Chains and RingsLitterature Talk

July, Monday 14th

Alex

Chains and RingsLitterature Talk

July, Monday 14th

Alex

Chains and rings

• Equilibria

• Thermodynamics

• Applications (Cyclics Corp.)

• Making Rings

Rings and Chains Equilibria

• Lactide

O O

O

O

O

OO

O

O

O

OO

O

OO

O

O

OO

O

OO

O

O

O

O

O

Rings and Chains Equilibria

• Oxymethylene

• Sulfur

Source: Allcock HR, Journal of macromolecular science – review in macromolecular chemistry, Vol C4, Issue 2, p149-189 (1970)

S

SS

S SS

SS

S S 4n

O O

OCH2 O

CH2

O ** n

O

OO

O

Thermodynamics

Source: Allcock HR, Journal of macromolecular science – review in macromolecular chemistry, Vol C4, Issue 2, p149-189 (1970)

Rx+Cy Cx+y G = H - TS

H<0S<0 Ceiling temperature

S>0 Chains only

H=0S<0 Chains only

S>0 Rings only

H>0S<0 Rings only

S>0 Flooring temperature

Thermodynamics

Ring size influence equilibrium:• 3,4: Negative significant enthalpy, high polymer

conversion• 5 to 7: Enthalpy term roughly equivalent to entropy term• 8 to 10: same conclusion than 3 and 4 membered rings• Greater: Easy polymerization

Tc depends on:• Monomer concentration (Tc increases with monomer

concentration for exothermic reaction)• Pressure (Tc increases with pressure)

Sources: Ivin K.J., Journal of Polymer Science: Part A: Polymer Chemistry, Vol 38(12), 2137-2146 (2000)

Hocker H, Keul H, Advanced Materials, V6, I1, p21-36 (1994)

Why using rings?

• Rapid ring-opening polymerization

• No measurable exotherm

• No by-products (because no end-groups)

• Yields high molecular weight polymers

• Low viscosity

• Low melting point when used in a mixture of rings

Source: Brunelle D.J., Journal of Polymer Sciences: Part A: Polymer Chemistry, Vol 46, 1151-1164 (2008)

Cyclics Corp.

• Use of cyclic butylene terephthalate– Low Viscosity– Thermal stability– Compatible with other polymers

• Produces polybutylene terephthalate– Good stiffness– Good chemical resistance– Good dimensional stability– Light weight

Source: www.cyclics.com

Cyclics Corp.

Applications:

• Rotational molding

• Casting

• Composites

• Coatings

• Additives

Source: www.cyclics.com

Making rings

• Early work allowed production of rings only through long reaction times, low productivity and extensive purification

• Work by Daniel Brunelle, from GE Global Research, lead to the many patents concerning ring polymerization, which in turn lead to Cyclics Corp.

Source: Brunelle D.J., Journal of Polymer Sciences: Part A: Polymer Chemistry, Vol 46, 1151-1164 (2008)

Making rings: characterization

• Work on Bisphenol A polycarbonate

• Reverse phase HPLC with dual wavelength detector set at 254 and 285nm

• Linear oligomers absorb strongly at 285 and 254 nm

• Cyclic compounds absorb 50 times more at 254 than at 285 nm.

Source: Brunelle D.J., Journal of Polymer Sciences: Part A: Polymer Chemistry, Vol 46, 1151-1164 (2008)

Making rings

Mechanism: Hydrolysis and condensation

Source: Brunelle D.J., Journal of Polymer Sciences: Part A: Polymer Chemistry, Vol 46, 1151-1164 (2008)

• All reactions must happen fast, to prevent build-up in reactant concentration and formation of polymer (higher than usual amount of catalyst)

• Good pH control is paramount to have reactive phenoxides in solution, and not phenols, without promoting cycle hydrolysis

• Catalyst used is very important and can lead to all possible outcomes:

Example of catalyst used Outcome

Et3N Cyclics and polymer

pyridine Linear oligomers

Pyridine (more severe conditions)

Hydrolysis

Polyethylene glycol No reaction

bischloroformate

Conclusion

• Research has been done on rings/chains equilibrium since the 50’s

• Using rings polymerization gives better handling conditions and higher MW polymers, with no by-products

• Good reaction control (pH, catalyst…) allows formation of rings instead of chains