Temperature and Deformation Sensors for Polymer Films

Presented by

CHRISTOPH WEDERF. Alex Nason ProfessorDirector Functional Polymer Labhttp://macromolecules.case.edu/

1,4-Bis(α-cyano-4-methoxystyryl)-2,5-dimethoxybenzene (C1-RG):

506/538 644

Synthesis 2002, 1185.

400 500 600 700 800

P

L In

tens

ity (a

.u.)

Wavelength (nm)

CN

OMe

CN

OMeMeO

OMe

CHCl3 solution neat dye crystals

Chameleon Polymers Excimer-Forming Sensor Dyes

Cyano-OPVs (and other dyes) change their (fluorescence) color upon aggregation

Förster, T.; Kasper, K. Z. Physik. Chem. NF 1954, 1, 275. Förster, T.; Kasper, K. Z. Elektrochem. Angew. Physik. Chem. 1955, 59, 976.

M*+M

M+M

(MM*)

Excim

erE

mission

Monom

erE

mission

M*+M

M+M

(MM*)

Excimer Formation

The reason for the fluorescence color change is the formation of excimers

Chameleon Polymers

Förster, T.; Kasper, K. Z. Physik. Chem. NF 1954, 1, 275. Förster, T.; Kasper, K. Z. Elektrochem. Angew. Physik. Chem. 1955, 59, 976.

M+M

M+M

Excimer Formation

The reason for the fluorescence color change is the formation of excimers

Chameleon Polymers

0 25 50 75 100

10

100

1000

Cou

nts

Time (ns)

Dye Aggregate (De)FormationChameleon Polymers

Optical ResponsePL

Absorption

Supramolecular StructureKinetics, Thermodynamics, Processing, Mixing

Material SystemHost Polymer, Dye Structure

(Nano)phase-separated blend Molecular mixture

StimulusDeformationTemperature

Moisture…

Stimulus

US 7,223,988 (2007). US 20070158624 A1.

R1

CN CHO

CHO

R2

R2

R1

CN

R1R2

R2

CN

THF

+ 2

K-tert-butanolate

Synthesis 2002, 1185. Polym. Prepr. 2005, 46(1), 506. Chem. Mater. 2006, 18, 946.

C1-RG C1-YB

Facile Synthesis – Readily TailoredCyano-OPVsR1 R2 Yield

C1-RG: OMe OMe 89 %C1-YB: OMe H 90 %C62-RG: 2-Ethylhexyloxy OMe 83 %BCB H H 91 %BCPEOB C≡C-Ph OC8H17 80 %C12-RG OC12H25 OMe 90 %C18-RG OC18H37 OMe 87 %C18-YB OC18H37 H 87 %C12-YB OC12H25 H 84 %C12OH-RG O(CH2)12OH H 85 %

• Readily synthesized • Easily derivatized (color/solubility) • Highly luminescent (including excimer)• Large shift between monomer & excimer• Stable: can be melt-processed at 280°C• Dye cost estimation: cents/pound polymer

C18-RG C18-YB

C1-RG

C18-RG C18-YB

C1-YB

Cyano-OPVs Solid State Structure and ‘Aggregachromic’ Effect

Adv. Mater. 2008, 20, 119.

R1

CN

R1R2

R2

CN

OC18H37

H37C18O

CNCN

O

OC18-RG

300 400 500 600 700 800

CHCl3 CHCl3/MeOH

Abs

orba

nce

(a.u

.)

Wavelength (nm)

C2-RY8

300 400 500 600 700 800

CHCl3 CHCl3/MeOH

Abs

orba

nce

(a.u

.)

Wavelength (nm)

CNCN

OC8H17

OC8H17

OC2H5

H5C2O

Macromol. Rapid Comm. 2006, 27, 1981.

Deformation of Host/Guest SystemsLight-Polarizing PL Polymers

Polymer (LLDPE) PL Dye (0.2 % w/w)

Co-extrusion

Compression molding

Uniaxial deformation

Adv. Mater. 1997, 9, 1035. J. Mater. Chem. 1999, 9, 2221. Chem. Mater. 2000, 12, 472. J. Phys. Chem. 2000, 104, 5221.

RR

O

O

RC8-BPB

EHO-BPB

Aggregate DeformationPolymers with Built-In Deformation Sensors

Adv. Mater. 2002, 14, 1625. Chem. Mater. 2003, 15, 4717. Chem. Mater. 2006, 18, 946.Macromolecules 2006, 39, 9581. Macromol. Rapid Commun. 2006, 27, 1981.Macromolecules 2007, 40, 2400. US 7,223,988 (2007).

Nanoscale dye aggregates in ductile or elastic polymers

Deformation causes mixing/dispersion

Emission changes from excimer to monomer

Absorption changes from aggregate to isolated molecule

Nanophase-separated blend Molecular mixture

Deformation

Mixing

ProcessingPolymers with Built-In Deformation Sensors

Ductile, semicrystalline polymers: PEs, PP, PETDuctile, glassy amorphous polymers: PETGRubbery amorphous polymers: TPUs

Tailor dye solubility / concentration to achieve phase separationControl formation of nanoscale aggregates (through processing)

PolymerDye (0.01 – 2 % w/w)

Extrusion

Compression Molding

Cool / Aggregate dye

PL spectra of quenched LLDPE*/C1-RG blend films as function of dye concentration:

LLDPE / C1-RG BlendsFluorescent Deformation Sensors

450 500 550 600 650 700 750 800

0.4% 0.2% 0.1% 0.05% 0.01%

PL In

tens

ity (a

.u.)

Wavelength (nm)

IE/IM increases with increasing dye concentration

Material changes from molecular solution to phase-separated system

Aggregation threshold depends on dye solubility (chem. structure & temperature)

Chem. Mater. 2003, 15, 4717. *xc= 58 %

IM

IE

OMe

OMe

O

CNCN

O

OMe

OMe

OMe

CNCN

MeOOMe

CNCN

MeO

•

�■

∆

C1-RG

C1-YB

C62-RG

2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.41E-3

0.01

0.1

1

10

D

ye C

once

ntra

tion

(% w

/w)

1/Tx103

Tm

C18-RGCN

H37C18O

CN

OMe

OMe

OC18H37

2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.41E-3

0.01

0.1

1

1030 C180 C

D

ye C

once

ntra

tion

(% w

/w)

1/Tx103

Tm

180 C

Polarized optical micrograph of a slow-cooled 0.40 % w/w C1-RG / LLDPE blend

Atomic force micrograph of a slow-cooled 0.40 % w/w C18-RG/ LLDPE blend

Thermodynamics (dye solubility) and kinetics (aggregation speed) need to be controlled (chemistry, processing) to produce nano-phase-separated blends

12 µm 300 nm

Deformation Sensors Phase Behavior of LLDPE / Cyano-OPV Blends

Deformation of LLDPE/C18-RG BlendsFluorescent Deformation Sensors

PL spectra of a 0.4% w/wLLDPE/C18-RG blend film:

Deformation causes pronounced fluorescence color changes.

Macromolecules 2007, 40, 2400.

500 550 600 650 700 750 800

PL

Inte

nsity

(a.u

.)

Wavelength (nm)

λ = 0 % λ = 350 %

0 200 400

5

10

15

20

25

30 0.10 %

I 500/I 65

0

Strain (l/l0-1)

0

10

20

30

40

50

Stre

ss (M

Pa)

IM/IE & stress of 0.1% w/w LLDPE/ C18-RG blend as function of strain:

Color-strain and stress-strain curves mirror each other

Polymers change PL and absorption color

Color-Strain ResponseFluorescent Deformation Sensors

0 200 400 600 800 1000 12000

1

2

3

4

5

6

7

8

0

10

20

30

40

50

60

I 500/I 65

0

Strain (l/l0-1)

Stamylan Dowlex BG Dowlex NG Attane PEO86

Stre

ss (M

Pa)

IM/IE and tensile stress of 0.4% w/wPE/C18-RG blends as a function of strain and PE crystallinity:

Extent of color change shows a significant dependence on the host polymer’s crystallinity.

Magnitude of the color change increases with decreasing strain rate

-> plastic deformation of PE crystals seems to be essential-> little color change in elastic regime-> response reflects the different viscoelastic behavior of the host polymers-> at low strain rate, dye is completely dispersedMacromolecules 2007, 40, 2400.

0 1 2 3 4 5 6 7 8 9 10 11 120

5

10

15

20

25

30

0

10

20

30

40

50

60

I M/I E

Strain (%)

5.0 x 10-5 /s 0.001 /s 0.01 /s 0.1 /s

Stre

ss (M

Pa)

IM/IE and tensile stress of 0.4% w/wPE(xc=36%)/C18-RG blends as a function of strain rate:

Non-Polyolefins

PL spectra of 2% w/w PET/C18-RGblend film before/after stretching at RT:

Approach is broadly applicable: other examples include non-polyolefins, glassy amorphous, and rubbery systems

Chem. Mater. 2006, 18, 946. Macromolecules 2006, 39, 9581. Macromol. Mater. Eng. 2009 In Press.

Fluorescent Deformation Sensors

500 550 600 650 700 750 800

PL

Inte

nsity

(a.u

.)

Wavelength (nm)

Thermoplastic polyurethane elastomerbefore/during/after stretching at RT:

OCN NCO

OHOH

O(CH2)12OH

NC

CN

HO(CH2)12O

OMe

MeO

OHO

OHn

+

+

+

TPU

Mn=1000

C12OH-RG

C12OH-RG

450 500 550 600 650 700 750 800

C12OH-RG

Solution Crystal

PL

Inte

nsity

(a.u

.)

Wavelength (nm)

Macromolecules 2006, 39, 9581. 0 100 200 300 4000.6

0.8

1.0

1.2

1.4

1.6

1.8

0

5

10

15

20

250

500

I M/I E

Time (sec)

Tens

ile S

tress

(MPa

)

Stra

in

450 500 550 600 650 700

Unstretched Stretched 700 %

PL

Inte

nsity

(a.u

.)

Wavelength (nm)

02/22/06

Polyurethane CopolymersFluorescent Deformation Sensors

Adv. Mater. 2005, 17, 1471. Chem. Mater. 2006, 18, 946. Macromol. Rapid Commun. 2006, 27, 1981. Macromol. Chem. Phys. 2007, 208, 572. US Patent Application filed.

Pictures of a PMMA film comprising ~5 % w/w C1-RGbefore (right) and after (left) exposure to 130 °C.

Temperature 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.40.1

1

1030 C

Dye

Con

cent

ratio

n (%

w/w

)

1/Tx103

Tg

180 C

Aggregate FormationTime Temperature Indicators (TTIs)

PL spectra of quenched PET / C18-RG blend films (0.9 % w/w) as a function of time annealed at 100 ºC:

Chem. Mater. 2006, 18, 946.

PET/C18-RGFluorescent TTIs

450 500 550 600 650 700 750 800

0 min 1 min 3 min 5 min 10 min 30 min 60 min

PL

Inte

nsity

(a.u

.)

Wavelength (nm)

Quenched PET/C18-RG blends phase-separate above Tg (76 ºC)PL color changes irreversibly.Rate of color change depends on temperature -> Time Temperature Integrators

0 5 10 15 20 25 30

0.9 wt.% 1.5 wt.% 2.0 wt.%

PL

Rat

io (I

M/I E)

Time (min)

IM/IE of quenched PET /C18-RG blend films containing 0.9 - 2 % w/wdye annealed at 100°C:

Plot of the natural logarithm of the aggregation rate constant, τ, plotted against 1/(T-Tg)

0.025 0.050 0.075

-4

-3

-2

-1

0

1

2

3

4

5

0.9% C18-RG / PET 1.5% C18-RG / PET 2.0% C18-RG / PET

ln(τ

)

1/(T-Tg)

No response below Tg; above Tg, kinetic data are well described by single exponential function

Decrease of τ with increasing temperature and dye concentration

Plots of ln(τ) against 1/(T-Tg) are linear

-> Emission color of blends is predictable function of thermal history-> Response of sensors is tailored by dye structure, concentration, Tg

0 5 10 15 20 25 30

PL

Rat

io (I

M/I E

)

Time (min)

90 °C 100 °C 110 °C 120 °C

IM/IE of quenched PET /C18-RG blend films (0.9 % w/w) annealed at between 90 and 120°C:

Kinetics (PET/C18-RG)Fluorescent TTIs

IM/IE = IM∞/IE∞ + Ae-t/τ IM/IE = IM∞/IE∞ + Ae-t/τ

Chem. Mater. 2006, 18, 946. Macromol. Chem. Phys. 2007, 208, 572 J. Mater. Chem. 2009, 19, 101.

2.4 2.5 2.6 2.7 2.80

1

2

3

4140 130 120 110 100 90

C18-RG C2-RY8

ln (τ

)

Temperature (1/K x 103)

Temperature (°C)

Aggregation of C2-RY8 is slower than C18-RG at comparable concentration

Speed Increases with concentration

Total control of aggregation speed in a system of given Tg!

-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.80

1

2

3

4

51 2

C18-RG C2-RY8

ln (τ

)ln(Concentration)

Concentration (% w/w)0.6

Kinetics (Dye Structure and Concentration)

Macromol. Chem. Phys. 2007, 208, 572.

1% w/w PETG/dye annealed at 100 °C

Fluorescent TTIs

Kinetics (Changing Tg)

Tg (and therewith threshold) is readily changed!Macromol. Chem. Phys. 2007, 208, 572. J. Mater. Chem. 2009, 19, 104-110.

τ (min) vs 1/T for 2 % w/w PAx blends

2 % w/w PAxblends after

annealing for 15h at indicated

temperature

Blends of C18-RG in a series of acrylate copolymers with different Tg

Fluorescent TTIs

Arrhenius plot  of  ln(t)  versus  1/T  for  blends  incorporating C18‐RG (black),  C2‐RY8 (blue),  C1‐YB (red),  and  BBS (olive).  Polymer  hosts  are  PMMA/PBMA  copolymers  (■),  PC  (○), TOPAS  6015  (□),  TOPAS  5013  (Δ),  PETG  (▼),  PET  (●),  and Epoxy (▲).

Kinetics (Changing Tg)Fluorescent TTIs

J. Mater. Chem. 2009, 19, 104-110.

Temperature

Aggregate Formation Upon PlasticizationMoisture Indicators

2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6

0.25

0.5

0.75

1

2.5

240 200 160 120 80 40 0

Con

cent

ratio

n (%

w/w

)

Temperature (1/K x 103)

Temperature (°C)

Tg

Moisture

J. Mater. Chem. 2007, 17, 2989. Moisture plasticizes polymer; drops Tg

450 500 550 600 650 700 750 800

Pristine After 7 months

Inte

nsity

(a.u

.)

Wavelength (nm)

Polyamide Blends

Quenched blends are stable for months at 0% RH

Exposure to water results in (PL) color change

Nylon 6/66 (PA)Tm = 190 °C, H2O uptake = 10.5%Tg ~ 49 °C

1.0% w/w C12OH-RG/PA, 0% RH

C12OH-RG/PA exposed to water

J. Mater. Chem. 2007, 17, 2989.

CN

CN

O(CH2)12OH

HO(H2C)12O

OCH3

OCH3

Moisture Indicators

450 500 550 600 650 700 750 800

PL

Inte

nsity

(-)

Wavelength (nm)

Humidity Effect

Exposure of quenched blends to moisture causes dye aggregation and leads to a pronounced color change

Color changes are irreversible

Single exponential aggregation kinetics

1.0% w/w C12OH-RG/PA, 97% RH

0 25 50 75 100 125 150 175 200 225 10000

1

2

3

4

5

6

33%RH

0%RH

53%RH

I 541/

I 644

Time (min)

97%RH

Moisture Indicators

Chemo-Responsive Materials

Cure @ 180- 200ºC

MonomersDye (1-3%)(Solvent)

Cool to RT

Chemical Stimulus

Kinetic control

Damaged Coating

Stimuli-Responsive Epoxy Coatings

Final Coating: molecular mixture

Chemical in coating lowers Tg and triggers dye aggregationPotential to visualize coating problems before corrosion occursACS Applied Materials & Interfaces in press.

Chemo-Responsive MaterialsStimuli-Responsive Epoxy Coatings

ACS Applied Materials & Interfaces in press.

Shape Memory Polymers Indicator for Set/Release Temperatures

Dicumyl peroxide (DCP)Poly(cyclooctene) (PCO)

O

H3C CH3

O

CH3H3C

n

0

20

40

60

80

100

120

140

160

180

200

0100

200300

400500

600700

2040

6080

Stra

in (%

)

Stre

ss (k

Pa)

Temperature ( oC)

(i)

(ii)

(iii)

(iv)

Deformation

Cooling/FixingUnloading

Recovery

*

(1.25% DCP, cured 30 min at 180ºC)

Kunzelman, J.; Chung, T.; Mather, P. T.; Weder, C. J. Mater. Chem. 2008, 18, 1082.

Commercial ‘Dyes’ That Do The TrickStimuli-Responsive Polymers

O

NO

N

Uvitex-OB One(FDA-Approved Optical Brightener)

J. Mater. Chem. 2009, 19, 104-110.

• Tamper-Evident Packaging Materials

• Security Features / Brand Protection

• Integrated Failure Indicators

- Protective Gear

- Load-bearing Materials (from fishing lines to climbing ropes)

- Coatings

• Built-In Temperature/Moisture History

(from steaks to drugs to electronic parts)

ApplicationsExcimer-Forming Dyes as Sensors

http://macromolecules.case.edu/

AcknowledgmentsGraduate StudentsMark Burnworth (Ph.D.)Jill Kunzelman (Ph.D.)James Kostka (M.S.)Joe Lott (Ph.D.)Brian Makowski (Ph.D.)JD Mendez (Ph.D.)Kadhiravan Shanmuganathan (Ph.D.)Charles Sing (M.S.)

PostdocsDr. Jeffrey CapadonaDr. Michael Schroers (now BASF)Dr. Liming TangDr. Otto van den Berg (now Arcelor M.)

UG StudentsConnor Evans, Nick Moon, Neeka Rodgers, Scott Seidel, Michelle Sing

Key Collaborators: Drs. Stuart Rowan, Dustin Tyler, Chris Zorman, Lynn Capadona

FundingALCOA NSF DMI-0428208, DMR-062767, CBET-0828155 APT Center (Case/VA Hospital) Army Research Office (DAAD19-03-1-0208 )Schlumberger Ohio Innovation ScholarshipNIH NSF-STC (DMR 0423914)DuPont F. Alex Nason Endowment