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Functional Polymer Blends: A General Approach for the Design of Optical Materials with Tailored Properties. Christoph Weder Department of Macromolecular Science and Engineering. Functional Polymer Blends. Summary. Approach:

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slide1

Functional Polymer Blends:

A General Approach for the Design of Optical Materials with Tailored Properties

Christoph Weder

Department of Macromolecular Science and Engineering

slide2

Functional Polymer Blends

Summary

Approach:

Blending of "passive" polymers with minor fractions of "active" guest molecules, which introduce selected functionalities.

Motivation:

Rather than developing new materials systems ‘from scratch’, the approach attempts to combine the property matrices and processing protocols of well-known polymers with the exceptional, readily tailored properties of functional organic molecules.

Challenges:

Characterize and control supramolecular architectures.

slide3

Functional Polymer Blends

Outline

Light-Polarizing Photoluminescent Systems

Excimer Probes

Functional Multilayer Films

Conclusions

slide4

Linear Polarization of Light

Introduction

Linearly polarized light is usually generated by the use of dichroic polarizers

Applications:

Liquid crystal displays, sunglasses, optical filters

Dichroic Polarizer:

Uniaxially oriented absorbing dyes, linearly polarized

absorption, efficiency < 45 %

Photoluminescent (PL) Polarizer:

Uniaxially oriented luminescent molecules, linearly polarized emission,

Combination of polarizer and ‘active’ color filter

slide5

Light-Polarizing PL Polymers

PL LCDs

Science 1998, 279, 835.

PCT IB98/00998 (1998)

slide6

Light-Polarizing PL Polymers

PL LCDs

Science 1998, 279, 835. WO 9901792 (1999)

slide7

Light-Polarizing PL Polymers

Security Features

WO 0019016 (2001)

slide8

Light-Polarizing PL Polymers

Processing

Adv. Mater.1997, 9, 1035.J. Mater. Chem. 1999, 9, 2221.

slide10

Light-Polarizing PL Polymers

Properties

Polarized absorption and emission of oriented ( = 80) 2 % w/w

EHO-OPPE / UHMW PE blend films

DRA = 57

DRE = 72

slide11

Light-Polarizing PL Polymers

Orientation Mechanism

Synth. Met.2001, 124, 113.

slide12

Light-Polarizing PL Polymers

Orientation Mechanism

slide13

Light-Polarizing PL Polymers

Orientation Mechanism

J. Phys. Chem.2000, 104, 5221.

slide14

Light-Polarizing PL Polymers

Patterning

Polarizer

unpolarized

90°

slide17

Cyano-OPVs

Excimer Formation upon p-p stacking

1,4-bis(a-cyano-4-methoxystyryl)-2,5-dimethoxybenzene BCMDB:

644

506/538

Synthesis 2002, 1185. US Patent Appl. filed.

slide18

Cyano-OPVs

Excimer Formation upon p-p stacking

1,4-bis(a-cyano-4-methoxystyryl)-benzene BCMB:

561

459/485

slide19

Cyano-OPVs

Excimer Formation upon p-p stacking

Birks, J. Photophysics of Aromatic Molecules, Wiley, New York 1970.

slide20

Cyano-OPVs

Synthesis

R1R2Yield

BCMDB: MeO MeO 89%

BCMB: MeO H 90%

BCEHODB: 2-Ethylhexyloxy MeO 83%

Synthesis 2002, 1185. US Patent Appl. filed.

slide21

Excimers as Molecular Probes

Diffusion Dyeing

Polymer filmDyeSolvent (toluene, CHCl3)

Diffusion dyeing

Rinsing, drying

slide22

Excimers as Molecular Probes

Diffusion-Dyed Polymer Blends

PL spectra of LLDPE / BCMDB blend film (~0.1 % w/w) - Influence of tensile deformation:

PL spectra of LLDPE / BCMDB

blend films:

[dye] (% w/w): (—) ~0.02, (—) ~0.06, (—) ~0.1, (—) ~0.3

Adv. Mater. 2002, 22, 1625-1629.; US Patent Appl. Filed.

slide24

Excimers as Molecular Probes

Diffusion-Dyed Polymer Blends

PL lifetime of LLDPE / BCMDB blend films (ex 481 nm):

[dye] / % w/w: ●~0.02, ●~0.1,■ ~0.1 stretched to 200 %

530 nm

650 nm

slide25

Excimers as Molecular Probes

Melt Processing of Blends

PolymerDye

Extrusion

Polymers: LLDPE, PP; Film thickness ~100mm;

Dye concentration 0.01 – 0.40 % w/w

slide26

Melt-Processed BCMBD/LLDPE Blends

Properties

PL spectra of freshly quenched LLDPE / BCMDB blend films:

[dye] / % w/w: (—) 0.01, (—) ~0.05, (—) ~0.1, (—) ~0.20, (—) ~0.40

slide27

Melt-Processed BCMBD/LLDPE Blends

Properties

PL spectra of LLDPE / BCMDB blend film (~0.18 % w/w) Influence of conditioning at room temperature:

Polym. Mater. Sci. Eng.2003, In Press.

slide28

Melt-Processed Blends

Phase Behavior

slide29

Melt-Processed BCMBD/LLDPE Blends

Conditioning

PL spectra of a LLDPE / BCMDB blend film (~0.18 % w/w) before / after conditioning at room temperature:

PL spectra of a LLDPE / BCMDB blend film (~0.18 % w/w) before / after conditioning at room temperature:

slide30

Melt-Processed Blends

Mechanical Deformation

PL spectra of a conditioned LLDPE / BCMDB blend film (~0.18 % w/w) before / after deformation to l = (l-l0)/l0 = 300 %

PL spectra of a conditioned LLDPE / BCMB blend film (~0.18 % w/w) before / after deformation to l = (l-l0)/l0 = 300 %

slide31

Excimers as Molecular Probes

Application

  • Anti -Tampering Films
  • Security Features / Brand Protection
  • Integrated Failure Indicators
  • - Protective Gear
  • - Load-bearing Structures
  • - Adhesives
  • .
  • .
  • .
slide32

AB Feedblock

Extruder A

Extruder B

Melt Pump B

Melt Pump A

Multipliers

Exit Die

Cross- Section of LayerMultiplier

Flow Direction

Layer Multiplier

Functional Multilayer Films

Process of Multilayering

E. Baer et al. Processing and Properties of Polymer Microlayered Systemsin Polymer Process Engineering 97; Coates, P.D. Ed.; The Institute of Materials, London:1997, 137-157.

slide33

n1

n2

n1

n2

Functional Multilayer Films

Reflective Films

Films with alternating layers of two polymers of different refractive indices are highly reflective.

slide34

n1

n1

n2

n2/n3/n2

n1

n1

n2

n2/n3/n2

n1

n1

Functional Multilayer Films

Photoreactive Films

A

B

C

  • Incorporation of photoreactive elements in reflective multilayer films
  • Multilayer films with alternating ‘inert’ and ‘photoreactive’ layers
  • Exposure of films changes RI of alternate photoreactive layers
  • By selectively exposing certain areas of a film to UV radiation, patterns can be produced due to the RI change in alternate layers
  • Low-cost, tuneable optical elements (dielectric mirrors, security features,…)
slide35

Functional Multilayer Films

Photoreactive Films

Polymers used for photoreactive multilayer films

Photodimerization reaction of cinnamic acid

  • Cinnamic acid dimerizes in a 2+2 cycloaddition reaction to form truxillic acid upon exposure to high-energy UV light (λ = 278 nm)
  • Upon dimerization the refractive index is reduced from 1.555 to 1.523
slide36

Effect of composition on Tg

Phase Behavior of PMMA-CA Blends

  • Tg of blends decreases with concentration of CA  CA has a plasticizing effect on PMMA
  • Homogeneous mixtures of PMMA-CA are obtained up to a concentration of 20% CA w/w
slide37

Photoreaction

Photophysical Behavior of PMMA-CA Blends

Change of the UV absorption spectrum of a PMMA-CA blend upon exposure to a 100 W air-cooled Hg lamp (higher intensity)

slide38

Refractive Index

Photophysical Behavior of PMMA-CA Blends

RI of blends increases linearly with composition

RI of blends decreases upon exposure to UV; The relative RI change increases with the concentration of CA

slide39

PMMA/PMMA-CA

Photopatterning of Multilayer Films

PMMA/PMMA multilayer film

PMMA-CA monolithic film

100 µm

PMMA/PMMA-CA (15 % w/w) 1024 layers, d = 50 nm

US Prov. Appl. filed

slide40

PC/PMMA-BZPO

Photopatterning of Multilayer Films

PC/PMMA-BZPO (0.1 % w/w) 1024 layers, d = 75 nm

J.Mater. Chem.2002, 12, 2620-2626 .

slide41

New Concepts

Functional Multilayer Films

< 5 nm

Orientation

Integration of PL dyes in

reflecting cavity:

Optically stimulated lasing?

“Forced assembly” of PL dyes: Spatially resolved (polarizing) energy transfer

“Forced assembly” of p- and n- type polymer semiconductors: Efficient charge separation?

slide42

Conclusions

Functional Polymer Blends

The blending of “passive” matrix polymers with minor amounts of “active” guest molecules represents an attractive, general concept for the design of functional polymer systems.

Adequate characterization and control of supramolecular architectures – at various levels – is important.

slide43

Acknowledgements

CWRU Weder Group CWRU Macro Science

Brent Crenshaw Ximei Sun Dr. Eric Baer

Akshay Kokil Ravisubash Tangirala Dr. Anne Hiltner

Christian Huber Eric Hittinger

Dr. Christiane Löwe Dr. Christoph Kocher CWRU Physics

Dr. Michael Schroers Dr. Quinghui Chu Dr. Kenneth Singer

ETHZ Materials ETHZ Chemistry

Dr. Cees Bastiaansen Dr. Bert Hecht Dr. Walter Caseri Dr. Alois Renn

Dr. Christoph Kocher Dr. Werner Trabesinger

Dr. Andrea Montali Prof. Urs Wild

Dr. Anja Palmans

Dr. Paul Smith

Dr. Theo Tervoort

Funding

3M Nontenured Faculty Award National Science Foundation DMR-0215342

DuPont Aid to Education Grant Sumitomo Bakelite Co.

DuPont Young Professor Grant The Goodyear Tire and Rubber Company

Hayes Foundation Equipment Grant The Petroleum Research Foundation

Landqart Co.