polymer blends, copolymers, and liquid crystal polymers · 2018. 1. 30. · polymer blends,...
TRANSCRIPT
Chapter 12.Chapter 12.Polymer blends, Copolymers, and
Liquid‐crystal polymers
12.1 Polymer blends
-Miscibility
y
MiscibilityΔGm <0
-Flory-Huggins interaction parameterΔΗm = kTχ12x1x2
ΔG = kT [(x1ln x1)/N1+ (x2ln x2)/N2 + χv1v2]ΔGm kT [(x1ln x1)/N1+ (x2ln x2)/N2 + χv1v2]
- Miscibility and compatibilization
Statistical thermodynamics for regular sol’n
• ΔSm by lattice modelFilli & l l i + ll– Filling n1 & n2 molecules in n1+n2 = n cells
• volume of 1 ≈ volume of 2 (small molecules)
Boltzmann relation S = k ln P– Boltzmann relation, S = k ln P • P ~ number of (distinguishable) ways
x ~ mol fractionn ~ numberx1 = n1/(n1+n2)
n = n1 + n2
x1 n1/(n1+n2)
– applying molar quantities,N ~ number of molesN = N1+ N2R = k NA
• heat of mixing– for small molecules in the absence of specific interaction b dbetw 1 and 2
ΔE ~ heat of vapΔE heat of vap
• free energy of mixing
• among polymersΔG = kT [(x1ln x1)/N1+ (x2ln x2)/N2 + χx1x2]ΔGm = kT [(x1ln x1)/N1+ (x2ln x2)/N2 + χx1x2]
– betw B and S ~ metastable
• B ~ binodal point
– at B, dG/dx1 = μ1 = μ2 = dG/dx2• local minor composition fluctuation
– raise energy
– back to homogeneous solution
• major fluctuation like nucleation• major fluctuation like nucleation
– phase separate to B comp
– ‘nucleation and growth’g
– outside B’s ~ stable
• single phase is stable
LCST vs. UCST
When?
Experimental detection of miscibility
Thermal analysis-Thermal analysis
-Microscopic analysisMicroscopic analysisSEM, TEM, AFM …
-Spectroscopy
what else?-what else?
Experimental detection of miscibility-Thermal analysis-Thermal analysis
miscible
miscibleImmiscible
miscible
miscible
Experimental detection of miscibility-SpectroscopySpectroscopy
Compatibilizationp
- Using compatibilizerex. block or graft copolymerg p y
- Reactive compatibilizationReactive compatibilization
Compatibilization – block or graft copolymer
Compatibilization – Reactive blendingp g
Principal polymer typesp p y yp
Morphologyp gy
How about their properties and applications?How about their properties and applications?
12.3 Copolymersp y
See p 361See p. 361
What will be the difference betweenWhat will be the difference between copolymers and blends?
Self‐assembly of Block Copolymers
PMMA PS B Sph.
A Sph.
Lamella
Sph.p
BA• Phase morphology depends on
relative polymer‐block chain lengths Gyroid
BCyl.
ACyl.
lengths• Length scale : 10 – 100 nm• PS‐b‐PMMA: PMMA can be easily
GyroidA B
ODTDisorderedy
removed (etched).fA (A component Volume Fraction)
spheres cylinders lamellae inversecylinders
inversespheres
gyroid inversegyroid
Cocontinuous gyroid phase
Copolymers combining elastomeric and rigid components
Segmented polyurethaneg p y
Tg of copolymers combining elastomeric and rigid componentselastomeric and rigid components
Block Copolymer Thin Film TemplateBlock Copolymer Thin Film Template
Ordering of diblock copolymer on a substratePerpendicular order of cylindrical domains of block copolymer can be obtained by tuning the interactions.
Using Random Copolymer Brushto Produce Neutral Surface
Passivation of SiOx Surfaceto Form Si-H Surfaceto Produce Neutral Surface to Form Si H Surface
t ~ L0
PSPSPMMAP(S-r-MMA)Silicon wafer
12.4 Liquid crystal polymersq y p y
Q What is LC state? Is it liquid or crystal?Q. What is LC state? Is it liquid or crystal?
LC polymer and mesogenic groupLC polymer and mesogenic group
Main chain LC polymer
Side chain LC polymers