Polymer Nanocomposities

Prof. V. KrishnakumarProfessor and Head

Department of PhysicsPeriyar University

Salem – 636 011, India

Nanocomposites

Small filler size: – High surface to volume ratio

• Small distance between fillers → bulk interfacial material

– Mechanical Properties • Increased ductility with no decrease of strength, • Scratching resistance

– Optical properties• Light transmission characteristics depends on particle size

"Composite Materials" are a new emerging class of materials to overcome the limitations of monolithic conventional materials.

Why Nanocomposites

Polymer Nanocomposites-Combination of a polymer matrix and inclusions that have at least one dimension (i.e. length, width, or thickness) in the nanometer size range known as polymer nano composities.

• Polymers are light weight

• Corrosion-resistant materials.

• Traditional composites: the length scale of the fillers is in micrometers.

What is a polymer?

• A long molecule made up from lots of small molecules called

• monomers.

All the same monomer

• Monomers all same type (A)

• A + A + A + A

• -A-A-A-A-• eg poly(ethene)

polychloroethene PVC

Different monomers

• Monomers of two different types A + B

• A + B + A + B -A-B-A-B-• eg polyamides • polyesters

Addition polymerisation

• Monomers contain C=C bonds

• Double bond opens to (link) bond to next monomer molecule

• Chain forms when same basic unit is repeated over and over.

• Modern polymers also developed based on alkynes R-C C - R’

Copolymerisation

• when more than one monomer is used.

• An irregular chain structure will result eg propene/ethene/propene/propene/ethene

• Why might polymers designers want to design a polymer in this way?

• (Hint) Intermolecular bonds!

Metallic Nanocomposites

Metals – size dependent property. Metallic nanoparticles + polymers Interesting for functional applications because the properties of nano- sized metals

(optical, magnetic, dielectric, and thermal transport properties) leave unmodified after embedding in polymers.

EM wave + nanomaterials

Surface Plasma Resonance effect

Various nonlinear susceptibilities

Nonlinear optical properties of nanomaterials

3rd optical nonlinearity of routine materials

Normally large 3rd nonlinear susceptibility and ultrafast response are difficult to achieve simultaneously however this can be achieved by using organic polymers

NLO Materials Third order NLO (m2/W)

Response time (S)

Large 3rd order and fast response time -Essential

Organic polymers 10-16 – 10-17 10-15

Semiconductors 10-17 10-13

Liquid crystals 10-7 10-6

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Host Polymer

possible to tailor the properties of composite materials by selecting, shaping and distributing the raw materials

can develop or design new materials with desired or improved properties

Versatility of Nano Composites

Agglomeration

Absorption band edge falls in invisible region

Monodispersed

Absorption edge falls in visible region

Band gaps of different bulk and nanocrystalline semiconductors

Material Bohr radius (aB) in Å

Bulk band gap (Eg ) in eV

Nano form-Band gap (En,g)

in eV

ZnS*

CdS† PbS

1530200

3.52.40.4

5.25.525.2

These differences in properties of nanoparticles are used in microelectronics, quantum dot lasers, chemical sensors, data storage, and a host of other applications

*Oleksandr L. Stroyuk, Volodymyr M. Dzhagan, Vitaliy V. Shvalagin, and Stepan Ya. Kuchmiy J. Phys. Chem. C 114 (2010) 220–225

†K. Manickathai, S. Kasi Viswanathan, M. Alagar, Indian J. Pure. Appl. Phys 46 (2008) 561-566

PropertiesDepend on Matrix, NanoFillers, etc

Improved Properties

Mechanical Properties (tensile strength, stiffness, toughness)

Thermal expansion

Thermal conductivity

Ablation resistance

Chemical resistance

Disadvantage

Viscosity increase (limits processability)

Sedimentation

Dispersion and distribution difficulties

Application

• Automobile (gasoline tanks, bumper, interior and exterior panels, etc…)

• Electronic and Electrical (Printed circuits and electronic components)

• Food packing (Containers)• Cosmetics (Controlled release of “active

ingredients)• Environment (Biodegradable materials)• Gas barrier (Tennis balls, food and beverage

packing)• Military and aerospace

Depend on Matrix, NanoFillers etc…