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Supramolecular Arrest and Activation for the Network for ation of Acid Catalyzed Epoxy Polymerization

Supramolecular Arrest and Activation for the Network formation of Acid Catalyzed Epoxy PolymerizationMatthew J. Spencer, James V. Crivello, Chang Y. RyuDepartment of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute

1

MotivationEpoxy network formation triggered byHardening AgentAcid generation with UV

Develop a one component system that cures quickly at low temperatures yet has RT stabilitySupramolecular chemistry

Matthew J. Spencer, James V. Crivello, Chang Y. Ryu

Structural AdhesivesPolyfuctional epoxide and polyamine hardening agentProblems with homogeneity, reaction begins upon mixing2

SystemSuper Acid Generation by Onium SaltsPhoto-initiation

Redox-initiation

Polymerizations monitored byOptical PyrometryRheology

Matthew J. Spencer, James V. Crivello, Chang Y. Ryu

Photo polymerization is simple but limited in its applications.

Thickness of sample limited by penetration depth of light.

Optical Pyrometry uses inferred camera to monitor temperature of reaction.

Rheometer can measure viscosity and elasticity and use these to establish the onset of crosslinking3

2620 mJ/cm2Matthew J. Spencer, James V. Crivello, Chang Y. Ryu

3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexane carboxylate Increased reactivity with 18 crown, complete suppression with 12 crown4

Ring Opening PolymerizationsHighly exothermic due to ring strain

Matthew J. Spencer, James V. Crivello, Chang Y. Ryu

2700 mJ/cm2

OP is well suited for highly exothermic reactions like ring opening polymerizations.

Temperature is show to be related to % converstion for initial portion of graph5

Supramolecular Arrest though Monomer DesignAlkyl glycidal ethers have long induction periods

Increasing coordination by the monomer

Matthew J. Spencer, James V. Crivello, Chang Y. Ryu

Neopentlyglycol diclycidyl etherTrimethylolpropane triglycidyl ether

Methyl glycidyl ether6

Dynamic Shear RheologyMatthew J. Spencer, James V. Crivello, Chang Y. Ryu

G* = G + iG = atan(G/G)

Descrbe dynamic shearComplex dynamic modulusG the elastic modulusG the viscous modulous7

Dynamic and Steady Shear Experiments

DynamicSteady

Model CompoundDipropylene Glycol Dyglicidal EtherMatthew J. Spencer, James V. Crivello, Chang Y. Ryu

Just under 2 hours at 25C and under 3 minutes at 60C

Steady shear provides method for in-situ mixing.

Agreement of steady and dynamic indication of acid dispersion 8

Modifying Reaction Kinetics with Crown Ethers

18-crown-6

1050 mJ/cm2Matthew J. Spencer, James V. Crivello, Chang Y. Ryu

2620 mJ/cm2 Modifying Reaction Kinetics with Crown EthersMatthew J. Spencer, James V. Crivello, Chang Y. Ryu

Increased reactivity with 18 crown, complete suppression with 12 crown10Matthew J. Spencer, James V. Crivello, Chang Y. Ryu

Dynamic Shear Experiments with 15-Crown-5 at 40C

Moles IOC-11 / moles Monomer ~ 0.002Crown is 10-20M% of monomer11

The Supramolecular Complex2,6-di-t-butylpyridine is a proton trap, but will not neutralize larger species like an tertiary oxonium ion

Crown ethers serve as a molecular ruler for acid species

Matthew J. Spencer, James V. Crivello, Chang Y. Ryu

Polyether ringPore Size (A)12-crown-4

1.2-1.515-crown-5 1.7-2.2

18-crown-6 2.6-3.2

Summary & Future WorkDevelopment of one component epoxy systemLong working life and low temperature cureControl of cationic ring opening polymerizationsMonomer DesignModifying reaction kinetics with crown ethersCrown ether size effect is observed

Epoxy BlendsNMR Complex Determination

Matthew J. Spencer, James V. Crivello, Chang Y. Ryu