Simultaneous multiple sample light scattering for analysis of polymer solutions

An instrument for performing Simultaneous Multiple Sample Light Scattering (SMSLS) is introduced, which allows multiple, independent polymer samples to be analyzed simultaneously. Three demonstrations of SMSLS capabilities are made; proof of the SMSLS ability to make absolute Rayleigh scattering ratio measurements on well‐defined standards, the monitoring of a biopolymeric degradation process (hyaluronate degradation using hyaluronidase), with subsequent determination of the Michaelis‐Menten constant, and an aggregation process (low concentration gelatin solutions). It is hoped that SMSLS will become a valuable tool for rapid screening and characterization of both equilibrium properties and nonequilibrium processes in polymer solutions. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2724–2732, 2004     

Acrylic block copolymer analysis by adsorption chromatography with evaporative light scattering detection

Block copolymers of methyl methacrylate and butyl methacrylate are characterized using silica adsorption chromatography with a toluene-2-butanone solvent gradient. Evaporative light scattering is the detection method for these otherwise hard to detect acrylic polymers. The homopolymer contamination in the diblock materials are well resolved from the diblock in the separation. The major separation mechanism is composition controlled, but the results also indicate a block length dependency on the separation mechanism.     

Structure of a styrene-butadiene-styrene block copolymer by light scattering..

The phase structure of a styrene-butadiene-styrene block copolymer (mol. wt. 21 000–98 0000– 21 000) film cast from tetrahydrofuran/methyl ethyl ketone is studied by light scattering. The scattered intensity I corresponding to V_v, H_v, V_h, and H_h polarization directions is measured as a function of scattering angle. From the In I vs sin² (θ/2) plots the domain sizes are found to be about 0.4 and 1.0 μ. The a values are independent of polarization directions. This proves that the domains are geometrically isotropic. The two sizes correspond to two correlation distances; the smaller value represents the extent of heterogeneity within a spherical domain and the larger valued the inter-domain separation distance.     

Dynamic light scattering applied to the synthesis of colloidal zeolite

The use of dynamic light scattering as an analysis method within the field of zeolite synthesis has proved to be a powerful and robust tool with which the particle size and the corresponding particle size distribution can be determined. The method has been employed in the evaluation of the crystallization of several types of colloidal zeolite from clear homogeneous solutions. Examples of such zeolites are zeolite N-Y, hydroxysodalite, and TPA-silicalite-1. The fact that the particle size can be determined in as-synthesized zeolite sols as a function of synthesis time enables one to follow, for example, the crystallization process in terms of particle size increase, the process of particle size tailoring as well as to obtain information on the growth mechanism in zeolite synthesis. The colloidal nature of sols following redispersion of zeolite powders and colloidal zeolite organosols has been assessed using dynamic light scattering. The advantages as well as problems associated with the use of dynamic light scattering for characterization of colloidal zeolites are discussed.     

Aqueous heterophase polymerization of styrene—a study by means of multi-angle laser light scattering

An online multi-angle laser light scattering study of ab initio surfactant-free styrene emulsion polymerization reveals unexpected results regarding the development of the dispersity during the whole reaction starting from mixing styrene and water at reaction temperature. The experimentally observed change in the dispersity, which is an indirect measure of the average characteristic size of the colloidal objects, allows the identification of three characteristic intervals. During interval A the equilibration of styrene in water is characterized by the formation of styrene domains, which increase in number and size until an equilibrium state is reached. This means that there is virtually no homogeneous/molecular styrene in water solution but rather nanodroplets of about 200 nm in diameter (assuming spherical shape) are formed. During interval B, after initiation of the polymerization and particle formation, the dispersity increases again as the average size decreases and the number of scattering objects increases. The polymer particles suck up the monomer from the monomer nanodroplets, which leads to the disappearance of the nanodroplets and to a decrease in the average size. During interval C the average size increases again due to the predominantly growth of the polystyrene particles.     

About the theoretical aspect of multiple light scattering: Silvy's theory

The general problem of light scattering in turbid media has been studied often. Compared to the exact solution for plane‐parallel diffusers, the Kubelka and Munk solution appears as an approximation. The photon diffusion model is also an approximate solution restricted to the case of low light absorption, for which the prior work of Silvy has been ignored. It gives interesting relations between Kubelka‐Munk conventional parameters and the more intrinsic quantities related to the properties of the media introduced by the photon model. © 2003 Wiley Periodicals, Inc. Col Res Appl, 28, 227–228, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.10149     

Contribution of multiple scattering to light transmittance by a collimated beam

A method to study the multiple scattering contribution in a scattering and/or absorbing enclosure traversed by a narrow radiation beam is presented. Based on the isotropic scattering assumption, we derive a set of simplified radiative transfer equations, which are solved numerically using a finite-element method. Results from an example calculation are given in terms of transmittance emerging at the top of the cylindrical model assumed. It is shown that Bouguer's law is valid for low single scattering albedo values (<0.4), but the validity limit shifts toward small optical depths as the albedo value increases. For high albedo values and thick optical depths, the multiple scattering effect dominates the emerging transmittance.     

Study of segmented ethylene terephthalate–caprolactone copolymer by differential refractometry and light scattering

A segmented ethylene terephthalate (ET)–caprolactone (CL) copolymer was characterized by light scattering in chloroform tetrahydrofuran and butanone. The flexibility of the copolymer chain is comparable with that of typical flexible chains, such as polystyrene. In the process of applying the Bushuk–Benoit light scattering theory to the segmented PET–PCL copolymer, we encountered not only the problem of finding three solvents with different refractive index but also the problem of determining the specific refractive index increments for the PET and PCL segments in the copolymer, i.e., ν_PET and ν_PCL . In principle, the approximate values of ν_PET and ν_PCL can be obtained from the PET and PCL homopolymers, respectively. In reality, it involves many practical problems, e.g., to find three solvents not only for copolymer but also for the PET and PCL homopolymers. In this study, a different method was used to find both ν_PET and ν_PCL , wherein the ν values of at least two segmented PET–PCL copolymers with different PET compositions were used. With ν_PET , ν_PCL , and ν, we characterized the absolute molecular weight. Further, we show that the composition of an unknown segmented PET–PCL copolymer can be estimated from ν_PET , ν_PCL , and ν. © 1994 John Wiley & Sons, Inc.     

流动注射光散射法测定水样中微量Pb（Ⅱ）

利用自制的流通池,提出了流动注射分析与光散射光谱法联用的技术;研究Pb^2＋与S^2-反应体系在470nm处散射光强度与溶液中Pb^2＋的浓度成线性关系,据此建立一种检测微量Pb（Ⅱ）的新方法;方法的线性范围为0-120μg/ml,相关系数r=0.9980,检出限为1.9989μg/ml,RSD=3.53%,测定频率为48次/h;测定结果表明本文所建立的方法简单快速,灵敏度高,化学试剂少。方法适用于测定水样中的微量铅,结果令人满意。     

利用多重光散射法对纳米TiO2水分散体系稳定性研究

通过多重光散射法研究了纳米TiO2水分散体系稳定性的影响因素。文章探讨了分散剂类型、pH和NaCl质量浓度对水分散体系稳定性的影响规律以及分散剂对纳米TiO2颗粒在水分散液中粒径变化、沉降的微观作用特性。结果表明：纳米TiO2颗粒的粒径在100～200 nm时易相互吸附团聚沉降,分散剂会在纳米TiO2颗粒表面吸附形成双电层,产生更大Zeta电位负值,增强颗粒间的排斥作用,减缓粒径增长和发生沉降的作用,从而提升分散液稳定性;纳米TiO2颗粒的较佳分散条件为：w(六偏磷酸钠)=0.05%,pH=9～10且不加电解质NaCl;多重光散射法与传统的吸光度测试实验所得结果基本相符。     

Simultaneous synthesis of a heat exchanger network with multiple utilities using utility substages

Heat exchanger network synthesis (HENS) has progressed by using mathematical programming-based simultaneous methodology. Although various considerations such as non-isothermal mixing and bypass streams are applied to consider real world alternatives in modeling phase, many challenges are faced because of its properties within non-convex mixed-integer nonlinear programming (MINLP). We propose a modified superstructure, which contains a utility substage for use in considering multiple utilities in a simultaneous MINLP model. To improve model size and convergence, fixed utility locations according to temperature and series connections between utilities are suggested. The numbers of constraints, discrete, and continuous variables show that overall model size decreases compared with previous research. Thus, it is possible to expand the feasible search area for reaching the nearest global solution. The model's effectiveness and applications are exemplified by several literature problems, where it is used to deduce a network superior to that of any other reported methodology.     

荧光碳点共振光散射法测定核酸的应用研究

以葡萄糖为碳源采用溶剂热法合成荧光碳点。利用共振光散射(RLS)技术研究了碳点与脱氧核糖核酸的相互作用,根据核酸在pH 8.8的Tris缓冲液中与碳点有很强的光散射信号,建立一种简便灵敏的测定核酸的方法。此方法中增强的RLS强度与核酸浓度在0.4～30μg/mL范围内呈线性关系,检出限为0.023μg/mL。将该法用于合成样品中核酸的测定,回收率在103%～106%之间,RSD<3.7%。     

Chemoenzymatic synthesis of Y-shaped diblock copolymer

Y-shaped diblock copolymer polycaprolactone-block-(polystyrene)₂ [PCL-b-(PSt)₂] was synthesized successfully by the combination of enzymatic ring-opening polymerization (eROP) and atom transfer radical polymerization (ATRP). CH₃O-terminated PCL was synthesized firstly by eROP of ε-caprolactone (ε-CL) in the presence of biocatalyst Novozyme 435 and initiator CH₃OH, subsequently the resulting PCL was converted to macroinitiator by the esterification of it with 2,2-dichloro acetyl chloride (DCAC). PCL-b-(PSt)₂ diblock copolymers were synthesized in an ATRP of the styrene with CuCl/2,2′-bipyridine as the catalyst system. The kinetic analysis of ATRP indicated a controlled/‘living’ radical polymerization. The structure and composition of obtained polymers were characterized with NMR, GPC and FTIR. The thermal behavior was characterized by differential scanning calorimetry (DSC).     

Small-angle neutron scattering measurement of block copolymer interphase structure

The notion of an interfacial layer at the domain boundary in block copolymers is reviewed and the possibility of its measurement by small-angle X-ray and small angle neutron scattering discussed. Values of the interfacial layer thickness and its volume fraction have been obtained for a range of styrene-isoprene copolymers. Interfacial layer thickness is not strongly dependent on molecular weight whilst the volume fraction shows a dependence more in line with the theory of Helfand.     

Theoretical analysis of light scattering properties of encapsulated rutile titanium dioxide pigments in dependent light scattering regime

Using numerical simulation, we study and compare the optical properties of model systems representing three types of scatterer: (a) standard TiO₂ pigments, (b) standard TiO₂ pigments encapsulated by a hard polymer shell and (c) standard TiO₂ pigments encapsulated by a layer of air and a polymer shell. Calculations are performed taking into account multiple and dependent light scattering regimes. Assuming an equivalent amount of TiO₂ in each system, results show that a standard TiO₂ pigment particle encapsulated by air could be a better opacifier than a standard un-encapsulated TiO₂ pigment because the presence of air could provide: (a) additional volume to the existing particle to scatter light; (b) better redistribution of the scattered field in the backward hemisphere; (c) a scattering cross-section less affected by crowding and (d) spacing effects due to the presence of the thin hard polymer shell which is required to encapsulate the air layer. Nonetheless, results also suggest that such benefits could probably not be exploited in real paint systems as encapsulated TiO₂ would only be more efficient than standard TiO₂ in a range of pigment volume filling fractions (PVC) that would not generate enough scattering efficiency to yield complete hiding as required by international standards.     

Small angle neutron scattering study of the structure of a triblock copolymer of styrene and isoprene during extension

A triblock copolymer with a styrene weight fraction of 0.41, has been examined at various extension ratios using small angle neutron scattering. The original ‘polycrystalline’ material with a face centred cubic arrangement of styrene domains acquires orientation as the extension ratio increases. Affine deformation is not obeyed at the supramolecular level and there is some evidence for non-uniform stress at this level.     

Facile synthesis and light scattering characteristics of polystyrene/poly(3,4-ethylenedioxythiophene) nanocomposite particles

Polystyrene/poly(3,4-ethylenedioxythiophene) (PS/PEDOT) nanocomposite particles with uniform size and well-defined morphology have been synthesized using the proposed strategy, which involves swelling of 3,4-ethylenedioxythiophene (EDOT) into PS seed particles, followed by its diffusion and polymerization on the PS surface. This process affords much more effective control over the structure and morphology of the resultant nanocomposites by changing the EDOT/PS weight ratio, reaction temperature, and the rate of addition of the doping acid. The PS/PEDOT nanocomposite particles have been extensively characterized using transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), elemental microanalyses and X-ray photoelectron spectroscopy (XPS). Furthermore, the correlation between nanostructure of the resultant nanocomposite particle and its electromagnetic response performance (e.g., mass extinction effect in infrared region) was investigated.     

Dynamic light scattering and ultrasonic investigations during the cure reaction of an epoxy resin

Brillouin scattering (BS), photon correlation spectroscopy (PCS), and ultrasonic (US) measurements were conducted to study the curing process of diglycidyl ether of bisphenol A with butane-1,4-diol at a curing temperature of 100°C. The experimental techniques probe the primary glass-rubber transition during the curing reaction. The primary relaxation time τ obtained from the BS and US velocity and absorption increases with curing time and hence the BS experiment measures τ at earlier stages of cure than the US experiment. The relaxation times at a different extent of reaction and for different measuring temperatures are consistent with BS, US, PCS, and DSC measurements and conform to a single reduced Vogel–Fulcher–Hesse–Tamann equation. Furthermore, the US experiments show evidence of secondary relaxations in the epoxy system.