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Photo-initiated Cationic Polymerization of Sustainable Epoxy Materials
Zheqin “Theodore” Yang
Graduate Student Department of Chemistry and Chemical Biology
Rensselaer Polytechnic Institute, Troy, NY, USA
2014 Rensselaer Nanotechnology Center Research Symposium
Wednesday, October 29, 2014
James V. Crivello and Chang Y. Ryu
National Science Foundation
Applications of Epoxy
�
J. Meziani, Wei Wang et al., Adv. Mater., 2009, 21, 2088−2092. Jia Liu, Z. J. Thompson et al. Macromolecules, 2010, 43 (17), pp 7238–7243.
O" "
Motivation Develop green and sustainable alternatives to the highly polluting and energy-intensive epoxy resin chemistry. 1. Substrates should be readily available in substantial quantities with minimum chemical modification. 2. Polymerization reaction should be rapid, energy efficient and solvent-free.
Approach
Soybean oil
Linseed oil
H2C
CH
CO2(CH2)7 CH
CO2(CH2)7
H2C CO2(CH2)7
CH
CH
CH
CH (CH2)7 CH3
CH2 CH CH CH2 CH CH CH2CH3
CH CH2 CH CH CH2 CH CH CH2CH3
H2C
CH
CO2(CH2)7 CH
CO2(CH2)7
H2C CO2(CH2)7
CH
CH
CH
CH (CH2)7 CH3
CH2 CH CH CH2 CH CH CH2CH3
CH CH2 CH CH (CH2)4CH3
Vegetable oils Ester-based Monomer Source with Unsaturated Bonds (Triglycerides with unsaturated fat)
Venturello, C. and D’Aloisio, R. J. Org. Chem. 1988, 53, 1553-1557
• No byproduct other than water • High conversion (>60%) • Easy workup
Epoxidation by Phase Transfer Catalyst
Crivello, J.V.; Lam, J.H.W. J. Polym. Sci., Part A: Polym. Chem., 1979, 17, 977−999. Crivello, J.V.; Lam, J.H.W. J. Polym. Sci., Part A: Polym. Chem., 1979, 17, 2877−2892.
6
Photo-initiated Cationic Polymerization
MtXn- = SbF6
- , PF6-, AsF6
-, BF4-, (C6F5)4F6
- etc
hγ
Drawbacks to Epoxidized Vegetable Oils as Monomers
• Low glass transition temperatures limit use to non-structural applications • Relatively slow photopolymerization rates
Optical Pyrometry Apparatus
2 wt% IOC-‐8
Photoinitiator:
Epoxidized linseed oil (ELO) Tg = 50 oC
Epoxidized soybean oil (ESO)
Butadiene-based comonomer
*
Cyclohexene, 4-‐ethenyl-‐
1,5-‐cyclooctadiene
Poly-‐butadiene
Cyclohexane, 1,2,4-‐triethenyl-‐
1,5,9-‐cyclododectriene
1,3-‐Butadiene
O O
O
O
O
O O
O
O
O
*
O
O
• Photointiator:
• Light Intensity: • 2354 mJ/cm2min
2 wt%
100 wt% ELO
CODD: 100 wt% CODD O O
• Photointiator:
• Light Intensity: • 2354 mJ/cm2min
CODD: 100 wt% CODD
2 wt%
100 wt% ELO
70 wt% ELO 30 wt% CODD 80 wt% ELO 20 wt% CODD
95 wt% ELO 5 wt% COD
90 wt% ELO 10wt% CODD
O O
100% wt TVCHT
60 wt% ELO 40 wt% TVCHT 80 wt% ELO 20 wt% TVCHT
O
O
O
100 wt% ELO
• Photointiator:
• Light Intensity: • 2354 mJ/cm2min
2 wt%
100% wt TVCHT
60 wt% ELO 40 wt% TVCHT 80 wt% ELO 20 wt% TVCHT
O
O
O
100 wt% ELO
100 wt% CODD
• Photointiator:
• Light Intensity: • 2354 mJ/cm2min
2 wt%
O O
Sample: 100%
Tsubstrate
UV pipet
Sample holder Tsubstrate= 90 °C
70 °C 50 °C 25 °C
• Photointiator:
• Light Intensity: • 2354 mJ/cm2min
2 wt%
O
O
O
Threshold temperature of autoacceleration
Monomer Temperature (°C)
Viscosity (Pa�S)
TVCHT
25 0.248
50
0.0327
70
0.0106
90
0.00510
CODD 25 0.0288
ELO 25
2.10
O
O
O
0 50 100 150 2000.00
0.05
0.10
0.15
0.20
0.25
0.30
Tan
δ
Temperature (°C)
100% ELO
90 wt% ELO/ 10 wt% VCHD
80 wt% ELO/ 20 wt% VCHD
70 wt% ELO/ 30 wt% VCHD
0 10 20 3050
60
70
80
90
100
110
Gla
ss t
rans
ition
Te
mp
(°C
)
VCHD content (wt%)
2 wt%
• Photointiator:
• Sample
Thickness: 100-120 µm
Light intensity: 3336 mJ/cm2 min
Irradiation time: 15s Samples were postbaked at 80℃ for 2h
VCHD:
* Error bar using t test (95%)
Conclusions • Unsaturated vegetable oils can be epoxidized and
polymerized into epoxy thermoset. However, their reactivity and thermal properties need to be improved. (e.g. Tg (ELO) = 50 oC)
• Butadiene-based epoxy comonomers show a good enhancement of reactivity and glass transition temperature (Tg to 110°C for a blend of 70 wt.% ELO/30 wt% VCHD, for example).
• A critical threshold temperature (~80°C) exists for autoaccelaration of photopolymerization of trivinyl cyclohexane triepoxide(TVCHT) and viscosity plays an important role in control the induction period.
VCHD:
TVCHT: O
O
O
CODD: O O
Acknowledgements
• Crivello/Ryu Research Group • RPI polymer center community