scholarly journals Local Dynamics of the Hydration Water and Poly(Methyl Methacrylate) Chains in PMMA Networks

2021 ◽  
Vol 9 ◽  
Author(s):  
Yoshihisa Fujii ◽  
Taiki Tominaga ◽  
Daiki Murakami ◽  
Masaru Tanaka ◽  
Hideki Seto
Keyword(s):  
Methyl Methacrylate ◽  
Bulk Water ◽  
Polymer Chains ◽  
Water Molecules ◽  
Hydration Water ◽  
Segmental Motion ◽  
Local Motion ◽  
Deuterium Labeling ◽  
Elastic Neutron ◽  
Poly Methyl Methacrylate

The dynamic behavior of water molecules and polymer chains in a hydrated poly(methyl methacrylate) (PMMA) matrix containing a small amount of water molecules was investigated. Water molecules have been widely recognized as plasticizers for activating the segmental motion of polymer chains owing to their ability to reduce the glass transition temperature. In this study, combined with judicious hydrogen/deuterium labeling, we conducted quasi-elastic neutron scattering (QENS) experiments on PMMA for its dry and hydrated states. Our results clearly indicate that the dynamics of hydrated polymer chains are accelerated, and that individual water molecules are slower than bulk water. It is therefore suggested that the hydration water affects the local motion of PMMA and activates the local relaxation process known as restricted rotation, which is widely accepted to be generally insensitive to changes in the microenvironment.

scholarly journals Ein Wasserstoffisotopieeffekt im CuSO4 * 5H2O

1969 ◽  
Vol 24 (10) ◽  
pp. 1502-1511
Author(s):  
Karl Heinzinger
Keyword(s):  
Water Vapor ◽  
Aqueous Solutions ◽  
Separation Factor ◽  
Room Temperature ◽  
Copper Ion ◽  
Hydrogen Isotopes ◽  
Bulk Water ◽  
Water Molecules ◽  
Hydration Water ◽  
Sulfate Solutions

Abstract There are two kinds of water in CuSO4·5H2O differing by their binding in the crystal. The oxygen of four water molecules is bonded to the copper ion, that of the fifth molecule is hydrogen bonded. It is shown that the D/H ratios of these two kinds of water differ by 5.7%, the light isotope being enriched in the water molecules coordinated with the copper ion. The results show that there is no exchange of the hydrogen isotopes during the time needed for dehydration at room temperature which takes several days. The assumption has been confirmed that the water coordinated with the copper ion leaves the crystal first on dehydration at temperatures below 50 °C. Additional measurements of the separation factor for the hydrogen isotopes between water vapor and copper sulfate solutions allow conclusions on the fractionation of the hydrogen isotopes between bulk water and hydration water in aqueous solutions.

scholarly journals Effect of preparation method on the properties of poly(methyl methacrylate)/mesoporous silica composites

2019 ◽  
Vol 2 (3) ◽  
pp. 363-370 ◽  
Author(s):  
M. A. Sibeko ◽  
M. L. Saladino ◽  
F. Armetta ◽  
A. Spinella ◽  
A. S. Luyt
Keyword(s):  
Thermal Stability ◽  
Mesoporous Silica ◽  
Methyl Methacrylate ◽  
Pore Size ◽  
Preparation Method ◽  
Polymer Chains ◽  
Melt Mixing ◽  
Poly Methyl Methacrylate ◽  
Mcm 41

Abstract The preparation method of a polymer composite and the filler loading are amongst the factors that influence the properties of the final composites. This article studies the effect of these factors on the thermal stability and thermal degradation kinetics of poly(methyl methacrylate) (PMMA)/mesoporous silica (MCM-41) composites filled with small amounts of MCM-41. The PMMA/MCM-41 composites were prepared through in situ polymerisation and melt mixing methods, with MCM-41 loadings of 0.1, 0.3, and 0.5 wt.%. The presence of MCM-41 increased the thermal stability of PMMA/MCM-41 composites prepared by melt mixing, but in the case of the in situ polymerised samples, the MCM-41 accelerated the degradation of the polymer. As a result, the activation energy was low and less energy was required to initiate and propagate the degradation process of these composites. The small-angle X-ray scattering (SAXS) measurements showed that the preparation method of the composites had no influence on the pore size of MCM-41, but the PMMAs used in the two methods both had shorter chains than the MCM-41 pore size. This allowed the polymer chains to be trapped inside the pores of the filler and be immobilised, as was observed from nuclear magnetic resonance (NMR) spectroscopy. The immobilisation of the polymer chains was more significant in the in situ polymerised samples.

Local motion of crosslinks for poly (methyl methacrylate) gels by the fluorescence depolarization method

1997 ◽  
Vol 39 (1) ◽  
pp. 109-116 ◽  
Author(s):  
Hiroyuki Aoki ◽  
Jun-ichi Horinaka ◽  
Shinzaburo Ito ◽  
Masahide Yamamoto
Keyword(s):  
Methyl Methacrylate ◽  
Local Motion ◽  
Fluorescence Depolarization ◽  
Poly Methyl Methacrylate

Molecular Dynamics Study of a KCl Aqueous Solution: Dynamical Results

1987 ◽  
Vol 42 (3) ◽  
pp. 227-230 ◽  
Author(s):  
M. Migliore ◽  
S. L. Fornili ◽  
E. Spohr ◽  
K. Heinzinger
Keyword(s):  
Diffusion Coefficients ◽  
Md Simulation ◽  
Bulk Water ◽  
Water Molecules ◽  
Hydration Water ◽  
Self Diffusion ◽  
Average Temperature ◽  
Velocity Autocorrelation ◽  
Dynamical Properties ◽  
Velocity Autocorrelation Functions

In this paper we report on dynamical properties of a 2.2 molal aqueous KCl solution as obtained from an 8.7 ps MD simulation at an average temperature of 289 K. Velocity autocorrelation functions, self-diffusion coefficients and spectral densities of the hindered translational and librational motions of the ions and the water molecules assigned to three subsystems - hydration water of the cations, hydration water of the anions and bulk water - are discussed.

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