Inverse problems in polymer characterization: Direct analysis of polydispersity with photon correlation spectroscopy

Provencher, Stephen W.

doi:10.1002/macp.1979.021800119

Cited by 803 publications

(478 citation statements)

References 30 publications

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“…The particle size distribution from DLS measurement was derived by deconvolution of the measured intensity autocorrelation function of the sample. 40 Generally, deconvolution was accomplished using a non-negatively constrained least squares (NNLS) 41,42 fitting algorithm, common examples being CONTIN, 43 Regularization, and the General Purpose and Multiple Narrow Mode algorithms 44,45 included in the Zetasizer Nano software. The distribution was obtained by the NNLS method using an alpha value, which is a function parameter of the fitting sensitivity of the raw data.…”

Section: Calculation Of the Distribution Of Various Proteins From Dlsmentioning

confidence: 99%

Polydispersity as a Parameter for Indicating the Thermal Stability of Proteins by Dynamic Light Scattering

et al. 2010

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Section: Calculation Of the Distribution Of Various Proteins From Dlsmentioning

confidence: 99%

Polydispersity as a Parameter for Indicating the Thermal Stability of Proteins by Dynamic Light Scattering

et al. 2010

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“…To obtain a distribution of relaxation rates in the studied system, spectra were analyzed by the line shape analysis 22 on the level of g (1) (q, t) instead of relying on an Inverse Laplace Transform of S(q, t) (e.g. CONTIN algorithm 32 ). The nonlinear-least-squares simplex-based minimization procedure fitted each g (1) (q, t) repeatedly to sums of stretched exponentials with different initial parameters and/or number of modes, checking for RMS error and numerical stability of the fits.…”

Section: Methodsmentioning

confidence: 99%

Spectral time moment analysis of microgel deswelling. Effect of the heating rate

Streletzky¹,

McKenna²

2008

J Polym Sci B Polym Phys

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Microgel nanoparticles were synthesized in aqueous solutions of neutral polymer hydroxypropylcellulose (HPC) through the self-association of amphiphilic HPC molecules and the subsequent cross linking at room temperature. Dynamic Light Scattering was used to study the transport properties of HPC microgels below and above the volume phase transition. Highly nonexponential, multimodal microgel spectra were observed and successfully analyzed by spectral time moment analysis. This article expands earlier results and focuses on the effect of the heating rate on microgel deswelling. During the fast heating two identified microgel modes with apparent hydrodynamic radii (R H ) of 25-30 nm and 400-650 nm collapse into one mode with R H = 100−150 nm. This indicates the shrinkage of microgel size distribution and an apparent decrease in the radius of larger microgels. During the slow heating, however, both microgel-identified modes remain present above T c . Although equally represented below the transition, the dominance of larger microgels' mode increases almost two fold with rising temperature above 40• C. Moreover, R H for this mode increases from 250-300 nm to about 800-850 nm with a multi-step temperature change from 40 to 42.5• C, indicating the growth (and not shrinkage) of microgels. The second mode is represented by the temperature independent R H , but its contribution goes down from about 50% to less than 10%.

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“…In order to characterize the hydrodynamic behavior of the suspended particles the multisampling time autocorrelation functions were analyzed by oneexponential fit (Microcal Origin  6.0) and by inverse Laplace transformation using the CONTIN 31 program.…”

Section: Methodsmentioning

confidence: 99%

“…31 This program determines G(Γ) by performing an inverse Laplace transform on equation (7). 8,33,34 Figure 3 shows time correlation functions well fitted through a single exponential for microemulsions containing either isoamyl or amyl alcohol as co-surfactant.…”

Section: Dynamic Light Scatteringmentioning

confidence: 99%

Water in soybean oil microemulsions as medium for electrochemical measurements

Mendonça¹,

Bica²,

Piatnicki³

2003

J. Braz. Chem. Soc.

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Microemulsões de água em óleo de soja (w/o ME) foram preparadas com dodecil sulfato de sódio (SDS) como surfactante e com os álcoois amílico ou isoamílico, como co-surfactantes. A composição 40,0% de óleo, 43,2% de álcool, 10,8% de SDS e 6,0% de água, em massa, na razão 1:4 [SDS]: [álcool], apresentou a maior estabilidade termodinâmica. O tamanho das gotículas e seu coeficiente de difusão nas microemulsões, D w/o , foram determinados por medidas de espalhamento de luz dinâmico (DLS). As reações de oxidação de ferroceno (Fc) e de água, e a redução de ácido oleico foram observadas nas ME por voltametria em um ultramicroeletrodo (ume) de disco de Pt. Os valores de D w/o determinados a partir de medidas eletroquímicas são menores do que os calculados a partir daquelas por DLS. Isto indica que a oxidação da água requer a difusão para o eletrodo tanto das gotículas como das moléculas de água nelas contidas. Os resultados evidenciam a possibilidade de determinação de analitos em óleos vegetais por métodos eletroanalíticos.Microemulsions of water in soybean oil (w/o ME) were prepared with sodium dodecyl sulfate (SDS) as surfactant and amyl or isoamyl alcohol, as co-surfactants. Microemulsions containing 40.0% oil, 43.2% alcohol, 10.8% SDS and 6.0% water in weight, in the ratio 1:4 [SDS]: [alcohol] showed the highest thermodynamic stability. The aqueous droplet size and its diffusion coefficient D w/o in the ME were determined through dynamic light scattering (DLS). Voltammetric measurements in the ME at a Pt disk ultramicroelectrode (ume) evidenced the oxidation of both water and ferrocene (Fc), and the reduction of oleic acid. The D w/o values calculated from the limiting current being lower than the ones obtained from DLS indicate that water oxidation probably requires diffusion towards the electrode of both the droplets and the water molecules from inside the droplets. The results show that electroanalytical determinations can be carried out in w/o ME. Keywords: microemulsions, soybean oil, voltammetry, ferrocene, oleic acid IntroductionEquilibria in water-oil interfaces have been studied in order to quantify solvent extraction as well as charge transfer processes. In this sense new analytical methodologies such as slow extrusion of water into a nonaqueous phase (and vice-versa) through a capillary, 1 the use of micrometric electrodes 2-3 and of microemulsions 4,5 (ME) have been proposed recently. Besides a significant decrease in costs and toxicity due to the decrease in organic solvents consumption, 6-8 water in oil ME allow to carry out electrochemical measurements due to the enhanced electrical conductivity imparted to the system by the presence of water.Microemulsions are thermodynamically stable systems composed of water, oil and surfactant, and, in some cases, an alcohol can be added as co-surfactant. 9-12 Their behavior is similar to the one of polar organic solvents and, although apparently homogeneous under visual observation, ME are actually microheterogeneous (perhaps nanoheterogeneous would be a better...

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Inverse problems in polymer characterization: Direct analysis of polydispersity with photon correlation spectroscopy

Cited by 803 publications

References 30 publications

Polydispersity as a Parameter for Indicating the Thermal Stability of Proteins by Dynamic Light Scattering

Polydispersity as a Parameter for Indicating the Thermal Stability of Proteins by Dynamic Light Scattering

Spectral time moment analysis of microgel deswelling. Effect of the heating rate

Water in soybean oil microemulsions as medium for electrochemical measurements

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