Length scale effect of PCL-PB-PCL on the light scattering and dynamics of network

The effect of length scale of triblock oil-soluble polymer (poly (ε-caprolactone)–poly butadiene-poly (ε-caprolactone)) (PCL-PB-PCL) on the properties of a water-in-oil (W/O) droplet microemulsion (R ~ 5.5 nm) has been studied as a function of the amount of added telechelic polymer. Small-angle X-ray scattering (SAXS) measurements show that the size of the droplets is not affected by the polymer addition but it induces attractive interactions at low concentration and repulsive ones at high polymer content. Measurements of the diffusion coefficient by dynamic light scattering (DLS) show different relaxations in mixed systems. The fast diffusion coefficient increases with increase in polymer concentration. At higher polymer content, the network formation leads to an additional slow relaxation mode in DLS that can be related to the formation of clusters of microemulsion droplets interconnected by the polymer. The collective diffusion of slow relaxations decreases with increase of polymer concentrations.     

Light scattering and SAXS of spherical to cylindrical transition of AOT/H2O/cyclohexane/PI

The mixture of polyisoprene with sodium-2-diethylhexyl sulfosuccinate (AOT)/H₂O/cyclohexane microemulsion is studied with the photon correlation spectroscopy (PCS) and small angel X-ray scattering (SAXS). The water with AOT induces nano-droplets inside the cyclohexane and addition of concentration and length scale of polyisoprene (PI) can change diffusion of nano-droplets. The collective diffusion coefficient (D_c) of nano-droplets decreased with increase in concentration of PI. From SAXS experiment, a spherical–cylindrical transition of nano-droplets by increase in polyisoprene concentrations observed that it can describe behaviour of diffusion.     

Length scale of polyisopirene and dynamic light scattering and structure of sodium-2-diethylhexyl sulfosuccinate/water/decane

The mixture of polyisopirene (PI) and sodium-2-diethylhexyl sulfosuccinate /decane/water microemulsion (ME) at AOT to water molar ratio (X = 30) and droplet mass fraction (m_f,drop = 0.08) was studied with dynamic light scattering and small-angle X-ray scattering (SAXS). The light scattering was used to obtain the diffusion coefficient of Brownian motion of the nano-droplets at different polymer concentrations and molecular weights (1000 and 4700) in the ME. The dynamics of the nano-droplets decreased with the increase of molecular weight (from 1000 to 4700) and concentration (from 0.01 to 0.09) of PI. The study of the structure by SAXS showed that with increase of PI (MW = 1000) mass fraction from 0.01 to 0.09 at ME, the size of the droplets changes from 4.5 to 4.3 nm and with increase of PI (MW = 4700) concentration at ME, the size of droplets changes from 4.8 to 4.4 nm. The size ratio of droplets to polymer decreased with increase of concentration and molecular weight of polymer and also the interaction between the droplets increased with increase of polymer concentration.     

Light scattering from swollen textured polymer network composites

Light scattering from a swollen textured heterogeneous polymer network is discussed using example of a network composite filled by spherical inclusions anisotropically distributed in the matrix. The dependence of the scattering intensity on the Fourier transform of the correlation function dry-state shear moduli fluctuations has been established. H_v scattering patterns from uniaxial textures and their ratio with the composite anisotropy parameter are analyzed. The sensitivity of the H_v scattering pattern on restrictions during the swelling is emphasized. © 1993 John Wiley & Sons, Inc.     

Light scattering study of complex formation between protein and polyelectrolyte at various ionic strengths

Formation of protein-polyelectrolyte complexes (PPCs) between bovine serum albumin (BSA) and potassium poly (vinyl alcohol) sulfate (KPVS) was studied at pH 3 as a function of ionic strength. Turbidimetric titration was employed by a combination of dynamic light scattering (DLS) and electrophoretic light scattering (ELS). The formal charge (Z(PPC)) of the resulting PPCs at different ionic strengths were estimated from ELS data by assuming the free draining and the non-free draining model. The radius of a BSA molecule in the complex was used in the former model for calculation of Z(PPC) with the Henry's equation, while in the latter case the hydrodynamic radius of a PPC particle determined from DLS was employed. The results obtained were compared with the Z(PPC) values calculated using a relation of Z(PPC)=n(b)Z(BSA)+alphaZ(KPVS), where Z(BSA) (> or =0) and Z(KPVS) (< or =0) denote the formal charge of BSA and KPVS, respectively. Moreover, n(b) is the number of bound proteins per complex composed of alpha polymer chains. It was suggested that the PPC between BSA and KPVS behaves as a free draining molecule during the electrophoresis, at least at a high ionic strength. Also suggested is that the PPC formation at low ionic strength follows a 1:1 stoichiometry in the charge neutralization.     

Preparation and characterization of SiO2 two-step aerogels

Aerogels are well suited as transparent insulation materials in solar architecture and collector systems. Their nanoporous structure provides a high solar transmittance and a low thermal conductivity, generally below 0.02 W m^–1 K^–1. Transparent aerogels with densities above 80 kgm^–3 can easily be prepared at room temperature via a one-step sol-gel process with subsequent supercritical drying. Separating hydrolysis and condensation via a two-step method allows the preparation of transparent ultra-low density SiO₂-aerogels. To optimize the optical properties, characterized by the scattering coefficient of the gels, we have investigated the influence of preparation parameters, such as pH-value of the sol-gel starting solution and macroscopic density, on the gel structure. To determine the nanostructure we performed spectral light scattering as well as small angle X-ray scattering (SAXS) measurements.     

Light scattering studies of copolymers. 1. Soluble hemoglobin--dextran complexes

Complexes between dextrans of different molar mass and bovine hemoglobin were synthesized by two different methods. In the alkylation method three and in the dialdehyde method, two hemoglobins are coupled on average to one dextran molecule. In both cases, the soluble hemoglobin-dextran complexes reversibly bind and release oxygen; the oxygen affinity is greater than that of free hemoglobin. Static and dynamic light scattering was used to determine the average molar mass M_u, the radius of gyration 〈S〉, and the hydrodynamic radius R_h of both the complexes and the single dextrans. Interpretation of these data is complicated due to the fact that the complexes are copolymers. When appropriate approximations are made, the results indicate that the complexes have a spherical shape and an internal structure of a multiple-chain network, where several dextrans are linked together by the hemoglobins. The number of single dextrans per complex increases as the molar mass of the single dextrans is decreased. The increment is greater in the dialdehyde than in the alkylation method. The probable reason is that in the dialdehyde method one hemoglobin can connect many dextrans simultaneously while in the alkylation method a hemoglobin is able to link maximally two dextrans. The ratio of the radius of gyration to the hydrodynamic radius decreases as the temperature is increased. This suggests a decrease of the solvent penetration length for the complexes and can be interpreted on the basis of the Deutsch-Felderhof theory for porous spheres. © 1994 John Wiley & Sons, Inc.     

Light scattering near and from interfaces using evanescent wave and ellipsometric light scattering

The broad range of interface light scattering investigations in recent years shows the power and the versatility of these techniques to address new and open questions in colloid and interface science and the soft condensed matter field. Structural information for polymers, liquid crystals, or colloids close to planar or spherical colloidal interfaces are either captured with long range light scattering resolution, or in a complementary approach by high resolution ellipsometric techniques. Of special interest is the dynamic behavior close to or in interfaces, since it determines material properties and responses to external fields. Due to the broad dynamical range and the high scattering contrast for visible light, interface light scattering is a key to elucidate soft matter interfacial dynamics. This contribution reviews experimental and related theoretical approaches for interface light scattering and further gives an overview of achievements based on such techniques.     

Network formation studied by temperature scanning Brillouin scattering and differential scanning calorimetry techniques. I. The cure of 1,4-butanediol diglycidyl ether with cis-1,2-cyclohexanedicarboxylic anhydride initiated by triethylamine

The network formation process of the triethylamine-initiated reaction of 1,4-butanediol diglycidyl ether with cis-1,2-cyclohexanedicarboxylic anhydride has been investigated by conventional differential scanning calorimetry and temperature scanning Brillouin light scattering as a new experimental method for the estimation of the reaction's conversion factor. The time-temperature evolution of the observed quantities (reaction enthalpy in the calorimetric measurements and hypersound velocity in the light scattering) reflects in both sets of experimental data, but results in different kinetic parameters obtained by the assumption of an Arrhenius behavior. These differences are ascribed to the relation of the observed properties with respect to the evolution of the reaction. The enthalpy production of the system observed in the calorimetric experiment is shown to be connected directly to the chemical reaction, whereas the change in the hypersound velocity measured by the light scattering method is sensitive to the solidification of the system. © 1995 John Wiley & Sons, Inc.     

Dynamic light scattering and small-angle neutron scattering studies on organogels formed with a gelator

Small-angle neutron scattering (SANS) and light scattering studies were carried out on an organogel consisting of a gelator, coded P-1, and dimethyl sulfoxide (DMSO). The gelator was made of an oligosiloxane stem and about eight branches of an amino acid derivative combined with a long alkyl chain. The amino acid part, N-n-pentanoyl-L -isoleucylaminooctadecane, was responsible for intermolecular association via hydrogen bonding between amide groups. After the complete dissolution of P-1 in DMSO at 85 °C, the solution was cooled, and the variations of the scattered light intensity were monitored as a function of the temperature. The scattered intensity increased drastically at about 40 °C when the P-1 concentration (C) was 3.5 g/L, and this indicated gel formation. The SANS results showed that the scattering intensity function was a monotonically decreasing function, regardless of C. A master relationship of the scattering intensity was obtained with respect to C. These scattering studies disclosed the following facts. First, gelation could be monitored as an abrupt increase in the intensity. Second, the gel was composed of randomly oriented bundlelike clusters. Third, the structure factor could be reduced by the gelator concentration, and this indicated the presence of a self-similar structure across the gelation threshold. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1841–1848, 2004     

Light scattering study of solubilization of organic molecules by block copolymer micelles in aqueous media

Block copolymers, when dissolved in a selective solvent, form spherical micelles. These micelles can selectively solubilize organic molecules otherwise insoluble in the pure solvent. In this study, we report solubilization of organic molecules by styrene-methacrylic acid block copolymer micelles in aqueous buffers. A light scattering technique was developed to determine the extent of micellar solubilization. Our results indicate that the extent of micellar solubilization depends on the chemical nature of organic molecules, specifically, on the interactions between the organic compound and polystyrene. A thermodynamic model has been developed to describe micellar solubilization. The theoretical calculation agrees reasonably well with the experimental results for two micellar samples examined. ©1995 John Wiley & Sons, Inc.     

Structural Characterization of Biomaterials by Means of Small Angle X-rays and Neutron Scattering (SAXS and SANS), and Light Scattering Experiments

Scattering techniques represent non-invasive experimental approaches and powerful tools for the investigation of structure and conformation of biomaterial systems in a wide range of distances, ranging from the nanometric to micrometric scale. More specifically, small-angle X-rays and neutron scattering and light scattering techniques represent well-established experimental techniques for the investigation of the structural properties of biomaterials and, through the use of suitable models, they allow to study and mimic various biological systems under physiologically relevant conditions. They provide the ensemble averaged (and then statistically relevant) information under in situ and operando conditions, and represent useful tools complementary to the various traditional imaging techniques that, on the contrary, reveal more local structural information. Together with the classical structure characterization approaches, we introduce the basic concepts that make it possible to examine inter-particles interactions, and to study the growth processes and conformational changes in nanostructures, which have become increasingly relevant for an accurate understanding and prediction of various mechanisms in the fields of biotechnology and nanotechnology. The upgrade of the various scattering techniques, such as the contrast variation or time resolved experiments, offers unique opportunities to study the nano- and mesoscopic structure and their evolution with time in a way not accessible by other techniques. For this reason, highly performant instruments are installed at most of the facility research centers worldwide. These new insights allow to largely ameliorate the control of (chemico-physical and biologic) processes of complex (bio-)materials at the molecular length scales, and open a full potential for the development and engineering of a variety of nano-scale biomaterials for advanced applications.     

Light Scattering Probes of Viscoelastic Fluids and Solids

In this article, we discuss recent advances in static and dynamic light scattering applied to soft materials. Special emphasis is given to light scattering methods that allow access to turbid and solid‐like systems, such as colloidal suspensions, emulsions, glasses, or gels. Based on a combination of single‐ and multispeckle detection schemes, it is now possible to cover an extended range of relaxation times from a few nanoseconds to minutes or hours and length scales below 1 nm up to several microns. The corresponding elastic properties of viscoelastic fluids or solid materials range roughly from below 1 Pa to several 100 kPa. Different applications are discussed such as light scattering from suspensions of highly charged colloidal particles, colloid and protein gels, as well as dense surfactant solutions.     

Light scattering studies of stereocomplex formation of stereoregular poly(methyl methacrylate) in solutions

The structure and stereocomplex formation of multi-stereoblock poly(methyl methacrylates) in three different solvents, acetone, tetrahydrofuran (THF) and chloroform, corresponding to strongly-, weakly- and non-complexing solvent, respectively, were investigated by a combination of static and dynamic laser light scattering. Our results revealed that the stereocomplex was caused by weak interactions, and could be melted at higher temperatures. In THF, the intermolecular and intramolecular interactions could be clearly separated at lower temperatures, and the structure of aggregated chains was linear. In acetone, a more compact structure was obtained, which was corroborated by the fact that the stereocomplex had a higher melting temperature than in THF.     

羧基化碳纳米管存在下茜素红-蛋白质的光散射光谱研究

本文报道了羧基化碳纳米管存在下茜素红-蛋白质的光散射光谱。与无羧基化碳纳米管时相比,其散射光强度明显增加。优化了影响体系光散射检测的实验参数。在实验选定最佳条件下,考察了散射光强度与蛋白质浓度的关系,发现在362 nm波长处散射光强度与牛血清蛋白(BSA)和人血清蛋白(HSA)浓度均在0.10～9.0 mg/L范围内呈线性关系,其检出限为0.053 mg/L。将该法用于人血清总蛋白含量的测定,结果令人满意。     

Characterization of gold nanoparticle bioconjugation by resonance light scattering correlation spectroscopy

<正>Gold nanoparticles(GNPs) have been widely used as probes and nanomaterials in certain biological and biomedical fields thanks to its special physical and chemical properties.However,it is still difficult to characterize GNPs-bioconjugates in solution,which has greatly limited further bioapplications of GNPs.In this study,we reported a single particle method for characterizing GNPsbiomolecules in solution using resonance light scattering correlation spectroscopy(RLSCS).The interaction of GNPs with bovine serum albumin(BSA) and thiol-modified oligonucletides were investigated.     

Characterization of polymer materials by scattering techniques,with applications to block copolymers

The application of six techniques—static and dynamic light scattering, small-angle neutron and X-ray scattering, neutron and X-ray reflectivity—to the characterization of polymer materials is summarized. Emphasis is placed on the similarities and differences among the various techniques, and on recent advances in experimental practice. Twelve examples from the recent literature are described, most of which concern block copolymers. A brief introduction to block copolymer properties is also provided.     

Strong diffuse scattering and lamellar morphologies of syndiotactic polystyrene: Polymorphic effects

Syndiotactic polystyrene (sPS) samples melt‐crystallized into neat α″‐ hexagonal and β′‐orthorhombic modifications were prepared at various temperatures thoroughly for extensive morphological studies. The lamellar morphologies of the as‐prepared sPS samples were investigated with small‐angle X‐ray scattering (SAXS) and transmission electron microscopy (TEM). For SAXS measured at 25°C, a barely observed scattering hump was detected for β′‐form sPS, whereas no discernible scattering feature was found for α″‐form sPS because of a small difference in the electron density between the crystalline and amorphous phases. For increased scattering contrast and strength, SAXS was carried out at 150°C so that more reliable morphological parameters would be obtained. In addition to the enhanced scattering peak relevant to the lamellar features, strong diffuse scattering near the beam stop was observed for both α″‐ and β′‐form sPS samples. The contribution of the diffuse scattering at low q regions (where q is the scattering vector) was rather prominent, obscuring the precise position of the scattering peak. On the basis of the Debye–Bueche theory, the strength and inhomogeneity length were derived to render the diffuse scattering. After the subtraction of the diffuse scattering from the observed intensities, scattering intensities exclusively associated with the lamellar features were obtained. Lamellar thicknesses were further derived from the one‐dimensional correlation function of the modified intensities, and a good agreement was reached in comparison with TEM results. From exhaustive TEM observations on the RuO₄‐stained samples, long and parallel lamellae were readily observed in β′‐form sPS. However, relatively irregular packing of lamellar stacks with short lateral dimensions was detected in the as‐prepared α″‐form sPS, leading to the absence of spherulitic birefringence under polarized optical microscopy. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2457–2469, 2003     

Light scattering and fluorescence photobleaching recovery study of poly(amidoamine) cascade polymers in aqueous solution

Diffusion coefficients of polyamidoamine cascade polymers (PAMAMs) were measured in aqueous solutions by dynamic light scattering and, after labeling with fluorescein isothiocyanate, by fluorescence photobleaching recovery. The dynamic light scattering results depended weakly on pH at a high salt concentration, but varied strongly with the concentration of added salt in the low-salt limit. The fluorescence photobleaching recovery values were almost independent of salt concentration. The difference between the two techniques is that thermodynamic nonideality strongly affects light scattering at the concentrations that are experimentally accessible. The hydrodynamic sizes from fluorescence photobleaching recovery were somewhat smaller than those from dynamic light scattering in the high-salt limit, despite attachment of the dye. Nevertheless, fluorescently tagged PAMAMs should make suitable markers and diffusion probes. © 1996 John Wiley & Sons, Inc.     

A rapid isocratic high-performance liquid chromatography method for determination of cholesterol and 1,2-dioleoyl-sn-glycero-3-phosphocholine in liposome-based drug formulations

A high-performance liquid chromatography (HPLC) method for the determination of cholesterol and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) in liposome-based drug formulations has been developed. Liposome formulations of anticancer agents (viz., paclitaxel, docetaxel, 7-ethyl-10-hydroxycamptothecin (SN38), doxorubicin, mitoxantrone and an antisense oligodeoxyribonucleotide, etc.) were prepared. These formulations contain DOPC, cholesterol and other lipids, such as tetramyristoyl cardiolipin or 1,3-bis(1,2-bis-tetradecyloxy-propyl-3-dimethylethoxyammonium bromide)propan-2-ol [(R)-PCL-2] in product-specific ratios. A simple HPLC method that uses isocratic elution and UV detection has been developed for simultaneous quantification of cholesterol and DOPC components of the liposome formulations. The chromatographic separation of these components is achieved using a C8 analytical column with 50 mM ammonium phosphate buffer (pH 2.7)-methanol (15:85, v/v) as mobile phase. Both cholesterol and DOPC peaks are well resolved and free of interference from other excipients or degraded impurities in the formulation. The method has been found to be linear (r > 0.999) over a wide concentration range of both analytes. This method offers the advantage of simultaneous quantitation of cholesterol and DOPC in various liposome-based formulations without any preprocessing of the sample, and has quantitation limits of 0.5 and 10 microg/mL for cholesterol and DOPC, respectively.