Poly(Vinylamine Hydrochloride) from Acrylic Acid
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Poly(vinylamine hydrochloride) from Acrylic Acid Submitted by: A. R. Hughes1a and T. St. Pierre1b Checked by: R. J. Thornton2a, R. D. Wingo2c, and O. R. Tarwater2a,b 1. Procedure a. Preparation of Acryloyl Chloride (Note 1) (CAUTION! Reagents and/or products in parts a through c are severe lachrymators. Reactions must be carried out in a good fume hood.) Thoroughly mix 300 g of acrylic acid (Eastman Kodak Co.) and 1000 g of benzoyl chloride (Eastman Kodak Co.) in a three-necked, 2 L, round bottomed flask equipped with a mechanical stirrer, a 20 cm Vigreux column plus distilling head, and nitrogen bubbler. Distill, with stirring under N2 atmosphere, and collect all product distilling below 80 oC in an ice-cooled receiver containing about 0.5 g of hydroquinone (Note 2). The yield of crude acryloyl chloride is 290 g (73%). Redistill the acryloyl chloride, and collect the fraction boiling from 74 - 79 oC in an ice-cooled receiver containing 0.5 g of hydroquinone to obtain 250 g (66%) of pure acryloyl chloride. Store at 0 oC in a tightly glass-stoppered flask. b: Conversion to Acryloyl Azide (Note 3) o Dissolve 250 g of practical-grade NaN3 (Eastman Kodak Co.) in 600 mL of cold water (0 C) in a three necked, 2 L, round bottomed flask equipped with a dropping funnel, mechanical stirrer, and thermometer. To the cold solution slowly add an ice-cold solution of 250 g of acryloyl chloride in 700 mL of toluene predried over molecular sieves (Linde 3A, 1/4 in). The mixture is maintained at 0 - 5 oC throughout the addition by immersing the flask in an ice bath. When the addition is completed (about 3 h), continue stirring at 0 - 5 oC for an additional h and let the mixture stand for 3 h at 0 oC. Separate the toluene layer in a 2 L separatory funnel, wash twice with 250 mL portions of ice-cold 10% Na2CO3 and then repeatedly with ice-cold H2 O until the washings are neutral (Note 1 2 Macromolecular Syntheses, Collective Volume 2 o 4). Pour the toluene solutions over CaCl2 and, after 20 min of vigorous stirring, let it stand at 0 C, if necessary (Note 5). c. Conversion to N-Vinyl-t-Butylcarbamate (NVTBC) (Note 3) To the apparatus shown in Figure 1 are added 50 mL of toluene and 7g of m-dinitrobenzene to flask A, 500 mL of redistilled t-butanol, and 7 mL of pyridine to flask B, and 250 mL of t-butanol and v 5 mL of pyridine to flask C. All glassware should be oven dried (160 ) and flushed with dry N2 while hot. The apparatus is flushed with dry N2 for 30 min before the toluene in flask A is boiled under N2 and the addition of the cold acryloyl azide solution is begun dropwise. As soon as gas flow from the decomposition of the acryloyl azide is indicated by increased bubbling, stop the N2 flow, and continue the addition smoothly until completion in 3 -4 h. Flask A is kept just boiling throughout and flasks B and C are kept just above the freezing point of the alcohol while the isocyanate and N2 together bubble through the stirred liquid. When the addition is complete, continue stirring in flasks B and C for about 3 h, and, then let combined solutions from flasks B anc C stand for at least 12 h. Pour the alcohol solution over about 2 L of ice, mix well, and add about 5 L of ice-cold H2O with vigorous stirring. Collect the precipitate by filtration, and wash several times with cold H2O (Note 6). Dry the product in vacuum until just dry. The yield of crude NVTBC is 140 g, melting point 63 - 65 oC (35% based on acryloyl chloride) (Note 7). The product is purified by sublimaiton at # 50 oC at pump vacuum (Note 8). The yield of sublimed product is 75 - 85%. Poly(Vinylamine Hydrochloride) from Acrylic Acid 3 d. Polymerization (Note 9) o To a freshly oven-dried (160 C, flushed with dry N2 while hot), 200 mL, round-bottomed flask, add 20 g of NVTBX, <100 mg of AIBN, and 67 mL of redistilled hexane (Note 10). Purge the mixture with dry N2 for 0.5 h, freeze with liquid N2, and alternately evacuate and pressurize with dry N2 at least ten times with the mixture frozen (Note 11). Seal the flask containing the frozen mixture under a slight N2 pressure with a mercury bubbler, warm to room temperature, and place in a 60 - 65 oC bath. The polymerization flask is left in the bath without stirring for about 30 h. Precipitated polymer should appear after 10 - 12 h (Note 12). The yield of polymer is 16.5 g (82.5%). The yield should be 78 -86% for a good polymerization of poly(N-vinyl -t-butylcarbamate), polyt (NVTBC). e. Hydrolysis (note 9) Dissolve 16.5 g of poly(NVTBC) in 100 mL of 95% ethanol and add this solution slowly to 200 mL of 1:1 (by volume ) of ethanol:concentrated HCl with vigorous stirring. Add concentrated HCl at about the same rate as the poly(NVTBC) solution to maintain the 1:1 volume ratio. Gas evolution is vigorous throughout. After the addition is complete, continue stirring for about 6 h or until gas evolution has ceased. Separate the product by filtration and wash it twice with 500 mL of acetone to obtain 9.9 g of poly(vinylamine hydrochloride) (97% yield based on 0.5 mol of H2O per repeat unit) (Note 13). 2. Notes 1. The checker used acryloyl chloride purchased from Polysciences, Inc. 2. Distillation must be slow (ca 3 h) to allow the reaciton to go to completion. 3. The checker conducted this step on a scale three times larger than reported and encountered neither unusual problems nor reduction in yield. 4. The washings should appear neutral to pH paper after the second and third washings. If not, it may be necessary to prepare additional NaN3 solution and repeat the toluene-solution addition. Practical-grade NaN3 was used and the reactivity of the reagent varied with each lot. To be certain of neutralization, precipitation in a silver nitrate solution can be used. 5. The delay before starting the next step should be as short as possible. 6. The product may not readily form a solid, but may appear as a thick oil. If allowed to stand in the cold for several hours, stirring will produce a solid product. o 7. A melting point below 63 indicates that the product contains trapped H2O which may be removed by sublimation. 8. The crude monomer will polymerize, but usually yields a high percentage of crosslinked polymer. 9. The checker conducted this step on a scale five times larger than that reported and encountered neither unusual problems nor reduction in yield. 10. The NVTBC will not dissolve in the hexane at room temperature, but when the temperature is brought to 60 oC to initiate the polymerization process, a homogeneous solution is formed. The AIBN is purified by recrystallization from ether and dried thoroughly under reduced pressure. The NVTBC is dried in a vacuum desiccator for several hours just prior to use. 11. Oxygen, or other contaminants having lone pairs of electrons, will inhibit the polymerization. Therefore, efficient purging is imperative. 12. The Poly(NVTBC) is soluble in the concentrated monomer, so no solid will be seen until a substantial fraction of the monomer is converted to polymer. 13. The incorporation of H2O into the dry polymer is confirmed by elemental analysis and titration as discussed in Section 3. 4 Macromolecular Syntheses, Collective Volume 2 14. The checkers characterized their products by NMR. Their spectra were in agreement with those of the submitters. 3. Characterizaion (Note 14) Spectral analyses are used for characterizaion of NVTBC, the poly(NVTBC), and the poly(vinylamine hydrochloride) (PVA-HCl), Viscosity data for poly(NVTBC) and PVA -HCl are useful, and titration data and elemental analysis can be used to characterize the PVA-HCl. Sublimation of NVTBC results in a white crystalline product: (a) mp 67-68 oC [lit. 67 oC]3; uv. max (spectral-grade cyclohexane) 214 nm (å 2.2 x 104); ir (KBr disc) 3320 (N-H), 1700 (C=O), 1650 (C=C), and 1365, -1 6 1400 cm [C-(CH3)3 characteristic doublet]; NMR (d acetone) 1.46ä [s, 9, -C-(CH3)3] 4.40 (m, 2, Ch2=CH); and 6.60 (m, 1, Ch2+CH) (ABX pattern), and 8.1 ppm (broad, 1, NH). The polymerization yields a white brittle solid, poly(NVTBC): NMR (d6 acetone) 1.46ä [s, 9, -C- (CH3)3], 1.6 (broad, 2, -CH-CH2), 3.7 (broad, 1, -CH-CH2-), and 5.8 ppm (broad, 1, O=C-N-H): çred = 0.29 dL/g (1.0 g/dL benzene 25o). The hydrolysis yields an off-white, fluffy solid, poly(vinylamine hydrochloride): ir (KBr pellet) -1 3400 (N-H); 2900, 2540, and 2350 (amine HCl), 1600 (N-H), and 1490 cm (N-H3+); NMR (D2O, 1M KCl) 2.35ä (broad, 2, CH-CH2) 3.90 ppm (broad, 1, Ch2-CH); çred = 0.41 dL/g(1.0 g/dL 1M KCl 25 o o C), [ç] = 0.37 dL/g (1M KCl 25 C). Analyses calculated for PVA-HCl with 1/2 H2O per repeat unit were: C 27.13, H 7.97, Cl 40.04, and N 15.82; found C 26.56, H 7.94, Cl 38.59, and N 15.29.