Inorganic-Organic Hybrid Materials - unipd.it · PDF fileTypes of Inorganic-Organic Hybrid Materials by Sol-Gel Processing Class I materials: ... (OEt)3 Ph Si(OEt)3 Ph Ph (EtO)3Si

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Bressanone Sept. 2006 Hybrid Materials 1

Inorganic-Organic Hybrid Materials


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CLASSICAL COMPOSITES

Property Improvement:• mechanical stability• thermal stability• photochemical stability

cm

µm

nm Hybrid Materials From Molecules to Nanobuilding Blocks

Various properties possible depending on precursors and processing

Composites – Hybrid Materials


Macroscopicphases

Molecular ornanoscalebuilding blocks

Composite Material

Hybrid Material

Compound 1 Compound 2

The goal is to create materials with specific combinations of properties by combining different molecular building blocks in various ratios and by controlling

their mutual arrangement

Control at the nanolevel

Hybrid Materials

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vs.

Problems: scatters light,mechanical properties, etc…

Control over homogeneity:• precursor selection (functional group)• reaction conditions: kinetics, solvent, etc.• interactions between the components

Homogeneity


at high temperatures and/or pressures (sintering, glass forming)

at low temperatures and pressures (molding, casting, etc.)

Processabilitymagneticnon-magneticinsulating to semiconductorsinsulating to conductiveElectronic and

magnetic properties

hydrophilichydrophilic or hydrophobicHydrophobicitybrittlerubbery (depending on Tg)strongflexiblehardelastic Mechanical propertieshighlowRefractive indexhighlowDensityhighlow (except polyimides)Thermal stabilityhighlowTg

ionic or covalentcovalent [C–C], van derWaals, H-bonding

Nature of bonds

Inorganic materials(glass, ceramics)

Organic materials(polymers)

Properties

Typical Properties of Organic and Inorganic Materials

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FormFunctionGeometry of the linkageConnectivityKind of linkage

Nanolego


Inorganic Building Blocks

SiO

OO

OTi

O O

O OO

O

Mechanical, optical, electrical, magnetical properties

Organic Building Blocks

H2C

CH2

H2C

CH2

Flexibility, elasticity, processability

Functional groups, crosslinking, polymerizabilityA

Si

O

O

H2C

O

Reduction of the crosslinking density, coupling sites between inorganic / organic components

Connecting Blocks

TiO Y

O XO

O

Nanolego: Building Blocks

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Zn(NO3)2 +

Zn4O(terephthalate)6O

OHO

HO

Self-Organization

Polymerization / Polycondensation

O

OR

CH3

COOR

COOR

CH3

CH3

COORO

OHO

HO

+ H2N NH2

O

O

HN

HN NH

O

OH

SiHO OH

OH

OH

SiHO OH

OH

SiHO OH

OH

O

SiHO OH

OH- H2O

OR

SiRO OR

OR+ H2O

Na4SiO4 + H+

Sol-Gel-Process

Nanolego: Linking the Building Blocks


Homogeneous distribution of the building blocks in the material

Stable distribution: no microphase separation

Interaction between the two components

Structure-property relationships

Inclusion of functionalities

Tailoring of

molecular structure ↔ nanostructure ↔ microstructure

(= hierarchical structure design)

Nanolego: Critical Issues

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PrecursorsMolecular precursorsClusters (nano-building blocks, NBB)Alkoxysilyl-substituted organic polymersPre-formed nanostructures

Classes of sol-gel hybrid materialsPhysically entrapped components Functionalized inorganic networksInterpenetrating networksDual networks


Network Modifiers (non-reactive organic groups)

Molecular Precursors

polymerizable organic groups⇒ inorganic-organic hybrid polymers

Precursors with Functional Organic Groups

O(RO)3Si

O

(RO)3SiO(RO)3SiO

O O

O

+ HS-Si(OR)3

Ti

ORORRO

groups with other organic functions

(RO)3Si(RO)3Si CH3(RO)3Si

NO2

NN

NR

OO

HN(EtO)3Si

NH

NH2(RO)3Si

(RO)3TiSO3(Co-phthalocyanine)

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Nano Building Blocks: Polyhedral Oligomeric Silsesquioxanes (POSS)


[SiW11O39(OSi2(C6H4CH=CH2)2)]4-

[(BuSn)12O14(OH)6]2+·2 methacrylate-

covalent interaction

electrostatic interaction

Nano Building Blocks: Functionalized Metal Oxide Clusters

Zr6O4(OH)4(methacrylate)12

Ti16O16(OEt)24(OPr)8

(same with OCH2CH2OC(O)C(Me)=CH2)

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Bridged Alkoxysilanes

Si(OR)3(RO)3Si

(CH2)n(CH2)nHN

HN

CHN (CH2)m-Si(OR)3

C

HN

O O

(RO)3Si-(CH2)m

(RO)3Si-(CH2)n-Si(OR)3

SO2(CH2)2ONNN

O

O

HN

(EtO)3Si

O

O

NH

(EtO)3Si

O

HN Si(OEt)3

NHNi

NH2

H2N NH Si(OR)3(RO)3Si

2+


Alkoxysilyl-Substituted Organic Polymers

H2C

CH3

COO Si(OMe)3

n(EtO)3SiO Si O Si(OEt)3

CH3

CH3

n

O (CH2)4-On

(EtO)3Si-(CH2)3 (CH2)3-Si(OEt)3

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Clays / Layered MaterialsPorous Materials

(Nano)Particles (Nano)Fibres, NanotubesPreformed Oligomers and Polymers

Pre-formed Nanostructures


Reduced degree of crosslinking of the inorganic networkPolarity changes (changes in hydrogen bonding)Reactivity change of the remaining alkoxide groups

(electronic and steric effect of the organic substituents)

These effects are an inevitable consequenceof the organic modification

Consequences of Introducing Organic Substituents

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Si(OR)4-nRnn = 1-3

Si(OR)3RSi(OR)2R2 Si(OR)R3

Silsesquioxanes

Polyhedral OligomericSilsesquioxanes

Oligo- and Polysiloxanes

OSi

OSi

OSi

OSi

R R R R

O O O

SiO

SiO

SiO

SiO

R R R R

O

O Si

O

Si

O

SiO

Si

O

O

Si

O

Si

O

O

O

O

Si

Si

O

RR

RR

R

R R

R

Si O

R'

R

n

R Si O

R

R

Si R

R

R

Dimers

Degree of Crosslinking


0.6 M in methanol, 25°CThe dashed line is pH vs. gel time forSi(OMe)4 (2.0 M in methanol, 60°C).

Influence on Reaction Rates

Example:Si(OR)3

(RO)3Si

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(acac = acetylacetonate, ftac =trifluoroacetylacetonate, dbzm = dibenzoylmethanide)

Influence on Reaction Rates



Classes of sol-gel hybrid materialsPhysically entrapped components Functionalized inorganic networksInterpenetrating structuresDual networks

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RR R

R

R

R RR R

R

RR

R

R R

RRR R

R

R

RR R

RR R

RR

RRRR

RRR

R R

Physically entrapped molecules, particles, etc.

Interpenetrating inorganicand organic networks

Modification of the gelnetwork by organic groups

Dual inorganic and organic networksconnected by covalent bonds

Types of Inorganic-Organic Hybrid Materials by Sol-Gel Processing

Class I materials: weak interactions

Class II materials: strong interactions


Entrapped Biomolecules

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NO-releasing glucose biosensor(cleaved NO suppresses degradation by bacteria)

Glucose oxidase in MeSi(OEt)3 Gel O Si (CH2)3HN (CH2)6 N

H

NOH

NOSiO2

OSi

CH3

in polyurethanM.H.Schoenfisch et al., 2004

Entrapped Biomolecules: Glucose Sensor


abrasion 9 µm

shrinkage 1,97 vol%

adhesion 25,8 / 27,6 MPa

Entrapped Inorganic Particles: Dental Filling

standarddental glass

particles(≈ 0,7 µm)

pyrogenicsilica

(≈ 40 nm)

+

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Entrapped Inorganic Particles: Controlled Release

in SiO2




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+

Sol-gel approach

SiRO

RORO

A MLnSiRO

RORO

A + MLn

SiRO

RORO

A

SiO

OO

A MLn

SiO

OO

A

+ MLn

+ E(OR) n

E(OR) n

SiRO

RORO

A MLnSiRO

RORO

A + MLn

+

SiRO

RORO

A + SiO

OO

A

+ MLn

SiO

OO

A MLn

Classical approach

Heterogenization of Homogeneous Catalysts


Sol-Gel-Prozeß

= katalytisch aktive Spezies

Poren

K

KK

K

K

K

K

K

K

sol-gelprocessing

catalytically active species

pores

SiRO

RORO

A MLn + Si(OR)4

SiO

OO

A MLnSiO2 /

Ru

Cl

Cl

P

PP

P

Si(OEt)3

Si(OEt)3Ph

Ph

Ph

Ph(EtO)3Si

(EtO)3Si

Examples:

A. Baiker et al., 1999

P(RO)3Si P Si(OR)3Rh

Cl

CO

Ph Ph

PhPh

U. Schubert et al., 1989More active in the hydrosilation of 1-hexene thanRh(CO)Cl(PR3)2

NH

(RO)3Si

O

NNH

NH2 2Cu2+

Catalyst for the oxidation of 3,5-di-tert.butylcatecholto the quinone M. Louloudi et al., 1998

Synthesis of N,N-diethylformamide from CO2, H2and diethylamine

Heterogenization of Catalysts by Sol-Gel Processing

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Photochromism: fast for optical switches, for eye protection, privacy shieldsslow for optical data storage, energy conserving coatings, etc...

Example: Spirooxazine derivative

Embedding in sol-gel coatings:For sufficient photochromism: dye concentration > 25 wt% → mechanical stability of sol-gel film is deteriorated.

Grafting of the dye to thesol-gel matrix → higher chromophoreconcentrations can be achievedwithout affecting the mechanical integrityof the sol-gel matrix

O

N

N

O

O

HN

Si(OEt)3

O

N

N O

N

N

hν1

Δ or hν2

Photochromic coating on paper

Coatings with Optical Properties




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IPN

Sequential two-step process:Second network isformed in the first

Sequential two-step process:Second network isformed in the first

Examples:Generation of the organic polymer in the pores of an inorganic porous material (in channels of zeolites or mesoporous materials, between sheets of a layered lattice, such as a clay mineral) ⇒ rigid inorganic moiety with a regular pore or channel structure in the nanoscaleInorganic structures form and interpenetrate an organic polymer (difficulties: incompatibility between the moieties ⇒ phase separation)

Interpenetrating Networks


Interaction via hydrogen bonds to silanol groups of the forming silicaOrganic polymers with hydrogen bonding ability:

N

n

NMe2On

OHn

O

O

nOMeO

n

OO

OH

n

poly(VP) poly(DMAA) poly(VA) poly(VAc) poly(MMA) poly(HEMA)

Si(OR)4 and/or RSi(OR)3H2O, [Kat]

No macro phase separation Resulting materials: high degree of homogeneity

and optical transparency

Important reaction parameter: pHChange of crosslinking density and interaction with polymer using RSi(OR)3/Si(OR)4 mixtures


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Nanostructured hybrid polymerU.Wiesner et al., 2004

Poly(isopren-block-ethylenoxide)swollen in THF/CH3Cl

Sol from GLYMO and Al(OsBu)3 (H2O/HCl)

+

O(RO)3SiO



O O

O H

Water

Solvent

HFTEOSAIBN

CatalystInorganic MonomerInitiatorOrganicMonomer

TEM images of the nanocomposites:

Increasing Sol-Gel Catalyst Concentration => Faster Reaction

C. L

. Jac

kson

et a

l.C

hem

. Mat

er.1

996,

8, 7

27

Addition of tetrakis(2-(acryloxy)ethoxy)silaneimproves homogenity


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+ Monomer(Polymerization)

+ Monomer(Polymerization)

+ Polymer

+ Polymeror

Layered solid Exfoliated layersLayered solid

Nanocomposites: Polymer-Clay



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15 μm glass fibre in polyolefin

1 nm thick montmorillonite sheet in epoxy resin


+

Polymer Porous Host

Direct Intercalation

Problems:Pore diameter ↔ size of PolymerDiffusion of polymer

⇒ Usually only end of polymer sits in pore but not the whole chain

Nanocomposites: Intercalation of Polymers in Pores

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+

Monomer Porous Host

Monomer

Intercalation Polymerization

Monomer is interacalated into the pores(vapor, liquid), then polymerization

T. Aida et al. 2000

Nanocomposites: Polymerization in Pores


T. Bein et al. 1992

T. Aida et al. 2000

Nanocomposites: Polymerization in Pores

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Dual Network Structures

Preparation strategies

Concomitant formation of the inorganic and organic structures

Stepwise formation of the organic and inorganic networksfrom pre-formed organic structuresfrom pre-formed inorganic structures

Options

Chemical composition of the inorganic component(s)Chemical composition of the organic component(s)Proportion of the inorganic/organic componentsCuring method (thermal / photochemical)Dimension of the inorganic / organic components (molecular, nanometer,

extended)

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Precursors Metal AlkoxidesMetal Salts

Sol

+ water (ev. catalyst or additives)- alcohol

HydrolysisCondensation

Hybrid Polymer

Gelation

Hardening (thermal or uv)

Concomitant Formation of Inorganic and Organic Network

formation of inorganic network

formation of organic network

Typical procedure

Gel

Many Examples:Coatings Section



Often used precursors

O(RO)3SiO

O(RO)3Si

O

O OH

(RO)3Si

O O

OO

O

or + Zr(OR)4

+ Si(OR)4, Zr(OR)4, Al(OR)3, etc.

increase of “inorganic / organic ratio”

+ acrylate, epoxide monomers, etc.

decrease of “inorganic / organic ratio”

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OO

O

O

O

O

O

O

O

O

O

O

O

O

OO

O

O

O

O

O

O

O

O

O

O

O

O

O

O

OO

O

O

OO

OO

O

O

O

O

O

O

O

O

O

O

O

O

O

O

OO

O

O

O

UV-polymerizationof methacryl groupsphoto-initiator, hν

thermal polymerizationof epoxy groupsΔT

O

O

OO

O

O

OO

O

O

OO

O

OO

O

O

O

O

OO

O

O

O

O

OO

O O

O

Sequentialformation of the organic network

*) SBU: Sequentially Built-up



O

CH2OSi

H2O / NaF

aq. ROMPSiO2 +

O

n4 CH2OH

O(CH2)2O

O

Si

4

H2O / NaF

Free RadicalPolymerization

SiO2 +

O O(CH2)2OH 4


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Coating or forming ofORMOCER®

(with chromophor as UV initiator)

Direct 3D-laser writing(2-photon polymerisation with

femtosecond laser pulses)

Development of the structure(removal of uncured

ORMOCER®)

Requirements for hardening:• precise focussing• 2-photon process• polymerisation in Ormocer® layer

(O2 protection)• chromophor as initiator

Photochemical Crosslinking (3D Laser Lithography)

Ormocer® = Organically modified Ceramics


CAD File Layer model‚Venus of Milo‘ in ORMOCER® (REM)


I am made from

ORMOCER®!

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1. inorganic condensation2. organic polymerization

acrylic monomer + polymer (incomplete polymerization)

inorganic condensationbetween fullypolymerized polyacrylate

(MeO)3Si(H2C)3O O

CH3 CH3

MeO O

x y

Low shrinkage by the use ofprepolymerized materials

Hybrid Polymers from Pre-Formed Organic Polymers

acrylic componentsilane component

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Porous Materials using Dendrimers as Templates

Hybrid Materials applying Dendrimers

A.-M

. Cam

inad

e, J

.-P. M

ajor

al, J

. Mat

er. C

hem

., 20

05, 1

5, 3

643-

3649

Hybrid Polymers from Pre-Formed Organic Polymers


Hybrid Polymers from Pre-Formed Inorganic Structures

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Property enhancements via POSSobserved in POSS-copolymers and blends

• Increased Tdec• Increased Tg• Reduced Flammability • Reduced Heat Evolution • Lower Density • Disposal as Silica • Extended Temperature Range • Increased Oxygen Permeability • Lower Thermal Conductivity • Thermoplastic or Curable • Enhanced Blend Miscibility • Oxidation Resistance • Altered Mechanicals • Reduced Viscosity

OSi

O

Si

O

SiO

Si

O

O

Si

O

Si

O

O

O

O

Si

Si

O

RR

RR

R

R R'

R

Improved Properties through ControlledReinforcement of Polymer Chains at the Molecular Level

www.hybridplastics.com




POSS for fire retardant materials

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Zr6O4(OH)4(5-norbornene-2-carboxylate)12 for ROMP

Zr6O4(OH)4(methacrylate)12for free radical polymerization

Polymerizable groups X

XX

X

X

XX

X

X

X

Polymerizable Metal Oxo Clusters



Metal Oxo Clusters as Initiators for ATRP

catalyst = pmdeta / CuBr or CuCl

= PMMA, PS, PtBuA

0 20 40 60 80 100 120 140 1600.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

Y=0,0058*XR=0,997

ln (M0/M) linear Fit for ln (M0/M)

Time [min]

ln (M

0/M)

0102030405060708090100

Conversion [%

]

e.g. Ti6O4(OOCCBrMe2)(OiPr)8

G.Kickelbick et al.

XXXX

XX

XX

X

+multifunctional initiator monomer + catalyst + solvent

Polydispersities <1.5.90% of the chain endsstill active after isolation


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Combination of polyoxometallates (electrochromism, photochromism, conductivity, redox activitities) + conjugated molecules and polymers⇒ electrically active organic materials (light emitting diodes, field-effect transistors, solid-state lasers)

Monofunctionalization of Mo6O192-

Examples:


Z. Peng et al. 2004


Z. Peng et al. 2004


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Mn12O12(OOC-CH=CH2)16

+ CH2=CMe-COOMeRadical polymerization

PMMA crosslinked by Mn12

Superparamagnetic„Mn12“total cluster spin S = 10

(4 MnIV, S = 3/2 + 8 MnIII, S = 2)

Magnetic Polymers



AFM

Si(OEt)4 + NH4OH„Stöber-Process“

OH OH OHOH

OHOHOH

OHOH

OH

OHOH

OHOH

OHOHOH

OHOH

OH OH OH

SiO2

Preparation of nanoparticles

Surface modificationSiO2

O

FG

SiO O

FG

SiO OO FG

SiOOO

SiO

OO FG

Si OO

O

FG

SiOOO

FG

Si

OO

OFG

O O O

FG

(RO) 3Si FG

(EtO)3Si(H2C)3O Br

O

CH3

CH3

(EtO)3Si(H2C)3ON

N CN

O

CH3NC

CH3CH3

Initiators at the surface, e.g.

Polymerization from the functionalised surface

G.Kickelbick et al.


Inorganic-Organic Hybrid Materials - unipd.it · PDF fileTypes of Inorganic-Organic Hybrid Materials by Sol-Gel Processing Class I materials: ... (OEt)3 Ph Si(OEt)3 Ph Ph (EtO)3Si

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