scholarly journals Comparison of Dynamic Light Scattering and Rheometrical Methods to Determine the Gel Point of a Radically Polymerized Hydrogel under Mechanical Shear

Micromachines ◽  
2020 ◽  
Vol 11 (5) ◽  
pp. 462
Author(s):  
Katinka Kohl
Keyword(s):  
Phase Transition ◽  
Light Scattering ◽  
Dynamic Light Scattering ◽  
Gel Point ◽  
Abrupt Increase ◽  
Nanocomposite Hydrogels ◽  
Experimental Parameters ◽  
The One ◽  
Preparatory Work

The phase transition of nanocomposite hydrogels made of N-isopropylacrylamide (NIPAm) and clay (Laponite® XLS) was investigated under mechanical shear influencing the gelation. The hydrogels were synthesized by free radical polymerization. For the processing of cross-linked gels, the phase transition (liquid–solid) and its dependence on mechanical stress are of paramount importance. On the one hand, the determination of the gel point (tg) is possible with rheometry and, on the other hand, with dynamic light scattering (DLS). With rotational rheometry, by identifying the abrupt increase of viscosity, the gel point is evaluated. The DSL is an alternative method to rheometry, to investigate hydrogels under the action of the shear flow, to make results comparable to the rheometric investigations, with and without shear. Experimental parameters were chosen based on preparatory work to obtain comparable results regarding the determination of the gel point of a radically polymerized NIPAm hydrogel.

scholarly journals Gel Point Determination of TEOS-Based Polymeric Materials with Application on Conservation of Cultural Heritage Buildings

2018 ◽  
Vol 2018 ◽  
pp. 1-7 ◽  
Author(s):  
R. Angulo-Olais ◽  
Juan F. Illescas ◽  
J. Aguilar-Pliego ◽  
C. A. Vargas ◽  
C. Haro-Pérez
Keyword(s):  
Light Scattering ◽  
Dynamic Light Scattering ◽  
Polymeric Materials ◽  
Gel Point ◽  
Noninvasive Technique ◽  
Heritage Buildings ◽  
Oscillatory Rheology ◽  
Materials Used ◽  
Gelling Time

Here we present measurements on the gel time of inorganic-organic materials used for stone preservation by means of rheology and dynamic light scattering. Our hybrid material is composed of tetraethyl orthosilicate (TEOS) and polydimethylsiloxane (PDMS) using a nonionic surfactant (n-octylamine) as a template. Moreover, zinc oxide (ZnO) nanoparticles are dispersed in the medium with the aim of obtaining a nanocomposite with potential biocide properties. In our case, we use the ZnO particles as tracers to infer from their scattered intensity mechanical information of the suspending medium. We have found that dynamic light scattering experiments provide similar information on the gelling time, about 30 hours, to that obtained from rotational rheology and oscillatory rheology. This result confirms the validity of light scattering, which is a noninvasive technique, to characterize mechanical properties of time evolving hybrid materials through nonperturbative and well-controlled experiments.

scholarly journals Detection Limits of DLS and UV-Vis Spectroscopy in Characterization of Polydisperse Nanoparticles Colloids

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
Emilia Tomaszewska ◽  
Katarzyna Soliwoda ◽  
Kinga Kadziola ◽  
Beata Tkacz-Szczesna ◽  
Grzegorz Celichowski ◽  
...  
Keyword(s):  
Light Scattering ◽  
Dynamic Light Scattering ◽  
Point Of View ◽  
Spectroscopy Analysis ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron ◽  
Vis Spectroscopy ◽  
The One

Dynamic light scattering is a method that depends on the interaction of light with particles. This method can be used for measurements of narrow particle size distributions especially in the range of 2–500 nm. Sample polydispersity can distort the results, and we could not see the real populations of particles because big particles presented in the sample can screen smaller ones. Although the theory and mathematical basics of DLS technique are already well known, little has been done to determine its limits experimentally. The size and size distribution of artificially prepared polydisperse silver nanoparticles (NPs) colloids were studied using dynamic light scattering (DLS) and ultraviolet-visible (UV-Vis) spectroscopy. Polydisperse colloids were prepared based on the mixture of chemically synthesized monodisperse colloids well characterized by atomic force microscopy (AFM), transmission electron microscopy (TEM), DLS, and UV-Vis spectroscopy. Analysis of the DLS results obtained for polydisperse colloids reveals that several percent of the volume content of bigger NPs could screen completely the presence of smaller ones. The presented results could be extremely important from nanoparticles metrology point of view and should help to understand experimental data especially for the one who works with DLS and/or UV-Vis only.

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