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

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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.  

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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