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Summary SEM (Structure and Properties of Materials)
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Summary of 29 pages for the course 4052STEVM at TU Delft (SEM Summary)
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Structuur en Eigenschappen van Materialen(SEM)
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4052 STEVM
,College 1 Introduction
Intermolecular forces
Electrically neutral molecules
Hydrogen bonding
Dipole-dipole interactions (vd Waals force)
Increases with increasing polarity for molecules of equal mass and size
Dispersion forces (vd Waals force)
Increases with molecular weight; atomic or molecular size
Are found in all substances
Ion and polar molecule
Ion dipole force
Increases as either the ionic charge or the magnitude of the dipole moment increases.
Intramolecular (bonding) forces
Covalent
Metallic
Ionic
The stronger the forces, the higher boiling point and melting point
Mixing and solubility
∆ G=−RT ln K a
∆ Gmix =∆ H mix−T ∆ S mix
Entropy favors mixing: T ∆ S mix >0
NO mixing for ∆ H mix >T ∆ Smix
Oplosbaarheid neemt toe met toenemende T vanwege gunstige ∆ S mix
, Hydrophobic effect
Water + apolar compound
1. The water molecules will form a hydration cage around the apolar compound
2. This reduces the hydrogen bonding capabilities of water
3. Preferred orientation of water molecules around apolar compounds causes loss of
entropy
Association of apolar substances in water leads to gain of entropy
Surface tension
The higher interaction means a higher energy penalty for a molecules on the surface
a measure of the net inward force that must be overcome to expand the surface area of a
liquid. Is the energy required to increase the surface area of a liquid by a unit amount
- Higher surface tension, higher interaction forces
Viscosity: resistance of a liquid to flow
- Higher viscosity, higher resistance, higher interaction forces
College 2 en 3 Polymer synthesis and step and chain growth
Polymeren
Thermoharders/sets: mixture of 2 component which react. Crosslinked at high
temperatures, keeps its shape
Thermoplasten: is vervormbaar
- Heat --> liquify
- Cool --> solidify
Homopolymeren: nA An
- Lengte
- Tacticiteit
Syndiotatic = crystalline: opposite configuration is adopted
at successive chiral centres
Atactic = amorphous: steric arrangement is random
Isotactic = semi crystalline: all of the repeat units have the
same configuration
- Vertakkingen
Co-polymeren: nA + mB AnBm
- Alterning: ABABABAB
- Random: AABABBBA
- Block: 1 polymeer is reactiever: AAABAA of eerst 1 polymeer laten reageren: AAABBB
- Sidechain or grafted: hoofdketen waaraan zijketens komen van een andere polymeer
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