2.1. Custom Polymer Synthesis
The synthesis of monomers and polymers is based on previously described procedures [
29,
30].
Synthesis of 3a (
Figure 2): Mono-
tert-butyl protected succinic acid (5.57 g, 32 mmol), 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide HCl (EDC, 6.60 g, 34.4 mmol) and anhydrous Dimethyl formamide (DMF, 30 mL) were added into a 250 mL flask and the mixture was stirred for 10 min in an ice bath. To this activated carboxylic acid, compound 1 (8.81 g, 24.6 mmol) dissolved in anhydrous DMF (5 mL) was added and the reaction was stirred overnight. After reacting, DMF was removed under vacuum and the product was extracted with Ethyl acetate (EtOAc, 150 mL). The organic layer was washed with water (50 mL, 1×), saturated NaHCO
3 solution (50 mL, 1×) and brine (50 mL, 1×) and dried over anhydrous Na
2SO
4. The product was purified by column chromatography (15% EtOAc and 85% Hexane).
Yield: 70%: 1H NMR (300 MHz, Chloroform-d) ppm 0.04–0.06 (m, 12H) 0.88–0.90 (m, 18H) 1.45 (s, 9H) 2.56 (t, J = 6.74 Hz, 2H) 2.67 (t, J = 6.58 Hz, 2H) 3.48 (t, J = 5.70 Hz, 2H) 3.56 (t, J = 5.86 Hz, 2H) 3.74 (t, J = 5.70 Hz, 4H).
Deprotection of TBDMS (t-butyl dimethyl silane) was performed by reaction with iodine (20% weight of product) in MeOH (15 mL) overnight. Na2S2O3 was added dropwise to quench the reaction until the solution turned from brown to colorless. The solvent was removed under vacuum and the product was extracted with CH2Cl2 (50 mL, 3×) and dried over anhydrous Na2SO4. The product was purified via column chromatography (MeOH-CH2Cl2 gradient solvent system, from pure CH2Cl2 to 5% MeOH and 95% CH2Cl2).
Diol 3a: Yield: 61%, 1H NMR (300 MHz, Chloroform-d) ppm 0.04–0.06 (m, 12H) 0.88–0.90 (m, 18H) 1.45 (s, 9H) 2.56 (t, J = 6.74 Hz, 2H) 2.67 (t, J = 6.58 Hz, 2H) 3.48 (t, J = 5.70 Hz, 2H) 3.56 (t, J = 5.86 Hz, 2H) 3.74 (t, J = 5.70 Hz, 4H).
To synthesize diols from ester derivatives of functionalized carboxylic acids (
Figure 2), diethanolamine 1a (2 equivalents) and the ester derivative of functionalized carboxylic acid (1 equivalent) were mixed and refluxed in a flask at 75 °C overnight. The product was subsequently purified by column chromatography (MeOH–CH
2Cl
2) and completely dried in high vacuum line.
Diol 3b: Yield = 76%, 1H NMR (300 MHz, CDCl3): ppm 1.16 (dd, 3H, J1 = 7.61 Hz, J2 = 7.32 Hz), 2.39–2.50 (m, 2H), 3.50–3.59 (m, 4H), 3.78–3.90 (m, 4H).
Diol 3c: Yield = 63%, 1H NMR (300 MHz, CDCl3) ppm 2.65–2.74 (dd, J1 = 7.61 Hz, J2 = 8.20 Hz, 2H), 2.95–3.00 (dd, J1 = 7.99 Hz, J2 = 8.20 Hz, 2H), 3.42 (t, J = 4.98 Hz, 2H), 3.54–3.57 (dd, J1 = 4.39 Hz, J2 = 4.98 Hz, 2H), 3.70 (t, J = 4.98 Hz, 2H), 3.85 (t, J = 4.68 Hz, 2H), 7.21–7.32 (m, 5H).
Diol 3d: 1H NMR (300 MHz, Chloroform-d) ppm 2.2 (M, 2H) 2.4 (d, J = 1.2 Hz, 3H) 2.65 (t, J = 7.0 Hz, 2H) 3.53–3.62 (m, 4H) 3.81 (t, J = 5.3 Hz, 2H) 3.91 (t, J = 5.2 Hz, 2H) 4.12 (t, J = 6.0 Hz, 2H), 6.14 (d, J = 1.2 Hz, 1H) 6.82–6.89 (m,2H) 7.50 (d, J = 8.8 Hz, 1H).
To synthesize the soybean oil monomer, diethanolamine (31.5 g, 0.3 mol) was added into a 500 mL round bottom flask. Subsequently, NaOCH3 (0.8 g, 14.8 mmol) was added and stirred at 110 °C until completely dissolved. Soybean oil (43.6 g) was added dropwise via funnel over 30 min. After addition, the reaction was stirred for another one hour at 110 °C under vacuum. EtOAc was added to dilute the reaction mixture, which was then washed with 15% NaCl solution (3×). The product was purified via column chromatography (5% MeOH and 95% CH2Cl2).
Diol 3e: 1H NMR (500 MHz, Chloroform-d) ppm 5.30–5.41 (m, 2.88H) 3.76–3.85 (m, 5.5H) 3.49–3.85 (m, 4H) 2.76–2.81 (m, 1.29H) 2.37–2.40 (t, J = 7.70 Hz, 2.09H) 2.00–2.07 (m, 3.38H) 1.63 (br. s., 2.11H) 1.26–1.1.39 (m, 18H) 0.87–0.99 (m, 3H).
Polyesterification of functionalized diols and diacids (
Figure 3) was accomplished by adding the functionalized diol (1 equivalent), diacid (1 equivalent) and 4-(Dimethylamino)pyridinium 4-toluenesulfonate (DPTS, 0.4 equivalent) into a flask, and the system was evacuated and backfilled with N
2 (3×). Anhydrous CH
2Cl
2 (2 mL for 1 mmol of diacid) was syringed into the reaction flask. The mixture was homogenized by warming to 40 °C for 1–2 min. Subsequently, the mixture was cooled on ice and diisopropylcarbodiimide (DIC) (3 equivalents) was added dropwise by syringe. The mixture was stirred for 48 h at room temperature. The polymer was purified by precipitation from cold
iso-propanol/methanol or dialysis against MeOH and dried under vacuum. Total equivalents of diols were equivalent to that of diacid if more than one functionalized diol was used in the reaction.
p(A-C4): 1H NMR (300 MHz, Chloroform-d) ppm 1.15 (t, J = 7.46 Hz, 3H) 2.39 (d, J = 7.46 Hz, 2H) 2.62 (br, 4H) 3.60–3.70 (m, 4H) 4.22–4.26 (m, 4H). Mn = 60 KDa, polydispersity index (PDI) = 1.1, Td: 238 °C, Tg: 5.3 °C.
p(A-C10): 1H NMR (500 MHz, Chloroform-d) ppm 1.14 (t, J = 7.34 Hz, 3 H) 1.29 (br. s., 8 H) 1.56–1.64 (m. 4 H) 2.22–2.35 (m, 4 H) 2.39 (q, J = 7.34 Hz, 2 H) 2.66–2.77 (m, 1 H) 3.58–3.64 (m, 4 H) 4.18–4.26 (m, 4 H) Mn: 78 KDa, PDI: 1.19, Td: 283 °C, Tg: −32 °C.
p(SC-C6): 1H NMR (300 MHz, Chloroform-d) ppm 0.87 (d, J = 6.8 Hz, 3H) 1.27 (d, J = 18.4 Hz, 16H) 1.59 (s, 15H) 2.04 (q, J = 6.2 Hz, 3H) 2.16 (t, J = 6.0 Hz, 2H) 2.39–2.30 (m, 12H) 2.59 (t, J = 7.0 Hz, 2H) 2.76 (t, J = 6.0 Hz, 1H) 3.61 (dt, J = 11.0, 5.5 Hz, 8H) 4.11–4.08 (m, 2H) 4.19 (d, J = 5.0 Hz, 7H) 5.34 (d, J = 5.5 Hz, 3H), 6.11 (s, 1H) 6.87–6.80 (m, 2H) 7.49 (d, J = 8.6 Hz, 1H) Mn: 11.9KDa, PDI: 2.13, Td: 320 °C, Tg: −20 °C.
Finally, the tBu-protected p(FD-C10) was deprotected by dissolving the polymer (1 g) in regular CH2Cl2 (6 mL), trifluoroacetic acid (TFA) (3 mL) and triisopropylsilane (50 μL) and stirred for 2 h. After the stirring incubation, TFA and CH2Cl2 were removed under vacuum and the polymer was precipitated into diethyl ether twice to obtain pure polymer.
p(FD-C10): 1H NMR (500 MHz, Chloroform-d) ppm 1.25–1.36 (m, 8H) 1.53–1.65 (m, 4H) 2.22–2.35 (m, 4H) 2.64–2.76 (m, 2.4H) 2.94–3.01 (m, 2.4H) 3.52 (t, J = 5.87 Hz, 2H) 3.58–3.69 (m, 2H) 4.12 (t, J = 5.75 Hz, 2H) 4.18–4.26 (m, 2H) 7.16–7.24 (m, 2H) 7.24–7.31 (m, 2H) Mn: 40KDa, PDI: 1.34, Td: 273 °C, Tg: −16 °C.