Supramolecular main-chain liquid crystalline polymers and networks with competitive hydrogen bonding: a study of flexible bis-acids and a mixture of flexible mesogenic bispyridyls and flexible polypyridyls

Steven R. Friday, Richard F. Miesen and Kurt N. WiegelDepartment of Chemistry, University of Wisconsin, Eau Claire, Eau Claire WI 54702

Background

Materials Used

Liquid Crystals•Materials that exhibit long-range and some short-range directional ordering in a fluid state.

•Composed of mesogens (shaped molecules) and flexible spacers

•Different types of mesogens based on molecular shape (calamitic: rod-shaped)

Molecular Self-assembly Through Hydrogen BondingNon-covalent interactions formed between two molecules through a hydrogen-bond resulting in a larger “associated” molecule

AD H

Observations Acknowledgements

O

O H N

• Complexes synthesized through standard melt-complex methodology• DSC data determined on a Mettler-Toledo STAR e1 DSC at 10°C/Min

heating rate unless otherwise noted• Optical micrographs were measured using a Mettler-Toledo FP82

Hotstage Mounted on an Olympus BHT polarizing light microscope at a 10°C/Min heating rate unless otherwise noted

This work was funded by the National Science Foundation (Award Number 1105256) and UW-EC Office of Research and Sponsored Programs and Matthew Hammers for his contributions to the project

Mesogenic Networks

• Combine characteristic of networks and liquid crystals• Couple physical deformations with liquid crystalline phase behavior• Thermoreversability through hydrogen bonding would introduce

lability and the ability to reorganize to these characteristics

Thermal Analysis

Wiegel Research: Careening from catastrophe to

catastrophe since 2000

Results/Observations

O

OO

O N

NN

NO

O

H

O

O

H

O

O

H

O

O

H

O

O

H

O

O

H

O

O

H

O

O

H

Supramolecular Networks

Tetraethyleneglycoxy bis-(4-benzoic acid)4 EO BBA

Pentaethyleneglycoxy bis-(4-benzoic acid)5EOBBA

HO

O

O CH2CH2O

O

OH

4,5

OO

O

N

N

N

OO

NN

2,2-Dimethyl-1,3-di-(4-pyridyloxy)propane(2 PD)

1,1,1-Tris(4-pyridloxymethylene)ethane(3 PD)

O

O

O

N

N

N

O N

Tetrakis(4-pyridyoxymethane)4PD

Tetraethyleneglycoxy bis-4-(4-oxystyryl)pyridine)4EO BSB

N

O CH2CH2O

N

3,4,5

Triethyleneglycoxy bis-4-(4-oxystyryl)pyridine)3EO BSB

Pentaethyleneglycoxy bis-4-(4-oxystyryl)pyridine)5EO BSB

• Networks vary clearing compositions based on• Functionality of crosslinking agents and flexibility (hydrogen bond donors and acceptor groups)

• Generally:• Increasing from 3EOBSB to 4EOBSB increases clearing compositions by increasing flexibility• Increasing from 4EOBSB to 5EOBSB decreases clearing compositions, likely from a dramatic melting

point decrease • Increasing functionality of networking agents increases clearing compositions• Increasing flexibility of hydrogen bond donors increases clearing compositions• Enantiotropic behavior observed only in some 5EOBBA systems• Smectic phases observed in systems with high degrees of flexibility

Complex Series Clearing Composition

Clearing Temperature Trend Smectic Clearing Composition Notes

4 EOBBA/3EOBSB/2PD 22.5% Decrease with loading n/a Monotropic on cool, no smectic phase4 EOBBA/3EOBSB/3PD 30% Decrease with loading n/a Monotropic on cool, no smectic phase4 EOBBA/3EOBSB/4PD 32.5% Decrease with loading n/a Monotropic on cool, no smectic phase4 EOBBA/4EOBSB/2PD 42.5% Decrease with Loading n/a Monotropic on cool, no smectic phase4 EOBBA/4EOBSB/3PD 50% Decrease with Loading n/a Monotropic on cool, no smectic phase4 EOBBA/4EOBSB/4PD  60% Decrease with Loading n/a Monotropic on cool, no smectic phase4 EOBBA/5EOBSB/2PD 32.5% Decrease with loading 10% Enantiotropic up to 10%4 EOBBA/5EOBSB/3PD 32.5% Decrease with loading 5% Enantiotropic at all concentrations4 EOBBA/5EOBSB/4PD  35% Decrease with loading 5% Enantiotropic at all concentrations5 EOBBA/3EOBSB/2PD 25% Decrease with loading n/a Monotropic on cool, no smectic phase5 EOBBA/3EOBSB/3PD 35% Decrease with loading n/a Monotropic on cool, no smectic phase5 EOBBA/3EOBSB/4PD  52.5% Decrease with loading n/a Monotropic on cool, no smectic phase5 EOBBA/4EOBSB/2PD 32.5% Decrease with loading n/a Monotropic on cool, no smectic phase5 EOBBA/4EOBSB/3PD 40% Decrease with loading n/a Monotropic on cool, no smectic phase5 EOBBA/4EOBSB/4PD  55% Decrease with loading n/a Monotropic on cool, no smectic phase5 EOBBA/5EOBSB/2PD 22.5-25% Decrease with loading 10% Enantiotropic at all concentrations5 EOBBA/5EOBSB/3PD 30-40% In progress 10% Enantiotropic at all concentrations5 EOBBA/5EOBSB/4PD 35% In progress 10% Enantiotropic at all concentrations

Integral -20.95 mJ normalized -4.55 Jg -1Onset 131.44 °CPeak 144.96 °CHeating Rate 10.00 °Cmin -1Integral -76.80 mJ

normalized -16.70 Jg -1Onset 105.11 °CPeak 114.01 °CHeating Rate 10.00 °Cmin -1

Integral 18.64 mJ normalized 4.05 J g -1Onset 145.00 °CPeak 141.51 °CHeating Rate -10.00 °Cmin -1

Integral 76.69 mJ normalized 16.67 J g -1Onset 107.60 °CPeak 105.50 °CHeating Rate -10.00 °Cmin -1

]4[RFM_4EOBBA_5E0BSB90%_3PD10%RFM_4EOBBA_5E0BSB90%_3PD10%, 4.6000 mg

]3[RFM_4EOBBA_5E0BSB90%_3PD10%RFM_4EOBBA_5E0BSB90%_3PD10%, 4.6000 mg

mW5

°C40 60 80 100 120 140 160 180

^exo

STARe SW 9.01Lab: METTLER

4EOBBA/5EOBSB/10%3PD 4EOBBA/3EOBSB4EOBBA/3EOBSB