Turbidity Spectroscopy Research Articles

Real-Time Monitoring of Particle Size in Emulsion Polymerization: Simultaneous Turbidity and Photon Density Wave Spectroscopy.

Particle size evolution in seeded semibatch emulsion polymerization is monitored by two real-time monitoring techniques: online turbidity spectroscopy (TUS) and inline photon density wave spectroscopy (PDWS). An automatic dilution system that withdraws a sample from the reactor and upon dilution transfers to the measurement cell is used for the online TUS analysis. A PDWS probe is immersed in the reactor and collects inline the scattered light directly from the reacting latex. The particle sizes retrieved from TUS and PDWS are compared to offline dynamic light scattering (DLS) values. The particle size obtained by TUS is close to the intensity-average particle size obtained offline by DLS, while the particle size obtained by PDWS lies closer to the number-average particle size from DLS.

Wavelength exponent based calibration for turbidity spectroscopy: Monitoring the particle size during emulsion polymerization reactions

Particle size and particle size distribution (PSD) are important properties of polymer latexes because they strongly affect the film formation and the rheological properties of the latexes. Thus, monitoring the particle size is of paramount importance during the production of waterborne polymeric dispersions, for which online/inline measurements of the particle size are required. Herein, turbidity spectroscopy (TUS) is used to measure the particle size of nanoparticles in dispersed media. Calibration curves based on a modified wavelength exponent method are introduced and assessed to monitor the evolution of a broad range of particle sizes in seeded semibatch emulsion polymerizations of methyl methacrylate, butyl acrylate, methacrylic acid (MMA/BA/MAA 51/47/2) terpolymers. It is shown that the wavelength exponent based calibration curves can be successfully used to retrieve the particle size during the polymerization process.

Growth rates and water stability of 2D boronate ester covalent organic frameworks.

We examine the growth rates, activation energies, and hydrolytic stability of multiple 2D boronate ester covalent organic frameworks by turbidity measurements, observing a 200-fold range in stability. The rate-determining step in boronate ester 2D COF growth is not in-solution condensation, but rather interlayer polymer stacking through a nucleation-elongation process.

Turbidity Spectroscopy for Characterization of Submicroscopic Drug Carriers, Such as Nanoparticles and Lipid Vesicles: Size Determination

To apply UV/Vis spectrometry for characterization of submicroscopic drug carriers, such as nanoparticles and lipid vesicles. We first investigated theoretically, within the framework of the Rayleigh-Gans-Debye approximation (RGDA), parameters affecting turbidity spectrum, τ(λ), of nanosized light scatterers. We then analyzed, within the framework of the RGDA, experimental turbidity spectra (λ = 400-600 nm) of extruded unilamellar vesicle (70 nm ≤ 2r ≤ 110 nm) suspensions to derive vesicle size, using dynamic light scattering results for comparison. We similarly studied the preparations polydispersity and lamellarity and monitored vesicle size changes. Turbidimetry suffices for accurate, fast, and viscosity-independent characterization of submicroscopic particles. Analysis of turbidity spectra, or more precisely wavelength exponent spectra (derivatives of logarithmic turbidity spectra), yielded similar average radii (r = 54.2 ± 0.2 nm; 46.0 ± 0.2 nm; 35.5 ± 0.1 nm) as dynamic light scattering (r = 55.9 ± 1.5 nm; 46.1 ± 0.4 nm; 36.1 ± 0.4 nm). Both methods also revealed similar suspension polydispersity and cholate-induced vesicle size changes in a few nanometer range. Despite its experimental simplicity, the widely accessible turbidimetric method provides accurate size values and is suitable for (continuous) monitoring size stability, or sameness, of submicroscopic drug carriers.

Kinetic and structural aspects of gelation in polyacrylonitrile-propylene carbonate system

Structural rearrangements in solutions of high-molecular-mass polyacrylonitrile in propylene carbonate upon phase separation were studied and quantitatively characterized by means of turbidity spectroscopy and oscillation rheometry with the use of previous data obtained via the light transmission technique. The kinetic features of separation of the new phase and the particle size growth were established. It was shown that there is a time lag between the onset of physical-gel formation in the system and the onset of phase separation. The average particle size that corresponds to the transition of the system into gel and determines the gel morphology at the subsequent further stages was found for different temperatures.

A Study of Structure Formation in Chitosan-Polyvinyl Alcohol Blends by Turbidity Spectroscopy

The structure formation of film samples of chitosan, polyvinyl alcohol, and their blends was studied by turbidity spectroscopy.

Optical characterization of tropospheric aerosols

Complex calculations of optical scattering using high-speed electronic computers have become so commonplace that the technology has evolved into several specialty fields, e.g., extinction spectroscopy, angular scattering measurements and nephelometry. As a consequence, the overall technology and our ability to remotely characterize or quantitatively analyze atmospheric aerosols might be further advanced than is realized by workers in the individual disciplines who do not have the time to keep up with advances in other disciplines. This paper examines techniques of transmission (extinction) and turbidity spectroscopy, polarization and angular scattering measurements and related developments and concludes that computer programs can be written to optimize desired parameters in interdisciplinary investigations.