A method of making a shape memory polymer (SMP), comprising steps of:
- a) synthesizing ethyl cellulose polymer (ε-caprolactone) (EC-PCL-OH) comprising steps of:
- i) adding 2.25 g of ethyl cellulose (EC) and 15 mL ε-caprolactone (PCL) to a first flask;
- ii) solubilizing the EC in the ε-caprolactone at 130° C. under argon atmosphere to make a first mixture;
- iii) adding 0.5 wt. % of stannous octoate to the first mixture and stirring at 130° C. for 6 hours under argon atmosphere to make a first polymer;
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- iv) cooling the first polymer to room temperature, and dissolving the first polymer in dichloromethane and precipitating EC-PCL-OH from n-hexane;
- b) synthesizing carboxylic acid-terminated ethyl cellulose polymer (ε-caprolactone) (EC-PCL-COOH) comprising the steps of:
- i) adding 16 g of the EC-PCL-OH, containing 14.3 mmol OH, and 300 mL of freshly dried dimethylformamide (DMF) to a second flask;
- ii) solubilizing the EC-PCL-OH in 1.431 g (14.3 mmol) of succinic anhydride;
- iii) adding 1.98 g (14.3 mmol) of triethylamine to the EC-PCL-OH to form a second mixture and stirring the second mixture at 45° C. under argon atmosphere for 16 h;
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- iv) cooling the second mixture to room temperature and precipitating EC-PCL-COOH from methanol;
- c) synthesizing furan-terminated ethyl cellulose polymer (ε-caprolactone) (EC-PCL-furan) comprising the steps of:
- i) transferring 7.5 g (containing 7.15 mmol COOH) of the EC-PCL-COOH to a third flask;
- ii) adding 250 mL of freshly dried dichloromethane to the third flask to make a third mixture;
- iii) solubilizing the EC-PCL-COOH and adding 0.622 mL (7.15 mmol) of furfuryl alcohol, 1.483 g (7.15 mmol) of DCC, and 0.0875 g (7.15 mmol) of DMAP to the third mixture;
- iv) stirring the third mixture at room temperature under argon atmosphere for 16 h;
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- v) filtering dicyclohexylurea from the third mixture and precipitating EC-PCL-furan from methanol;
- d) synthesizing 4,10-dioxatricyclo[5.2.1.02,6]dec-8-ene-3,5-dione (product A) comprising the steps of:
- i) transferring 13.48 g (137 mmol) of maleic anhydride and 80 mL of benzene to a fourth flask;
- ii) solubilizing the maleic anhydride;
- iii) adding 10 mL (137 mmol) of furan to the fourth flask and stirring at room temperature under argon atmosphere for 24 h to make a fourth mixture;
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- iv) precipitating product A from the fourth mixture, removing the product A from the fourth mixture, and washing the product A three times with a washing solution;
- e) synthesizing 4-(2-hydroxy-ethyl)-10-oxa-4-aza-tricyclo[5.2.1.02,6]-dec-8-ene-3,5-dione (product B) comprising the steps of:
- i) suspending 10 g (60.2 mmol) of the product A in 25 mL of freshly dried methanol in a fifth flask with a reflux condenser;
- ii) adding 3.64 g (60.2 mmol) of ethanolamine to the fifth flask to make a fifth mixture;
- iii) refluxing the fifth mixture for 24 h;
- iv) cooling the fifth mixture to room temperature and crystalizing to form crystals of product B;
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- v) collecting the crystals by a vacuum filtration;
- f) synthesizing N-maleimide-terminated ethyl cellulose polymer (ε-caprolactone) (EC-PCL-maleimide) comprising the steps of:
- i) transferring 7.5 g (containing 7.15 mmol COOH) of the EC-PCL-COOH to a sixth flask;
- ii) adding 250 mL of freshly dried dichloromethane to the sixth flask;
- iii) solubilizing the EC-PCL-COOH;
- iv) adding 1.499 g (7.15 mmol) of the product B, 1.483 g (7.15 mmol) of DCC, and 0.0875 g (0.715 mmol) of DMAP to the sixth flask to make a sixth mixture;
- v) stirring the sixth mixture at room temperature under argon atmosphere for 16 h;
- vi) filtering dicyclohexylurea from the sixth mixture, precipitating EC-PCL-maleimide from methanol, and filtering and drying the EC-PCL-maleimide by vacuum;
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- vii) heating the EC-PCL-maleimide at 105° C. for 6 h to eliminate furan therefrom;
- g) preparing a cross-linked network in the EC-PCL-furan by a Diels-Alder reaction comprising steps of:
- i) heating and blending 6.1 g (7.15 mmol) of the EC-PCL-furan and 5.7 g (7.15 mmol) of the EC-PCL-maleimide at 105° C. for 30 minutes to form a seventh mixture;
- ii) placing the seventh mixture in a mold;
- iii) keeping the mold constantly under load of 10 kg at 65° C. in an oven for 72 h;
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- iv) cooling the mold to room temperature, recovering a first SMP from the mold as a flat sheet, and keeping the sheet at room temperature for 7 days to form a second SMP;
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- h) heating and blending the second SMP at 120° C. for 20 minutes to make a final SMP,
- wherein the network structure of the final SMP is formed by linear EC backbones which are linked by grafted PCL chains, and
- whereby a switching temperature of shape memory polymer is tunable.