Team:TU Darmstadt/Project/Chem/Methods

Synthesis of prepolymers and characterization

 

Thermal polyesterification of itaconic acid (IA), polyethylene glycol 400

 

1.1

Polymers were prepared in dependence on the experimental procedures of Barrett et al.[1]

The procedure requires exact masses. Therefore an analytical balance (4 decimal places) was used and if not otherwise stated PEG as well as itaconic acid were pre-dried before use on a high vacuum line (< 10-3 mbar) overnight.

To avoid contamination with oxygen during the reaction and to remove produced water, common Schlenk technique was applied. As inert gas argon was used.

 

 

Group-Leader:

Fabian Rohden (FR)

 

Members:

Anastasia Weyrich (AW)

Stefan Zens (SZ)

Sebastian Jäger (SJ)

 

 

A1

Date: 02/06/15 – 03/06/15

Lab members: AW, SZ

 

Preparation process:

A 50 mL Schlenk flask was loaded with 1.213 g (3.033 mmol, 1 eq.) PEG-400 and 0.395 g (3.032 mmol, 1 eq.) itaconic acid and flushed with argon. Within 20 minutes the mixture was heated up to 100 °C with an oil bath and stirred under argon atmosphere. As a colorless melt had formed the vacuum was applied (3·10-2 mbar) and the mixture was stirred at 100 °C for 17 h. The slightly yellow viscous liquid was cooled down to room temperature. 

For a picture of A1 see appendix.

 

Analysis:

No further analyses were performed.

 

 

A2

Date: 09/06/15 – 10/06/15

Lab members: FR, SJ

 

Preparation process:

A 25 mL Schlenk tube was loaded with 2.169 g (5.422 mmol, 1 eq.) PEG-400, 0.705 g (5.420 mmol, 1 eq.) itaconic acid and capped with a septum. Within an hour the mixture was heated up to 145 °C with an oil bath and stirred under argon atmosphere. As a colorless melt had formed the vacuum was applied (< 10-3 mbar) and the mixture was stirred at 145 °C for 24 h. The slightly yellow viscous liquid was cooled down to room temperature.

For a picture of A2 see appendix.

 

Visual Observations:

During the reaction itaconic acid recrystallised on the flask surface which wasn’t dipped into the oil bath. Therefore the ratio between itaconic acid and PEG-400 has changed.

 

Analysis:

The product was analyzed by differential scanning calorimetry DSC to identify the glass transition (Tg) temperature.

The Tg of A2 is -4.7 °C.

DSC-Plot A2

Figure 1: DSC- Plot of A2. The Tg of A2 is -4.7 °C

 

 

A3

Date: 11/06/15 – 12/06/15

Lab members: FR, SJ, AW, SZ

 

Preparation process:

A 10 mL Schlenk tube was loaded with 2.675 g (6.688 mmol, 1 eq.) PEG-400, 0.869 g (6.679 mmol, 1 eq.) itaconic acid and capped with a septum. The mixture was heated up to 145 °C with an oil bath on air. No vacuum was applied and the mixture was stirred on air at 145 °C for 24 h. The orange-colored viscous liquid was cooled down to room temperature.

 

Visual Observations:

The orange-colored product was more viscous than A1 and A2. For a picture of A3 see appendix.

 

Analysis:

DSC

The product was analyzed by differential scanning calorimetry DSC to identify the glass transition (Tg) temperature.

The Tg of A3 is -45.8 °C.

DSC-Plot A3

Figure 2: DSC- Plot of A3. The Tg of A3 is -45.8 °C

 

1H-NMR

The product was analyzed by 1H-NMR to ensure that double bonds are still intact in the product.

Figure 3 shows the spectrum with an enlargement of the olefin region.

NMR A3

Figure 3: 1H-NMR (300 MHz) of A3 in CDCl3

 

Solubility Tests

<tbody> </tbody>

Solvent

Solubility of Product A3

H2O

good

THF

very good

CHCl3

very good

EtOH

very good

MeOH

good

The solubility of product A3 increases with hydrophobicity of the solvent. But it is still good soluble in water and methanol. This indicates that alkene cross linking during the synthesis not occurred. And the polymer is linear shaped.

 

 

A4

Date: 11/06/15 – 12/06/15

Lab members: FR, SJ, AW, SZ

 

Preparation process:

A 20 mL snap-cap vial was loaded with 1.912 g (4.779 mmol, 1 eq.) PEG-400, 0.622 g (4.781 mmol, 1 eq.) itaconic acid and capped with a septum. The snap-cap vial was flushed with argon for 5 minutes and heated up to 145 °C with an oil bath. The snap-cap vial was almost complete dipped into the oil bath to avoid crystallization on the cold glass surface. The formed colorless melt was then stirred under slight vacuum for 24 h. Afterwards the orange-colored viscous liquid was cooled down to room temperature.

 

Visual Observations:

The orange-colored product was more viscous than A1 and A2. Viscosity and colour were comparable with A3. For a picture of A4 see appendix.

 

Analysis:

DSC

The product was analyzed by differential scanning calorimetry DSC to identify the glass transition (Tg) temperature.

The Tg of A3 is -49.1 °C.

DSC-Plot A4

Figure 4: DSC- Plot of A4. The Tg of A4 is -49.1 °C

 

1H-NMR

The product was analyzed by 1H-NMR to ensure that double bonds are still intact in the product.

Figure 5 shows the spectrum with an enlargement of the olefin region.

NMR A4

Figure 5: 1H-NMR (300 MHz) of A4 in CDCl3.

 

 

A10

Date: 16/07/15 – 17/07/15

Lab members: FR, AW

 

Preparation process:

A 20 mL snap-cap vial was loaded with 2.2750g (5.688 mmol, 1 eq.) PEG-400, 0.7388 g (5.679 mmol, 1 eq.) itaconic acid and capped with a pierced aluminium foil. The mixture was heated up to 145 °C with an oil bath on air. No vacuum was applied and the mixture was stirred on air at 145 °C for 21 h. The brown-colored viscous liquid was cooled down to room temperature.

 

Visual Observations:

The brown-colored product was more viscous than A8 but less viscous than A7 and A9.

 

Analysis:

DSC

The product was analyzed by differential scanning calorimetry DSC to identify the glass transition (Tg) temperature.

The Tg of A10 is -46.9 °C.

DSC-Plot A10

Figure 6:DSC- Plot of A10. The Tg of A10 is -46.9 °C.

 

 

 

Thermal polyesterification of itaconic acid (IA), polyethylene glycol 400 (PEG-400) and xylitol

1.2

 

Polymers were prepared in dependence on the experimental procedures of Barrett et al.[1]

The procedure requires exact masses. Therefore an analytical balance (4 decimal places) was used and if not otherwise stated PEG as well as itaconic acid and xylitol were pre-dried before use on a high vacuum line (< 10-3 mbar) overnight.

 

 

A5

Date: 30/06/15 – 01/07/15

Lab members: FR, SJ, AW, SZ

 

Preparation process:

A 20 mL snap-cap vial was loaded with 0.997 g (2.491 mmol, 0.43 eq.) PEG-400, 0.3833 g (2.519 mmol, 0.44 eq.) xylitol, 0.7503 g (5.767 mmol, 1 eq.) itaconic acid and capped with a pierced aluminium foil. The mixture was heated up to 145 °C with an oil bath on air. No vacuum was applied and the mixture was stirred on air at 145 °C for 17.5 h. The orange-colored gel was cooled down to room temperature.

 

Visual Observations:

The orange-colored product was a ductile gel. For a picture of A5 see appendix.

 

Analysis:

Solubility Tests

<tbody> </tbody>

Solvent

Solubility of Product A5

H2O

no

THF

no

Aceton

no

EtOH

no

MeOH

no

The gel wasn’t soluble in any solvent. Even by applying ultrasound no dissolving occurred. This is probably due to high cross linking with xylitol.

 

 

A6

Date: 30/06/15 – 01/07/15

Lab members: FR, SJ, AW, SZ

 

Preparation process:

A 20 mL snap-cap vial was loaded with 1.2775 g (3.194 mmol, 0.58 eq.) PEG-400, 0.2038 g (1.339 mmol, 0.25 eq.) xylitol, 0.7099 g (5.457 mmol, 1 eq.) itaconic acid and capped with a pierced aluminium foil. The mixture was heated up to 145 °C with an oil bath on air. No vacuum was applied and the mixture was stirred on air at 145 °C for 17.5 h. The orange-colored viscous liquid was cooled down to room temperature.

 

Visual Observations:

The orange-colored product was a ductile gel. For a picture of A6 see appendix.

 

Analysis:

Solubility Tests

<tbody> </tbody>

Solvent

Solubility of Product A6

H2O

no

THF

no

Aceton

no

EtOH

no

MeOH

no

The gel wasn’t soluble in any solvent. Even by applying ultrasound no dissolving occurred. This is probably due to high cross linking with xylitol.

 

 

A8 

Date: 16/07/15 – 17/07/15

Lab members: FR, AW

 

Preparation process:

A 20 mL snap-cap vial was loaded with 3.4567 g (8.642 mmol, 0.90 eq.) PEG-400, 0.0973 g (0.640 mmol, 0.067 eq.) xylitol, 1.2492 g (9.602 mmol, 1 eq.) itaconic acid and capped with a pierced aluminium foil. The mixture was heated up to 145 °C with an oil bath on air. No vacuum was applied and the mixture was stirred on air at 145 °C for 21 h. The orange-colored viscous liquid was cooled down to room temperature.

 

Visual Observations:

The orange-colored product was a viscous liquid. A8 was less viscous than A10, A7 and A9.

 

Analysis:

DSC

The product was analyzed by differential scanning calorimetry DSC to identify the glass transition (Tg) temperature.

The Tg of A8 is -44.8 °C. 

DSC-Plot A8

Figure 7:DSC- Plot of A8. The Tg of A8 is -44.8 °C.

 

 

A9

Date: 16/07/15 – 17/07/15

Lab members: FR, AW

 

Preparation process:

A 20 mL snap-cap vial was loaded with 1.5400 g (3.850 mmol, 0.95 eq.) PEG-400, 0.0205 g (0.135 mmol, 0.033 eq.) xylitol, 0.5257 g (4.041 mmol, 1 eq.) itaconic acid and capped with a pierced aluminium foil. The mixture was heated up to 145 °C with an oil bath on air. No vacuum was applied and the mixture was stirred on air at 145 °C for 21 h. The brown-colored viscous liquid was cooled down to room temperature.

 

Visual Observations:

The brown-colored product was a viscous liquid. A9 was more viscous than A7, A10 and A8.

 

Analysis:

DSC

The product was analyzed by differential scanning calorimetry DSC to identify the glass transition (Tg) temperature.

The Tg of A9 is -44.4 °C.

DSC-Plot A9

Figure 8:DSC- Plot of A9. The Tg of A9 is -44.4 °C.

 

 

 

Thermal polyesterification of itaconic acid (IA) and polyethylene glycol 200 (PEG-200)

 

Polymers were prepared in dependence on the experimental procedures of Barrett et al.[1]

The procedure requires exact masses. Therefore an analytical balance (4 decimal places) was used and if not otherwise stated PEG as well as itaconic acid were pre-dried before use on a high vacuum line (< 10-3 mbar) overnight.

 

 

A7

Date: 16/07/15 – 17/07/15

Lab members: FR, AW

 

Preparation process:

A 20 mL snap-cap vial was loaded with 3.0745 g (15.373 mmol, 1 eq.) PEG-200, 2.000 g (15.373 mmol, 1 eq.) itaconic acid and capped with a pierced aluminium foil. The mixture was heated up to 145 °C with an oil bath on air. No vacuum was applied and the mixture was stirred on air at 145 °C for 21 h. The orange-colored viscous liquid was cooled down to room temperature.

 

Visual Observations:

The orange-colored product was a viscous liquid.

 

Analysis:

DSC

The product was analyzed by differential scanning calorimetry DSC to identify the glass transition (Tg) temperature.

The Tg of A7 is -37.1 °C.

DSC-Plot A7

Figure 9:DSC- Plot of A7. The Tg of A7 is -37.1 °C.

 

 

A11

Date: 28/07/15 – 30/07/15

Lab members: FR, SJ

 

Preparation process:

A 20 mL snap-cap vial was loaded with 12.3079 g (61.540 mmol, 1 eq.) PEG-200, 8.0030 g (61.514 mmol, 1 eq.) itaconic acid and capped with a pierced aluminium foil. The mixture was heated up to 145 °C with an oil bath on air. No vacuum was applied and the mixture was stirred on air at 145 °C for 42 h. The orange-colored viscous liquid was cooled down to room temperature.

 

Visual Observations:

On the surface of the orange-colored viscous liquid a rigid gel has formed. For a picture of A11 see appendix.

 

Analysis:

DSC

The product was analyzed by differential scanning calorimetry DSC to identify the glass transition (Tg) temperature.

The Tg of A11 is -37.4 °C.

DSC-Plot A11

Figure 10: DSC- Plot of A11. The Tg of A11 is -37.4 °C.

 

 

A12

Date: 28/07/15 – 30/07/15

Lab members: FR, SJ

 

Preparation process:

A 20 mL snap-cap vial was loaded with 12.2955 g (61.478 mmol, 1 eq.) PEG-200 and 8.0025 g (61.511 mmol, 1 eq.) itaconic acid. For this experiment itaconic acid wasn’t pre-dried under high vacuum. The vial was capped with a pierced aluminium foil and the mixture was heated up to 145 °C with an oil bath on air. No vacuum was applied and the mixture was stirred on air at 145 °C for 42 h. The orange-colored viscous liquid was cooled down to room temperature.

 

Visual Observations:

On the surface of the orange-colored viscous liquid a rigid gel has formed. For a picture of A12 see appendix.

 

Analysis:

DSC

The product was analyzed by differential scanning calorimetry DSC to identify the glass transition (Tg) temperature.

The Tg of A12 is -37.1 °C.

DSC-Plot A12

Figure 11:DSC- Plot of A12. The Tg of A12 is -37.1 °C.

 

 

A13

Date: 12/08/15 – 13/08/15

Lab members: SJ

 

Preparation process:

A 500 mL round bottom flask was loaded with 90.88 g (454.4 mmol, 1 eq.) PEG-200 and 59.12 g (454.4 mmol, 1 eq.) itaconic acid. For this experiment itaconic acid wasn’t pre-dried under high vacuum. The flask was capped with a pierced aluminium foil and the mixture was heated up to 145 °C with an oil bath on air. No vacuum was applied and the mixture was stirred on air at 145 °C over night. The orange-colored viscous liquid was cooled down to room temperature.

 

Visual Observations:

At 143 °C IA was completely dissolved and a slightly yellow melt has formed. The produced water condensed partially on the wall of the flask. For a picture of A13 during and after synthesis see appendix.

 

Analysis:

DSC

The product was analyzed by differential scanning calorimetry DSC to identify the glass transition (Tg) temperature.

The Tg of A13 is - 40.8 °C.

DSC-Plot A13

Figure 12: DSC- Plot of A13. The Tg of A13 is -40.8 °C.

 

 

A15

Date: 18/08/15 – 19/08/15

Lab members: SJ, AW, SZ

 

Preparation process:

A 1 L round bottom flask was loaded with 302.9 g (1.51 mol, 1 eq.) PEG-200 and 197.0 g (1.51 mol, 1 eq.) itaconic acid. For this experiment itaconic acid wasn’t pre-dried under high vacuum. The flask was capped with a pierced aluminium foil and the mixture was heated up to 145 °C with an oil bath on air. No vacuum was applied and the mixture was stirred on air at 145 °C for 31 h. The orange-colored viscous liquid was cooled down to room temperature.

 

Visual Observations:

After 24 h a viscous orange-colored liquid has formed. The loss of mass during synthesis doesn’t correspond to the calculated mass loss due to produced and evaporated water (2 eq. water by high conversion). A sample for DSC analysis was taken and the mixture was stirred for 7 h. Afterwards another sample for DSC analysis was taken. For a picture of A15 see appendix.

 

Analysis:

DSC

The product was analyzed by differential scanning calorimetry DSC to identify the glass transition (Tg) temperature.

The Tg of A15 after 24 h at 145 °C is -39.9 °C.

The Tg of A15 after 31 h at 145 °C is -37.9 °C.

DSC-Plot A15a

Figure 13: DSC- Plot of A15 after 24 h at 145 °C. The Tg of A15 is -39.9 °C.

 

DSC-Plot A15b

Figure 14: DSC- Plot of A15 after 31 h at 145 °C. The Tg of A15 is -37.9 °C.

 

 

 

Thermal polyesterification of itaconic acid (IA) and ethylene glycol (EG)

 

1.4

Polymers were prepared in dependence on the experimental procedures of Barrett et al.[1]

The procedure requires exact masses. Therefore an analytical balance (4 decimal places) was used and if not otherwise stated EG as well as itaconic acid were pre-dried before use on a high vacuum line (< 10-3 mbar) overnight.

 

 

A14

Date: 12/08/15 – 13/08/15

Lab members: SJ

 

Preparation process:

A 20 mL snap-cap vial was loaded with 1.6155 g (26.027 mmol, 1 eq.) EG and 3.3853 g (26.021 mmol, 1 eq.) itaconic acid. For this experiment itaconic acid wasn’t pre-dried under high vacuum. The vial was capped with a pierced aluminium foil and the mixture was heated up to 145 °C with an oil bath on air. No vacuum was applied and the mixture was stirred on air at 145 °C over night.

 

Visual Observations:

During the reaction a film of ethylene glycol condensed on the vial wall. This is due to the boiling point of EG (197 °C). In this way the exact IA/EG ratio could be changed. The yellow-colored polymer is a rigid gel and not applicable for 3D printing. For a picture of A14 see appendix.

 

 

 

Analysis of the prepolymers with GPC

 

The prepolymers A10, A12, A13 and A15 were additionally analyzed by GPC (Gel permeation chromatography) to detect the average molar mass.

 

Method:

The metering was performed with the PSS Suprema HS column connect to a RID detector. NaNO3 (0.1 mol/l) was used as eluent by a flow rate of 1 ml/min and polyacrylic acid as polymerstandard for the calibration.

 

Results:

All assays were smaller than the smallest polymerstandard of 1250 g/mol. Therefor the average molar mass was not definable.

Overlaying the assays allows the comparison of the different prepolymers. Thereby, one can see that the polymers A 12, A13 and A15 are very similar and only A10 has a different curve. This reflect the composition of the prepolymers. While A10 is out of PEG 400 and IA, the prepolymers A12-A15 are out of PEG 200 and IA.

GPC Überlagerung

Figure 15: GPC-Plot of A10 (light blue), A12 (blue), A13 (yellow) and A15 (black).

 

 

 

Curing of prepolymers

 

3.

Prepolymers were mixed with different amounts of Ciba® DAROCUR 1173 photoinitiator and streaked on microscope glass slides. The slides were placed for different periods of time under UV-light 254 nm.

For pictures of the cured prepolymers see appendix.

<tbody> </tbody>

Prepolymer/

sample

Photoinitiator

[wt-%]

Curing time (254 nm)

5 min

10 min

15 min

PEG-400

1

 

 

 

A2

1

 

 

 

A3

 2.3

-

-

currugation, soft

A4

 1.8

-

-

currugation, soft

A7

2

-

-

solid

A8

2

-

-

gel

A9

2

-

-

gel

A10

2

-

-

gel

A11

0

currugation, soft

currugation, soft

currugation, soft

A11

 0.5

currugated skin

currugated skin

currugated skin

A11

1

currugated skin

currugated skin

currugated skin

A11

2

currugated skin

currugated skin

currugated skin

A11

4

almost solid, plain

plain solid

plain solid

A11

9

plain solid

plain solid

plain solid

A12

0

currugation, soft

currugation, soft

currugation, soft

A12

 0.5

plain skin

plain skin

plain skin

A12

1

plain skin

plain skin

plain skin

A12

2

plain skin

plain skin

plain skin

A12

4

almost solid, plain

plain solid

plain solid

A12

9

plain solid

plain solid

plain solid

By UV-curing of A8 on a polystyrene petri dish an interesting effect was observed. The hydrophilic hydroxyl groups of xylitol lead to formation of prepolymer drops due to the hydrophobic polystyrene surface of the petri dish. This effect is interesting because it could prevent adhesion of the polymer on the basin of the 3D printer during UV curing. Unfortunately A8 doesn’t cured by UV light, even not with 6 % DAROCUR 1173. For a picture see appendix.

 

 

 

References:

[1]        Barrett et al., Macromolecules 2010, 43, 9660-9667.

 

 

 

Appendix

 

Pictures of prepolymers during and after synthesis

 

Figure 15

Figure 16: From left to right A1 – A4 after synthesis

 

Figure 16

Figure 17: A5 and A6 after synthesis.

 

Figure 17

Figure 18: From left to right A12 – A11 after synthesis.

 

Figure 18l DSC-Plot A18r

Figure 19: A13 and A14 during (left) and after synthesis (right).

 

Figure 19

Figure 20: A15 during heating up. At 131 °C no melt has formed and the white itaconic acid can be seen.

 

 

 

Pictures of cured prepolymers

 

Figure 20

Figure 21: UV-curing of A3 and A4 after 15 min.

 

Figure 21

Figure 22: UV-curing of A11 after 5, 10 and 15 min.

 

Figure 22

Figure 23: UV-curing of A12 after 5 and 10 min.

 

Figure 23

Figure 24: UV-curing of A8 and A15 on glass and on a polystyrene petri dish after 5 min 254 nm. 6 % DAROCURE 1173 was used.