The dynamics of ultra-thin polymer filmsAlberto D’Amore and Luigi Grassia

Department of Aerospace and Mechanical Engineering The Second University of Naples - SUN, Aversa (CE), 81031, Campania, Italy

Ultra thin films (thickness h < REE) of glassy polymers such as polystyrene (PS) can show:

a) anomalously large thickness changes

b) unexpected dewetting properties

c) large shifts in the glass temperature Tg.

The present discussion focuses mainly on point a).de Gennes picture

the first term describes cohesion, and is minimal for θ = 0. The second term describes the Leibler-Sekimoto network and is minimal for θ = ψc

nmhc 1051.02.0

Reiter 1994 Macromolecules

Orts 1993 PRL

Kanaya 2004 PRE

52.8 nm

29.0 nm

Mukherjee et al. 2002 PRE

Film thickness

dd

dk

d

dT

v

vv

r

exp3

1

0

t

0 T aaa

td

dd

dGd

d

dB ijijijij 3

1

00

3

1iii

Modeling the interplay between structural relaxation and viscoelasticity

reduced time: time-temperature-stress-volume superposition

T [°C]

40 60 80 100 120 140 160 180 200 220 240 260

volu

me

[g/c

m3 ]

0.86

0.88

0.90

0.92

0.94

0.96

0.98

KAHR model10 MPa20 MPa50 MPa100 MPa

log t /s

-5 -4 -3 -2 -1 0 1 2 3 4 5 6 7

G [

GP

a]

10-4

10-3

10-2

10-1

100

101

135°C140°C142°C145°C150°C155°C

T [°C]135 140 145 150 155

log

a T

-4

-3

-2

-1

0

1

2

3

4

experimental dataWLF fit

Grassia & D’Amore PRE 2006

time [s]

10-6 10-5 10-4 10-3 10-2 10-1 100 101 102 103 104 105 106 107 108

Poi

sson

's R

atio

0,32

0,34

0,36

0,38

0,40

0,42

0,44

0,46

0,48

0,50

0,52

300 nm5nm

Temperature

370 380 390 400 410 420 430 440

sp

ecifi

c v

olu

me

0,926

0,928

0,930

0,932

0,934

0,936

0,938

0,940

0,942

0,944

NTE ZTEnmh

h

h

G

GbulkR

tfR 3000

8.1

0

Forrest et al. 2005 PRLMcKenna et al. 2005 Science