Chapter 12.
Chapter 12.
Polymer blends, Copolymers, and
Liquid‐crystal polymers
12.1 Polymer blends
-Miscibility
y
Miscibility ΔG
m<0
-Flory-Huggins interaction parameter ΔΗ
m= kTχ
12x
1x
2ΔG = kT [(x
1ln x
1)/N
1+ (x
2ln x
2)/N
2+ χv
1v
2]
ΔG
mkT [(x
1ln x
1)/N
1+ (x
2ln x
2)/N
2+ χv
1v
2]
- Miscibility and compatibilization
Statistical thermodynamics for regular sol’n
• ΔS
mby lattice model
Filli & l l i + ll
– Filling n
1& n
2molecules in n
1+n
2= 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 fraction n ~ number x1 = n1/(n1+n2)
Å n = n1 + n2 x1 n1/(n1+n2)
– applying molar quantities,
N ~ number of moles N = N1+ N2
R = k NA
• heat of mixing
– for small molecules in the absence of specific interaction
b d
betw 1 and 2
ΔE ~ heat of vap ΔE heat of vap
• free energy of mixing
• among polymers
ΔG = kT [(x
1ln x
1)/N
1+ (x
2ln x
2)/N
2+ χx
1x
2]
ΔG
m= kT [(x
1ln x
1)/N
1+ (x
2ln x
2)/N
2+ χx
1x
2]
– betw B and S ~ metastable
• B ~ binodal point
– at B, dG/dx1 = μ1 = μ2 = dG/dx2
• local minor composition fluctuation Æ – 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 analysis Microscopic analysis
SEM, TEM, AFM … -Spectroscopy
what else?
-what else?
Experimental detection of miscibility -Thermal analysis
-Thermal analysis
miscible miscible Immiscible
miscible
miscible
Experimental detection of miscibility
-Spectroscopy Spectroscopy
Compatibilization p
- Using compatibilizer
ex. block or graft copolymer g p y
- Reactive compatibilization Reactive compatibilization
Compatibilization – block or graft copolymer
Compatibilization – Reactive blending p g
Principal polymer types p p y yp
Morphology p gy
How about their properties and applications?
How about their properties and applications?
12.3 Copolymers p y
See p 361
See p. 361
What will be the difference between What will be the difference between
copolymers and blends?
Self‐assembly of Block Copolymers
PMMA PS
BSph.
A Sph.
Lamella p Sph.
A B
• Phase morphology depends on relative polymer‐block chain
lengths
GyroidB Cyl.
A Cyl.
lengths
• Length scale : 10 – 100 nm
• PS‐b‐PMMA: PMMA can be easily
Gyroid A B ODT
Disordered
y removed (etched).
fA (A component Volume Fraction)
spheres cylinders lamellae inverse
cylinders
inverse spheres
gyroid inverse
gyroid
Cocontinuous gyroid phase
Copolymers combining elastomeric and rigid components
Segmented polyurethane g p y
Tg of copolymers combining
elastomeric and rigid components
elastomeric and rigid components
Block Copolymer Thin Film Template
Block Copolymer Thin Film Template
Ordering of diblock copolymer on a substrate
Perpendicular order of cylindrical domains of block copolymer can be obtained by tuning the interactions.
Using Random Copolymer Brush to Produce Neutral Surface
Passivation of SiOx Surface to Form Si-H Surface
to Produce Neutral Surface to Form Si H Surface
t ~ L0
PS PS PMMA
P(S-r-MMA) Silicon wafer
