The demand for new ionic liquid (IL)-based systems to
selectively
sequester carbon dioxide from gas mixtures has prompted the development
of individual components involving the tailored design of IL themselves
or solid-supported materials that provide excellent gas permeability
of the overall material as well as the ability to incorporate large
amounts of ionic liquid. In this work, novel IL-encapsulated microparticles
comprising a cross-linked copolymer shell of β-myrcene and styrene
and a hydrophilic core of the ionic liquid 1-ethyl-3-methylimidazolium
dicyanamide ([EMIM][DCA]) are proposed as viable materials for CO2capture. Water-in-oil (w/o) emulsion polymerization of different
mass ratios of β-myrcene to styrene (i.e. 100/0, 70/30, 50/50,
0/100) yielded IL-encapsulated microparticles, where the encapsulation
efficiency of [EMIM][DCA] was dependent on the copolymer shell composition.
Thermal analysis using thermogravimetric analysis (TGA) and differential
scanning calorimetry (DSC) revealed that both thermal stability and
glass transition temperatures depend on the mass ratio of β-myrcene
to styrene. Images from scanning electron microscopy (SEM) and transmission
electron microscopy (TEM) were used to observe the microparticle shell
morphology as well as measure the particle size perimeter. Particle
sizes were found to be between 5 and 44 μm. CO2sorption
experiments were conducted gravimetrically using TGA instrumentation.
Interestingly, a trade-off between CO2absorption capacity
and ionic liquid encapsulation was observed. While increasing the
β-myrcene content within the microparticle shell increases the
amount of encapsulated [EMIM][DCA], the observed CO2absorption
capacity did not increase as expected due to reduced porosity compared
to microparticles with higher styrene content in the microparticle
shell. [EMIM][DCA] microcapsules with a 50/50 weight ratio of β-myrcene/styrene
showed the best synergistic effect between spherical particle diameter
(32.2 μm), pore size (0.75 μm), and high CO2sorption capacity of ∼0.5 mmol CO2/g sample within
a short absorption period of 20 min. Therefore, core–shell
microcapsules composed of β-myrcene and styrene are envisioned
as a promising material for CO2sequestration applications.