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Motivation. Nanocomposites: What are they? A Class of polymeric composites in which the filler materials are at the “nanometer” scale. Why are they important?

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motivation
Motivation

Nanocomposites: What are they?

A Class of polymeric composites in which the filler materials are at the “nanometer” scale.

Why are they important?

They are known for their enhanced mechanical and other physical properties such as flame resistance. This is true even for very low filler contents, compared to the parent matrix.

What are we doing with them?

At present, proper understanding of microstructure-property correlations in nanocomposites is lacking.

Using a block copolymer matrix and ‘wettable’ silica-type fillers with well-defined geometries, we generate a nanocomposite model system.

used block copolymers
Used block copolymers

Polystyrene-b-polyisoprene

PS-b-PI

Polyisoprene-b-polyethyleneoxide

PI-b-PEO

synthesis of hairy fillers

Dissolution

Synthesis of ‘hairy’ fillers

The use of block copolymers as a structure directing agent allows synthesis of inorganic materials with well defined reproducible geometries and wettable surfaces.

experimental techniques
Rheometry

Small angle X-ray scattering (SAXS)

detector

X-ray

sample

Experimental techniques
  • Data analysis in terms of:
  • Storage Modulus (G’)
  • Loss Modulus (G’’)
  • Loss Tangent (tand)
  • Peak Position (q*)
  • Peak Intensity (I(q*))
  • Peak width (FWHM)
matrix and filler characterization

Sol Gel

Precursors

Matrix and filler characterization

Block copolymer matrix

PS-b-PI

  • PS-b-PI diblock copolymer
  • Mn=20800 g/mol
  • PDI=1.06
  • fPS=0.55
  • Lamellar morphology
  • d=18.7nm

Block copolymer template for fillers

Fillers

PI-b-PEO

plates, d=21.4nm

rods, d=22.0nm

spheres, d=19.9nm

neat ps b pi copolymer
Neat PS-b-PI copolymer

SAXS

Rheology

SAXS: TODT =178°C

Rheology: TODT =176°C

hybrid containing spheres 0 5wt
Hybrid containing Spheres (0.5wt%)

SAXS

Rheology

SAXS: TODT =167°C

Rheology: TODT =166°C

SFM image

hybrid containing long rods 0 5wt
Hybrid containing long rods (0.5wt%)

SAXS

Rheology

SAXS: TODT =153°C

Rheology: TODT =159°C

SFM image

hybrid containing short rods 0 5wt
Hybrid containing short rods (0.5wt%)

SAXS

Rheology

SAXS: TODT =161°C

Rheology: TODT =163°C

SFM image

hybrid containing large plates 0 5wt
Hybrid containing large plates(0.5wt%)

SAXS

Rheology

SAXS: TODT =163°C

Rheology: TODT =164°C

SFM image

hybrid containing small plates 0 5wt
Hybrid containing small plates(0.5wt%)

SAXS

Rheology

SAXS: TODT =162°C

Rheology: TODT =162°C

SFM image

conclusions
Conclusions
  • Addition of fillers (0.5wt%) leads to significant and complex changes in the order-disorder transition temperature, TODT, of the matrix block copolymer.
  • TODT is suppressed with increasing magnitude in the sequence: sph<lam<cyl.
  • Addition of the fillers causes a broadening of the transition temperature window in the sequence: sph<cyl<lam.
  • This is consistent with an increase of the peak width in SAXS as well as a broadening of the transition window observed in dynamic mechanical measurements.
comparison of t odt
Comparison of TODT

0.5wt%

5wt%

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