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 ~ bi d l i t• B ~ binodal point

– at B, dG/dx1 = μ1 = μ2 = dG/dx2• local minor composition fluctuation

‐ betw the two S’s ~ unstableS ~ i d l i t ~ d2G/d 2 0 • local minor composition fluctuation 

– raise energy

– back to homogeneous solution

• S ~ spinodal point ~ d2G/dx2 = 0 • Local minor composition    fluctuation  g

• major fluctuation like nucleation

– phase separate to B comp

‐lower the energy‐fluctuation stabilized‐phase separate (1‐rich + 2‐rich)

– ‘nucleation and growth’

– outside B’s ~ stable

• single phase is stable

• ‘spinodal decomposition’co‐continuous to discontinuous

• single phase is stable

Melt-miscibleMelt miscible

SDNG SDNG

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

poly(A-alt-B)poly(A-co-B)p y( )poly(A-g-B)poly(A-b-B)p y( )

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

High capacity, self-assembled MOS decoupling capacitorscapacitors

IBM

IEEE ELECTRON DEVICE LETTERS, VOL. 25, NO. 9, SEPTEMBER 2004

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 Surface

t ~ L0

PSPMMA

Science, 275, 1458 (1997)

PMMA

Silicon waferP(S-r-MMA)

High capacity, self-assembled MOS decoupling capacitorscapacitors

IBM

IEEE ELECTRON DEVICE LETTERS, VOL. 25, NO. 9, SEPTEMBER 2004

Solvent annealing Solvent annealing –– long range orderlong range order

PS-PEO

Adv. Mater., 16, 226 (2004)

Mesoporous Silicates Replicated from Block Copolymer Templates in Supercritical Fluids

Pai et al Science (2004)Pai et al., Science (2004)

A highly ordered mesoporous silicate film prepared by infusion and condensation of TEOS within a preorganized PEO127-b-PPO48-127 48b-PEO127 BCP film dilated with scCO2 followed by calcination.

UltrahighUltrahigh--density nanowire arrays grown density nanowire arrays grown in selfin self assembled diblock copol me templatesassembled diblock copol me templatesin selfin self--assembled diblock copolymer templatesassembled diblock copolymer templates

PS-PMMA block copolymer :PS-PMMA block copolymer :20 nm diameter PMMA cylinders hexagonally packed in PS matrixg y pSpin coating onto conducting substrateUV exposure removes PMMA block andpolymerize PSFormation of 14 nm pores Electrodeposition of Co to obtain arrayElectrodeposition of Co to obtain array

Science, 290, 2126 (2000)

X ray scattering patterns at an angle of incidence at 45°X-ray scattering patterns at an angle of incidence at 45°.

(A)Before PMMA removal(A)Before PMMA removal(B)After PMMA removal

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