Gradients of glass transitions temperature in lignocellulosic cell walls highlighted by micro- thermal analysis scan (SThM)

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Gradients of glass transitions temperature in

lignocellulosic cell walls highlighted by micro- thermal analysis scan (SThM)

Jean-Eudes Maigret, Js Antoniow, M Chirtoc, Johnny Beaugrand, Patrice Dole

To cite this version:

Jean-Eudes Maigret, Js Antoniow, M Chirtoc, Johnny Beaugrand, Patrice Dole. Gradients of

glass transitions temperature in lignocellulosic cell walls highlighted by micro- thermal analysis scan

(SThM). COST FP0802: Hierarchical structure and mechanical characterization of wood., Aug 2011,

Helsinki, Finland. 13 p. �hal-02804338�

GRESPI

Gradients of Glass Transitions Temperature in

Lignocellulosic Cell Walls Highlighted by Micro-Thermal Analysis Scan (SThM)

Jean-Eudes MAIGRET ^a , Jean Stéphane ANTONIOW ^b , Mihai CHIRTOC ^b , Johnny BEAUGRAND ^a , Patrice DOLE ^a.

a INRA - URCA, UMR 614 FARE, 2 esplanade Roland Garros, 51100 Reims

b GRESPI-ECATHERM EA 4301, URCA, UFR Sciences, BP 1039, 51687 Reims

636 nm

0.00 nm

COST FP0802, Helsinki

24 ^th August 2011 100x100 µm

¹

500 µm

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I - Experimental Set Up

II - µ-TMA Mode (µ-Thermo-mecanometry) III - Scanning Mode

IV - Mapping of a plant cell wall Conclusions / perspectives

Summary

2

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Transition vitreuse

Fusion

Etat fondu

Transition vitreuse

Fusion

Etat fondu

Tg

Glassy State Rubbery State

The mechanical properties depend strongly on the state of mobility of the molecular chains

I- Experimental Set Up

The Glass Transition

“Hard and brittle” “Soft and stiff”

Mobility

3

Stress Natural fibers

Heat Water

Mecanical stress

Modification of => the mobility of the chains

=> Tg

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0 50 100 150 200 250

20 40 60 80 100

Theoretical Approach

m%

P I S1 S2 S3

Lignin

Hémicellulose

Cellulose

Tg of anhydrous wood polymers

[1] Tg _[1]

[1] Popa V.I., Hemicelluloses, In: Polysaccharides in Medicinal Applications, 1996, 107-124.

heterogeneous repartition of polymers in the cell wall

+

Different range of T _g

Gradients of T _g

4

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Resistive Wollaston tip : Pt _0.9 Rh _0.1 wire

 = 5 m, L = 200 m

SThM = AFM + Resistive Wollaston Tip

Alternating Current

direct current

Electrical measurement : P ₁

Topo

636 nm

0.00 nm

4,44 mW 4,58 mW

Measure of

: the thermal conductivity the thermal diffusivity

Poplar 100x100 µm ² T = 120°C

Flux

[2] Pollock, H.M., and Hammiche, A., J. Phys. D: Appl. Phys. 34(9), R23, (2001).

[3] Wang, C., Thermochimica Acta, 423, 89, (2004).

Glue Mirror

5

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II- µ-TMA Mode

-Tests on PLA samples (Tg = 58°C) -

6 PLA

40 °C

55 °C

The probe sinks in the sample at a temperature comparable to the Tg of the PLA.

80 °C

-0,4 -0,35 -0,3 -0,25 -0,2 -0,15 -0,1 -0,05 0

0,00 0,50 1,00 1,50

'pla40°c cte 'pla50°c cte

'pla55°c cte 'pla80°c cte

Série3 Série4

z (µm)

t (mn)

40°C 50°C

55°C

80°C

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Local Thermal Analysis on a Poplar Cell Wall

z displacement of the thermal probe

Cell Wall LR White Resin

5

3 4

2 1 Glass Transition

Zone

T ≈ 100 °C T

(p) ≈ 90 °C

Resin Rubbery State Glassy State

X 5

z (µm )

50 µm

3600 nm

15 µm

Cell Wall (Topographic images, v

= 20 µm.s

, room HR)

20 40 60 80 100 120 140 160

Temperature (°C)

7

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III- Scanning Mode

Influence of Scan Speed on the Local Temperature

Topography Thermal Flux

T _probe = 80°C, V _scan decreasing

Best compromise between spatial resolution / sensitivity : v = 20 – 50 µm.s ^-1

A

8

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Topography and thermal signatures versus temperature (v = 20 µm.s ^-1 )

Analysis of a PET Sample

5 1 2 3

4

6

H eat F lo w (W .g

) T (°C) Differential Scanning Calorymetry

9

1 2

0 3 4

5 6

Thermal Flux (mW)

Temperature Setpoint (°C)

20 70 80 90 120 250

z displacement (µm)

20 70 80 90 120 250

Temperature Setpoint (°C)

1

3

5

0 T

Tg

recrystallization Melting

T _probe (°C) Calibration curve

T

( °C)

2

3

4

5

0 1 6

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30 °C 75 °C 110 °C 180 °C

Glass transition zone Rubbery State Fluid zone Glassy State

IV - Mapping of a plant cell wall Influence of Temperature

Size of images : 5 µm x 5 µm; Scan speed: 20 µm/s

T o p o g rap h y T h er mal F lu x

10

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Spatial Distribution of Surface T _g on a Double Cell Wall of Poplar

The resolution of the probe limites the identification of the T _g of the different sublayers

11

Surface profile

Resin Cell wall

Cell wall Resin

0 1 2 3

Glass transition area

Mi ddl e lamel la

Tg

= 70°C Temperature (°C)

z d isp lac eme n t (µm)

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=> Measure at a lower scale : use of nanoscale sensors (to come)

=> Improved modeling parameters affecting the measurement

(in progress)

- Thermal expansion of the probe - Influence of adhesion

- ...

Conclusions / Perspectives

12

www.bruker.com

2.5 µm

=> The feasibility of mapping a plant cell wall has been demonstrated.

=> The resolution of the Wollaston

tip is too low to discriminate the T _g

of the different sublayers.

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Acknowledgements

This work has been financially supported within the framework of the State-to-Country Contract MATOREN.

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13