POLYMER NANOCOMPOSITES :

MOLECULAR APPROACHES TO TAILORING SURFACES

Dr. S. SivaramNational Chemical Laboratory,

Pune-411 008, INDIA

Tel : 0091 20 2589 3030Fax : 0091 20 2589 3355

Email : sivaram@ems.ncl.res.inVisit us at : http://www.ncl-india.org

Oklahoma State UniversityStillwater

May 24, 2010

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH)

Mission

To provide scientific industrial Research industrial Research

& Development that maximizes the

economic, environmental &

societal benefits for the people

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH (CSIR)

ESTD.

Multi-disciplinary multi-locationchain of 37 research laboratoriesLargest chain of publicly funded laboratoriesTotal staff strength of 18000 ; scientific and technical staff : 13000

ESTD.1942

THE PURPOSE OF THIS LABORATORY IS TO ADVANCE

KNOWLEDGE AND TO APPLY CHEMICAL SCIENCE FOR

THE GOOD OF THE PEOPLE

J W McBain

NCL : A SNAP SHOT

• Established : 1950• Location : Pune, India• Total personnel

• Permanent Staff : 730 Scientific : 206Technical : 330Administrative : 194

• Research Fellows (CSIR, UGC) : 440• Project Staff (M.Sc’s) : 382• Post doctoral fellows : 24

One of the largest publicly funded research institution in IndiaOne of the oldest research institutions of independent India

NCL AT A GLANCE

• Over 220 scientific staff with PhD • Interdisciplinary research centre with interests in polymer

science, organic chemistry, catalysis, materials chemistry, chemical engineering, biochemical sciences and process development

• Excellent infrastructure for measurement science and chemical informationinformation

• 400 + graduate students pursuing research towards doctoral degree; about 80 students awarded Ph.D. degree by the University of Pune every year; a strong and young talent pool which renews every few years

• Publish the second largest number of peer reviewed papers in chemical sciences (~ 450) , file the largest number of patents, both in India and overseas ( > 50) and produce the largest number of Ph.Ds in chemical sciences in India

SCIENTIFIC DIVISIONS

BIOCHEMICALSCIENCES

CATALYSISCHEMICAL ENGINEERING

AND PROCESSDEVELOPMENT

PHYSICAL ANDMATERIALSCHEMISTRY

PLANT MOLECULARBIOLOGY

CHEMICALENGINEERING

SCIENCE

MATERIALS CHEMISTRY INCLUDING

NANO MICROBIAL ANDENZYME SCIENCE

PLANT TISSUECULTURE

SCIENCE

CATALYSIS,REACTORS AND

SEPARATION

PROCESS DEVELOPMENT

NANO MATERIALS

THEORY ANDCOMPU-

TATIONALSCIENCE

BIOCHEMICALENGINEERING

SCIENTIFIC DIVISIONS

POLYMER SCIENCEAND ENGINEERING

ORGANIC CHEMISTRY

POLYMERCHEMISTRY

SYNTHETICMETHODOLOGIES

POLYMER PHYSICS

COMPLEX FLUIDSAND POLYMERENGINEERING

CHEMICAL BIOLOGY

PHOTOCHEMISTRY

SUPRAMOLECULARCHEMISTRY

CARBOHYDRATE CHEMISTRY

PROCESS R&D

NCL : RESOURCE CENTRES

- National Repository of Molecules (2007)- NCL Innovations ( 2006)

– Digital Information Resource Centre (2003)– Combi Chem Bio Resource Centre (2002)– Centre for Materials Characterization (2002)– Centre for Materials Characterization (2002)– Central NMR Facility (1998)– Catalyst Pilot Plant (1995)– National Collection of Industrial Microorganism

(1950)

RESEARCH PLATFORMS

• Clean Technology- Solid catalysts- High specificity / atom economy- Green solvents

• Chemistry in Unusual Media- Supercritical CO2 and water- Supercritical CO2 and water- Aqueous media- Ionic liquids- Reaction in dispersions, suspensions and emulsions- Solid state reactions

• Industrial (white) Biotechnology- Bio-catalysis and bio-transformations- Bio-based building blocks for performance chemicals - Fermentation processes Contd….

RESEARCH PLATFORMS

• Chemistry Toolboxes- Chiral switches / single enantiomers- Microencapsulation- Synthetic chemistry tool boxes (e.g. Suzuki coupling,catalytic hydrogenation, metathesis, click chemistry etc.)

- Crystal engineering and polymorphmism- Crystal engineering and polymorphmism

• Unusual Reaction Conditions- Photochemistry / photocatalysis- Electrochemistry- Microwave- Sono-chemistry- Plasma

Contd….

RESEARCH PLATFORMS

• New Processes / Product Strategies

- Chemical product engineering- Micro-reaction engineering- Novel reactor and mixer designs- Novel reactor and mixer designs- Novel separation processes especially membrane basedprocesses- Computational modeling, simulation and visualization

- Process intensification / smaller footprint of process plants- Modular and mobile manufacturing- Energy and water use efficiency- Effluent and waste minimization

� Nano-science and Nano-technology (2005)�Chemical Biology (2007)�Scientific Computing (2008)� Micro-reactor Engineering(2008)

CENTERS OF EXCELLENCE

� Micro-reactor Engineering(2008)�Materials for Solar Energy and Fuel Cells (2010)� Clean Coal Technologies (2010)

• Nano-composite is a hybrid material whose distinct

components are dispersed on a scale of nanometers.

• New class of fillers : nano-particles, nano-tubes / fibers

and nano-clays

• Typically < 5 % of the filler is required to obtain remarkable

WHAT ARE POLYMER NANOCOMPOSITES?

• Typically < 5 % of the filler is required to obtain remarkable

improvement in properties.

• Mechanical, thermal, electrical, optical, magnetic, barrier

and flame retardant properties are improved without

significant loss in toughness and clarity.

MACRO- AND NANO-COMPOSITES

MACROCOMPOSITES

• Short or long fibers dispersed in an organic polymer matrix

• Fibers: Glass, carbon,

NANOCOMPOSITES

• Multiphase material comprising of a matrix polymer and a dispersed inorganic phase

• Inorganics : clay, silica, • Fibers: Glass, carbon, boron

• Interfacial strength between the matrix and fiber determine properties

• Inorganics : clay, silica, mica, zeolites, molybdenum oxides/ sulfides

• Properties determined by the size of the dispersed inorganic phase (typically in nanometer sizes)

IIT-Madras 020905

FROM STRUCTURAL TO FUNCTIONAL MATERIALS

STRUCTURALMATERIALS

FUNCTIONALMATERIALS

MACROCOMPOSITES• Wetting and hydrophilic Interactions

BIOCOMPOSITES•Molecular self assembly•Hydrogen bondingInteractions

• Adhesive forces•Hydrogen bonding•Hydrophobic interactions

NANOCOMPOSITES•Intercalation and exfoliation•In-situ polymerization andpolymerization in constrained spaces•Hydrophobic interactions and electrostatic force

IIT-Madras 020905

Rigid rod fillers, polymer-polymer nanocomposites

Clays, Mica, Aluminosilicates

Macroscopically dispersed clays,

conventional inorganic fillers

POLYMER NANOCOMPOSITES :MOLECULAR HYBRIDS

1 D 2 D 0D/3D

POLYMER CLAY NANOCOMPOSITES SIMULTANEOUSLY EXHIBIT PROPERTIES OF BOTH 2D AND 3D HYBRIDS

STRUCTURE OF CLAYS

Montmorillonite Mx(Al4-xMgx)Si8O20(OH)4

Hectorite Mx(Mg6--xLix)Si8O20(OH)4

Saponite MxMg6Si8-xAlx) O20(OH)4

• Layered alumino silicates containing tetrahedral and octahedral sheets

• Stacked two dimensional oxy-anions are separated by hydrated cations

• The gallery cations can be replaced by soft organic cations,

examples, alkylammonium, alkyl phosphonium. This expands the inter-

gallery distances and also renders the gallery hydrophobic

STRUCTURE OF POLYMER CLAY NANO-COMPOSITES

• X-ray diffraction- most common technique to determine the

structure of nano-composites – shift in the d 001 peak

• Intercalated structures lead to well defined X-ray patterns

• Exfoliated structures show featureless XRD pattern due to

loss of ordered layered structures

• TEM offers the direct evidence for de-lamination of clay

platelets

• Rheological tools offer new insights into the structure of

nano-composites; In- situ techniques of structure

development during processing are also emerging as

powerful tools

TYPES OF NANOCOMPOSITES

PREPARATION OF NANOCOMPOSITES

• Melt intercalation

• In situ intercalative polymerization

• Solution Mixing d 001 peak

Reactive Modifiers

Ring opening Polymerization

CaprolactamCaprolactone

Radical Polymerization

Vinylbenzyl alkylammonium

cation

Olefin

IN SITU POLYMERIZATION AND REACTIVE MODIFIERS FOR CLAY

O N

N O11

O

BrBr

Thermoset Polymers

epoxy resins

Living or Controlled

Condensation Polymerization

PET, PBO, PU, PI

Olefin Polymerization

Catalyst on Clay

O

OO

N

N Cl

S

NS

NBr

HOO

N

NCl

Controlled Polymerization

POLYMER NANOCOMPOSITES : UNMET CHALLENGES

• Poor understanding of the nature of interface between the nano-particle and the polymer

- Surface modification of the nano-particle; compatibility and stability of the modifiers to polymer processing conditions

- Ability of polymer to wet the surface of the particle; nature of adsorption process of the macromolecule on the surface of the inorganics

- Inability to assess whether the nature of interface remains unchanged after thermal processing

• Inability to derive generalized rules of behavior for nano-composites

- PP-clay nano-composites show property enhancements, whereas, PE-clay nano-composites show no property improvement

- With PP , property enhancements are observed with higher MFI materials( lower MW), whereas, no enhancements are observed with lower MFI materials

- The relative roles of internal modifiers and externally added modifiers (compatibilizers) are inadequately understood

- Clays and nano-particles influence crystallization rates of semi-crystalline polymers. They are not just inert fillers.

POLYMER NANOCOMPOSITES : UNMET CHALLENGES

• Polymer nanocomposites predominantly restricted to polar polymers, e,g, Nylon, epoxy, poly(aniline)s . Polypropylene is the only widely studied non polar polymer. This is indicative of the difficulties in tailoring hydrophilic clay surfaces for compatibility with non polar polymers

• With clays, quarternary ammonium salts of long chain fatty acids are predominantly used as modifiers to render the inter layer gallery of clay somewhat hydrophobic. However, it is well known that such ammonium compounds are not very thermally stable and decompose below the melt processing temperatures of most polymers. Consequently, it is uncertain whether the structure of the clay remains in tact after melt processing.

TAILORING INTERFACES : TWO APPROACHES

� Use of organic modifiers which have reactive functionalities capable of becoming part of a polymer chain. This approach tethers the polymer chain within the interlayer gallery of the clay. The other end of the modifier molecule is bound to the clay The other end of the modifier molecule is bound to the clay surface through weak electrostatic forces

� Use of polymers with polar groups in the chain capable of interacting with the inter - gallery cations through electrostatic forces

SYNTHESIS OF POLYCARBONATE (PC) - CLAY NANOCOMPOSITES VIA IN-SITU POLYMERIZATION :

TAILORING INTERFACES THROUGH CHEMICAL TAILORING INTERFACES THROUGH CHEMICAL TETHERING OF POLYMER CHAINS

PC-NANOCOMPOSITES USING CLAY

MODIFIED WITH QUATERNARY ALKYL AMMONIUM SALTS

In-situ melt polymerization of bis- Phenol Awith diphenyl carbonate at 250°C resulted inthe formation of intercalated nanocomposite

Molecular weights of the polymer was low(Mn: ~9500)

Thermogravimetric analysis of the organoclay

Hoffmann degradation by ββββ- H elimination

N

C

R

R

CC

H 3

+

H O -

H

CC

+

NR

RH 3C

Ph3P+

Br-

N

N

CH3

CH3+

Br-

Hexadecyltriphenylphoshonium bromide (C16P)

Hexadecyl-1,2-dimethylimidazolium bromide (C16IMI)

THERMAL STABILITY OF PHOSPHONIUM AND

IMIDAZOLIUM MODIFIED CLAYS

bromide (C16IMI)

C16IMI-MMT

C16P-MMT

300 °C

17.8 Å

17.8 Å

21.5 Å

Entry no: 8

C16P-MMT

Inte

nsi

ty (

a.u

)PC/CLAY NANOCOMPOSITES WITH PHOSPHONIUM

CATIONS AS MODIFIERS

Ph3P

Br

2 4 6 8 10

17.8 Å

17.8 Å

Entry no: 6

Entry no: 7Inte

nsi

ty (

a.u

)

2 ThetaPC/C16P-MMT 3.6 wt% at different resolutions

Formation of phase separated nanocomposites

SYNTHESIS OF REACTIVE MODIFIERS

CH3

O

CH3

O

O O

CH3

O

O

OH10

CH3

O

OH10

CH3NaCl/H2O

DMSO

PhOH/HCl SHCOOH

OH

OH11

OH

Br11 CBr4/PPh3

OH Br10

NaOMe/MeOH

OHOH

PPh3

N

N

Br

OH

OH

11 PPh3

+Br

NN

OH

OH

11 +

BPAIMIBPAP

Entry Organoclay Catalyst a Wt % of MMT

Mole ratio (DPC: BPA: BPA

equivalents in organoclay)

Tg(°C)

Poly(carbonate)s b

Tg(°C)

Mn x 10-3 c

Mw/Mnc

1 - TMAH/NaOH - 108: 100: 0 146 - 22.1 2.31

2 BPAP-MMT TMAH/NaOH 1.8 108: 99.6: 0.45 124 122 4.4 1.93

3 BPAP-MMT - 1.8 108: 99.6: 0.45 145 144 24.5 1.74

PREPARATION OF PC/CLAY NANOCOMPOSITES

USING PHOSPHONIUM CATIONS AS MODIFIERS

4 BPAP-MMT - 3.6 108: 99.1: 0.91 144 138 20.7 2.26

5 BPAP-MMT - 5.3 108: 98.6: 1.36 145 134 25.0 2.77

6 C16P-MMT - 1.8 108: 100: 0 141 144 15.0 1.81

7 C16P-MMT - 3.6 108: 100: 0 143 142 16.5 1.76

8 C16P-MMT - 5.3 108: 100: 0 142 143 18.8 1.69

a TMAH: 10-4 mmol/mol of BPA, NaOH: 10-6 mmol/mol of BPA b obtained from the nanocomposite after ion exchange with LiCl

c by GPC in CHCl3 and calculated with respect to polystyrene standards

THERMAL STABILITY OF ORGANOCLAYS MODIFIED WITH THE REACTIVE MODIFIERS

R

OHR

240 °C

300 °C The first step in degradation of BPAP-MMT and BPAIMI-MMT is likely due tothe decomposition of the bis-phenolmoiety. However, such degradation isless likely once the bis-phenol moietyis incorporated into a polymer chain

OH

OH

+OH

PC- NANOCOMPOSITES WITH CLAYS MODIFIED WITH THE REACTIVE MODIFIERS

Exfoliated structures result using clays with modifiers containing reactive functionalities while only intercalated structures are

obtained when the clays used do not have a reactive functionality

3.6 %

PC/CLAY NANOCOMPOSITES WITH REACTIVE MODIFIERS BEARING PHOSPHONIUM CATIONS

PPh311

HO Br

5.3 %Good dispersion of the clay

indicative of exfoliated structures.

OH

1.8 %

0

400

800

1,200

1,600

2,000

2,400

Entry no: 1

Entry no: 3Entry no: 4Entry no: 5

E' (

MP

a)

0

400

800

1,200

1,600

2,000

Entry no: 1

Entry no: 6

Entry no: 7

Entry no: 8

E' (

MP

a)

Ph3P

Br

PPh311

OH

HO Br

DYNAMIC MECHANICAL BEHAVIOR

0 40 80 120 160 200Temperature (°C)

0 40 80 120 160 200Temperature (°C)

• Increase in storage modulus is higher for exfoliated nanocomposites obtained using reactive modifiers

• Relatively slower relaxation behavior for the exfoliated nanocomposites is attributed to the restricted mobility of polymer chains anchored to the clay surface.

Entry Organoclay Catalyst a Wt % of

MMT

Mole ratio (DPC: BPA: BPAequivalents in organoclay)

Tg(°C)

Poly(carbonate)s b

Tg (°C) Mn x 10-3 c

Mw/Mnc

9 BPAIM-MMT TMAH/NaOH 3.6 108: 99.1: 0.91 128 132 8.3 1.91

10 BPAIM-MMT - 3.6 108: 99.1: 0.91 126 131 8.2 1.94

11 C16IM-MMT - 3.6 108: 100: 0 132 138 10.3 2.05

PREPARATION OF PC/CLAY NANOCOMPOSITES USING IMIDAZOLIUM CATIONS AS MODIFIERS

a TMAH: 10-4 mmol/mol of BPA, NaOH: 10-6 mmol/mol of BPA a TMAH: 10-4 mmol/mol of BPA, NaOH: 10-6 mmol/mol of BPA b obtained from the nanocomposite after ion exchange with LiCl c by GPC in CHCl3 and calculated with respect to polystyrene standards

• Extensive depolymerization was observed resulting in low molecular weight PC.

• This is indicative of decomposition of the modifier during polymerization resulting in free imidazole formation.

• Imidazoles in high concentration are known to be efficient depolymerization agents for PC

N NR'

R

OH

HO R

OH

O

N N

R'

2 4 6 8 10

0

5000

10000

15000

20000

23.0 Å

Entry no: 10

BPAIM-MMT

Inte

nsi

ty (

a.u

)

2 Theta

PC/CLAY NANOCOMPOSITES WITH IMIDAZOLIUM

CATIONS AS MODIFIERS

Exfoliated structures using modifiers with reactive functionality

2 4 6 8 10

5000

10000

15000

27.6 Å

18.5 Å

Entry no: 11

C16IM-MMT

Inte

nsi

ty (

a.u

)

2 Theta

Intercalated structures using modifiers with no reactive functionality

CONCLUSIONS

Modified clay

reactive groupNo reactive group

ExfoliatedIntercalated

SYNTHESIS OF Syndiotactic - POLYSTYRENE (s PS) -CLAY NANOCOMPOSITES :

TAILORING INTERFACES THROUGH USE OF TAILORING INTERFACES THROUGH USE OF SULFONATED POLYSTYRENE IONOMERS AS MODIFIERS

HCH2C CH2

HC

x y

SO3H

CH2HC

n

H3C C O SO3H

O

C2H2Cl4/ CHCl3

HCH2C CH2

HC

x y

SO3- M+

M OH/MeOH

Where M+ = Na+, K+ or Rb+

70 °C/3 hours

PREPARATION OF SULFONATED s-PS IONOMERS

sPS was sulfonated to different levels (0.5, 2.0, 3.2 and 3.8 mol%) and neutralized with alkali salts (NaOH, KOH, RbOH)

STRUCTURE OF s-PS/ORGANOCLAY NANOCOMPOSITES

• In the nanocomposite, s-PS penetrates into a fraction of the clay galleriesand the gallery expands to 21.0 Å.

• The peak at around 2θ = 6.8° in the sPS and sPS/organoclay nanocomposite isdue to the 1 1 0 reflection of the αααα crystalline form.

• The organoclay tactoids remain in tact without any substantial intercalationdue to limited interaction of s-PS with the organoclay layers in view of the lowsurface energy of the sPS.

STRUCTURE OF SULFONATED S-PS IONOMER/ORGANOCLAY

NANOCOMPOSITES

Sulfonation level (%)

Clay gallery height (Å)

H+ Na+ K+ Rb+

0.5 18.4 19.0 26.3 27.2

2.0 22.0 29.4 * *

3.2 26.0 31.5 * *

Degree of dispersion of the organoclay in the polymer matrix improves with anincrease in the degree of sulfonation.

Increase in the size and polarizability of the cation (Na+<K+<Rb+) result inhigher degree of dispersion even at low degrees of sulfonation.

3.2 26.0 31.5 * *

3.8 29.0 34.0 * *

STRUCTURE OF SULFONATED SPS IONOMER -CLAY NANOCOMPOSITES

SsPS 3.8 mol % NaSsPS 3.8 mol %

SsPS and NaSsPS/ organoclay nanocomposites showintercalated structures whileKSsPS and RbSsPS formexfoliated structures.

KSsPS 3.8 mol % RbSsPS 3.8 mol %

Stronger ion-dipole interaction with higher polarizable (softer) cations act as bridge between negatively charged clay layers and the

polyanions.

Sulfonation level (%)

Crystallization temperature (oC)

Without clay Nanocomposite

H+ Na+ K+ Rb+ H+ Na+ K+ Rb+

0.5 234 233 233 232 234 236 236 236

2.0 225 199 189 193 228 209 218 223

3.2 222 183 183 194 222 205 215 222

CRYSTALLIZATION BEHAVIOR OF SULFONATED s-PS IONOMER/ORGANOCLAY NANOCOMPOSITES

3.8 212 * * * 212 163 184 198

* Do not crystallize on cooling from the melt

• TCC decreases with increasing degree of sulfonation indicating inhibition ofcrystallization. Crystallization was further inhibited when the H+ ion was replaced bydifferent cations like Na+, K+ and Rb+.

•Organoclay layers reduce the tendency of ions to aggregate causing thecrystallization rate to increase.

• Exfoliated nanocomposites show better crystallization rate than the intercalated onesbecause of the uniformly dispersed clay layers in the polymer matrix .

CONCLUSIONS

� Exfoliated sPS ionomer/organoclay nanocomposites were prepared viasolvent casting.

� Higher degree of sulfonation leads to better interaction with the polar silicatesurface of the organoclay resulting in better dispersion.

� Increase in the size and polarizability of the cation (Na+<K+<Rb+) result inhigher degree of intercalation/exfoliation even at low degrees of sulfonation.

� Nanocomposites prepared using more thermally stable 1-hexadecyl-2,3-dimethylimidazolium cation modified clay are amenable to being processed attemperatures upto 300 °C without any appreciable degradation.

� The dispersed silicate clay layers partially restores the reduced crystallizationrates of sPS ionomers by disrupting the ionic aggregation.

THANK YOU

Synthesis of Polyurethane Clay Nanocomposites via In-situ Polymerization

Objectives

• To prepare fully exfoliated PU-clay nanocomposite

• To improve the interaction of the polymer with clay by tethering the polymer chain on to the clay surface tethering the polymer chain on to the clay surface

• To tether the PU chain on the clay surface by choosing a suitable modifier for the clay

IIT-Madras 020905

HO-R-OH Organoclay

(hydrophobically modified)

Organoclay (short chain

hydroxy amines)Prepolymer

(OCN-R-NCO )

Chain extension

diolOCN-R-NCO

Cured

Solvent casting

PU- Nanocomposites - Literature

PU Organoclay

(hydrophobically modified)

Solvent casting

Above methods results in only intercalated nanocomposites

+NH3

OH

OH

2,3-dihydroxypropylammonium ion(2 OH Mont)

+NH3

(CH2)11

CH3

Dodecyl ammonium ion(12 CH3 Mont)

Literature

The modifier having small chain diols show very little intercalation, whereas the modifier with a long alkyl chain shows better intercaltion as seen from increase in the d-spacing from 1.6 nm of the organoclay to 2.4 nm in the nanocomposite

- Tien YI, Wei KH, Macromolecules, 34, 9045 (2001)

Reaction of Organoclay with Isocyanate

30

60

TR

AN

SM

ITT

AN

CE

C30B/PI C25A/PI

1710 cm-1

3310 cm-1

Bis(hydroxyethyl)ditallowammonium ionTH

TH

NOOH H

+

N

TH

H3C+

CH

(1)

Closite 30B

Closite 25A

3000 2000

WAVENUMBER

Dimethyltallow-(2-ethylhexyl)ammonium ion

CH3

(2)

Closite 25A

where TH = tallow group

Organoclay containing the modifier with hydroxyl group reacts with isocyanate to form urethane linkage

Closite 30B

NCO

Bis(hydroxyethyl)ditallowammonium ionTH

TH

NOOH H

+

(1)TH

TH

NOOC C

O ON N

H H+

PU-Nanocomposites in toluene medium

OHN

OH

TH

TH

+

N O

CH3

OCN

H

O

O N

O

H

CH3

NCO

+THO O

NCO content 9 % Closite 30B

Intercalated nanocomposite

OH

OH

+N

THOO N

HNH

CH3 CH3

OHN

OH

TH

TH

+

N O

CH3

OCN

H

O

O N

O

H

CH3

NCO

NCO content: 9 %

PU-Nanocomposites in DMF medium

OH OHTH

+N

TH

THOO N

HNH

O O

CH3 CH3

NCO content: 0 %

As the organoclay is mixed with prepolymer all the NCO is consumed

Effect of amount of TMP on nanocomposite structure

OH

OH

OH

OHN

OH

TH

TH

++

N O

CH3

OCN

H

O

O N

O

H

CH3

NCO

+ OH

OH

As the amount of TMP increases, the extent of intercalation increases

Effect of introduction of branch points in the polymer on nanocomposite structure

As the mol % of the branching agent (trimethylol propane)increases , the amount of intercalation increased as seen fromthe shift in the 001 peak towards lower 2 theta

IIT-Madras 020905

60°C/ 6 h

Nanocomposite by In-Situ Polymerization

Intercalated

HO

OH

CH3

NCO

NCO

+

2-ethyl-1,3-hexanediol 2,4-Toluenediisocyanate

Structure of modifiers Intercalated

Closite 30B

Bis(hydroxyethyl)ditallowammonium ionTH

TH

NOOH H

+

(1)

Closite 25A

where TH = tallow group

Dimethyltallow-(2-ethylhexyl)ammonium

N

TH

H3C+

CH3

NOO

H

HH H

+

Bishydroxyethylammonium ion

OC

Structure of modifiers

d) Closite 25A/PUe) Closite 30B

f) Closite 30B/PU

Nanocomposites by In-Situ Polymerization

a) OC

b) OC/PUc) Closite 25A

When the organoclay is mixed with the monomers and then polymerized, only intercalated nanocomposites are formed

Synthesis of PU-Nanocomposites

NOC

Bis(hydroxyethyl)dihydogenatedtallowammonium ion

H3C N

H

C

O

O H3C

N

N

H

C

O

O

COPrepolymer terminated with diisocyanate

NCO content 8.1%

Closite 30B

TH

TH

NOOH H

+

TH

NOOC C

O ON N

H H+

TH

NOOC CN N

OH

OH

PU-Nanocomposite

NCO content 6.4%

NOOH H

H

H+ +

HH NOO

TH

TH

Bis(hydroxyethyl)ditallBis(hydroxyethyl)ammonium ion (OC) Bis(hydroxyethyl)dihydrogenated tallow ammonium ion

(Closite 30B)

Effect of long alkyl chain

Presence of hydroxyl groups along with the hydrophobic group improves the extent of intercalation as seen from the increase in d-spacing from

Presence of long alkyl chain in the modifier along with the hydroxyl groups improved the extent of intercalation of polymer in to the clay gallery

from the increase in d-spacing from 18.0 Å for the organoclay to 35.0 Å for the nanocomposite.

When there is no hydrophobic group, the nanocomposites formed shows very little intercalation as seen from the increase of d-spacing from 13.4Å for the organoclay to 16.4 Å for the nanocomposite.