Rheological Design of Sustainable Block Copolymers Alex Mannion - - PowerPoint PPT Presentation

Rheological Design of Sustainable Block Copolymers

Alex Mannion Advisors: Frank Bates, Chris Macosko Final Oral Examination Augsut 4th, 2016

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Safety moment: proper hand washing

jst.umn.edu

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Rheological design Paint Food Cosmetics Biological systems

“The rheological behavior of block copolymers is perhaps the least understood of all categories of complex fluids…”

– Professor Ron Larson, Dept. of Chemical Engineering, U. of Michigan1

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Block copolymers

AB diblock copolymer

AB diblock copolymer ABA triblock copolymer ABABA… multiblock copolymer

Morphology Architecture

1. “Structure and Rheology of Complex Fluids,” Oxford University Press, Ronald G. Larson, 1999. Dalsin, S. J.; Bottlebrush Polymers: Synthesis, Rheology, and Self-Assembly, 2016

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Sustainability

Ellen MacArthuer Foundation, “The New Plastics Economy: Rethinking the Future of Plastics,” 2016

Past… Future…

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Thesis Outline

Chapter 2 Chapter 4 Chapter 6 Chapter 3 Chapter 5 Chapter 7

Chewing Gum Branched Multiblock Copolymers Practical Materials

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Goal:

• Replace conventional chewing gum ingredients

with new materials to simplify formulation

• Maintains the same sensory profile

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Next generation chewing gum

What is chewing gum’s rheological fingerprint?

Morgret, L., Science-Based Design of High Performance Bubblegum, 2005

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Gum materials

Important deformation regimes1

• shear strains: 10-1000%
• shear rates: 10-100 s-1
• shear stresses: >104 Pa
• 1. Anderson et al., J. Oral Rehabil., 2002; Steffe J., Rheological Methods in Food Processing Engineering, 1992

Chewing gums Bubble gums Sample preparation Mouth chewing

Ralph DeLong, UMN, Dentistry

S (Pa-sn) n GR (Pa)

(s)

30100 0.228 24300 0.0440

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Linear viscoelasticity (LVE): oscillatory shear

S: stiffness n: strength of gel network

Critical gel equations1 Fitting parameters Rouse model equations

S (Pa-sn) n 30100 0.228

• 1. Chambon et al., J. Rheol, 1987

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Start up of steady uniaxial extension

L0 L

Constant Hencky strain rate: Uniaxial extension: Transient extensional viscosity:

Large strains at break ( > 4.0) correlate with desirable sensory feel Larger stresses at break for bubble gums  stabilizes bubble blowing

Chewing gums Bubble gums

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Block copolymer blends for chewing gum applications

What is chewing gum’s rheological fingerprint? Fragile critical gel fluid with high extensibility Goal: Next generation chewing gum Block copolymers

• Microphase separate  tunable solids
• Precise control over molecular architecture

Glass Rubber ABA triblock AB diblock

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High extensibility Softener, “critical gel” behavior

Why use block copolymers?

Mn (kg/mol) wPLA AB 7.4 0.41 ABA 95.1 0.36

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Mn (kg/mol) wPLA AB 7.4 0.41 ABA

A = poly(D,L-lactide) B = poly(cis-1,4-isoprene)

ABA triblock/AB diblock blends: extension

Lee, S. Structure and Dynamics of Block Copolymer Based Soft Materials, 2011

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Three component system

Investigated effects of

• Polymer composition
• Molecular weight

A A B B A B A

Poly(D,L-lactide) (L) Glassy, Tg ≈ 50 °C Poly(ε-decalactone) (D) Rubbery, Tg ≈ -50 °C

dimethanol benzene Sn(Oct)2 toluene 110 °C, 4 h ε-decalactone Sn(Oct)2 130 °C, 12 h D,L-lactide Benzyl alcohol

Synthesis

Advantages:

• High conversion, well-controlled
• Scalable
• Renewable/FDA approved materials

Synthesized polymers

Sample Mn

*

[kg mol-1]

fPLA Đ# DL-S1 5.6 0.15 1.11 DL-S2 8.0 0.33 1.13 DL-S3 9.0 0.41 1.18 DL-M1 32 0.09 1.05 DL-M2 38 0.21 1.06 DL-M3 46 0.32 1.06 LDL-1 102 0.05 1.07 LDL-2 112 0.11 1.09 LDL-3 133 0.23 1.06

Targeted a range of PLA weight fractions for three sets of polymers:

*calculated from end-group analysis of 1H-NMR #determined from room-temperature size-exclusion chromatography (SEC) †determined from differential scanning calorimetry (DSC)

L L D

Three polymer species

D L D L

Produced 24 blends 80% diblock 20% triblock

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Effect of triblock composition

(DL-S2) (LDL-1, LDL-2, or LDL-3)

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L L D D L

Vary PLA weight fraction 80 wt.% 20 wt.%

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Effect of diblock molecular weight

L L D

20 wt.%

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80 wt.%

:

Vary diblock ratio (2:0, 1:1, or 0:2) D L D L

Small angle X-ray scattering Exact morphology does not matter!

(DL-S2) (DL-M2)

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Blends for chewing and bubble gums Best blends: Key rheological parameters:

L L D D L

Polymer LDL-2 …with short DL diblocks

Future work

• Increase strain at break with multiblock architecture

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Thesis Outline

Chapter 2 Chapter 4 Chapter 6 Chapter 3 Chapter 5 Chapter 7

Chewing Gum Branched Multiblock Copolymers Practical Materials

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Blown film extrusion

Shear viscosity low at high rates Extensional viscosity high at high rates

Goals:

• Stable bubble
• Controlled thickness
• Fast through-put

Rheological targets:

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One commercial success story: poly(lactide) (PLA)

lactic acid lactide polylactide sugar

• H2O

catalyst

• ~$1 per lb
• Mechanically similar to

polystyrene

• Compost 100% in ~45 days

Natureworks.com

Applications Properties

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Deficiencies of commercial PLA Poor mechanical properties Poor melt strength

TD MD

Extensional rheology Blown film extrusion Tensile testing

Machine direction (MD) Transverse direction (TD)

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Toughening PLA with multiblock architecture

Poly(D,L-lactide) Tg ≈ 50 °C Elastomeric block Tg << 25 °C

• Effectively toughens PLA1
• Accessible TODT

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n

Bridging domains act as reinforcements greater toughness More bridges per molecule, the tougher the material

dangling ends loop bridge

• 1. Panthani et al, Macromolecules, 2013 2. Wu et al., Macromolecules, 2005

Panthani et al, Macromolecules, 2015

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Tuning processability with long chain branching

Long chain branching can lead to strain hardening1

Long chain branch Short branch

• 1. Meissner et al., J. Appl. Polym. Science, 1972

1) Polymer composition 2) Block lengths (~Mc) 3) Accessible TODT Versatile and robust platform: Linear multiblock (DL)n Star diblock DL-4

• Branched multiblock

(DL-4)n

• Linear triblock

LDL

Strategy

couple x x couple x x

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Synthesis and characterization

dimethanol benzene Sn(Oct)2 toluene 110 °C, 4 h toluene pyridine 25 °C, 2 h ε-decalactone Sn(Oct)2 130 °C, 12 h Sample MW

[kg/mol]$

<n> fPLA

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І LDL linear triblock 18.4

• 0.72

1.14 DL-4 star diblock 39.7

• 0.73

1.10 (DL)n linear multiblock 159 5.6 0.72 1.92 (DL-4)n branched multiblock 151 2.3 0.73 2.00

*calculated from 1H-NMR end group analysis $determined with SEC in room temp THF with a MALS detector

†determined with SEC in room temp THF with a RI detector

sebacoyl chloride D,L-lactide pentaerythritol

Linear Branched Size exclusion chromatography (SEC) Synthesis

<n> = number of subunits in final multiblock

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Estimating branching from SEC with multi-angle light scattering (MALS)

Contraction factor: Hyperbranched Linear chain: g = 1 4-arm star: g = 0.63 “Comb-like” High molecular weight species resemble a comb polymer SEC-MALS

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Key advantages of branched multiblock

Strain hardening due to branching

(DL)n linear multiblock (DL-4)n branched multiblock

Multiblocks have increased toughness Tensile testing Extensional rheology

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Key limitation: gelation

couple

… leads to a gel Too much coupling agent… Gel point equation:

Af + Bg

2 3 4 5 2

∞

3.0 2.0 1.7 3 4.0 2.0 1.6 1.4 4 3.0 1.8 1.5 1.4 5 2.7 1.7 1.4 1.3 fE gE

Values of <n> at gel point:

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New approach: A2 + B2/B3 +

A2

PLA diol, 19 kg mol-1

Approach

• B2

B3

Theory SEC

Coupling Branching Amount of B3

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Estimating branching from SEC with multi-angle light scattering (MALS)

SEC-MALS High molecular weight species becoming increasingly branched

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Extensional behavior

bPLA-95 bPLA-90 bPLA-80 bPLA-50 Extensional rheology

Temperature: 120 °C

Amount

• f B3

• B3

Easily adoptable to triblock copolymers

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Outlook

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A2

• B2

Approach With A2 + B2/B3 reaction, can easily tune:

• Coupling extent (<n>)
• Amount of branching
• Viscosity

Applicable to reactive extrusion

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Thesis Outline

Chapter 2 Chapter 4 Chapter 6 Chapter 3 Chapter 5 Chapter 7

Chewing Gum Branched Multiblock Copolymers Practical Materials

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Collaborators

Branched Multiblock Polymers

• Dr. David Giles
• Dr. Debbie Schneiderman
• Matt Irwin
• Maxwell Nagarajan

Pressure Sensitive Adhesives

• Dr. Tessie Panthani
• McKenzie Coughlin
• Joel Updyke

Blown Film Extrusion

• Dr. Mike Manno
• Tuoqi Li
• Liangliang Gu
• Jacob Wright
• Joseph Schaefer

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Acknowledgements Collaborators

Chewing Gum

• Prof. Marc Hillmyer
• Prof. Sangwoo Lee
• Prof. Randy Ewoldt
• Dr. Luca Martinetti
• Dr. Mark Martello
• Dr. Debbie Schneiderman
• David Giacomin
• Renxuan Xie
• Willy Voje
• Tao Yang
• Les Morgret
• Rafael Bras
• Niku Tseng

Funding

L.E. and D.H. Scriven Fellowship

Facilities

• Minnesota Characterization Facility
• Polymer Characterization Facility
• Hillmyer Group

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Acknowledgements, part 2 Bates Group Macosko Group

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Acknowledgements, part 3

Maxwell Nagarajan (MIT) Sangwoo Lee (RPI)

Frank Bates Chris Macosko

Mentors Army of undergraduate researchers Team Foam

Willy Voje (U. Washington) Marc Hillmyer Joel Updyke McKenzie Coughlin Jacob Wright Joseph Schaefer

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Acknowledgements, part 4 Fellow graduate students Mannion Clan

Matt Irwin Tessie Panthani Debbie Schneiderman Jeff Ting Sid Chanpuriya Meghan Peter Brian a.k.a. “Dad” Elizabeth a.k.a. “Mother”

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Acknowledgements, part 5

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Thesis Outline

Chapter 2 Chapter 4 Chapter 6 Chapter 3 Chapter 5 Chapter 7

Chewing Gum Branched Multiblock Copolymers Practical Materials

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