Chemistry in 21st Century

National Centre for Catalysis ResearchINDIAN INSTITUTE OF TECHNOLOGY MADRAS

APRIL 2010

Coverage and ReasonsTitle

Periodic properties of elements

Nomenclature and isomerism of coordination compounds

Nuclear reactions and carbon dating

Types of hybridization and geometry of molecules

Chemical equilibrium – Le Chatliers principle

Colloids and applications

Faradays laws and Kohlrausch’s law

Extraction of Metals

Spontaneous and non spontaneous reactions

Corrosion and its prevention

Properties and packing in solids

Wave equation and its significance

Petroleum and Petro chemicals

Bonding in molecules

Conventional concepts of bonding has to undergo change – Why?

Behaviour of molecules and reactivity of molecules – what is so special selectivity?

Geometry of the molecules, manifestations of molecules – functioning of molecules.

Architecture in solids – transport restrictions

Electrochemistry turns chemistry to be fully green

Behaviour of electrons – responsible for the science that is usually generated

Nuclear structure – evolution period and also energy conversion process

20th Century Chemistry• It was a silent revolution• Ammonia synthesis provided a means for food• FCC operation brought engineering marvel• Zeolites and solid state materials –

revolutionized electronic industry• Super conductors – energy concept changed

colours• Water will it be another wonder molecule this

century

WEAK INTERACTIONS

• Assembly appears to be the order these days – these assembly can arise out of weak interactions

• Weak interactions may be hydrogen bonding, van der waals forces and simple over lap of the least amount of charge cloud.

• Assembly assumes particular geometries, like helical structure, nano-coils, nano-twisted wires and many others – these resemble the bio-molecules

What is Green Chemistry?

It is better to prevent wastethan to clear it up afterwards % Atom economy is the new % yield

The strive towards theperfect synthesis Benign by design

Environmentally friendlyand economically sound?!?

The Twelve Principles of Green Chemistry

• It is better to prevent waste than to treat or clean up waste after it is formed.• Synthetic methods should be designed to maximize the incorporation of all materialsused in the process into the final product • Wherever practicable, synthetic methodologies should be designed to use and generate substances that possess little or no toxicity to human health and the environment• Chemical products should be designed to preserve the efficacy of function whilstreducing toxicity• The use of auxiliary substances (e.g. solvents) should be made unnecessarywherever possible and innocuous where used• Energy requirements should be recognized for their environmental and economic impacts and should be minimized. Synthetic methods should be carried out at ambient temperature and pressure• A raw material of feedstock should be renewable rather than depleting wherever technically and economically possible• Unnecessary derivatization (e.g. protecting groups) should be avoided wherever possible• Catalytic reagents (as selective as possible) are superior to stoichiometric reagents• Chemical products should be designed so that at the end of their function they do not persist in the environment and breakdown into innocuous degradation products• Analytical methodologies need to be further developed to allow for real-time inprocess monitoring and control prior to the formation of hazardous substances• Substances and the form of substances used in a chemical process should bechosen so as to minimize the potential for chemical accidents, including releases, explosions and fires

A Series of Reductions

Cost

Energy

Materials

Waste

Risk &Hazard

Nonrenewables

Reducing

How Efficient is Chemical Manufacturing?

E-factors

Industry Product tonnage Kg by-products / Kg productOil refining 106 – 108 < 0.1Bulk Chemicals 104 – 106 1 - 5Fine chemicals 102 – 104 5 - 50+Pharmaceuticals 10 - 103 25 - 100+

Industrial Ecology Goals for Green Chemistry

• Adopt a life-cycle perspective regarding chemical products and processes

• Realise that the activities of your suppliers and customers determine, in part, the greenness of your product

• For non-dissipative products, consider recyclability

• For dissipative products (e.g. pharmaceuticals, crop protection chemicals) consider the environmentalimpact of product delivery

• Perform green process design as well as green product design

Some Barriers to Adopting Greener Technology

· Lack of global harmonisation on regulation / environmental policy

· Notification processes hinder new product & process development

· Lack of widely accepted measures of product or process “greenness”

· Lack of technically acceptable 'green' substitute products and processes

· Short term view by industry and investors

· Lack of sophisticated accounting practices focussed on individual processes

· Difficult to obtain R&D funding

· Difficult to obtain information on best practice

· Lack of clean, sustainable chemistry examples & topics taught in schools & universities

· Lack of communication / understanding between chemists & engineers

· Culture geared to looking at chemistry not the overall process / life cycle of materials

The Chemical Industry in the 21st Century

Meeting social, environmental and economic responsibilities

• Maintaining a supply of innovative and viable chemical technology

• Environmentally and socially responsible chemical manufacturing

• Teaching environmental awareness throughout the education process

Twilight Can Turn into ““A”” New Dawn

Twilight creates illusion of light getting stronger. Twilight then fades into a dark night. It is always darkest before dawn. If we solve our energy crisis, the 21stcentury will be our greatest dawn. If we fail, we will have a dark future.

Aggregation is it universal?

• Having seen single molecules and their behaviour one has to turn the attention to aggregates.

• Why aggregates, it appears it is the natures way of preserving and fostering things – trees, plants, animals, human beings everything live as aggregates and care for the total aggregated assemblies and not for the individual species.

Aggregation

• The existence of single molecules can be understood from the point of view of minimization of free energy

• Aggregates how do they minimize the energy?• What is the driving force for this aggregation?• What is the type of interactions present in

aggregation?

Weak bonding is the cause for aggregation?

• What are weak bonding and how do they cause the aggregation?

• What are the energies involved in these weak forces?

• Are there a variety of these weak forces?• Do they have any constraints in geometry,

functionality, and electronic configuration?• How these weak forces account for the stabilities

observed

How Universal are aggregates?

• Many bio-molecules are aggregates • Materials are always aggregates but the

dimensionality ( uni, bi and tri dimensions) impart unique properties Why?

• Not only dimensions but also size in nanoscale and bulk scale they are different – shows aggregation has a role to play even in terms of the number of species aggregating?

Geometry has this a role in Aggregation

• This is a question one has to ask at this time• It is known that the helical structure of vital species

like DNA, collagen and other species? Why helical structure why not strings and wires and ropes?

• Twisted configurations why are they more stable than strings and wires?

• Nano coils and nano architectures how are they become more stable?

Some examples of aggregates in molecular systems• Water when aggregated becomes less dense

than water in liquid state but for all others the density increases when solidification – to show that both directions the change can take place on aggregation.

• Some time back people talked on “poly water” a concept which has been subsequently discarded – Why and why poly water cannot exist – any concept has evolved

Assembly why this is universal?

Directed Assembly addresses the fundamental scientific issues underlying the design and synthesis of new nanostructured materials, structures, assemblies, and devices with dramatically improved capabilities for many industrial and biomedical applications.

It focuses on discovering and developing the means to assemble nanoscale

building blocks with unique properties into functional structures under well-controlled, intentionally directed conditions.

Directed assembly is the fundamental gateway to the eventual success of technology.

It is based upon well-integrated research efforts that combine computational design with experimentation to discover novel pathways to assemble functional multiscale nanostructures with junctions and interfaces between structurally, dimensionally, and compositionally different building blocks. These efforts are leading to new methodologies for assembling novel functional materials and devices from nanoscale building blocks that will lead to novel applications of nanotechnology to spur industry into the 21st century.

Control of Polymer Supermolecular MorphologyControl of Polymer Supermolecular Morphology

A collaborative effort between L.S. Schadler, R.W. Siegel, Y. Akpalu (RPI) and ABB focuses on using nanoparticles to control the supermolecular morphology of semicrystalline polymers and their properties. The figure shows the effect of 20 nm diameter TiO2 nanoparticles dried or coated with N-(2-aminoethyl)3-aminopropyl-trimethoxysilane (AEAPS) on low-density polyethylene (LDPE). There is no change in unit cell dimension, degree of crystallinity, average lamellar thickness, or average spherulite size. The supermolecular structure, however, is impacted. Neat LDPE and the dried sample exhibit a well-defined, impinging, banded spherulite structure. The nanoparticles are embedded between the lamellae. In great contrast, no well-developed banded spherulites are observed in the AEPS sample, in which nanoparticles segregate to inter-spherulitic regions. This supermolecular structure is critical in controlling electrical breakdown strength in LDPE.

0 2.5 5

5

2.5

0 m m m

Figure: AFM tapping mode images of the supermolecular structures of (a) neat LDPE (b) LDPE filled with more compatible dried TiO2 nanoparticles and (c), LDPE filled with non-compatible AEAPS coated TiO2 nanoparticles.

Some examples of aggregation

In the next few slides ( mostly reproduced from literature and none of them are our own) we demonstrate how aggregated systems are relevant, perform and exhibit unusual properties.

These are chosen randomly and no specific significance to be attached to the choice.

What is the aggregation that we talk about?

Molecule of DNA Protein moleculeCarbon nanotube

water molecule

Water molecules – 3 atomsProtein molecules – thousands of atomsDNA molecules – millions of atomsNanowires, carbon nanotubes – millions of atoms

What are Nanostructures?At least one dimension is between 1 - 100 nm2-D structures (1-D confinement):• Thin films• Planar quantum wells• Superlattices1-D structures (2-D confinement):• Nanowires• Quantum wires• Nanorods• Nanotubes0-D structures (3-D confinement):• Nanoparticles• Quantum dotsDimensionality, confinement depends on structure:• Bulk nanocrystalline films• Nanocomposites

Si0.76Ge0.24 / Si0.84Ge0.16 superlattice

2 m

Si Nanowire Array

Multi-wall carbon nanotube

http://www.aip.org/mgr/png/2003/186.htm

Thin FilmsNanoscale Thin Film• Single “two dimensional” film, thickness < ~100 nm• Electrons can be confined in one dimension;

affects wavefunction, density of states• Phonons can confined in one dimension; affects thermal

transport• Boundaries, interfaces affect transport

Bulk crystal

a

Free standing thin film

d

Thin film

Substrate

http://scsx01.sc.ehu.es/waporcoj/charlas/cursodoctorado/12

Nanowires• Solid, “one dimensional”• Can be conducting, semiconducting, insulating• Can be crystalline, low defects• Can exhibit quantum confinement effects (electron, phonon)• Narrowing wire diameter results in increase in

band gap• Narrowing wire diameter can result in

decrease in thermal conductivity• New forms include core-shell and superlattice nanowires

2 m

Si Nanowire Array

Nanotube defined – a long cylinder with inner and outer nm-sized diameters Nanowire defined – a long, solid wire with nm diameter Si/SiGe NanowiresAbramson et al, JMEMS (2003)

Wu et al, Nanoletters, Vol. 2, 83 – 86 (2002)

Carbon NanotubesCarbon nanotube properties: • One dimensional sheets of hexagonal network of carbon rolled to form tubes• Approximately 1 nm in diameter• Can be microns long• Essentially free of defects• Ends can be “capped” with half a buckyball• Varieties include single-wall and multi- wall

nanotubes,ropes, bundles, arrays• Structure (chirality, diameter) influences properties:

– Semiconducting vs. metallic– Thermal, electrical conductance– Mechanical strength, elasticity

Multi-wall carbon nanotube

http://www.aip.org/mgr/png/2003/186.htm

Armchair

Zigzag

Chiralhttp://physicsweb.org/article/world/11/1/9/1

Other Nanotubes…Boron nitride nanotubes• Resistance to oxidation,

suited for high temperatures• Young’s modulus of 1.22 TPa • Semiconducting• Predictable electronic

properties independent of diameter and # of layers

SiC nanotubes:• Resistance to oxidation• Suitable for harsh

environments• Can functionalize surface Si

atoms

Boron nitride nanotubes

adopt various shapes

(red=boron, blue=nitrogen):

http://pubs.acs.org/cen/topstory/7912/7912notw1.html

SiC nanotubes grown at NASA

Glenn:

http://www.grc.nasa.gov/WWW/RT2002/5000/5510lienhard.html

Energy Applications: Conversion, Generation and Storage

Metal organic framework for

hydrogen storage

Replace conventional material with nanocomposite

to enhance performance

I

Cold

Hot2 m

Abramson et al, JMEMS, in review.Rosi et al, Science, Vol. 300, pp. 1127 -1129 (2003).

Dresselhaus group, MIT

Energy Applications: CatalysisOil refinement: zeolites are nanoporous (pores 3 – 10 Å) crystalline solids with well-defined structures (“molecular sieves”) used in oil refinement – increases gasoline yield from each barrel of crude oil by 50% Porous zeolite structure

2 atomic layer thick Au nanoclusters on TiO2

http://www.bza.org/zeolites.html

http://www.iaee.org/documents/p03eagan.pdf

Energy Applications: LEDsChange the nanostructure of Si (a very cheap material) to become nanoporous and visible light is emitted!

Use quantum dots (quantum confinement) for light emission

Cross-hairs of p-type and n-type nanowires (to get a p-n junction)

http://www.trnmag.com/Stories/2002/103002/Nanoscale_LED_debuts_103002.html

Quantum dot layers

Network of nanowires

http://www.trnmag.com/Stories/011701/Crossed_nanowires_make_Lilliputian_LEDs_011701.html

Energy Applications: LEDsQuantum dots/ nanocrystals are smaller than the wavelength of light, so they do not scatter light; scattering can reduce optical efficiency by up to 50%!

Energy Applications: BatteriesChange electrode materials by nanostructuring (texturing) to improved electrical performance; nanoscale particles boost energy storage and power delivery by reducing the distance Li ions travel during diffusion

Nanobattery: Fill a nanoscale membrane with an electrolyte, cap with electrodes; contact with a probe tip

Energy Applications: SolarSolar cells integrated into roof shinglesNanoscale crystals of semiconductor coated with light-absorbing dye emit electronsNanostructured diamond solar thermal cells capture light, which heats the lattice, which emits electrons; small tip gives high energy electrons

Tetrapods (the light absorbing materials) double the efficiency of plastic solar cells because they always point in the right direction

http://www.spacer.com/news/solarcell-01b.html

Nanostructured diamond solar thermal cells

Branched tetrapod

Dendritic Macromolecules as Unimolecular Micelles for Organic Solutes

(Stribaet al. 2002, Angwate. Chemie. Int. Ed., 41 (8), pp 1329-1324)

MD Simulations of the Meijer Dendrimer Box Mikliset al. 1997, JACS, 131, 7458

Catalytic DendriticMacromolecules(AstrucD. and Chardac, F. Chem. Rev. 2001, 101, 2991-3023)

Dendrimer-Encapsulated Zero Valent Metal Clusters(Scott et al. J. Phys. Chem. B. 2005, 109, 692-704)

Bioactive Dendritic Macromolecules(Chen et al. 2000, Biomacromolecules,1 (3): 473-480)

Fate, Transport and Toxicity of Dendritic aggregates

• Numerous dendrimers their toxicity and bio-distribution studies have carried out during the last 5 years

• –The effects of dendrimer core and terminal group chemistry, size, shape, hydrophobicity on dendrimer interactions with cell membranes and toxicity are becoming known and understood.

• •Only a limited number of studies have been published on the fate and tranport of dendrimers in the environment

• –Sorption of dendrimers onto mineral surfaces

Basic Research Needs to Assurea Secure Energy Future - Role of aggregates

Materials Research to Transcend Energy Barriers Energy Biosciences Research Towards the Hydrogen Economy Energy Storage Novel Membrane Assemblies an example of

aggregates Heterogeneous Catalysis- aggregate site density Energy Conversion- Energy Utilization Efficiency Nuclear Fuel Cycles and Actinide Chemistry Geosciences 

Some concepts already in vogue• The concept of “ensemble effect” in catalysis is well known – this is a

form of the aggregates that we call.• The concept of “active site” is known in catalysis but these are not

single atom site but some sites in particular locations with definite neighbours this is another version of aggregated sites.

• The concept of metal support interaction or as a matter of fact SMW interactions always imply an aggregated site – therefore the concept of aggregation and they behaving differently is known. SMSI and other interactions do not involve specific bonds and should be involving weak interactions.

• Weak interactions and its manifestations are therefore already known but has not been specifically indicated or identified.

Energy Source

% of U.S. Electricity

Supply

% of Total U.S. Energy

SupplyOil 3 39Natural Gas 15 23Coal 51 22Nuclear 20 8Hydroelectric 8 4Biomass 1 3Other Renewables 1 1

Drivers for the Hydrogen Economy:Drivers for the Hydrogen Economy:

0

2

4

6

8

10

12

14

16

18

20

22

1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 2020 2025

Mill

ions

of B

arre

ls p

er D

ay

Domestic ProductionDomestic

Production

Actual Projected

Light Trucks

Heavy Vehicles

Year

Air

MarineMarine

RailOff-roadOff-road

Cars

Pass

enge

r Ve

hicl

es

• Reduce Reliance on Fossil Reduce Reliance on Fossil Fuels Fuels

• Reduce Accumulation of Reduce Accumulation of Greenhouse GasesGreenhouse Gases

The Hydrogen Economy

solarwindhydro

fossil fuelreforming

nuclear/solar thermochemical

cyclesH2

gas orhydridestorage

automotivefuel cells

stationaryelectricity/heat

generation

consumerelectronics

H2O

production storage use in fuel cells

Bio- and bioinspired

9M tons/yr

150 M tons/yr(light cars and trucks in 2040) 9.70 MJ/L

(2015 FreedomCAR Target)

4.4 MJ/L (Gas, 10,000 psi) 8.4 MJ/L (LH2)

$3000/kW

$30/kW(Internal Combustion Engine)

H2

Fundamental IssuesFundamental Issues The hydrogen economy is a compelling vision:

- It potentially provides an abundant, clean, secure and flexible energy carrier

- Its elements have been demonstrated in the laboratory or in prototypes However . . .

- It does not operate as an integrated network- It is not yet competitive with the fossil fuel economy in cost, performance, or reliability- The most optimistic estimates put the hydrogen economy

decades away Thus . . . - An aggressive basic research program is needed, especially in gaining a fundamental understanding of the interaction between hydrogen and materials at the nanoscale

Hydrogen Production versus other fuel sourcesHydrogen Production versus other fuel sources

Current status: • Steam-reforming of oil and natural gas produces 9M tons H2/yr• We will need 150M tons/yr for transportation• Requires CO2 sequestration.Alternative sources and technologies: Coal:

• Cheap, lower H2 yield/C, more contaminants• Research and Development needed for process development, gas separations, catalysis, impurity removal.

Solar: • Widely distributed carbon-neutral; low energy density.• Photovoltaic/electrolysis current standard – 15% efficient• Requires 0.3% of land area to serve transportation.

Nuclear: Abundant; carbon-neutral; long development cycle.

Fossil Fuel Reforming Intermediate TermMolecular level understanding of catalytic mechanisms, nanoscale catalyst design, high temperature gas separation

Solar Photoelectrochemistry/PhotocatalysisLight harvesting, charge transport, chemical assemblies, bandgap engineering, interfacial chemistry, catalysis and photocatalysis, organic semiconductors, theory and modeling, and stability

Bio- and Bio-inspired H2 ProductionMicrobes & component redox enzymes, nanostructured 2D & 3D hydrogen/oxygen catalysis, sensing, and energy transduction, engineer robust biological and biomimetic H2 production systems

Nuclear and Solar Thermal HydrogenThermodynamic data and modeling for thermochemical cycle (TC), high temperature materials: membranes, TC heat exchanger materials, gas separation, improved catalysts

Priority Research Areas in Hydrogen ProductionPriority Research Areas in Hydrogen Production

Dye-Sensitized Solar Cells

Ni surface-alloyed with Au to reduce carbon poisoning

Synthetic Catalysts for H2 Production

Thermochemical Water Splitting

Current Technology for automotive applications • Tanks for gaseous or liquid hydrogen storage. • Progress demonstrated in solid state storage materials.System Requirements• Compact, light-weight, affordable storage. • System requirements set for FreedomCAR: 4.5 wt% hydrogen for 2005, 9 wt% hydrogen in the near future. • No current storage system or material meets all targets.

Hydrogen Storage PanelHydrogen Storage Panel

Gravimetric Energy DensityMJ/kg system

Volu

met

ric

Ener

gy D

ensi

tyM

J / L

sys

tem

0

10

20

30

0 10 20 30 40

Energy Density of Fuels

proposed DOE goal

gasoline

liquid H2

chemicalhydrides

complex hydrides

compressed gas H2

Ideal Solid State Storage Material• High gravimetric and volumetric density (9 wt %)• Fast kinetics• Favorable thermodynamics• Reversible and recyclable• Safe, material integrity• Cost effective• Minimal lattice expansion• Absence of embrittlement

Fuel Cells and Novel Fuel Cell Materials Panel

Current status: Limits to performance are materials, which

have not changed much in 15 years.

Challenges: Membranes Operation in lower humidity, more strength, durability and higher ionic conductivity.

Cathodes Materials with lower overpotential and resistance to impurities. Low temperature operation needs cheaper (non- Pt) materials. Tolerance to impurities: S, hydrocarbons, Cl.

Anodes Tolerance to impurities: CO, S, Cl. Cheaper (non or low Pt) catalysts.Reformers Need low temperature and inexpensive reformer catalysts.

2H2 + O2 2H2O + electrical power + heat

Chemical Oxidation:

Liberates e-

Chemical Reduction:

Consumes e-

Anode (Oxidation)

Cathode (Reduction)

Ionic Conductor (Membrane)

e-’s

External LoadNOT TO SCALEOxygen (O2)Fuel:

Reaction Products

IonTransp.

Reaction Products

H2, CH4, CH3OH

Fuel Cell ModelTHE ISSUE: better, cheaper, more durable, impurity tolerant materials. Most must/will be structured on the nanoscale.

Frank DiSalvo (Cornell)

Electrode/Membrane DesignVery challenging. Electrodes need to support three percolation networks: electronic, ionic, fuel/oxidizer/product access/egress.

2 –5 nm

20 -50 m

Alloys vs. Ordered Intermetallics

(A) (B)

Alloy; e.g. Pt/Ru (1:1) Ordered Intermetallic e.g.

BiPt

“Electrocatalytic Oxidation of Formic Acid at an Ordered Intermetallic PtBi Surface”, E. Casado-Rivera, Z. Gál, A.C.D. Angelo, C. Lind, F.J. DiSalvo, and H.D. Abruña, Chem. Phys. Chem. 4, 193-199 (2003)

Cyclic Voltammetry in 0.1 M H2SO4 + 0.125 M formic acid solution at a sweep rate of 10 mV/s

88

Enhanced Catalytic Activity for Formic Acid Oxidation

E(V) vs. Ag/AgCl

-0.2 0.20.0 0.4 0.6 0.8 -0.2 0.0 0.2 0.4 0.6 0.8 1.0

0.063 mA/cm2 2.4 mA/cm2

Pt PtBi

Expanded

Basic Research Needs for the Hydrogen EconomyBasic Research Needs for the Hydrogen Economy

Cross-Cutting Research Directions Nanoscale Materials and Nanostructured Assemblies Catalysis

- hydrocarbon reforming- hydrogen storage kinetics- fuel cell and electrolysis electrochemistry

Membranes and Separation Characterization and Measurement Techniques Theory, Modeling and Simulations Safety and Environment

Hydrogen Studies

the hydrogen economy requires

breakthrough basic research to find new materials and processes

define a new state of the art

universal finding:

Directed Assembly addresses the fundamental scientific issues underlying the design and synthesis of new nanostructured materials, structures, assemblies, and devices with dramatically improved capabilities for many industrial and biomedical applications.

It focuses on discovering and developing the means to assemble nanoscale

building blocks with unique properties into functional structures under well-controlled, intentionally directed conditions.

Directed assembly is the fundamental gateway to the eventual success of

nanotechnology. It is based upon well-integrated research efforts that combine computational design with experimentation to discover novel pathways to assemble functional multiscale nanostructures with junctions and interfaces between structurally, dimensionally, and compositionally different building blocks. These efforts are leading to new methodologies for assembling novel functional materials and devices from nanoscale building blocks that will lead to novel applications of nanotechnology to spur industry into the 21st century.

Nanoparticle Control of Polymer Supermolecular Nanoparticle Control of Polymer Supermolecular MorphologyMorphology

A collaborative effort between L.S. Schadler, R.W. Siegel, Y. Akpalu (RPI) and ABB focuses on using nanoparticles to control the supermolecular morphology of semicrystalline polymers and their properties. The figure shows the effect of 20 nm diameter TiO2 nanoparticles dried or coated with N-(2-aminoethyl)3-aminopropyl-trimethoxysilane (AEAPS) on low-density polyethylene (LDPE). There is no change in unit cell dimension, degree of crystallinity, average lamellar thickness, or average spherulite size. The supermolecular structure, however, is impacted. Neat LDPE and the dried sample exhibit a well-defined, impinging, banded spherulite structure. The nanoparticles are embedded between the lamellae. In great contrast, no well-developed banded spherulites are observed in the AEPS sample, in which nanoparticles segregate to inter-spherulitic regions. This supermolecular structure is critical in controlling electrical breakdown strength in LDPE.

0 2.5 5

5

2.5

0 m m m

Figure: AFM tapping mode images of the supermolecular structures of (a) neat LDPE (b) LDPE filled with more compatible dried TiO2 nanoparticles and (c), LDPE filled with non-compatible AEAPS coated TiO2 nanoparticles.

Thank you all for your patience