF8 fibers exhibited complex structural transformation on heating from the AS state, and there existed a strong correlation between Ep and the microstructure developed. The AS fibers exhibited the highest Ep value. The Ep decreased progressively on heating at temperatures below the cold crystallization temperature (Tcc), where the microstructure remained unperturbed. The β-phase transformed to γ- or α′-phase (Cγ-/Cα′-crystals) above Tcc, and such a structural transformation led to a reduction of ...

A chemical bath deposition (CBD) method was applied to grow zinc oxide nanorod arrays on transparent conductive oxides acting as templates for the synthesis of TiO2/ZnO nanostructures (TiO2/ZNR) followed by HCl etching, and then these nanostructures were assembled as anodes in dye-sensitized solar cells. The ZnO nanorods, predominantly grew with good crystallinity along c-axis, exhibit wurtzite structure with smooth surface. Etching of the TiO2/ZNR by HCl changes the most preferential crystal plane of ZnO from (002) to (100) and significantly increases the atomic ratio of Ti/Zn. Optical absorption measurements indicate a band gap energy of 3.1 eV for ZNR and TiO2/ZNR. Increasing the spin coating time (SCT) of TiO2 on ZNR increases the PL intensity. The seed layer number (SLN) of ZnO exerts moderate influence on the photo-to-electricity conversion and an optimum SLN was observed for this study.

We identified the conformational structure, aggregation behavior and photophysical properties of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) in various toluene/nonane solutions dependent on nonane content. In dilute solution region (e.g., below the overlap concentration, c*), static light scattering (SLS) revealed that the stiffness of MEH-PPV decreased as nonane content was increased, attributed to a stronger interaction force between MEH-PPV backbones. However, MEH-PPV chains presented a more extended-wormlike conformational structure in toluene. Therefore, a looser intermolecular micellelike aggregates occurred easily between the ether side chains of MEH-PPV at the concentration exceeded the overlapping concentration in toluene and toluene/nonane solutions. Nevertheless, at higher nonane content, the micellelike aggregates were became highly compacted by the π–π complex force between MEH-PPV backbones, dominating the dynamic behaviors and photophysical properties of MEH-PPV in toluene/nonane solution. These results proved that two types of segmental association with distinct stability were identified for the MEH-PPV/toluene/nonane solutions upon prolonged aging. The highly stable, which could not be disrupted by heating, was attributed to the interaction force between ether side chains of MEH-PPV in both solutions. Other type was a weaker affinity force through π–π complex, which could be disrupted thermally, making the micellelike aggregates more compact to form the network structure in MEH-PPV-enriched at higher nonane content.

The influence of electrodeposited time (EDT) on Ag–In–Se species growth onto TiO2 films for possible semiconductor-sensitized solar cells (SSSCs) application was investigated. XRD analysis illustrated that the Ag–In–Se film was predominantly comprised by AgInSe2 species with tetragonal body structure and crystal size of 6.05–7.50 nm when EDT was in the region of 15–60 min at a bias of −1.25 V (verse Hg/Hg2SO4 (MSE)). Scanning electron microscope (SEM) indicated a high porosity of AgInSe2/ITO morphology, permitting electrolytes freely percolated through these films. The prepared AgInSe2 films exhibited n-type semiconductor behavior with two band gap energies at 1.27 and 1.80 eV. Photoelectrochemical measurement reflected that open circuit potential varied little with EDT, however, significant change was associated with short circuit current and fill factor (FF), causing the AgInSe2/TiO2 films with EDT of 45 min exhibited the best solar to electricity conversion efficiency of 0.26%. The AgInSe2/TiO2 films with EDT of 45 min demonstrated the longest electron lifetime according to the open circuit voltage decay analysis.

In this study, we explore the orientation of crystals formed within the lamellar domains of a diblock copolymer composed of two crystallizable blocks, that is, poly(l-lactide)-block-polyethylene (PLLA-b-PE). The orientation of both PLLA and PE crystals with respect to the lamellar interface was examined under two types of crystallization condition with a broad range of crystallization temperatures (Tc). The first type was the “two-stage crystallization”, where the PLLA block was allowed to crystallize before PE. The second was the “one-stage crystallization”, where PLLA and PE blocks competed to crystallize. A homeotropic crystal orientation was always observed for the PLLA crystals, with the crystalline stems lying parallel to the lamellar normal regardless of the crystallization condition, except when Tc approached the glass-transition temperature of PLLA, where the orientation became random. A homogeneous crystal orientation with the PE crystalline stems oriented perpendicular to the lamellar normal wa...

A dual-emission nanoprobe that can sense changes in the environmental pH is designed based on the concept of pH-responsive Förster resonance energy transfer induced by the conformational transition of an associating polyelectrolyte, N-palmitoyl chitosan, bearing a donor (Cy3) or an acceptor (Cy5) moiety. We demonstrate that the developed pH-responsive nanoprobe can be used to ratiometrically image and thus discriminate the pH changes in the biological environment at different length scales.

We identified the formation of nanowhiskers of poly(3-hexylthiophene) (P3HT) in the gel with xylene in situ by means of small-angle X-ray scattering (SAXS). In the freshly prepared solution, the rodlike segments of P3HT were found to form local network aggregates characterized by the mass fractal dimension of ca. 2.5. Upon prolonged aging at room temperature, the originally viscous liquid solution transformed into a gel, in which a rodlike entity with the cross-sectional radius of gyration of 7.31 nm was disclosed. Real-space observation of the morphology of the film cast from the gel revealed the presence of long nanowhiskers. The fact that the width and height of these whiskers closely agreed with those of the rodlike entity in the gel deduced from model fitting of the SAXS profile indicated that the nanowhiskers were present in the wet gel. Time-resolved SAXS experiment revealed that the nanowhisker formation was accompanied by the crystallization of P3HT. The ultimate crystallinity attained in the nan...

The gelation behavior of the solution of a conjugated polymer, poly(9,9-dioctylfluorene) (PF8), with a poor solvent, methylcyclohexane (MCH), induced by aging at room temperature has been investigated. Light scattering and optical microscopy revealed that the gelation was driven by a macrophase separation occurred through a spinodal decomposition mechanism. Although the spinodal decomposition could proceed to the late stage, the interconnected morphology was arrested to give rise to the gel property of the system. The phase-separated gel was composed of an isotropic phase and a PF8-enriched liquid crystalline phase. The liquid crystalline phase was further found to consist of sheetlike aggregates (as revealed by small-angle X-ray scattering) in which a fraction of the PF8 chains formed the β-phase (as disclosed by the optical spectra) which dominated the photoluminescence spectrum of the gel. The PF8/MCH gel could be disintegrated by moderate heating to ca. 70 °C. This gel-to-sol transition was accompanie...

The crystallization behavior of the blends of two crystalline−amorphous diblock copolymers bearing chemically different crystalline block has been studied. A series of lamellae-forming blends of a ...

We probed the gelation and its effect on the photophysical property of a conjugated semiconducting polymer, poly(9,9-dioctylfluorene-2,7-diyl) (PF8), in toluene. The conformational structure characterized by the radius of gyration and the persistence length of PF8 in the dilute toluene solution depended strongly on temperature, where the conjugated chains exhibited a more extended conformation as the temperature was raised. The interchain interaction above the overlap concentration induced aggregation of PF8 to form network clusters in the solution. Gelation took place when the semidilute PF8 solutions were cooled and subsequently aged at −20 °C. The gel composed of the dynamically arrested PF8-enriched phase and the isotropic phase due to the occurrence of a macrophase separation at the subambient temperature. The PF8-enriched phase was mesomorphic, consisting of sheetlike aggregates or membranes. A fraction of the PF8 chains or segments within these sheetlike aggregates formed the β-phase which dominate...

Modified asphalts using polymeric additives, including isotactic polypropylene (iPP) and different degrees of chlorinated polypropylene (CPP), have been prepared and examined using differential scanning calorimetry (DSC), scanning electron microscopy (SEM), rotational viscometer, and dynamic shear rheometer (DSR) in this study. The results of DSC studies show that different levels of the crystallization occur in asphalt/iPP blends because most of the crystallinity of iPP remain intact in the blend, while those asphalt samples having CPP tend to affect the thermal behavior in the DSC thermograms because of increasing the amorphous region of CPP. From the images of SEM, the distinctions of the phase distributions between the asphalt/iPP and asphalt/CPP blends illustrate that the chlorine content in CPP is a significant factor in controlling its compatibility with asphalt. The rheological studies show that the asphalt blends containing CPP (26 wt% of Cl) exhibit higher viscosity in terms of higher temperature to get Newtonian behavior and display superior rutting resistance to avoid permanent deformation at high temperature. POLYM. COMPOS., 29:518‐524, 2008. a 2008 Society

The structure of poly(9,9-dioctylfluorene-2,7-diyl) (PF8) in deuterated toluene solutions at concentrations ranging from 0.60% to 7.0% (w/v) has been investigated by means of small-angle neutron scattering (SANS) and nuclear magnetic resonance (NMR) spectroscopy. PF8 chains exhibited aggregation above 1.0%, where the corresponding SANS profiles were characterized by the superposition of an aggregate component and a dynamic component associated with the transient network formed by interchain overlap. The 1H NMR resonance lines for both the polymer as well as for the residual protons in the solvent showed large upfield shift at higher concentrations, indicating strong polymer−solvent interaction. At a higher concentration (4.5%) an additional resonance line was observed in the aromatic regions of both the 1H and the 2H spectra that has been attributed to a residual anisotropic chemical shift of the solvent molecules. The later phenomenon is suggestive of the existence of magnetically anisotropic aggregate d...

The morphology and thermal properties of isothermal crystallized binary blends of poly(propylene-co-ethylene) copolymer (PP-co-PE) and isotactic polypropylene (iPP) with low molecular weight polyethylene (PE) were studied with differential scanning calorimeter (DSC), dynamic mechanical analysis (DMA), polarized optical microscopy (POM) and wide-angle X-ray diffraction (WAXD). In PP-co-PE/PE binary blends, however, the connected PE acted as a phase separating agent to promote phase separation for PP-co-PE/PE binary blends during crystallization. Therefore, the thermal properties of PP-co-PE/PE presented double melting peaks of PE and a single melting temperature of PP during melting trace; on the other hand, at cooling trace, the connected PE promoted crystallization rate because of enhanced segmental mobility of PP-co-PE during crystallization. At isothermal crystallization temperature between the melting points of iPP and PE, the binary blend was a crystalline/amorphous system resulting in persistent remarkable molten PE separated domains in the broken iPP spherulite. And then, when temperature was quenched to room temperature, the melted PE separated domains were crystallized that presented a crystalline/crystalline system and formed the intra-spherulite segregation morphology: these PE separated domains/droplet crystals contained mixed diluent PE with connected PE components. On the other hand, in the iPP/PE binary blends, the thermal properties showed only single melting peaks for both PE and iPP. Moreover, the glass transition temperature of iPP shifted to lower temperature with increasing PE content, implying that the diluent PE molecules were miscible with iPP to form two interfibrillar segregation morphologies: iPP-rich and PE-rich spherulites. In this work, therefore, we considered that the connected PE in PP-co-PE functioned as an effective phase separating agent for PP and diluent PE may be due to the miscibility between connected PE and diluent PE larger than that between PP and dispersed PE.

The isothermal crystallization kinetics and morphology development of isotactic polypropylene (iPP) blended with small loading of nanostructure of polyhedral oligomeric silsesquioxane (POSS) were studied with differential scanning calorimetry (DSC), polarized optical microscopy (POM), and wide-angle X-ray diffraction (WAXD). The crystallization behaviors of iPP/POSS composites presented an unusual crystallization behavior during isothermal and nonisothermal crystallization conditions. The exothermic morphologies of isothermal and nonisothermal crystallization of iPP/POSS composites changed remarkably with increasing POSS. Moreover, the developments of spherulitic morphology for iPP/POSS composites showed that the major dispersed POSS molecules became nanocrystals first and then aggregated together forming thread- or network-like morphologies, respectively, depending on POSS content, which was observed. It implies that these major POSS nanocrystals' morphologies appeared as an effective nucleating agent and promoted the nucleation rate of iPP, whereas the minor dispersed POSS molecules that had slight miscibility between iPP retarded the nucleation and growth rates of iPP in the remaining bulk region. Therefore, the isothermal crystallization showed a single exothermic peak at pure iPP and POSS-1.0, whereas at POSS-2.0 and POSS-3.0, displayed the multi-exothermic peaks during isothermal crystallization. These faces indicated that POSS molecules were both influence on the transport of iPP chain in the melted state and on the free-energy of formation the critical nuclei of iPP assisted by the POSS structures were observed. Therefore, we postulated that the crystallization mechanisms of multi-exothermic peaks in isothermal crystallization may proceed to combine the “ nucleating agent inducing nucleation of iPP event assisted by the POSS domains ” that the nucleation of iPP does occur preferentially on the surfaces of the POSS “threads” or “networks” structures, and “ nucleation and growth of iPP in the remaining bulk melted iPP region retarded by dispersed POSS molecules ”. Therefore, effects of POSS content on the isothermal and nonisothermal crystallization behaviors of iPP/POSS composites due to the POSS molecules partially miscible with iPP, at very small loading of POSS molecules, promoted or retarded the rates of nucleation and growth of iPP depending on the POSS content and crystallization temperature were discussed.

In this work, the effect of cononsolvency on the phase transition and preferential adsorption phenom- enon behaviors of poly(N-isopropylacrylamide)/methanol/ water ternary solutions was studied. In this cononsolvent system, the DV E , DG m , and v12 values show a nonlinear behavior and the minimum values of DV E and DG m , while the maximum value of v12 at /2 is around 0.7. These facts indicated that one water molecule could directly bond with one methanol molecule to form the H2O� � MeOH complex. The H2O� � MeOH complex structure was found to remarkably affect the phase transition of poly(N-isopro- pylacrylamide) (PNIPAM) in ternary solution. However, at the composition of mixed cononsolvent, /2 0.7, the PNIPAM molecules may preferentially adsorbed pure methanol molecules. PNIPAM ternary solutions were transparent and no transition occurred in this region. This indicates that the PNIPAM coils exhibited a much-extended confor- mation in solutions. In contrast, at 0.2 < /2 < 0.4 and 0.4 < /2 < 0.7, PNIPAM molecules preferentially adsorbed water and methanol molecules, respectively, and also adsorbed large amount of H2O� � MeOH complexes. In these regions, the clathrate-like structure around the side chain of PNIPAM molecule became more defected with adsorbing H2O� � MeOH complex. Therefore, we consid- ered that the various thermodynamic behaviors between PNIPAM and mixture solvents must be related different preferential adsorption phenomena, which were mainly related to different degrees of polymer-solvent interaction and structures of solvent used. 2007 Wiley Periodicals, Inc. J Appl Polym Sci 107: 2732-2742, 2008

Semirigid conjugated polymers have received much scientific and technological interest due to their unique electrical and photonic semiconducting properties. Spectroscopic studies have indicated that these polymers underwent interchain aggregation in the solution state even at large dilution; however, the origin of this event and the structure of the resultant aggregates remained the crucial issues to be resolved. In the present study, we revealed that the interchain aggregation of a conjugated polymer, poly(2,3-diphenyl-5-hexyl-1,4-phenylenevinylene) (DP6-PPV), in solutions with chloroform and toluene generated network aggregates with the hydrodynamic radii of several micrometers. Small angle neutron scattering (SANS) demonstrated that the internal structure of these aggregates could be characterized by the mass fractal dimensions of 2.2-2.7. The networks were looser in chloroform but became highly compact in the poorer toluene solvent due to severe segmental association. Increasing the temperature alleviated the segmental association in toluene while largely retaining the mass fractal dimension of the aggregates. However, the interchain aggregation was never completely dissipated by the heating, suggesting the existence of two types of segmental association with distinct stability. The highly stable segmental association that could neither be solvated by chloroform nor be disrupted thermally in toluene was attributed to the pi-pi complex already present in the DP6-PPV powder used for the solution preparation. The chains tied firmly by this complex formed network aggregates in the solution and hence reduced the entropy of mixing of the polymer. In the poorer toluene solvent, further segmental association took place within the preexisting aggregates, making the networks more compact. This type of segmental association could be disrupted by moderate heating, and its occurrence was ascribed to the poor affinity of the aliphatic side chains of DP6-PPV for toluene.

The crystallization kinetics and morphology development of pure isotactic polypropylene (iPP) homo- polymer and iPP blended with atactic polypropylene (aPP) at different aPP contents and the isothermal crystallization temperatures were studied with differential scanning calo- rimetry, wide-angle X-ray diffraction, and polarized opti- cal microscopy. The spherulitic morphologies of pure iPP and larger amounts of aPP for iPP blends showed the neg- ative spherulite, whereas that of smaller amounts of aPP for the iPP blends showed a combination of positive and negative spherulites. This indicated that the morphology transition of the spherulite may have been due to changes the crystal forms of iPP in the iPP blends during crystalli- zation. Therefore, with smaller amounts of aPP, the spher- ulitic density and overall crystallinity of the iPP blends increased with increasing aPP and presented a lower de- gree of perfection of the g form coexisting with the a form of iPP during crystallization. However, with larger amounts of aPP, the spherulitic density and overall crystallinity of the iPP blends decreased and reduced the g-form crystals with increasing aPP. These results indicate that the aPP molecules hindered the nucleation rate and promoted the molecular motion and growth rate of iPP with smaller amounts of aPP and hindered both the nucleation rate and growth rate of iPP with larger amounts of aPP during isothermal crystallization. 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1093-1104, 2007

Epoxy/TiO2 composites were prepared by solution mixture method, in which epoxy resin and nano-TiO2 liquid were mixed in the presence of methyl isobutylketone. According to the experimental results, hydrogen bonds can be formed by mixing TiO2 particles and epoxy resin. The SEM analysis suggests that TiO2 particles are uniformly distributed within the material, while some silver streaks occur at the surface of materials. Besides, thermo-resistance and mechanical property of materials are found to improve with the addition of TiO2, but degrades if the nano-TiO2 is the excess of 3%. Furthermore, these properties can be improved with the increasing concentration of methyl isobutylketone. POLYM. COMPOS., 27:195–200, 2006. © 2006 Society of Plastics Engineers.

The thermal properties and morphological development of isothermally crystallized isotactic polypropylene (iPP) blended with nanostructured polyhedral oli- gomeric silsesquioxane (POSS) molecules at very small loading of POSS were studied with differential scanning calorimeter (DSC), thermal gravimetric analysis, dynamic mechanical analysis, polarized optical microscopy (POM), and wide-angle X-ray dif- fraction (WAXD). The result of DSC indicated that the crystallization rate of iPP increases with the increase in POSS contents during crystallization; moreover, the melting temperature of iPP/POSS nanocomposites slightly decreases, while the heat of fusion increases with the addition of POSS molecules at melting and remelting traces. The storage modulus and thermal stability, respectively, remarkably decrease, while the glass transition temperature of isothermally crystallized iPP/POSS nano- composites increases slightly with the increase in POSS contents. The morphologies results of WAXD and POM show that the POSS molecules form about 35 nm sized nanocrystals and aggregate to form thread-like and network structure morphologies, respectively, in the molten state even when the POSS content is very small. These results, therefore, suggest that the interaction force between the POSS molecules should be larger than the force between POSS molecules and iPP matrix; however, those interactions depend on the chain length of functionalized substituents on the POSS cage. Therefore, the POSS molecules aggregate forming nanocrystals and act as an effective nucleating agent for iPP and influence the thermal properties of iPP/ POSS nanocomposites due to the shorter chain length of functionalized substituents

The purpose of this study was to research the compatibility and application of polyvinylpyrrolidone (PVP)/chitosan blended polymers. The polymers were synthesized at different weight ratios and tested using techniques such as Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis to evaluate the compatibility of the blended materials. Incompatibility occurred when the quantity of chitosan exceeded 75%. The addition of PVP was beneficial for the thermal stability of chitosan, but resulted in inferior strength performance. Furthermore, the blended polymers did not show a color-enhancement effect, but did show elevated water absorption, chlorine resistance, and colorfastness. In addition, the treated fabrics with a higher chitosan ratio in the blended polymer had antimicrobial properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 885–891, 2006

The thermal properties and morphology development of isotactic polypropylene (iPP) homopolymer and blended with low molecules weigh atactic polypropylene (aPP) at different isothermal crystallization temperature were studied with differential scanning calorimeter and wide-angle X-ray scattering. The results of DSC show that aPP is local miscible with iPP in the amorphous region and presented a phase transition temperature at TcZ120 8C. However, below this transition temperature, imperfect a-form crystal were obtained and leading to two endotherms. While, above this transition temperature, more perfect a- and g-form crystals were formed which only a single endotherm was observed. In addition, the results of WAXD indicate that the contents of the g-form of iPP remarkably depend both on the aPP content and isothermal crystallization temperature. Pure iPP crystallized was characterized by the appearance of a- and g-forms coexisting. Moreover, the highest intensity of second peak, i.e. the (0 0 8) of g-form coexisting with (0 4 0) of a-form, and crystallinity were obtained for blended with 20% of aPP, the g-form content almost disappeared for iPP/aPP blended with 50% aPP content. Therefore, detailed analysis of the WAXD patterns indicates that at small amount aPP lead to increasing the crystallinity of iPP blend, at larger amount aPP, while decreases crystallinity of iPP blends with increasing aPP content. On the other hand, the normalized crystallinity of iPP molecules increases with increasing aPP content. These results describe that the diluent aPP molecular promotes growth rate of iPP because the diluent aPP molecular increases the mobility of iPP and reduces the entanglement between iPP molecules during crystallization. q 2005 Elsevier Ltd. All rights reserved.

Modified asphalts using polymeric additives, such as isotactic polypropylene (iPP) and maleated polypropylene (MPP), for asphalt binders were prepared and characterized for potential usages in pavement construction. The differential scanning calorimetry (DSC) studies show that most of the crystallinity of iPP remains intact in the asphalt binders, but MPP exhibits more interaction with the asphalt due to the increase of the amorphous region of MPP. The phase distributions and rheological properties of the modified asphalts were examined by scanning electron microscope (SEM) and dynamic shear rheometer (DSR), respectively. The images of SEM show that the MPP-rich phase is larger than the iPP-rich phase in asphalt blends, which contributes to more dispersion of the polymer into the asphalt phase in the asphalt/MPP blend. From the rheological studies, the asphalt blends containing iPP exhibit higher viscosity in terms of higher temperature to get Newtonian behavior and have a higher performance grade for rutting resistance at high temperature and frequency. POLYM. ENG. SCI., 45:1152–1158, 2005. © 2005 Society of Plastics Engineers

An assay of biomarkers consisting of alpha-fetoprotein (AFP) is reported. Real-time measurements of the effective relaxation timeτeff, when the biofunctionalized magnetic nanoparticles (BMNs) were conjugating with biotargets, were made. The BMNs are anti-alpha-fetoprotein (antiAFP) coated onto dextran-coated iron oxide nanoparticles labeled as Fe3O4-antiAFP. It was found that the effective relaxation time,τeff, increases as the association of AFP and Fe3O4-antiAFP evolves. We attribute this to the enhanced Brownian motion of BMNs when magnetic clusters are present during the conjugation. We found that saturation magnetization,Ms, increases when the concentration of AFP increases. This is due to the fact that more magnetic clusters are associated in the reagent, and therefore theMsincreases when the concentration of AFP increases. The change of effective relaxation time and saturation magnetization shows a behavior of logistic function, which provides a foundation for assaying an unknown amount of biomolecules. Thus, we demonstrate sensitive platforms for detecting AFP by characterizingτeff. The detection platform is robust and easy to use and shows promise for further use in assaying a broad number of biomarkers.

In this work, the aggregation behavior of polyvinyl chloride/dioxane (PVC/DOA) solution was discussed through light scattering and viscometric measurements. From the static light scattering results, PVC/DOA solution has a negative value of the second virial coefficient, A2 value (ca. 23:65 £ 10 24 cm 3 mol g 22 U at 308C, implying that a repulsive force appeared between PVC chains and DOA. The dynamic light scattering results indicate that the dynamic behavior of PVC solution could be classified into three regions by increasing the concentration of PVC. In the infinite dilution region,âhaC , 1; the single relaxation mode is considered related to the translational diffusion of the individual PVC coil. In the hydrodynamic screen region, 1 ,âhaC , 4; the relaxation time distribution was divided into two major relaxation modes; i.e. the fast mode resembled that of the individual PVC coil in the dilute solution, and the slow mode is considered related to the cluster formed from the aggregation of several individual coils. At higher concentrations, âhaC . 4; the polymer coils start to overlap and entangle further, then the third relaxation mode due to the transient gel network originated from the aggregation of the clusters in the concentrated solution was observed. On the other hand, the relative amplitudes of middle and slow modes for semi-dilute solutions decrease with increasing temperature. At a temperature of about 508C, only a broad relaxation mode was observed indicating that intermolecular aggregation is disintegrated with increasing temperature, but the intramolecular aggregation of an isolated chain still exists due to the poor affinity of DOA to PVC chains in this temperature region. The poor solubility of the solvent used should be more favorable to the intramolecular aggregation of PVC chains, resulting in comparatively complex dynamic behaviors in semi-dilute solutions. q 2000 Elsevier Science Ltd. All rights reserved.

In this work, the effects of polymer–solvent interaction on the aggregation behaviour of poly(vinyl chloride) (PVC) solutions were studied through elastic light-scattering and viscosity measurements. The resulting Zimm plots of PVC solutions showed that the value of the second virial coefficient, A2, of PVC/bromobenzene (BrBz) solution is higher than that of PVC/dioxane (DOA) solution at the same temperature. The radius of gyration, Rg, in PVC/BrBz solution is larger than in PVC/DOA solution, indicating that PVC chains in a good solvent (BrBz) must be more extended than those in a poor solvent (DOA). The θ temperatures are about 32°C and 68°C for PVC/BrBz and PVC/DOA solutions, respectively. The resulting temperature dependence of Rg showed that PVC/BrBz solution exhibits the coil–globule transition, while no transition is observed in PVC/DOA solution in the temperature measuring range. The chain overlapping concept was used to discuss the degree of heterogeneity of PVC solutions. The results showed that PVC/DOA solution is more heterogeneous than PVC/BrBz solution. Time-resolved light-scattering measurements indicated that the spinodal decomposition rate of PVC/DOA solution was faster than that of PVC/BrBz solution. However, the gelation time of PVC/BrBz solution was shorter than that of PVC/DOA solution. These facts may imply that the more extended chains in PVC/BrBz solution are advantageous to the intermolecular association necessary for gelation. The scattered profiles (I(q) vs. q) showed that the scattered intensity of PVC/DOA solution is much higher than that of PVC/BrBz solution at the same concentration. A scattered maximum was observed in PVC/DOA solution while no other peak appeared in PVC/BrBz solution. The different aggregation or gelation behaviour observed for PVC/DOA and PVC/BrBz solutions must be concerned with different degrees of spinodal decomposition in the solution state, which is mainly related to the different degrees of polymer–solvent interaction.

In this work, the network structure and chain mobility of dried polyvinyl chloride/dioxane (PVC/DOA) gels prepared by the freeze-drying method are studied by SEM, FT i.r., WAXD, EDTA and pulsed NMR analyses. The results of FT i.r. and WAXD show no remarkable change in the crystallinity of either dried or wet PVC gels; however, the elasticity of wet gels and the gelation time of semi-dilute solutions exhibit remarkable changes with increasing concentration, C and molecular weight, M w of the polymer. From SEM results, the dried gel morphology consists of a fibril-like structure and the mesh size of the gel network decreases, resulting in the glass transition temperature ( T g ) shifting to higher temperatures with increasing M w and C . The results of pulsed NMR (CPMG method) for wet gels show that spin–spin relaxation time, T s 2 and T l 2 , respectively, related to the immobile and mobile components decrease, and the fractional amount of the immobile component, f l increases, while that of the mobile component, f f decreases with increasing M w and C . On the other hand, similar results are also found in freeze-dried gels from the pulsed NMR experiment (FID method). These facts in both wet and dried gels are considered to be due to the reduction of chain mobility related to the increase in the aggregation of polymer chains or the number of junction points in the gel network. The change in elasticity of PVC/DOA gels must be mainly related to the chain mobility of the network structure but not to the crystallinity of gels.

In this study, the relationship between the polymer-solvent interaction and the network structure of poly(vinyl alcohol) (PVA) gels prepared with organic solvents such as N-methylpyrrolidone (NMP) and ethylene glycol (EG) are investi- gated. The values of the intrinsic viscosity (h) and Huggins constant k* of dilute PVA solutions indicate that the attractive interaction between PVA and NMP is higher than that between PVA and EG. The X-ray result shows that PVA-EG gels have a (101) diffraction peak of PVA crystal that appeared at about 2uA 197, while PVA-NMP gels only show a broad amorphous scattering peak. On the other hand, Fourier transform infrared results of PVA/EG gels also clearly show an intense peak at 1141 cm 01 due to the crystalline absorption. The results of H 1 pulsed nuclear magnetic resonance show that the spin-spin relaxation time, T s and T l, respectively, related to the poly- mer-rich and polymer-poor components decrease, and the fractional amount of the polymer-rich component, f s , increases, while that of the polymer-poor component, f l , decreases with an increase in the concentration of polymer. At a given concentration, the value of f s in the PVA-EG gel is larger than that in the PVA-NMP one. These facts indicate that the crystallinity in the PVA-EG gel is higher than that in the PVA- NMP gel, implying that the aggregation of PVA chains is much easier in the poor solvent, EG, than in the good solvent, NMP. The structural change with aging time in the PVA-EG gel is very remarkable because of the significant syneresis, indicating that the opaque PVA-EG gel with higher crystallinity has a comparatively heteroge- neous and unstable network structure than the PVA-NMP gel does. q 1998 John Wiley &

In this work, the structure and drawability of dried formalized gel films prepared from the formalization of high molecular weight polyvinyl alcohol (PVA) aqueous solutions were studied. Structure changes in PVA crystal were found in the formalized samples, i.e., the spacing of the (100) plane for PVA crystal became much larger while that of the (020) plane became smaller, indicating that some disordered crystals were formed from formalized PVA chains. The crystal relaxation temperature, Tαc, and its dependence on the draw ratio in formalized films were lower than those in original the PVA. Irrespective of the lower crystalline properties and the crystal relaxation temperature, the drawability of formalized PVA films could not be improved. The crystal orientation function, fc, decreased as the degree of formalization at a given draw ratio was increased, indicating that the acetal groups in the amorphous region must be a hindrance to the drawing of the formalized PVA. These results implied that the drawability of PVA is not only related to the properties of the crystalline region but also to those of the amorphous region.

In this work, the structure and physical properties of polyvinyl chloride (PVC) gels prepared from the solutions of bromobenzene (BrBz) and dioxane (DOA) under different gelation conditions are studied. The average size of the junction point for PVC gels in the initial gelation state are the combination of ca. two to three chains in width and ca. six to eight syndiotactic sequences in length to form a fibril-like network structure, irrespective of the species of solvents used, the molecular weight and the concentration of the polymer. Because the size of the junction point/microcrystal is too small, the results of wide angle X-ray diffraction (WAXD) shows only a broad intensity peak, implying that the crystallinity is very low for PVC gels. However, the X-ray intensity peak of amorphous scattering in PVC/DOA gel is sharper than that in PVA/BrBz gel, indicating that PVC/DOA gel has a thicker network structure due to a larger degree of polymer aggregation. The morphology of the gel is investigated from the observation of dried gel prepared from the freeze-drying method using electron microscopy. The results show that the gel morphology consists of a fibril-like structure and the mesh size of the network decreases with increasing polymer concentration. The difference in physical properties, such as the modulus of gels, may be considered to be mainly due to the aggregation degree of amorphous chains related to the solvent type, the concentration and molecular weight of polymer.

Vertically aligned ZnO/TiO2(VA-ZnO/TiO2) core-shell composites deposited on ZnO-seeded indium tin oxide (ITO) glasses have been synthesized by a chemical bath deposition approach for growing one-dimensional ZnO structure followed by a spin procedure for coating TiO2on the surface of ZnO structure. The influences of the cycles of spin coating of TiO2(CSCT) on the properties of VA-ZnO/TiO2and performances of the assembled DSSCs were studied. The power conversion efficiency of the VA-ZnO/TiO2-based DSSC measured under illumination of 100 mW/cm2and AM 1.5 can reach 0.81%, representing 93% improvement when compared with that of the pristine VA-ZnO electrode (0.42%). The intensity-modulated photocurrent spectroscopy (IMPS) and electrochemical impedance spectroscopy (EIS) were applied to study the kinetics and interfacial transfer of the photogenerated electrons. Both the photocurrent and power conversion efficiency correlate well with the steady state electron density. Enlargement in surface area and dye adsorption, suppression of dissolution of Zn2+, diminishment in electron recombination, and fast transfer of injected electrons from excited dyes to TiO2conduction bands arising from coating TiO2on VA-ZnO are regarded as the predominant causes for this improvement.

We investigated the gelation behavior of the blend of two light-emitting polyfluorenes, i.e., poly(9,9-dioctylfluorene-2,7-diyl) (PF(8)) and poly[9,9-di(2-ethylhexyl)-fluorenyl-2,7-diyl] (PF(2/6)), in solutions with methylcyclohexane (MCH). Upon prolonged aging at room temperature, dynamic light scattering revealed that phase separation in the initially well-mixed solutions occurred via spinodal decomposition, yielding a PF(8)/PF(2/6)-enriched phase and an isotropic solvent-rich phase. Sheetlike aggregates in which a portion of the PF(8) chains adopted the β conformation were formed in the polymer-enriched phase, as revealed by small-angle X-ray scattering and optical spectroscopy. Macroscopically, the phase separation transformed the original viscous liquid solution into a gel. Measurements of the gelation temperature (T(gel)), gel-to-sol transition temperature (T(g-s)), and spinodal decomposition temperature (T(SD)) indicated that gelation (and hence phase separation) became more difficult with increasing content of PF(2/6). The presence of PF(2/6) also hindered formation of the β-phase of PF(8.) Therefore, the microstructure and photophysical properties of PF(8)/PF(2/6) in MCH solution can be tuned by the composition of the two polymers.

The conformational structure and the interchain aggregation behavior of a semirigid conjugated polymer bearing a decyl side chain, poly(2,3-diphenyl-5-decyl-1,4-phenylenevinylene) (DP10-PPV), in solutions with chloroform and toluene have been investigated by means of small-angle neutron scattering (SANS), static light scattering (SLS) and dynamic light scattering (DLS). The radius of gyration, persistence length, and the second virial coefficient of the polymer in dilute solution as determined by SLS were higher in chloroform than in toluene; consequently, the polymer assumed a more extended wormlike chain conformation in the former. The difference in the strength of interaction in the two solvents gave rise to contrasting aggregation behavior of the polymer in the semidilute regime. While only a minor fraction of the polymer underwent segmental association in chloroform, a considerable fraction of it formed clusters (microgels) with several micrometers in size in toluene. These clusters were further found to consist of sheetlike nanodomains. Compared with the DP-PPV bearing a shorter hexyl side chain, DP6-PPV, the aggregates of DP10-PPV in toluene were weaker as they could be easily disrupted by moderate heating. This was attributed to a lack of strong pi-pi interaction between the DP10-PPV segments due to the greater steric hindrance imposed by the longer decyl side chains.

Segments of conjugated polymers display the propensity to aggregate in solutions with common organic solvents. Here we revealed that the segmental aggregation of a conjugated polymer, poly(9,9-bis(2-ethylhexyl)fluorene-2,7-diyl), (PF2/6), in toluene was stabilized by the polymer-solvent complex formation through pi-pi stacking induction of solvent molecules and polymer segments. In this case, a portion of the solvent was trapped inside the aggregate domains upon bringing the system to the subambient temperatures. The residence time of these associated solvent molecules became long enough to yield a separate upfield-shifted NMR resonance. The line-shape of this resonance revealed alignment of the polymer segments in the aggregates. A portion of the solvent was frozen in the compact structure due to the formation of strong polymer-solvent complex.