Inorganic-Organic Hybrid Materials

Inorganic-Organic Hybrid Materials

Bressanone Sept. 2006

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1

Composites – Hybrid Materials

cm

µm

nm

CLASSICAL COMPOSITES

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

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From Molecules to Nanobuilding Blocks

Various properties possible depending on precursors and processing


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Composite Material

Compound 1

Macroscopic phases

Compound 2

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Molecular or nanoscale building blocks

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


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2

Homogeneity

vs.

Problems: scatters light, mechanical properties, etc… Control over homogeneity: • precursor selection (functional group) • reaction conditions: kinetics, solvent, etc. • interactions between the components


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Typical Properties of Organic and Inorganic Materials

Properties

Organic materials (polymers)

Inorganic materials (glass, ceramics)

Nature of bonds

covalent [C–C], van der Waals, H-bonding low low (except polyimides) low low elastic flexible rubbery (depending on Tg) hydrophilic or hydrophobic

ionic or covalent high high high high hard strong brittle hydrophilic

insulating to conductive non-magnetic at low temperatures and pressures (molding, casting, etc.)

insulating to semiconductors magnetic at high temperatures and/or pressures (sintering, glass forming)

Tg Thermal stability Density Refractive index Mechanical properties

Hydrophobicity Electronic and magnetic properties Processability


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3

Nanolego

Form Function Geometry of the linkage Connectivity Kind of linkage


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Nanolego: Building Blocks Inorganic Building Blocks O

O

O O

Si

O

O Ti

O

Mechanical, optical, electrical, magnetical properties

O

O O

Connecting Blocks

O

H2C

O

Si

O

O O

X Ti

O

Y O

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

Organic Building Blocks Functional groups, crosslinking, polymerizability

A

Flexibility, elasticity, processability H2 C

H2 C C H2

C H2


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4

Nanolego: Linking the Building Blocks Polymerization / Polycondensation CH3

COOR

CH3

COOR

CH3

COOR

O

HO

OR

O

+ O

H2N

HN

O

O

HN

O

NH2

OH

NH

Sol-Gel-Process RO

Si

OR OR

HO + H2O

Si

OH OH

OH

OR

HO - H2O

+ H+

HO

Si

OH OH

O

OH Na4SiO4

Si

HO

Si

OH OH

OH OH

Self-Organization Zn(NO3)2 + HO O

Zn4O(terephthalate)6

O

OH


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Nanolego: Critical Issues

¾ Homogeneous distribution of the building blocks in the material ¾ Stable distribution: no microphase separation ¾ Interaction between the two components ¾ Structure-property relationships ¾ Inclusion of functionalities ¾ Tailoring of molecular structure ↔ nanostructure ↔ microstructure (= hierarchical structure design)


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Precursors Molecular precursors Clusters (nano-building blocks, NBB) Alkoxysilyl-substituted organic polymers Pre-formed nanostructures

Classes of sol-gel hybrid materials Physically entrapped components Functionalized inorganic networks Interpenetrating networks Dual networks


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Molecular Precursors Network Modifiers (non-reactive organic groups) (RO)3Si CH3

(RO)3Si

(RO)3Si

Precursors with Functional Organic Groups (RO)3Si (RO)3Si

O O

+ HS-Si(OR)3

(RO)3Si

(RO)3Si

O

O RO

(EtO)3Si

O Ti

N

H N

O O

N

N R

OR

OR

(RO)3TiSO3(Co-phthalocyanine)

polymerizable organic groups ⇒ inorganic-organic hybrid polymers


NO2

O

O

NH2

N H

groups with other organic functions

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Nano Building Blocks: Polyhedral Oligomeric Silsesquioxanes (POSS)


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Nano Building Blocks: Functionalized Metal Oxide Clusters

Ti16O16(OEt)24(OPr)8 (same with OCH2CH2OC(O)C(Me)=CH2)

Zr6O4(OH)4(methacrylate)12 covalent interaction

[(BuSn)12O14(OH)6]2+·2 methacrylate[SiW11O39(OSi2(C6H4CH=CH2)2)]4-


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electrostatic interaction

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Bridged Alkoxysilanes

(RO)3Si

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

Si(OR)3

H N

(RO)3Si-(CH2)m

H (CH2)n N

H N (CH2)n

C

H N

H N (CH2)m-Si(OR)3

O

O (EtO)3Si

C

O O N

N

N H

(EtO)3Si

H N

SO2(CH2)2O

N

O O

Si(OEt)3

O

2+ NH

(RO)3Si

H2N


NH2 Ni

NH

Si(OR)3

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Alkoxysilyl-Substituted Organic Polymers

CH3 (EtO)3SiO

Si

O

Si(OEt)3 n

CH3

(EtO)3Si-(CH2)3 O


CH3

H2 C

n C

O

(CH2)4-O

n

O

Si(OMe)3

(CH2)3-Si(OEt)3

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Pre-formed Nanostructures (Nano)Particles

Preformed Oligomers and Polymers

Clays / Layered Materials

Porous Materials


(Nano)Fibres, Nanotubes

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Consequences of Introducing Organic Substituents

¾ Reduced degree of crosslinking of the inorganic network ¾ Polarity changes (changes in hydrogen bonding) ¾ Reactivity change of the remaining alkoxide groups (electronic and steric effect of the organic substituents)

These effects are an inevitable consequence of the organic modification


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9

Degree of Crosslinking Si(OR)4-nRn n = 1-3

Si(OR)2R2

Si(OR)3R R

R

R

Si

Si

Si

O

O O

R

R Si

Si

O

O

O

O

O

O O

O

Si

Si

Si

Si

R

R

R

Silsesquioxanes R R

O Si O Si O

O

R R

O n

O

R

Si(OR)R3 R

Si O

Si R

R

R

R'

Oligo- and Polysiloxanes

Dimers

R Si O O R O Si

Si

OR Si O O Si Si O O R R

R

Polyhedral Oligomeric Silsesquioxanes


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Influence on Reaction Rates Example:

(RO)3Si

Si(OR)3

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


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Influence on Reaction Rates

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


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Classes of sol-gel hybrid materials Physically entrapped components Functionalized inorganic networks Interpenetrating structures Dual networks


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Types of Inorganic-Organic Hybrid Materials by Sol-Gel Processing Physically entrapped molecules, particles, etc.

Interpenetrating inorganic and organic networks

Class I materials: weak interactions

R R RR R

Class II materials: strong interactions

RR

R R R R RR

RR

R R

RR R R R R R

R RR RR R R

R R

RRR R R

Modification of the gel network by organic groups


Dual inorganic and organic networks connected by covalent bonds

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Entrapped Biomolecules


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Entrapped Biomolecules: Glucose Sensor NO-releasing glucose biosensor (cleaved NO suppresses degradation by bacteria)

O

Glucose oxidase in MeSi(OEt)3 Gel

SiO2

Si

CH3 OH

N NO H O Si (CH2)3 N (CH2)6 N H

in polyurethan

M.H.Schoenfisch et al., 2004


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Entrapped Inorganic Particles: Dental Filling abrasion 9 µm

shrinkage 1,97 vol% adhesion 25,8 / 27,6 MPa

pyrogenic silica (≈ 40 nm)

+ standard dental glass particles (≈ 0,7 µm)


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13

Entrapped Inorganic Particles: Controlled Release

in SiO2


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Heterogenization of Homogeneous Catalysts Classical approach RO

RO

RO

Si

RO

Sol-gel approach

+ MLn

A

RO

Si

A

RO

MLn

+ MLn

A

O Si

A

Si

O

MLn

A

MLn

O

O

+ MLn

+ MLn

Si

O

+

A

RO

A


Si

Si

O

E(OR) n

A

RO

O

RO

O

RO

O

RO Si

MLn

+ E(OR) n

O

RO

A

RO

+

O

Si

RO

RO

RO

RO

RO

Si

A

O

+

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Heterogenization of Catalysts by Sol-Gel Processing RO Si

RO

A

MLn

Examples:

+ Si(OR)4

RO

Si

O

A

Ph

C O

Ph P

Si(OR)3

Ph

MLn

O

(EtO)3Si

Poren pores

(EtO)3Si

sol-gel Sol-GelProzeß processing

Ph Cl P Ru P Ph Cl

Ph P P Ph

Si(OEt)3

Si(OEt)3

Synthesis of N,N-diethylformamide from CO2, H2 and diethylamine A. Baiker et al., 1999

K K

Cl Rh

P

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

O

SiO2 /

Ph (RO)3Si

K K

K

O

K

K

(RO)3Si

K K

aktive Spezies = katalytisch catalytically active species

N H

NH2 N

Cu2+

NH 2

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


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Coatings with Optical Properties Photochromism: fast for optical switches, for eye protection, privacy shields slow for optical data storage, energy conserving coatings, etc... Example: Spirooxazine derivative

hν1

N N

O

Δ or hν2

N N

O

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 the sol-gel matrix → higher chromophore concentrations can be achieved without affecting the mechanical integrity of the sol-gel matrix

Si(OEt)3 HN

O N N

O

O

Photochromic coating on paper


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Interpenetrating Networks Sequential Sequentialtwo-step two-stepprocess: process: Second Secondnetwork networkis is formed formedin inthe thefirst first

IPN Examples: ¾ 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 nanoscale ¾ Inorganic structures form and interpenetrate an organic polymer (difficulties: incompatibility between the moieties ⇒ phase separation)


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Interpenetrating Networks Interaction via hydrogen bonds to silanol groups of the forming silica Organic polymers with hydrogen bonding ability:

n

n NMe2

O

OH

n

n

n

O

O

OMe

n O

O

O

N

OH poly(VP)

poly(DMAA)

poly(VA)

poly(VAc)

poly(MMA)

poly(HEMA)

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

No macro phase separation Resulting materials: high degree of homogeneity and optical transparency

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


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Interpenetrating Networks

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

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

(RO)3Si

O O

Nanostructured hybrid polymer U.Wiesner et al., 2004


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Interpenetrating Networks Organic Monomer

Inorganic Monomer

Catalyst

Solvent

AIBN

TEOS

HF

Water

O

OH

C. L. Jackson et al. Chem. Mater. 1996, 8, 727

O

Initiator

Addition of tetrakis(2-(acryloxy)ethoxy)silane improves homogenity

TEM images of the nanocomposites:

Increasing Sol-Gel Catalyst Concentration => Faster Reaction


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Nanocomposites: Polymer-Clay

Layered solid

Layered solid

+ Monomer (Polymerization)

Exfoliated layers

+ Polymer

+ Monomer (Polymerization) or + Polymer


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Nanocomposites: Polymer-Clay


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Nanocomposites: Polymer-Clay 15 μm glass fibre in polyolefin

1 nm thick montmorillonite sheet in epoxy resin


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Nanocomposites: Intercalation of Polymers in Pores

Direct Intercalation

+

Polymer

Porous Host

Problems: ¾ Pore diameter ↔ size of Polymer ¾ Diffusion of polymer ⇒ Usually only end of polymer sits in pore but not the whole chain


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Nanocomposites: Polymerization in Pores

Monomer Intercalation

+

Monomer

Polymerization

Porous Host

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

T. Aida et al. 2000


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Nanocomposites: Polymerization in Pores

T. Aida et al. 2000

T. Bein et al. 1992


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Dual Network Structures Preparation strategies Concomitant formation of the inorganic and organic structures Stepwise formation of the organic and inorganic networks ¾ from pre-formed organic structures ¾ from pre-formed inorganic structures Options

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


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Concomitant Formation of Inorganic and Organic Network Typical procedure

Metal Alkoxides Metal Salts + water (ev. catalyst or additives) - alcohol

Precursors

Hydrolysis Condensation

Sol Gelation

formation of inorganic network

Gel formation of organic network

Hardening (thermal or uv)

Many Examples: Coatings Section

Hybrid Polymer


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Concomitant Formation of Inorganic and Organic Network Often used precursors O (RO)3Si

(RO)3Si

O

(RO)3Si

O

O O

O

or O

OH

O

O

+ Zr(OR)4

O

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

+ acrylate, epoxide monomers, etc.

increase of “inorganic / organic ratio”

decrease of “inorganic / organic ratio”


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Concomitant Formation of Inorganic and Organic Network O O

O

O

O

O

O

O

O

O O

O

O

Sequential formation of the organic network

UV-polymerization of methacryl groups

photo-initiator, hν O O

O

O

O

O

O

O

O O

O O

O

O

O

O

O

O

O O

O

O

O

O

O

O

O

O

O

O

O

O

O

O

O

O

O

O

O

O

O O

O

O

O

thermal polymerization of epoxy groups

ΔT O O

O

O

O

O O

O

O O O

O

O

O

O O

O

O O

O

O

O

O

O O


O

O

O

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O

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*) SBU: Sequentially Built-up

Concomitant Formation of Inorganic and Organic Network O H2O / NaF Si CH2O

SiO2

4

O

CH2OH n

H2O / NaF O(CH2)2O Si 4


aq. ROMP

O +

Free Radical Polymerization

SiO2 +

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O

O(CH2)2OH 4

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Photochemical Crosslinking (3D Laser Lithography) Coating or forming of ORMOCER® (with chromophor as UV initiator)

Direct 3D-laser writing (2-photon polymerisation with femtosecond laser pulses) Requirements for hardening: Development of the structure (removal of uncured ORMOCER®)

•

precise focussing

•

2-photon process

•

polymerisation in Ormocer® layer (O2 protection)

•

chromophor as initiator

Ormocer® = Organically modified Ceramics


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Photochemical Crosslinking (3D Laser Lithography) CAD File

Layer model

‚Venus of Milo‘ in ORMOCER® (REM)

I am made from ORMOCER®!


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Photochemical Crosslinking (3D Laser Lithography)


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Hybrid Polymers from Pre-Formed Organic Polymers CH3

Low shrinkage by the use of prepolymerized materials

CH3

x

acrylic component silane component

(MeO)3Si(H2C)3O

O

y MeO

O

1. inorganic condensation 2. organic polymerization

acrylic monomer + polymer (incomplete polymerization)

inorganic condensation between fully polymerized polyacrylate


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Hybrid Polymers from Pre-Formed Organic Polymers A.-M. Caminade, J.-P. Majoral, J. Mater. Chem., 2005, 15, 3643-3649

Hybrid Materials applying Dendrimers

Porous Materials using Dendrimers as Templates


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Hybrid Polymers from Pre-Formed Inorganic Structures


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Hybrid Polymers from Pre-Formed Inorganic Structures Improved Properties through Controlled Reinforcement of Polymer Chains at the Molecular Level

R O Si

R

Si

R

Si

O Si

O

O R Si O Si

R'

O

O O

O RO O

Si

R

Si O R

www.hybridplastics.com


Property enhancements via POSS observed 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

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Hybrid Polymers from Pre-Formed Inorganic Structures POSS for fire retardant materials


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Hybrid Polymers from Pre-Formed Inorganic Structures Polymerizable Metal Oxo Clusters X

X

X X

X

X X

X X Polymerizable groups X

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

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


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Hybrid Polymers from Pre-Formed Inorganic Structures Metal Oxo Clusters as Initiators for ATRP multifunctional initiator + monomer X

X

+

catalyst

X X X

X X X

+ solvent

= PMMA, PS, PtBuA

X

catalyst = pmdeta / CuBr or CuCl

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

0.9

100

0.7

ln (M0/M)

G.Kickelbick et al.


80

Y=0,0058*X R=0,997

70 60

0.5

50

0.4

40

0.3

Polydispersities