1. Christopher Fenoli
Department of Chemical and Biological Engineering
University of Colorado
Synthesis of Novel Trithiocarbonates and Allyl
Sulphides and their Application into the
Advances in Covalent Adaptable Networks

2. Photoresponsive
Networks
Organic
Synthesis
Polymer
Chemistry and
Engineering
On-Demand Adhesives
Thiol-yne Networks
CAN’s

3. Photopolymerization Applications:
Spatiotemporal Control
10/07/15 6
www.hologramsolution.com
www.westdesmoinesdentalnews.com
www.wikipedia.org
www-me.ccny.cuny.edu
Stereolithography
Holographic
Materials
Dental
Composites

4. Polymerization And Shrinkage Stress
http://www.google.com/annealingplastics.com https://encrypted-tbn2.gstatic.com/images
Warping Warping
www.webmedcentral.com/articlefiles/831eaa29d56c 4f2098e3a76b9f 73d50b.j pg
Shrinkage and Cracking
in a Dental Material
 Viscous Liquid
 Less dense
 More Dense
 Crosslinked solid

5. • Crosslinks and backbone bonds
cleave and reform
• Adaptable chemical and physical
structure
Physical Networks
Covalent Networks
Covalent adaptable networks
(CANs) have advantageous
aspects of both physical
and covalent networks
CANs
Covalent Adaptable Network Paradigm
ThermoplasticsThermosets C A N s
stimulus

6. Covalent Adaptable Networks (CANs)
Addition-fragmentation in the network alleviates stress as bonds are
broken and reformed
General AFCT Mechanism
Fenoli, C., Wydra, J., & Bowman, C. (2014).
Macromolecules. 47(3) pp. 907-915Science, 308, 1615 (2005); Advanced Materials 18, 218

7. S SR2 R3
Allyl Sulfide Trithiocarbonates
Easily Accessible
Synthetically
– Little color and no
odor
– Mediocre Chain
Transfer Agents
Synthetically Challenging
– Require toxic, costly,
harsh reagents,
excesses of strong
bases, and low yields
– Colored and Foul Odor
– Excellent Chain
Transfer Agents
AFCT Moeities

8. Addition-
Fragmentation
Covalent Adaptable Network
Photoinduced Plasticity
for Mechanopatterning
C.J. Kloxin et al., Advanced
Materials, (2011)
Self-Healing Materials
Matyjaszewski, Angewandte
Chemie, 50, 1660 (2011)
Photoplasticity
Wayne Cook, Macromolecules, 45,
9734 (2012)
Photoplasticity in
Thiol-ene Network
Scott, T. F., (2005) Science N.Y.,
308(5728), 1615–7.
In-Situ Stress Reduction
Park, H. Y., (2012). Dental
Materials:
28(8), 888–93.

9. Proposed Molecular Structures
C – B – A – B – C
S S
S
R R
O
O
O
O
Ex:
Systematic variation in structure
Functionality Impacts AFT Photoplasticity Efficiency
1.A: Imparts the AFT component
2.B: Imparts the Mechanochemical Properties
3.C: Allows for Network Incorporation
A = SH SH
S
SH SH B = Linker C = OH
O
OH
O

10. Specific Aim 1: Development of a facile multi-faceted
synthetic approach for the design of novel AFCT
monomers
Allyl Sulfide Trithiocarbonates
 First Generation monomers for CAN’s
Trithiocarbonates Allyl Sulphides
Amamoto, Y., Kamada, J., Otsuka, H., Takahara, A., & Matyjaszewski, K. (2011). Repeatable photoinduced self-healing of covalently cross-linked
polymers through reshuffling of trithiocarbonate units. Angewandte Chemie (International Ed. in English), 50(7), 1660–3.
Kloxin, C. J., Scott, T. F., Park, H. Y., & Bowman, C. N. (2011). Mechanophotopatterning on a photoresponsive elastomer. Advanced Materials (Deerfield
Beach, Fla.), 23(17), 1977–81.

11. Trithiocarbonate Synthesis
Fenoli, C. R. and Bowman, C. N. (2014). Synthesis of novel trithiocarbonate and allyl sulfide containing monomers.
Polymer Chemistry, 5 (1), 62-68. Cover article: Polymer Chemistry, Volume 4, Issue 1, 2014.
Aoyagi, N., Ochiai, B., Mori, H., & Endo, T. (2006). Mild and Efficient One-Step Synthesis of Trithiocarbonates Using
Minimum Amount of CS 2. Synlett, (4), 0636–0638.

12. RAFT Monomer Implementation
C – B – A – B – C
Radical Chain Growth
Polymerizations
Thiol-Michael
Addition
0-100% of Acrylate
Component
Post-Polymerization
Stress Relaxation
Adhesion
Mechanopatterning
 0-100% of Acrylate
Component
 In-Situ Polymerization
Stress Relaxation
 Low Stress Thermosets
 Post-Polymerization
Stress Relaxation
Step-growth/Hybrid
 0-100% of Acrylate or
Alkyne Component
 In-Situ Polymerization
Stress Relaxation

13. Specific Aim 2: Exploration of the structure-property
relationships of CRAFT monomers effect on stress relaxation in
bulk polymerizations and photoplasticity studies
• Thiol-acrylate with triethylamine as base catatyst
Thiol-Michael “Click” Reaction for the Formation
of Covalent Adaptable Networks (CAN’s)
Original network
Initiation &
Bond Exchanges
Rearranged Network
RAFT unit
Initiator
Generated
Radical
Re-formed
Bond
PETMP
TEGDA RAFT Diacrylate

14. Stress(MPa)
Time (min)
Light on (365 nm, 20 mW/cm2
)
10% Strain
Stress Relaxation via Photoinduced Plasticity
Networks formed by Michael Addition are Capable of Relaxation of Stress
C.J. Kloxin et al., Advanced Materials, 2011

15. Photoplasticity: Structure-Property Effects on Stress
Relaxation
The resins were formulated with a 1:1 stoichiometric ratio based on functional groups of PETMP and TEGDA and the RAFT
comprising 50% of the acrylate functionalities.
20 mW/cm2
irradiation using 1% by weight DMPA at 365 nm for 30 minutes.
Fenoli, C. (2014).. Macromolecules, 47(3), 907–
9015

16. Simultaneous Shrinkage Stress ~ Conversion MeasurementSimultaneous Shrinkage Stress ~ Conversion Measurement
LVDTLVDT
SampleSample
Cure LightCure Light
CantileverCantilever BeamBeam Cantilever ClampCantilever Clamp
Quartz RodQuartz Rod
Generally need to measure conversion and stress simultaneously
Lu, Stansbury, Dickens,Eichmiller, Bowman, J. Mater. Sci.: Mater. Med.15 1097 (2004).

17. In-Situ Photopolymerization Stress Relaxation
in Chain Growth Polymerization
Irradiation:
0.1 mW/cm2
, 365 nm, 0.25 wt% DMPA
 Control ( )
containing
Bisphenol A
diacrylate and
TEGDA
 Experimental( )
contains 1.5%
Alkene TTC
Alkene Trithiocarbonate
1.5% bw
Bisphenol A
TEGDA
70% bw 28.5% bw

18. Wydra, J. W., Fenoli, C. R., Cramer, N. B., Stansbury, J. W., & Bowman, C. N. (2014). Journal of Polymer Science Part A:
Polymer Chemistry, 52(9) pp. 1315-1321.
All samples contained 0.25 wt % DMPA and were irradiated at 5 mW/cm2
365 nm filtered UV light on the tensometer.
In-Situ Photopolymerization Stress Relaxation
in Hybrid Polymerization
3 1
RAFT monomer

19. RAFT Monomer Implementation
C – B – A – B – C
Radical Chain Growth
Polymerizations
Thiol-Michael
Addition
0-100% of Acrylate
Component
Post-Polymerization
Stress Relaxation
Adhesion
Mechanopatterning
 0-100% of Acrylate
Component
 In-Situ Polymerization
Stress Relaxation
 Low Stress Thermosets
 Post-Polymerization
Stress Relaxation
Step-growth/Hybrid
 0-100% of Acrylate or
Alkyne Component
 In-Situ Polymerization
Stress Relaxation

20. Stress Reduction in Thiol-yne Systems by a RAFT
Alkyne
• “Click” nature
• Step-growth nature
• Reaction can be carried out in a multitude of reaction conditions
• Great resurgence in literature in the past 5 years.

21. Synthesis of Novel RAFT alkyne
Prior art involving allyl sulphides suffered from a side
reaction
Trithiocarbonates are better chain transfer agents

22. Mechanisms for Stress Relaxation
a. AFCT Mechanismb. Aryl Alkyne Reversibility through 2nd
step addition

23. Polymerization Stress Reduction in Thiol-yne
System
• 2.5 mole % RAFT added
• 3 wt% HCPK
• Irradiated at 365nm for 30 minutes.
0
0.5
1
1.5
2
2.5
3
3.5
0% 20% 40% 60% 80% 100%
ShrinkageStress(MPa)
Alkyne Conversion(%)
 Control
2.5% RAFT
Pure thiol-yne system
•Tetrafunctional thiol (PETMP), 1,7 octadiyne
•Mole % of octadiyne removed = Mole% of RAFT added
1
2

24. Polymerization Stress Reduction in
Thiol-yne:Acrylate System
• 5, 10, 15 mole % RAFT added
• 3 wt% HCPK
• Irradiated at 365nm for 30 minutes.
Control
5.0 mol% RAFT
 10.0 mol% RAFT
Δ 15.0 mol% RAFT
Hybrid System
• 1.4:1:1 ratio of bisphenol A ethoxylated diacrylate, PETMP, and 1,7-octadiyne
based on the moles of functional groups
0%
20%
40%
60%
80%
100%
0 5 10 15 20 25 30
AlkyneConversion(%)
Time (min)
0
0.2
0.4
0.6
0.8
1
0% 20% 40% 60% 80% 100%
ShrinkageStress(MPa)
Alkyne Conversion (%)
1.4
2
1

25. Stress Reduction at Comparable
Polymerization Rates
Control
10mW/cm2
15.0% RAFT/
170mW/cm2
Δ 15.0% RAFT/
10mW/cm2
• 15 mole % RAFT added at 10 and 170mW/cm2
• 3 wt% HCPK
• Irradiated at 365nm for 30 minutes.
17x Increase

26. Specific Aim 3: The implementation of the new RAFT
monomers into various stimuli responsive polymer
networks for new material applications.
Photo-Responsive Polymer Networks enabling Covalent,
Repositionable, and Green Adhesion by RAFT-Mediated
Covalent Adaptable Networks
 On-Demand Adhesion
 Spatio-temporal Control
 Internetwork Bond reshuffling

27. Internetwork Adhesion studies
0 2 4 6 8 1 0
0 . 0 0
0 . 0 4
0 . 0 8
0 . 1 2
0 . 1 6
0 . 2 0
MaximumShearStress(MPa)
U V E x p o s u r e T im e ( m in )
A v g . T e n s ile S t r e n g t h
() The thiol-Michael resin adhered at room temperature.
() The thiol-Michael adhered at 60 o
C.
() The thiol-Michael resin with 3% latent DMPA adhered at room temperature
• Irradiated at 20 mW/cm2
 Thiol-Michael “click” with PETMP and TEGDA 0.3 mm
thick film

28. Underwater Adhesion

29. Green Adhesion
Mechanism of Initiation
 RAFT trithiocarbonates act as Iniferters
 Three hour sunlight exposure yielded a sample with maximum shear stress
of 35% +/- 9% in relation to material tensile strength
 20 mW/cm2
of 365 nm light which achieved only 29% +/- 10%

30. Repositionable, Recyclable Adhesion
0
5
10
15
20
25
30
35
1 2 3 4 5
MaximumShearStress(kPa)
Trial
 The maximum shear stress (kPa) of the () alkyl trithiocarbonate
debonded and re-adhered.
 This process was repeated 5 times with the same resin.
 Each point represents a single trial and each trial is an average
of three distinct lap shear measurements.
S S
S
OO
O O

31. Adhesive Patterning
Hydrophilic
Hydrophobic
Overlay
Hydrophilic
Hydrophobic
• Hydrophobic Resin: PETMP, TEGDA, Phenyl allyl sulfide: Contact angle 75
• Hydrophilic Resin: ETTMP, PEG 575 diacrylate, Ebecryl 8402, Phenyl allyl sulfide: Contact angle 50
• Irradiated at 46mW/cm2
for 1 minute
Dry Wet Dry

32. Summary
 New Synthetic Design of RAFT monomersNew Synthetic Design of RAFT monomers
 Structure-Property Relationships: Allow forStructure-Property Relationships: Allow for
Enhanced Stress Relaxation in Chain growth, StepEnhanced Stress Relaxation in Chain growth, Step
growth, Hybrid systems, and Thiol-Michaelgrowth, Hybrid systems, and Thiol-Michael
Photoplasticity StudiesPhotoplasticity Studies
 Allows On-Demand and Tunable AdhesionAllows On-Demand and Tunable Adhesion

33. Future Directions
• Temperature Dependence on Photoplasticity
• Incorporate RAFT into SMASH networks
• EPR Studies
• Mechanochemical Project
• Triple Shape Memory
• Strain Free Mechanopatterning

34. Acknowledgments
Funding Sources
Photopolymerizations IUCRC and
NSF
Christopher N. Bowman
Jeff Stansbury
Charles Musgrave
Gayla Berg
Parag Shah
James Wydra
Devatha Nair
Bowman-Stansbury Group