“I cannot teach anybody anything; I can only make them think.”
-Socrates-
MY TEACHING PHILOSOPHY
Academic teaching has always had a dual significance: students are trained to become the new and ideally improved generation of scientists and, in parallel, the instructor (naturally a lifelong learner as a scientist) is offered the opportunity to continuously improve his/her capabilities through the dynamic interaction with their students. Like any marriage, both parties must be happy for it to work. On the one hand, via teaching, students must first see for themselves the beauty of the taught subject that will then guarantee their engagement. Once engaged, an effective and joyful teaching strategy will not only build their scientific confidence through the advance of their knowledge, but will also help them evolve into critical thinkers, able to encounter challenges far beyond the taught subject. On the other hand, the teacher needs to make sure that all these things will happen harmoniously; this will definitely provide the satisfaction that their significant mission is successful.
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PHYSICAL CHEMISTRY OF COLLOIDS
MASTER COURSE; SPRING SEMESTER 2019, UNIV. OF LUXEMBOURG
LECTURE NOTES (PDF VERSION)
LECTURE 1
keywords
• Colloid (continuous phase, disperse phase)
• Brownian motion, diffusion
• Interface (surface)
• Lyophobic, solvophobic (hydrophilic, hydrophobic)
• Types of colloids (suspensions, emulsions, foams)
• Colloidal stability
• Enthalpic (ionic, vdW, H-bonds, aromatic) & entropic (steric, hydrophobic effect, depletion attraction) interactions
• Energy scales of interactions
LECTURE 2
keywords
• Interfacial (surface) tension
• Intermolecular forces (IM)
• Types of IM (dipolar, H-bonds, vdW)
• Keesom, Debye & London forces
• Repulsive (hard-core) interactions
• Lennard-Jones potential
• Hydrogen bonding
• Relative magnitudes of IM
LECTURE 3
keywords
• Young-Laplace equation
• Radii of curvature for spheres & cylinders
• Measuring interfacial tension (geometric & force methods)
• Capillary rise
• Pendant drop (& captive bubble)
• Du Noüy ring & Wilhelmy plate
• Maximum bubble pressure
• The hydrophobic effect + examples
• Surfactant (amphiphile, lipid, detergent)
• Types of surfactants (ionic, neutral, zwitterioninc…)
• Effect of surfactants on surface tension
• Critical Micelle Concentration (CMC)
LECTURE 4
keywords
• Surfactant adsorption at interfaces
• Application of surfactant adsorption to colloidal dispersions
• Surfactant-induced surface tension decrease
• Micelles
• Change of properties @ CMC
• Krafft point, Cloud point
• Micelle shape
• Critical Packing Parameter
• Thermotropic & Lyotropic liquid crystals
• Wetting & Wettability
• Three-phase contact line
• Contact angle
• Young’s equation
• Wetting regimes
• Spreading parameter
LECTURE 5
keywords
• Advancing & receding contact angle
• Contact angle hysteresis
• Wenzel model, effect of increasing/decreasing roughness
• Cassie-Baxter model
• Ultrahydrophobic surfaces (Lotus effect)
• Critical surface tension, Zisman plot
• Wetting series
• Surface treatment for changing wettability (physical/chemical)
• Electric double layer (EDL)
• Origin of electric charge @ interfaces
• Bjerrum length
LECTURE 6
keywords
• Top-down vs. bottom-up preparation methods
• Mechanical comminution
• Laser ablation
• Electrical disintegration
• Peptization or chemical dispersion
• Ultrasonic dispersion
• Oxidation/reduction methods
• Stoeber process (sol-gel)
• Pyrolysis
• Emulsion polymerization
• Dispersion & suspension polymerization
LECTURE 7
keywords
• Models of the EDL: Helmholtz, Gouy-Chapman, Stern
• Poisson-Boltzmann equation
• Debye screening length
• Zeta potential
LECTURE 8
keywords
• Hamaker description of vdW forces (microscopic)
• Basic assumption of Hamaker
• General form
• Hamaker constant
• Lifshitz approach (macroscopic)
• Key results of Lifshitz theory
• The DLVO theory
• Primary & secondary minima & their physical meaning
LECTURE 9
keywords
• Steric stabilization
• Steric stabilizers & requirements
• Fischer theory
• Electrosteric stabilization
• Bridging flocculation
• Depletion attraction
• Solvation (hydration) forces
• Hydrophobic interaction (particles)
• Surface aggregation of colloids
• structural evolution of aggregates
• gelation, glass transition, crystallization
LECTURE 10
keywords
• emulsions: macro-emulsions & micro-emulsions (& stability)
• types of emulsifiers
• destabilization mechanisms (flocculation, coalescence, phase separation, Ostwald ripening)
• energy input for emulsification, hydrodynamic instabilities
• Bancroft rule
• Pickering emulsions
• Foams
• Similarities & differences between foams & emulsions
• Foaming agents
• Methods for preparing foams
• Froth flotation
• Stages in foam lifetime
