2 research outputs found
Synthesis of Aspirin-loaded Polymer–Silica Composites and their Release Characteristics
This study describes a novel approach
to the synthesis of polymer–drug–silica
nanocomposites via encapsulation/isolation of drug molecules, introduced
into the polymer matrix by the silica gel. For the first time, tetraethoxysilane
(TEOS) gelation in the vapor phase of the acidic catalyst is presented
as an efficient method to enter the silica gel nanoparticles into
the polymer–aspirin conjugate. The conducted studies reveal
that the internal structure of the polymer carrier is significantly
reorganized after the embedding of aspirin molecules and the silica
gel. The total porosity of the polymer–drug–silica nanocomposites
and the molecular structure of the silica gel embedded in the system
strongly depend on the conditions of the silica source transformation.
Additionally, the release of the drug was fine-tuned by adapting the
conditions of hydrolysis and condensation of the silica gel precursor.
Finally, to prove the usefulness of the proposed synthesis, the controlled
release of aspirin from the polymer–drug–silica nanocomposites
is demonstrated
Positron Probing of Liquid-free Volume To Investigate Adsorption–Desorption Behavior of Water in Two-Dimensional Mesoporous SBA‑3
Transport of fluids
through channels and cavities of nano/mesoporous
materials is of paramount importance in various fields of science
and industry. The transport properties can be well derived from the
adsorption–desorption behavior of fluids. Positron annihilation
lifetime spectroscopy (PALS) allows probing adsorption–desorption
of water from 2D mesopores of SBA-3. In situ study of the size of
evolving water-free volumes during successive stages of adsorption
and desorption is a sensitive way to elucidate the course of pore
filling and emptying. The changes of positron annihilation parameters
indicate that adsorption of water is mediated through the formation
of isles on the surface of the pore walls, and these, in turn, develop
into water plugs. Subsequently, these plugs grow and consecutively
join together when the distance between them decreases to ca. 1 nm
until the complete capillary condensation occurs. Akin to adsorption,
desorption of water from the pores involves the formation of cavities
capped with water plugs. The final stage of desorption shows the presence
of water trapped in micropores in the pore walls. The linear dependence
between the volume of water and the intensity of the water-related
positronium component allows to estimate the amount of water in the
system. The study highlights an approach to understand adsorption–desorption
mechanism of liquids in mesopores by probing liquid-free volumes using
ortho-positronium