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Valentina Valenz Polymer and Material Chemistry University Inglés 30 fichas

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  1. 1POLYMER (definition)large molecules made up of identical building blocks (monomers)
  2. 2POLYMER (properties)- waxy solids
    - no molecular weight
    - no boiling point
    - no melting point
    - mixture of structures
  3. 3THERMOPLASTICS- polymers melt when heated, resolidify upon cooling
    - linear polymers (polyethylene, polypropylene, polyester)
  4. 4THERMOSETS- polymers do NOT melt when heated
    - decompose at high temperature
    - usually cross-linked (bakelite, vulcanised rubber)
  5. 5CONDENSATION POLYMERS (reaction scheme)- from monomers
    - loss of a small molecule    CONDENSATION POLYMERS (reaction scheme)
  6. 6ADDITION POLYMERS (reaction scheme)- all vinyl polymers
    - need to be unsaturated    ADDITION POLYMERS (reaction scheme)
  7. 7STEREOCHEMISTRY (double bond)STEREOCHEMISTRY (double bond)
  8. 8STEREOCHEMISTRY (site of reaction)STEREOCHEMISTRY (site of reaction)
  9. 9REGIOCHEMISTRYalmost always head to tail, some errors may occurREGIOCHEMISTRY
  10. 10TACTICITYchiral centres in vinyl polymers occur in evert second carbon
  11. 11ISOTACTIC SYNDIOTACTIC ATACTICISOTACTIC SYNDIOTACTIC ATACTIC
  12. 12COPOLYMERSmade from two monomers
    BLOCK: AAABBB
    ALTERNATING ABABAB
    RANDOM: AABABBB
  13. 13DIFFERENTIAL SCANNING CALORIMETRYDIFFERENTIAL SCANNING CALORIMETRY
  14. 14DIFFERENTIAL SCANNING CALORIMETRY- thermoanalytical technique
    - measures the difference between amount of heat required to increase temp of sample v. reference
  15. 15GLASS TRANSITION- the point at which rotation around single bonds becomes much easier
    - hard -> rubbery (slide + rotated_
    - below Tg: chains are entangled, glassy, brittle
    - above Tg: chains can pass each other, polymer softens, loses strength
  16. 16∆ at GLASS TRANSITION- heat capacity of polymer
    - refractive index "
    - coefficient of thermal expansion
    - electrical properties
  17. 17INCREASE/DECREASE OF GLASS TRANSITIONINCREASED BY: - pendant groups on backbone (require more energy to rotate as they are big)
    - rigid backbone structure
    - crosslinking
    - attractive forces (h-bonding)
    - molecular mass
    - stereochemistry
    DECREASED BY: plasticisers that act as lubricants
  18. 18POLYMER CRYSTALLIZATION- dependant on linearity/branched polymer
    - more difficult to crystallise than small molecules
    - many degrees of freedom (rotational + translational)
    - micro crystallites -> areas that are stereo regular -> rigidity and strength
    - polymers with no regular structure are amorphous (elasticity, toughness, impact resistance)
  19. 19MELTING TEMPERATURE- increased by side chains
    - dependant on polymer size/structure and crystalline/amorphous domains
    - wide temperature range
    - micro crystallites affect optical properties and transparency
  20. 20Tg v Tmfor most linear polymers
    0.5Tm ≤ Tg ≤ 0.8 Tm
  21. 21NUMBER AVERAGE MOLAR MASS, MnMi = relative molecular mass of species i
    Ni = number of molecules per species of i
    Mn should be close to distribution peak    NUMBER AVERAGE MOLAR MASS, Mn
  22. 22WEIGHT AVERAGE MOLAR MASS, Mw- properties of polymer dictated by longest molecule
    - small mole fraction->bulk polymer
    - always greater than max    WEIGHT AVERAGE MOLAR MASS, Mw
  23. 23DISPERSITYDm = Mw/Mn
    - polydispersity index (PDI>1)
    - only relevant for monodmal polymer
    high values are desirbale for processing properties
  24. 24END GROUP ANALYSIS- end group tends to be different from main chain
    - comparing end group to main chain will give Mn
    - titration + NMR
    - small polymers
  25. 25COLLIGATIVE PROPERTIES- dependant on number of molecules (Mn)
    - lowering of vapour pressure
    - increased boiling point
    - decreased freezing point
    - small polymers
  26. 26SOLUTION VISCOSITY- cheap, easy to set up, quick
    [ŋ] approximation of Mw = limiting viscosity at concentration 0
    - dependant on solvent, temp., press., polymer type, polymer MM    SOLUTION VISCOSITY
  27. 27GEL PERMEATION CHROMATOGRAPHY- separates molecules by size = molar mass distribution
    - dilute polymer solution passed through gel column
    - large molecules do not get stuck in pores efflux first
    - small molecules last
    - measured using refractive index & light scattering&viscosity = TRIPLE DETECTION
    - give Mn, Mw, D, distribution
  28. 28CHAIN POLYMERISATION (defintion)adds one monomer at a time
    monomer concentration decreases steadily
    high MM polymer is formed immediately, no change
    long reaction times increase yield not MM
    material either monomer or "completed polymer"
  29. 29STEP POLYMERISATIONany two species can react
    monomer disappears early in reaction
    Polymer MM rises steadily, exponential increase at the end
    long reaction time = higher MM
    monomer, oligomers, and polymers present at all stages
  30. 30KINETICS OF STEP REACTIONS

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University Polymer and Material Chemistry Fichas sobre Sin título, creado por Valentina Valenz el 19/05/2016.
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