| dc.description.abstract | Oil is still the prime energy resource that the world relies on. With the expectation of the
global economic growth, the oil consumption will grow faster over the coming decades.
The oil extraction technology influences the oil price and usage efficiency, drawing lots
of attention of both researchers and engineers. Interface and colloids play an important
role in this multidisciplinary field. This thesis mainly introduces colloid promoted oil
extraction with two focuses on enhance oil recovery (EOR) and oil well cement.
As one type of colloidal particles, microgels exhibit unique properties among others. The
solvent-microgel interaction can respond to the environmental stimulation such as
temperature, pH, and so on. Due to the synergy between core and shell, strong
functionalities are accessible for core-shell microgels. In this thesis, we developed
microgels with hydrophobic, rigid poly-2,2,2-trilfuoroethyl methacrylate (PTFMA) core
and tunable thickness of the hydrophilic, soft Poly(N-isopropylacrylamide-co-acrylic
acid) (P(NIPAM-co-AAc)) shell. The behavior of the microgels at oil/water and
oil/water/solid interfaces have been explored towards the application of the oil extraction
technology.
The core-shell microgels are able to stabilize oil-in-water Mickering emulsion. Capsule
with dual-level controlled permeability can be fabricated from as-formed emulsion,
which has the potential to be used in controlled gelation. The distribution of fluorescent
microgels in the vicinity of the oil/water/solid three-phase contact line (TPCL) is then
quantitatively investigated for a better understanding of the particles initiated wettability
alteration. There are close packed microgel (CPM) layers around the TPCL of the oil
droplet with an acute contact angle. Since no wedge film is observed to form at oil and
solid interface, the microgel-initiated wettability alteration is attributed to the force
imbalance caused by the adsorption of microgels at interfaces rather than the disjoining
pressure. The behavior of core-shell microgels has been investigated at the oil/water
interface under compression and expansion. Typical core-shell microgels undergo
viscoelastic and then elastic deformation which corresponds to the mechanical
characteristics of shell and core, respectively. The stability of core-shell microgels at
oil/water interface is mainly determined by the deformability of surrounding part of
microgels. | nb_NO |
