Fabrication and Evolution of Mesostructures in Fluorinated Organosilicate Mesoporous Thin Films

Ji-In Jung, Jae Young Bae and Byeong-Soo Bae*Department of Materials Science and Engineering, KAIST, Daejeon 305-701, Republic of Korea

*E-mail: bsbae@kaist.ac.kr http://www.sol-gel.net/lomc

Department of Materials Science and EngineeringKorea Advanced Institute of Science and Technology (KAIST)

Introduction

PFASs with long perfluoroalkyl chains act as a structure directing agent.

Different interaction with templates cause the different mesostructure formation

range.

The chain length of PFASs affected the formation of mesostructure and thermal-

induced mesostructure change.

The increase of calcination temperature caused the change of the composition,

mesostructure, and optical property in the mesoporous fluorinated organosilicate

films.

Conclusions

Experiments

Self-Assembly of Surfactants

0.01N HCl

Add methanol

Filtering & spin coating

Heat treatment

TMOS

PFASs

3-FPTMS

13-FOTES

17-FDTMS

SiF3C

OR

OROR

CF2

SiF2C

CF2

F2C

CF2

F3COR

OROR

SiOR

ORORC

F2

F2C

CF2

F2C

CF2

F2C

CF2

F3C

Surfactants for Experiment

Experimental Purposes

Fluorinated mesoporous organosilicate

films

Mesoporous silica films

PFASs with perfluoroalkyl

groups

Synthesis of fluorinated mesoporous organosilicate films with surfactants and chain lengths of PFASs

Physical characteristics of fluorinated films depending on chain lengths of PFASs and kind of surfactants

→ Optical property (n) & hydrophobicity & formation scheme

Thermal induced mesostructure and composition change

XRD Patterns of the Films Confirmation of Perfluoroalkyl Groups PFASs Chain Length Effect

Fabrication of Films with Pluronic F68

Thermal-Induced Mesostructure Change Future Works

Kind of Mesoporous Structures

Used in membrane, sensor, and optical and electroni devices.

→ Investigation of microstructure, composition and optical

property in the fluorinated organosilicate films

Evaporation Induced Self-Assembly (Film)

Experimental Routes

PFASs

Unit cell parameter /nmContact

angle / o

Mesoporous

structure

Refractive

indexAs-

synthesizedCalcined

3-FPTMS 4.34 3.00 67.7Hexagonal 1.268

Cubic 1.135

13-FOTES 4.53 3.92 99.1 Hexagonal 1.256

17-FDTMS 4.86 4.17 108.4 Hexagonal 1.240

PFASs with long perfluoroalkyl chain act as templates!

PFASs, the Role of Templates

Fabrication of Films with CTACl

XRD Patterns of the Films Thermal Analysis of the Films

XRD patterns

Comparison of Mesostructure Formation

Formation Scheme

Possibilities for a variety of application in optics !

The increase calcination temperature cause the decomposition perfluoroalkyl groups.

References

1600 1400 1200 1000 800 600 400

(c) (b) (a)

after 450oC calcined

after 350oC calcined

as-synthesized

Ab

so

rba

nc

e (

a.u

.)

Wave number (cm -1)

(a) 1060 cm-1

Asymmetric stretching

mode of Si-O-Si bond

(b) 1146 cm-1

Bending mode of Si-CH2 of

perfluoroalkylsilane

(c) 1206 cm-1

Symmetric stretching mode

of C-F bond of

perfluoroalkyl chain

Mesoporous fluorinated

organosilicate thin films

were calcined at 350 oC.1 2 3 4 5 6 7 8 9

3-FPTMS

13-FOTES

17-FDTMS

Inte

nsi

ty (

a.u

.)

2 (degree)

x3

2 3 4 5 6 7 8

(f)650oC

550oC

450oC

350oC

(e)

(d)

(c)

(b)

(a)

150oC

as-synthesized

Inte

nsi

ty (

a.u

.)

2 (degree)

As-synthesized 150 C 350 C 450 C 650 C0.0

0.2

1.2

1.4

1.381.351.2261.441.457

o oo o

Re

fra

cti

ve

In

de

x

Heat Treatment

17-FDTMS3-FPTMS 13-FOTES

0 100 200 300 400 500 6000.0

0.2

0.4

0.6

0.8

1.0

1.2

Ato

mic

Ra

tio

Temperature (oC)

O/Si C/Si F/Si

1 2 3 4 5

Inte

nsi

ty (

a.u

.)

2 (degree)

SubstrateF68(Cubic)

SubstrateP123 (Hexa)

SubstrateF68 (Cubic)P123 (Hexa)

Substrate

100 nm

91 nm

133 nm

Hexagonal Cubic LamellarCubic

Amphiphilic surfactant

Hydrophilic head Group

Hydrophobic tail

Surfactant concentration increase

Micelle

Burn off surfactant

Surfactant+

Inorganic precursor

(Silica et al.)

Formation of Mesoporous Materials

Inorganic-Organic Hybrid Mesoporous Materials

Si OCH3

OCH3

OCH3

H3CO

Stirring for 24 hr

Add surfactant

TMOSPFAS + 0.01 N HCl

[CHCH33(CH(CH22))xxN(CHN(CH33))33]Cl]Cl

CTACl (x=15)CTACl (x=15)

Alkyl-ammonium halide cationic surfactant

Hydrophilic head group

Hydrophobic tail group

CH2CH2O CH2CHO

CH3

HO HN/2

CH2CH2ON/2

M

PEO : Hydrophilic (water-soluble)

PPO : Hydrophobic (water-insoluble)

PEO-PPO-PEO triblock copolymer

Pluronic F68 (N=153, M=29)

Spherical micelle

After calcined

[ CTACl ] / [ TMOS ] (x263)

50 43 40 35 30 20 1510

H C

H

H

H H H H

Silica

3-FPTMS

13-FOTES

17-FDTMS H

C C

H H HH

H

H

H C* C

H

H

H : HexagonalC : CubicC* : Hexagonal/Cubic

2 4 6 8 10

d(100) a0

6.54 nm 7.55 nm

d(100) a0

6.31 nm 7.28 nm

d(100) a0

6.31 nm 7.28 nm

d(100) a0

5.97 nm 6.89 nm

200

200

200

200

100

100

100

100

R'=8

R'=4

R'=2

R'=6

Inte

nsit

y (a

.u.)

2 (degree)

2 4 6 8 10

d(100) a0

5.59 nm 6.45 nm

d(100) a0

5.48 nm 6.33 nm

d(100) a0

6.22 nm 7.18 nm

d(100) a0

5.93 nm 6.85 nm

200

200

200

200

100

100

100

100

R'=8

R'=6

R'=4

R'=2

Inte

nsit

y (

a.u

.)

2 (degree)

2000 1600 1200 800

(c)(b)(a)

550oC

450oC

400oC

350oC

As-synthesized

Ab

so

rba

nc

e (

a.u

.)

Wavenumber (cm -1)

0 100 200 300 400 500 600 700 80040

50

60

70

80

90

100

Temperature (oC)

We

igh

t (%

)

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

De

riv. We

igh

t (% / oC

)

Fluorinated Mesoporous

Silica Mesoporous

[Surfactants] / [Silanes]

5 10 15 20 25 30 454035

CTACl

F68

CTACl

F68

J.I. Jung; J.Y. Bae; B.S. Bae J. Mater. Chem. To be submitted (2004). J.I. Jung; J.Y. Bae; B.S. Bae Chem. Mater. To be submitted (2004). J.Y. Bae; J.I. Jung; B.S. Bae J. Mater. Res. To be submitted (2004). J.Y. Bae; O.H. Park; J.I. Jung; K.T. Ranjit; B.S. Bae Micropor. Mesopor.

Mater. 67, 265 (2004). O.H. Park; S.Y. Seo; J.I. Jung; J.Y. Bae; B.S. Bae J. Mater. Res. 18,

1039 (2003). C.J. Brinker; Y. Lu; A. Sellinger; H. Fan Adv. Mater. 11, 579 (1999). A. Stein; B.J. Melde; R.C. Schroden Adv. Mater. 12, 1403 (2000). G. Wirnsberger; B.J. Scott; B.F. Chmelka; G.D. Stucky Adv. Mater. 12,

1450 (2000).

FT-IR spectroscopy

As-synthesized After calcined FT-IR spectroscopy

Pluronic F68 copolymer decomposes above 350 oC.

Mesoporous fluorinated organosilicate thin films

were calcined at 400 oC.

TGA Curves

Silica wall

Fluorinated group

Although surfactant concentration is very low, mesoporous films are mainly formed by long perfluoroalkyl chain (As template).

Mesostructure Changes Compositional Change Refractive Index Change

20nm

20nm

3-FPTMS and CTACl After calcination at 550 oC, the cylindrical pores are maintained.

350 oC 550 oC

20nm

20nm

17-FDTMS and CTACl After calcination at 550 oC, a less ordered and broken mesostructure was formed.

350 oC 550 oC

Multi-mesostructured Films

Photochromic Dye- Applicable for optical waveguide, shutters,

light modulators, and optical storage media- For optical shutter applications, a fast

response time is required. - Study about the effect of hydrophobicity and

pore size

OH

OH

OH

HO

OH

OH

OH

O H

O H O H

HO

HO

<Hydrophilic>

CFn

CFn

CFn

CF

n

CF

n

CF

n

CF

n

CF

n

CF

n

Fn

CFn

C

F n

C

<Hydrophobic>

Fast response time

& long switching

cycle is expected.

1 2 3 4 5 6 7 8 9

3-FPTMS

13-FOTES

17-FDTMS

x2

Inte

nsi

ty (

a.u

.)

2 (degree)

It is possible to form the multi-layered films with thickness and different pore surface property such as pore size and pore structure.

[Multi-layer with different pore size and pore structure]

As-synthesized

F68 used

- The repulsionrepulsion of

hydrophobic

perfluoroalkyl chain &

hydrophilic PEO chain.

CTACl used

- The hydrophobic hydrophobic

interactioninteraction of

hydrophobic chain of

CTACl & hydrophobic

perfluoroalkyl chain.