Sol-gel, self-assembly and phase

separation pathways to multiporous

films, gels and aerogels

Galo Soler Illia

Instituto de NanoSistemas, UNSAM

www.unsam.edu.ar/institutos/ins

UNSAMknowledge generation

through interdiscipline

7 Research Groups in 2019

Research Projects

• Nanomaterials Design

• Surface Tailoring

• BioSensors

• Nano-optics

• Nanomedicine

• Adsorbents

www.unsam.edu.ar/ins

Instituto de Nanosistemas

INS UNSAM

@insunsam

October 2019

Buenos Aires

9

© C. Sanchez, Collège de France

Hierarchical Structures: tailoring multiscale porosity

Sanchez, BL Su Chem. Soc. Rev., 2017

Si

OR

ORRO

RO

molecule

Si

OR

O

OR

RO

Si

OR

RO

RO

dimer

Nano-

object

Molecular Chemistry (connections, bonds…)

CONNECTIVITY/ Building Blocks

Colloid Chem. (Interactions)

Morphology/ OBJECT

AssemblyH2O

Nanomaterials through soft chemistry

“La Chimie crée

son objet”

“We can hope to recreate all

the substances that can be

developed since the very

beginning […] using the

same forces that Nature

puts into action to do so.”Marcellin BerthelotLa Synthèse Chimique,

1876

A Toolbox to

Hierarchical Materials

– Sol-Gel• Understanding inorganic polymerization

• Tuning Nanobuilding Blocks

– Self-Assembly• Spontaneous processes towards ordering

• Controlling interactions

– Phase Separation• Controlling separation processes through

Interactions

– Processing• How to tune these processes along time

Sanchez, BL Su Chem. Soc. Rev., 2017

From solution to sol

Hydrolysis:

Fe (H2O)63+ + H2O Fe(OH)(H2O)5

2+ + H3O+

Ti (i- O Pr)4 + H2O Ti(OH)(OPr)3 + HOPrO

H

Condensation: O

Al(H2O)5OH2+ + Al(H2O)5OH

2+ [(H2O)4Al Al(H2O)4]4+

O

H

salt

alkoxide

Hydrolysis

Mz+

M

OH2

OH2

OH2

OH2 M

OH2

OH2

OH2

OH+ H2O

Hydrated cation

+ H3O+

M

OH2

OH2

OH2

OH2d++

d+-

MXz + z X- (aq)Mz+ (aq)

Mz+ :O

H

Hd+

d+

d+

d-

Condensation

Livage et al Progr. Solid State chem 1988, 18, 259

Ti...O

...O...O

O

Hd

TiO...

...O O...

O

H

d Ti

O......O O...

Ti...O

...O...O

O

H2O+

oxolation

Oxolation (oxo bridge) or

olation (hydroxo bridge)

processes can take place,

depending on the precursor

charge, pH and ligand.

The condensation reaction

continues until an average

electronegativity equivalent

to the one of the external

nucleophiles is attained

(Livage-Henry-Sanchez)

Molecular Metallic Precursors

• Purity

• High yield

• Selectivity in synthesis

• Ease of handling

• Low toxicity

• Solubility

• Volatility (CVD)

• High Control of Hy/Cond

• Addition of functional groups

• Multinuclear precursors

Si

OR

OR

RO

RO

Ti

O

OO

O

CH3

CH3 CH3

CH3

Ti

O

OO

O

RR

Alkoxide Carboxylate M-diketonate

Proton Transfer: -OR replaced by –OH (Nucleophilic substitution).

Hidrolysis of Alkoxides

+ H2OTi

OR

ORRO

RO

Ti

OR

OHRO

RO

+ ROHM M

Factors affecting hidrolysis rate:

1) Nature of the cation

2) Nature of the alkyl group

3) Solvent

4) Concentration

5) Water:metal ratio, rw = [H2O]/[M]

6) Temperature

Generally:

Highly dependent on coordination (SN2)

Slow and pH-dependent for Si

Fast for TM (hexacoordinated)

Si

RO

RO

RO

O R + O+

H

HH Si

-

RO

RO

RO

O+

R

HO

+

H

Hd d

Example: silica hydrolysis

Pohl and Osterholz, 1985

Leaving

Group

Si

RO

RO

RO

OH + +R OH H+

Reaction rate is found to depend on:

•[Si]

•pH

•rw=[H2O]/[Si]

• Molecular effects (inductive, steric, charge…)

Silica condensation

Si-OR + HO-Si Si-O-Si + ROH

Si-OH + HO-Si Si-O-Si + H2O

alcoxolation

oxolación

From monomer to dimer

• Acid or base catalized

•R-Si(OH)3 presents a minimum

Minimum gel formation rate atpH 2

• Coincides with pzc of SiO2

• Polymerization increases acidity

• Silanol groups intervene in

polymerization

• Acid conditions: elongated

polymers

Si-O-Si extended condensation

Stable sols at high pHs

• Fast polymerization

• Electrostatic repulsion hinder

gelation

Basic Catalysis

Acid Catalysis

Polymeric species are less reactive upon growth

Linear species form, then crosslink

Polymeric species are more reactive

upon growth.

Condensed species coagulate

TM alkoxide hydrolysis and condensation

J. Blanchard et al, J. non-Crystalline Solids 2000

rw = 0,1

0,3

0,5

0,7

1 (8 min)

4d

17O RMN

µ2

O

Ti

Ti

µ3

O

Ti

TiTi

µ4

O

Ti

TiTi Ti

SAXS

Ti

O

OO

O

Alkoxide d(M)

Zr (OEt)4 +0,65

Ti (OEt)4 +0,63

VO (OEt)3+0,46

Si (OEt)4 +0,32

Summary…

• Silica, three broad

regimes

– pH5, branched growth

and precipittion

• Non-silica (e.g., MO2)

– More reactive

– Closo objects that can

aggregate

– Control through

acidity or complexation

8a Escuela de Síntesis de

Materiales: Procesos Sol-Gel

Buenos Aires,

Total control of

size, shape, and “philicity”

Surface Charge control

pHpiepH < pHpie pH > pHpie

philicity control

hidrofóbico hidrofílico

Si

O

SiO

Si

ORRO

OOSiOR

OSi OSi

Si

O

SiO

Si

OH

OH

OOSi

OH

OSi OSi

linear closo

fractal

Coupling Sol-Gel and Self Assembly

for organized matter

Organised CdS Stupp et al., Science, 1997

Mesoporous Silica Beck et al., Nature, 1992

Sol-Gel: Soft Synthesis methods (low T)

Self-Assembly: Controlled Organization at

the mesoscale (2-50 nm)

Organised NBBOrganised Voids

concentration

Surfactant Micelle Liquid Crystal

Concentration

Hydrophilic

Head

Hydrophobic

Tail

Self-Assembly using surfactantsPrecise Supramolecular fingers

Micelle

(NanoObject)Surfactant

Asymmetric Molecule

Lyotropic assembly

Liquid Crystal (LC)

Spontaneous Organization of asymmetric molecules

Thermodynamic Control of Weak Interactions

cmc

Porous Materials:

scales of porosity

microporous

mesoporous

Mesoporous Oxides Using supramolecular templating

Mesostructured

Precursor

“Fossile LC”

Mesoporous

Oxide

Elimination of

the Template

Sol-Gel +

Self-Assembly

Micelles or LLC as templates (Supratemplates)

Periodic Porous Network, Robust Systems

High Surface (200-1000m2/g)

Ordered Monodisperse Pores, 2-50 nm

Accessibility

RRRR

RR

Multifunctional

Material

Functionalization

MX4

M

X

XX

X

Surfactant

(Template)

Inorganic

Precursor

Soler-Illia et al., Chem. Rev., 2002

Precipitation

True LC templating

TLCT

Evaporation-Induced

Self-Assembly

EISA

Exotemplating

Sole

r-Illia

an

d A

zza

ron

i., C

hem

. S

oc. R

ev.

20

11

Example: Titania Films(photocatalysis, photovoltaics, optics)

Film Production by dip- or spin coating

TiCl4 or TET/H+precursors

Nonionic Block Copolymer templates

Controlled water (r, RH%)

Template size

Small, Hydrophilic Ti-oxo clusters

Fluidity Thin Titania filmd=100-300nm

(interference)

0.5 cm

Review: Soler-Illia et al, Nanoscale, 2012

n m n

O

CH3

OOH O H

PEO PPO PEO

Mesoporous Titania Thin Films

TEM

Soler-Illia et al. Nanoscale. 2012, Soler-Illia and Innocenzi Chem. Eur. J. 2006,

C. Sanchez et al, Chem. Mater. 2008, Malfatti et al. Chem. Mater. 2013

SAXS

02

4

6

8

10

0

2

4

20

30

40

50

60

70

XR

D In

tens

ity (a.u

)

RH %h=H

2O/Ti

Which are the important variables?Water Influences Organization

Low water:

poor

organisation

High water:

excellent

organisation

Roles of water

Evaporation Rate

Hydrolysis of Ti(IV)

Template Folding

h= Water IN

RH%= Water OUT

Crepaldi et al., JACS., 2003

How do these

mesostructures

form?

Disordered

micelle array

Isotropic solution: c < cmc

CMC

Humidity

H2O regulation

Solvent

evaporation

Formation of a

liquid crystal

Isolated

template

molecules

Pu

lling

dire

ctio

n

Disordered

micelle array

Isotropic solution: c < cmc

CMC

Humidity

H2O regulation

Solvent

evaporation

Formation of a

liquid crystal

Isolated

template

molecules

Pu

lling

dire

ctio

n

Brinker et al. Adv. Mater. 1999

D. Grosso et al., Chem. Mater., 2002

E. L. Crepaldi et al., JACS., 2003

Soler-Illia and Innocenzi Chem. Euro. J. 2006

Assembly of

NanoBuilding

Blocks (ANBB)

Film

Thickness

Sol Film

Syncrotron-SAXS in-situ

Formation Process of MP Films

Time

10 s 60 s 70 s 80 s 2 min 30 min

Interferometry

Crepaldi et al., J. Am. Chem. Soc., 2003Grosso et al., Adv. Funct. Mater., 2004

Competition of

Stiffening

sol-gel / viscosity

Organisation

(rearrangement)

substrate

Solvent Evaporation

Micelle formation

Mesophases

Micelle

Alignment/

OrganizationDrying Line

Worm Like

Phase

ContractionEtOH

evaporation

ORGANIZATION

Stiffening (viscosity/condensation)

Controlling the Building blocks

Initial Solution

Soler-Illia and Innocenzi Chem. Euro. J. 2006

80 n m

H = 4

50 nm

H = 0.5

100 nm

100 nms = 0.003 s = 0.01

d-110 = 13,45

d-110 = 15,38

Understanding Organization

Simulations (Q. Tang-M.Müller)

ABC template / TiO2 NP

Tunable interaction potential

Equilibrium and Dynamics

Disorder-to-order

Q. Tang et al., Phys. Chem. Chem. Phys., 2017

D

e

M(II) oxohydroxyde NBB

N. Tarutani et al. ACS Nano., 2016

LDH nanocluster

Controllable size

0.5-10 nm diam.

Controlling Ni(II)

NBB diameter

Reaction time

/ min

Reaction rate

/ mol%

Diameter

/ nm

1 32 0.24

5 45 0.99

60 98 1.88

Combination of homogeneous

alkalinization and complexation

N. Tarutani et al.

Chem. Mater., 2016

Optimizing NBB size

using simulation

(N. Tarutani + Q. Tang)

N. Tarutani, Q. Tang, et al. Chem. Mater, 2019

M. Takahashi and N. Tarutani (OPU)

A successful predictive experiment at

LNLS synchrotron

N. Tarutani et al. Chem. Mater., 2016

N. Tarutani, et al. J Sol-Gel Sci Tech, 2018

Soler-Illia, Sanchez, Lebeau, Patarin., Chem. Rev., 2002

Soler-Illia and Azzaroni., J. Sol-Gel Sci. Tech., 2011 Chem. Soc. Rev., 2011

Soler-Illia et al., Nanoscale., 2012; S. Alberti et al., Chem. Commun., 2015

High surface area

Controlled pore size and interface

Confinement effects

P. Innocenzi et al., Chem. Mater., 2011

Controlled phase separationmicroemulsion templates

poreneck

As-prep

HT-aged

Schmidt-Winkel et al., Chem Mater., 2000

Mesostructured cellular

foams (MCF)Produced by microemulsion

templating

Hydrothermally stable

Pores and “windows”

controllable

Controlled phase separationthrough inorganic polymerization

K. Nakanishi, J. Sol-Gel Sci. Tech, 2000

Review: K. Nakanishi, J. Porous Mater., 1997; Acc. Chem. Res., 2007;

K. Nakanishi, J. Porous Mater., 1997

How to control phase separation

Silica-polymer interactions

Versus

Entropy loss due to silica condensation

Enthalpic Systems: repulsion betweenpoly/solvent

Entropic Systems: 2 inmiscible polys

Poly + solvent

Inorg + solvent

Inorg + Poly

Solvent

Tanaka et al., J. Chromatogr., 2002

h < 1

Controlled Phase Segregation

in macro-mesoporous titania films

•Macroporous Oxides

•Micron scale compatible with

biospecies (enzymes,

membranes, antibodies, cells)hydrophobic Ti-

oxo clusters

ORTi

OR

OH

OTi

TiOR

OR

OR OR

HOTi

OR

OR OR

RO

Fuertes and Soler-Illia, Chem. Mater 2006

Nakanishi., J. Porous Mater., 1997

O

O

…O

OO

Ti

HO

EtO

O

Ti

EtO

O

CH2CH2OH

•Clusters associate with

PEG

•Solvent phase

segregates (spinodal)O O

O O

Poly ethylene glycol

(PEG)

Droplet templating

Enthalpic Systems

Entropic Systems

Poly + solvent

Inorg + solvent

Inorg + Poly

Solvent

3050 3000 2950 2900 2850 2800 2750 2700

0.00

0.01

0.02

0.03

0.04

0.05

0.06

TP22 / PEG2000

Absorb

ancia

(u.a

.)

Número de onda (cm-1)

25 C

75 C

130 C

200 C

250 C

300 C

350 C

Wavenumber (cm-1)

FTIR

MEB

75ºC

130ºC

200ºC 350ºC

3050 3000 2950 2900 2850 2800 2750 2700

0.00

0.01

0.02

0.03

0.04

0.05

0.06

TP22 / PEG2000

Absorb

ancia

(u.a

.)

Número de onda (cm-1)

25 C

75 C

130 C

200 C

250 C

300 C

350 C

3050 3000 2950 2900 2850 2800 2750 2700

0.00

0.01

0.02

0.03

0.04

0.05

0.06

TP22 / PEG2000

Absorb

ancia

(u.a

.)

Número de onda (cm-1)

25 C

75 C

130 C

200 C

250 C

300 C

350 C

Wavenumber (cm-1)

FTIR

MEB

75ºC

130ºC

200ºC 350ºC

Mostly

Enthalpy-driven system

Polymer Integrated

with Ti-oxo NBB

Multiscale porosity

5 m

5 m

MACROPores(by phase separation)0,1 to 2 m

•Ti-oxo/PEG complex

•Phase segregation of Solvent

• PEG acts as separator

•Hierarchical porosity

NO

O

O

O

O

O

Ti+

Ti

O

Ti

O

OTi

+

OH

OTi...OTi...

OTi...

OTi...

OTi...• Mesoporous walls (3 nm)

• Functions included

From swelling to

controlled phase

separation

Template (F127) +

Swelling agent (PPG) +

Co-Solvent (THF)

Malfatti et al., Chem. Mater., 2009

Design of Bimodal porous titania

Malfatti et al., Chem. Mater., 2009

Fuertes et al. Chem. Mater., 2006

Zelcer et al. J. Mat. Chem. 2009, 2012

Template (F127) +

Swelling agent (PPG) +

Co-Solvent (THF)

0 510 15

20 2530 35

40

0.000

0.004

0.008

0.012

0.016

14

16

18

20

P =

[PP

G]/[T

i]

inte

rpore

dis

tance / n

m

VTHF

0 510 15

20 2530 35

40

0.000

0.003

0.006

0.0090.012

0.015

0

20

40

60

80

100

120

140

160

P =

[PP

G]/[T

i]

La

rge

po

re d

iam

ete

r /

nm

VTHF

a b

0 510 15

20 2530 35

40

0.000

0.004

0.008

0.012

0.016

14

16

18

20

P =

[PP

G]/[T

i]

inte

rpore

dis

tance / n

m

VTHF

0 510 15

20 2530 35

40

0.000

0.003

0.006

0.0090.012

0.015

0

20

40

60

80

100

120

140

160

P =

[PP

G]/[T

i]

La

rge

po

re d

iam

ete

r /

nm

VTHF

0 510 15

20 2530 35

40

0.000

0.004

0.008

0.012

0.016

14

16

18

20

P =

[PP

G]/[T

i]

inte

rpore

dis

tance / n

m

VTHF

0 510 15

20 2530 35

40

0.000

0.003

0.006

0.0090.012

0.015

0

20

40

60

80

100

120

140

160

P =

[PP

G]/[T

i]

La

rge

po

re d

iam

ete

r /

nm

VTHF

a b

0 510 15

20 2530 35

40

0.000

0.004

0.008

0.012

0.016

14

16

18

20

P =

[PP

G]/[T

i]

inte

rpore

dis

tance / n

m

VTHF

0 510 15

20 2530 35

40

0.000

0.003

0.006

0.0090.012

0.015

0

20

40

60

80

100

120

140

160

P =

[PP

G]/[T

i]

La

rge

po

re d

iam

ete

r /

nm

VTHF

a b

0 510 15

20 2530 35

40

0.000

0.004

0.008

0.012

0.016

14

16

18

20

P =

[PP

G]/[T

i]

inte

rpore

dis

tance / n

m

VTHF

0 510 15

20 2530 35

40

0.000

0.003

0.006

0.0090.012

0.015

0

20

40

60

80

100

120

140

160

P =

[PP

G]/[T

i]

La

rge

po

re d

iam

ete

r /

nm

VTHF

0 510 15

20 2530 35

40

0.000

0.004

0.008

0.012

0.016

14

16

18

20

P =

[PP

G]/[T

i]

inte

rpore

dis

tance / n

m

VTHF

0 510 15

20 2530 35

40

0.000

0.003

0.006

0.0090.012

0.015

0

20

40

60

80

100

120

140

160

P =

[PP

G]/[T

i]

La

rge

po

re d

iam

ete

r /

nm

VTHF

a b

Bellino et al, Small 2014, Mater. Today Comm. 2016

Review: Catalano et al. Bioelectrochem. 2015

Enzyme+NP@MesoporesEnergy Nanosystems

Concurrent

polymerizationsol-gel versus organics

Drisko et al., Chem. Mater., 2010

Titania

Macro-meso monoliths

Complex system

Double role of surfactant

Drisko et al., Microporous Mesoporous Mater., 2011

ACS Appl.Mater. Interf., 2012

Multimodal templating

using “the forces of Nature”

PDMS~20m

Colloidal Latex ~200nmMicelles~10 nm

MEB

200 m20 m200 m

MEB

200 m20 m200 m

MEB

200 m20 m200 m

MEB

200 m20 m200 m

Sea Urchin Stucky, Whitesides, Pine 1998, 2001

Conclusions

• Chemical Control of

building blocks and

interactions is essential

• Sol-Gel chemistry (NBB)

– Composition, shape, size, surface, charges…

• Self-Assembly

– Driving forces towards order

(central, vectorial, local)

• Phase Separation

– Controlling microSpace

• Processing

– Coordinating kinetics and transport