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Synthese of Diels-Alder polymers

Reagens

The reactants, the monomers, used in the synthesis of the reversible DA-polymer network system were purchased from Sigma-Aldrich:

  • ˆ(A): 2 Jeamine D-series: Poly(propylene glycol) bis(2-aminopropyl ether) with average degree of polymerization n (determined by nuclear magnetic resonance spectroscopy): 
    • n = 44.2: J2000, Mn = 2640 g/mol
    • n = 71.1: J4000, Mn = 4200 g/mol
  • ˆ(B): furfuryl glycidyl ether (FGE, 96 %)
  • (C): 1,1'-(methylenedi-1,4-phenylene)bismaleimide (DPBM, 95%)

Reagens used for the polymerization of the Diels-Alder network

Polymerization

In this section it is explained how the DA-polymers are synthesized. J4000 and J2000 material is synthesized into sheets while J400 is synthesized into powder. For each step the chemical reaction is explained followed by a description of the practical actions required to preform this step. The following amounts of DA-polymer material was made:

  • DPBM-FGE-J4000: 100x100 mm sheet with a 0.75 mm  thickness.
  • DPBM-FGE-J2000: 100x100 mm sheet with a 0.50 mm  thickness.

Step 1: epoxy-amine reaction

In a first step, FGE was irreversibly bonded to Jx (x = 400, 2000, and 4000) through an epoxy-amine reaction, yielding a furan functionalized compound. This reaction was performed at 60 °C for minimum 7 days after which the reaction was completed at 90 C° (to speed up the reaction) for 2 days.

Epoxy-aminer-reaction

In practice: Pour the FGE and the Jeffamine together. The following amounts were used: 

Step 1

  • Heat the solution using an oil bath to 60°C  for minimum 7 days. Stir continuously using a magnetic stirrer. 
  • Increase the temperature to 90°C for another 2 days. 

Step 2: Network formation

In a second step, the furan functionalized compound (FGE-Jx) was mixed with DPBM in a stoichiometric ratio of one (r= nMaleimide / nFuran = 1) to obtain the reversible polymer network through DA reaction. Prior to the DA reaction, the DPBM was dissolved in chloroform (a 20 w% solution) to obtain a homogeneous reversible network. 

Network formation

In practice: Pour the FGE and the Jeffamine together. The following amounts were used: 

Step 2

 

  • Pour the chloroform at the FGE-Jx
  • Add the DPBM to the solution
  • Stir at room temperature for at least 2 hours, using a magnetic stirrer, until a completely homogeneous solution is obtained

Step 1: practical

Step 3

The chloroform has to be evaporated out of the solution and the thermo-reversible network has to be formed. The chloroform is extracted by increasing the temperature to 60°C at vacuum. The thermo-reversible network is formed by slowly cooling down the sheet after the chloroform has been completely extracted.

In practice: The following amounts were used to develop the DPBM-FGE-Jx sheets:

  • DPBM-FGE-J4000: 28.1 ml
  • DPBM-FGE-J2000: 18.8 ml

Step by Step:

  •  1 hour at 30°C and atmospheric pressure
  • gradually increase the temperature up to 660°C
  • gradually decrease the pressure up to vacuum.
  • remain at 60°C and vacuum until all bells are removed
  • remain for 3 days at 50°C and vacuum
  • cool down slowly (5°C/hour) to ambient temperature after which the synthesis is completed