Hollow polymer particles are applied in various fields
owing to
their high specific surface area and inner volume. The hollow regions
in such particles are generally synthesized using a template. However,
chemical agents must be used to remove the templates, which is associated
with a high environmental load. To address this problem, we previously
established a method for synthesizing hollow polymer particles without
a template. However, the mechanism underlying this synthesis was unclear,
which this study aimed to rectify. First, azo compounds were dissolved
in a styrene monomer phase, and soap-free emulsion polymerization
was performed to produce polystyrene particles. The azo compounds
were incorporated into the polystyrene particles from the monomer
phase at a polymerization temperature greater than the melting point
of the azo compounds. Finally, the polystyrene particles were heated
at a temperature greater than the 10 h half-life temperature of the
azo compounds to emit nitrogen gas, and the azo compounds were decomposed
to prepare the hollow regions in the polystyrene particles. However,
the resulting particles were not hollow when the azo compound was
not incorporated into the polystyrene particles. By comparing the
melting behavior of different azo compounds, this study elucidates
the mechanism underlying our template-free method for synthesizing
hollow polystyrene particles.
Subcritical water, which is an effective solvent for polar and nonpolar substances, has been used to extract numerous natural ingredients. In this study, subcritical water was used to extract bioactive substances from apple peel in a batch process in the temperature range of 100–175 °C for 5–60 min. The Fourier-transform infrared spectroscopy results revealed that phenolic compounds were released from apple peel in the aforementioned temperature range. The ultraviolet–visible spectra of the liquid products at 280 nm revealed the high content of phenolic compounds in the extracts. The high-performance liquid chromatography results demonstrated that the yield of procyanidin B2 was approximately 2.28 mg/g of dried apple peel when extraction was performed at 150 °C for 15 min.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.