ZIMMERMAN PAUL (US)
CHAZOVACHII PAUL TAKUNDA (US)
ROBO MICHAEL (US)
MCNEIL ANNE (US)
MARSH NEIL (US)
JAMES MARTIN IAN (US)
PROCTER & GAMBLE (US)
US20050037144A1 | 2005-02-17 | |||
US20100322996A1 | 2010-12-23 | |||
US20100330860A1 | 2010-12-30 | |||
US20050101208A1 | 2005-05-12 | |||
US6095996A | 2000-08-01 | |||
US20050037144A1 | 2005-02-17 | |||
US20100322996A1 | 2010-12-23 | |||
US20100330860A1 | 2010-12-30 | |||
US20050101208A1 | 2005-05-12 | |||
US6095996A | 2000-08-01 |
THAT WHICH IS CLAIMED: 1. A method for preparing a pressure sensitive adhesive from one or more sodium polyacrylate-based superabsorbent polymers, the method comprising: (a) providing a solution comprising one or more sodium polyacrylate-based superabsorbent polymers; (b) decrosslinking the one or more sodium polyacrylate-based superabsorbent polymers to provide one or more decrosslinked sodium polyacrylate-based superabsorbent polymers; (c) optionally sonicating the one or more decrosslinked sodium polyacrylate- based superabsorbent polymers to provide one or more chain-shortened sodium polyacrylate-based superabsorbent polymers; (d) protonating the one or more decrosslinked and/or chain-shortened sodium polyacrylate-based superabsorbent polymers to provide one or more protonated decrosslinked and/or chain-shortened polyacrylic acid-based superabsorbent polymers; and (e) esterifying the one or more protonated decrosslinked and/or chain-shortened polyacrylic acid-based superabsorbent polymers to provide a pressure sensitive adhesive. 2. The method of claim 1, wherein the one or more sodium polyacrylate- based superabsorbent polymers are derived from a disposable personal hygiene product. 3. The method of claim 2, wherein the disposable personal hygiene product is selected from the group consisting of a baby diaper, an adult incontinence product, and a feminine hygiene product. 4. The method of claim 1, wherein the decrosslinking of the one or more sodium polyacrylate-based superabsorbent polymers comprises contacting the one or more sodium polyacrylate-based superabsorbent polymers with a base to provide one or more decrosslinked sodium polyacrylate-based superabsorbent polymers. 5. The method of claim 4, wherein the base is an inorganic base. 6. The method of claim 5, wherein the inorganic base is selected from the group consisting of NaOH, KOH, Na2CO3, and K2CO3. 7. The method of claim 4, further comprising removing the base from the one or more decrosslinked sodium polyacrylate-based superabsorbent polymers. 8. The method of claim 7, wherein the removing of the base from the one or more decrosslinked sodium polyacrylate-based superabsorbent polymers comprises dialyzing the one or more decrosslinked sodium polyacrylate-based superabsorbent polymers using a molecular porous membrane tubing. 9. The method of claim 1, wherein the decrosslinking of the one or more sodium polyacrylate-based superabsorbent polymers comprises decrosslinking the one or more sodium polyacrylate-based superabsorbent polymers. 10. The method of claim 1, further comprising removing residual crosslinked sodium polyacrylate-based superabsorbent polymers from filtering the one or more decrosslinked sodium polyacrylate-based superabsorbent polymers by one or more methods selected from the group consisting of filtration, centrifugation, and decantation. 11. The method of claim 1, wherein the protonating of the one or more decrosslinked sodium polyacrylate-based superabsorbent polymers comprises (i) contacting the one or more decrosslinked sodium polyacrylate-based superabsorbent polymers with a cation exchange resin or (ii) titrating the one or more decrosslinked sodium polyacrylate-based superabsorbent polymers with HCL or H2SO4. to provide one or more protonated polyacrylic acid-based superabsorbent polymers. 12. The method of claim 11, wherein the cation exchange resin comprises a sulfonic acid functional group. 13. The method of claim 1, wherein the esterifying of the one or more protonated polyacrylic acid-based superabsorbent polymers comprises contacting the one or more protonated polyacrylic acid-based superabsorbent polymers with one or more organohalide compounds. 14. The method of claim 13, wherein the one or more organohalide compounds comprises a primary or a secondary organohalide compound. 15. The method of claim 14, wherein the primary or secondary organohalide compound comprises at least one halogen atom selected from the group consisting of Cl, Br, and I. 16. The method of claim 14, wherein the primary or secondary organohalide compound comprises a C1-C12 straight-chain or branched alkyl group. 17. The method of claim 13, wherein the one or more organohalide compound is selected from the group consisting of methyl iodide, ethyl iodide, n-butyl bromide, n- octyl bromide, propargyl bromide (3-bromo-1-propyne), ethyl bromoacetate, ethyl chloroacetate, (1-bromoethyl)benzene, benzyl chloride, benzyl bromide, isobutenyl chloride (3-chloro-2-methylprop-1-ene), 2-ethylhexylbromide, and 2-ethylhexylchloride. 18. The method of claim 13, wherein the one or more organohalide compounds comprises a protecting group to provide one or more protected esterified protonated polyacrylic acid-based superabsorbent polymers. 19. The method of claim 18, wherein the protecting group is selected from the group consisting of tert-butoxycarbonyl (BOC) or 9-fluorenylmethoxycarbonyl (FMOC). 20. The method of claim 18, further comprising deprotecting the one or more protected esterified protonated polyacrylic acid-based superabsorbent polymers. 21. The method of claim 1, wherein the esterifying of the one or more protonated polyacrylic acid-based superabsorbent polymers comprises contacting the one or more protonated polyacrylic acid-based superabsorbent polymers with one or more promoters. 22. The method of claim 21, wherein the one or more promoters is selected from the group consisting of 1,1,3,3-tetramethylguanidine (TMG), triethylamine, and pyridine. 23. The method of claim 1, wherein the esterifying of the one or more protonated polyacrylic acid-based superabsorbent polymers is done in a polar aprotic solvent. 24. The method of claim 23, wherein the polar aprotic solvent is selected from the group consisting of dimethyl sulfoxide (DMSO) and N,N-dimethylformamide (DMF). 25. A pressure sensitive adhesive prepared the method of claim 1. 26. An article comprising the pressure sensitive adhesive of claim 25. 27. The article of claim 26, wherein the article is selected from the group consisting of pressure sensitive tape, a bandage, a label, note pads, a decal, a stamp, an envelope, a sticker, packaging, automobile trim, and a film. 28. A method for preparing a pressure sensitive adhesive from one or more sodium polyacrylate-based superabsorbent polymers, the method comprising: (a) providing one or more sodium polyacrylate-based superabsorbent polymers; and Ĩb) contacting the one or more sodium polyacrylate-based superabsorbent polymers with one or more alcohols in the presence of an acid for a period of time at a predetermined temperature to provide a pressure sensitive adhesive. 29. The method of claim 28, wherein the one or more sodium polyacrylate- based superabsorbent polymers are derived from a disposable personal hygiene product. 30. The method of claim 29, wherein the disposable personal hygiene product is selected from the group consisting of a baby diaper, an adult incontinence product, and a feminine hygiene product. 31. The method of claim 28, wherein the one or more alcohols is selected from the group consisting of 2-ethylhexanol, 3-bromopropanol, and combinations thereof. 32. The method of claim 28, wherein the one or more alcohols is selected from 2-ethylhexanol, 3-bromopropanol, and combinations thereof. 33. The method of claim 31, wherein the one or more alcohols is 2- ethylhexanol. 34. The method of claim 28, wherein the acid is selected from the group consisting of tosylic acid and sulfuric acid. 35. The method of claim 28, wherein the one or more alcohols is present in about a 1:2 ratio relative to an acrylic acid repeat unit of the one or more sodium polyacrylate-based superabsorbent polymers. 36. The method of claim 28, wherein the one or more alcohols is present in about a 1:1 ratio relative to an amount of water. 37. The method of claim 28, wherein the predetermined temperature is about 120 °C. 38. The method of claim 28, wherein the period of time is about three hours. 39. The method of claim 28, wherein the method does not require a step of removing water. 40. The method of claim 28, wherein the method is performed in a pressure vessel. 41. A pressure sensitive adhesive prepared by the method of claim 28. 42. An article comprising the pressure sensitive adhesive of claim 41. 43. The article of claim 42, wherein the article is selected from the group consisting of pressure sensitive tape, a bandage, a label, note pads, a decal, a stamp, an envelope, a sticker, packaging, automobile trim, and a film. |
Scheme 2. Comparing the computed free energies for the first and last esterification. 1.3.4 Generating and Characterizing PSAs. PAA fragments were first prepared with varying M w by sonicating samples of PAA SPP (5.0% w/v) or decrosslinked PAA P&G (5.0% w/v) at three different time points (between 2–20 min). After sonication, PAA P&G fragments were dialyzed with DI H 2 O to remove excess NaOH and protonated using DOWEX ion exchange resin. Each sample was then concentrated, freeze-dried, and ground into a fine powder, which was then treated with 2-ethylhexanol (5 equiv relative to the repeat unit) and H 2 SO 4 (0.25 equiv) at 120 °C for 8 h. U.S. Provisional Patent Application No. 62/890,943, filed August 23, 2019, which is incorporated herein by reference in its entirety. The resulting poly(2- ethylhexyl acrylate) (P(2-EHA)) was purified by precipitation, followed by drying under high vacuum. The resulting polymer M w spanned 450–1000 kg/mol for P(2-EHA) SPP and 700–1200 kg/mol for P(2-EHA) P&G , depending on the sonication time. Li et al., 2015. The adhesive properties of the synthesized PSAs were evaluated using rheology and analyzed with respect to Chang’s viscoelastic window (VW), which classifies different adhesive types. Chang, 1991. In this approach, the VW for each PSA is constructed from the dynamic storage (G¢) and loss (G¢¢) moduli at representative bonding and debonding frequencies of 0.01 and 100 Hz, respectively. The corresponding VW for each adhesive is the rectangular region bounded by these four moduli (FIG. 35). The G¢ at each frequency describes an adhesive’s resistance to shear, and this term generally increases in samples with more chain entanglements (e.g., with increasing M w ). The G¢¢ at each frequency describes an adhesive’s ability to dissipate energy. Chang noted that most existing PSAs appear between the G¢ and G¢¢ bounds of 10 3 and 10 6 Pascals (Pa) at the aforementioned bounding frequencies, and can be grouped into the quadrants (and central region) highlighted in FIG. 35. Most consumer PSA-based products are found in either quad 3 or the central region (e.g., office tape, sticky notes, bandages, and removable labels), which is signified by low-to-medium G¢ and G¢¢. All the adhesives synthesized from repurposed PAA P&G fall within quad 3 and the central region (FIG.35). That is, the PSAs are soft enough to flow and wet a substrate at the bonding frequency, while hard enough to hold onto a substrate, and peel cleanly at the debonding frequency. As expected, the VWs are higher with shorter sonication times due to the higher M w , and as a consequence, increase in chain entanglements. Similar results were observed with PAA SPP . Overall, the viscoelastic properties of the synthesized PSAs suggest they would be useful for applications such as removable general-purpose adhesives, including tapes, bandages, and sticky notes. 1.3.5 Summary In summary, the presently disclosed subject matter provides a facile, 3-step method to synthesize commercially relevant PSAs by repurposing superabsorbent poly(acrylic acid). Because this process uses waste polymer as the feedstock, it provides a more sustainable alternative to disposal in a landfill or incineration. Advantages of this approach include: (i) the fact that the chain-shortening process requires less energy than needed to synthesize acrylic acid monomer, and (ii) the quantitative esterification without needing to remove the water byproduct. The synthesized adhesives fall within the viscoelastic windows utilized in most commercial PSAs. One can target a specific window simply by varying the sonication times to form polymers with different molecular weights. Notably, these adhesives were achieved without the need for crosslinking, which is often necessary for acrylic PSAs. Overall, the sustainable nature and potential scalability of this approach should inspire alternative repurposing methods for petroleum-sourced polymers. 1.4 Materials All chemicals were used as received unless otherwise mentioned. Polyacyrlic Acid (PAA) with molecular weight listed as 750 kg/mol (PAA SPP ) was purchased from Scientific Polymer Products. PAA SIGMA1 (listed as 240 kg/mol), PAA SIGMA2 (listed as 450 kg/mol), Dowex ® Marathon ™ MSC hydrogen form (23–27 mm), p-toluenesulfonic acid (p-TsOH), 2-ethylhexanol (2-EHOH), dimethyl sulfoxide (DMSO), sodium hydroxide, sulfuric acid, and sodium nitrate were purchased from Millipore Sigma. Methanol (MeOH) and sodium chloride (NaCl) were purchased from Fisher Scientific. Tetrahydrofuran (THF) was purchased from OmniSolv. Glacial acetic acid was purchased from Acros Organics. Deuterated solvents: Chloroform (CDCl 3 ), pyridine-d5, and deuterium oxide (D 2 O) were purchased from Cambridge Isotopes. Sodium polyacrylate (PAA P&G ) was provided by Procter & Gamble. Sonicated polymer fragments were dialyzed in deionized (DI) water using Spectra/Por molecular porous membrane tubing (molecular weight cut-off: 3.5 kg/mol). Pressure tube vessels were purchased from Thomas Scientific. Jacketed beakers were purchased from Sigma Aldrich (cat#: Z202738-1EA). 1.5 General experimental and instrumentation 1.5.1 Sonication – Sonication was performed at 100% amplitude (amp) using a Sonics and Materials Vibra-cell VCX 600 Ultrasonic Liquid Processor equipped with a 13 mm replaceable tip probe. A 3.5 cm inner diameter, 9 cm height jacketed beaker was used for all sonication procedures. Cold water (10–15 °C) was flowed through the jacket while stirring the polymer solution at 500 rpm. A thermocouple was immersed into the polymer solution to monitor temperature. The temperature was generally observed to increase to 45–50 °C from 10–15 °C during sonication. The power from the outlet was monitored using a kill-a-watt meter (#P4400). The maximum power (P max ) reading observed at the beginning of sonication was recorded. The maximum specific energy (w max ) for chain- shortening PAA of mass (m) for time (t) was determined using equation (2). 1.5.2 NMR Spectroscopy – Unless otherwise noted, 1 H and 13 C NMR spectra for all compounds were acquired at room temperature. Chemical shift data are reported in units of d (ppm) relative to tetramethylsilane (TMS) and referenced with residual solvent. Multiplicities are reported as follows: singlet (s), doublet (d), doublet of doublets (dd), triplet (t), quartet (q), multiplet (m), broad resonance (br). Residual water is denoted by an asterisk (*). For all 1 H NMR spectra for polymers, a 5 s acquisition time was used with a 25 s relaxation delay in between each pulse. 1.5.3 Size Exclusion Chromatography (SEC) for PAA SPP and PAA P&G fragments – Sonicated PAA SPP and PAA P&G fragments were then diluted (to 1–1.5 mg/mL) with 0.1 M NaNO 3 (aq) /ethylene glycol (99:1 v/v) and filtered through a Titan3™ Nylon syringe filter (0.45 µm) into a SEC vial. Polymer molecular weight (M) and dispersity (Ɖ) were determined by comparison with PEG/PEO EasiVial standards from Agilent at 40 °C in 0.1 M NaNO 3 (aq) on a Waters SEC (Waters 1515 Isocratic HPLC pump, 717plus autosampler, RI detector Model 214 and UV-PDA detector Model 487) equipped with four Ultrahydrogel columns: 120 (WAT011565), 250 (WAT011525), 500 (WAT011530) and 1000 (WAT011535). 1.5.4 SEC for polyacrylate based PSAs (pressure-sensitive adhesives) – The synthesized PSAs were dissolved (1–2 mg/mL polymer) in THF with mild heating and filtered through a PTFE filter (0.45 mm) into an SEC vial. Polymer molecular weight (M) and dispersity (Ɖ) were determined by comparison with poly(methyl methacrylate) ReadyCal-Kit standards from Perfect Separation Solutions at 40 °C in THF on an SEC (Waters APC PUMP and Sample manager, Waters APC RI detector serial #H15URI545M and Wyatt uDAWN 1067UD 3-Angle light scattering detector) equipped with a Shodex HFIP-G 8B Guard Column, 2-Shodex HFIP-806M Columns (serial numbers E28T0045, E2960061, and E2910020, 7.8x300 mm in series). 1.5.5 Rheological measurements on PSAs –Rheological measurements were taken on an AR2000ex rheometer (TA Instruments) with a 25 mm serrated parallel plate. PSA ( 650 mg) was loaded to achieve a 1,250 µm layer thickness and measurements were taken at 25 °C. The frequency sweeps were performed between 0.1 and 100 Hz. 1.6. Evaluating Polymer Recovery and Chemical Structure After Sonication Three batches of 0.500% w/v PAA solution were prepared by dissolving PAA SPP (750 kg/mol, 250 mg, 3.47 mmol) with DI H 2 O (50.0 mL each) in jacketed beakers equipped with stir bars. The PAA solutions were stirred at 300 rpm for 15 h at rt. Then, the PAA solutions were sonicated for 20 min. Next, the polymer solutions were concentrated under reduced pressure to dryness, spiked with a known amount of DMSO (1.14, 1.16, and 1.09 mmol, respectively) and redissolved with D 2 O for quantitative 1 H- NMR^spectroscopic analysis. An average recovery of 87% was determined based on relative integrations. See FIG. 1. Table 1. Average recovery after sonication determined from three trials based on amount of DMSO (mmol), normalized integration for peak a (I a ), mass of polymer sonicated (250 mg) and molar mass of PAA repeat unit (72.06 g/mol). 1.7 Effect of time and concentration on sonicating of PAA SPP Triplicate batches of PAA SPP solution (0.50, 1.0, and 2.5% w/v) were prepared by dissolving PAA (250, 500, and 1250 mg) with DI H 2 O (50.0 mL each) in jacketed beakers equipped with stir bars. NaCl (100 mg, 1.71 mmol) was added to each batch to lower the solution viscosity. The PAA solutions were stirred at 300 rpm for 15 h at rt. The 5.0% w/v sample was dissolved differently due to the need for more vigorous stirring. While stirring with a large stir bar, PAA SPP (7500 mg) was slowly added to a 500 mL glass bottle with DI H 2 O (150 mL). NaCl (300 mg, 5.13 mmol) was added to lower the solution viscosity. The PAA solutions were stirred at 300 rpm for 15 h at rt. Thereafter, portions of this solution (50 mL) were transferred to jacketed beakers. The PAA solutions were sonicated for 20 min while collecting 0.50–1.0 mL aliquots at 1, 2, 5, 10, 15, and 20 min. The aliquots were diluted (to 1–1.5 mg/mL) with 0.1 M NaNO 3 (aq)/ethylene glycol (99:1 v/v) and analyzed via SEC. See FIG. 2. Table 2. Maximum power (P max ) consumed during sonication for PAA SPP at 0.50% w/v. Maximum specific energy (w max ) values were determined using equation 2. Table 3. Weight average molecular weight (M w ), dispersity (Ɖ), and specific energy (w max ) data for sonications of PAA SPP at 0.50% w/v. See FIG. 3. Table 4. Maximum power (P max ) consumed during sonication for PAA SPP at 1.0% w/v. Maximum specific energy (w max ) values were determined using equation 2. Table 5. Weight average molecular weight (M w ), dispersity (Ɖ), and specific energy (w max ) data for sonications of PAA SPP at 1.0% w/v. See FIG. 4. Table 6. Maximum power (P max ) consumed during sonication for PAA SPP at 2.5% w/v. Maximum specific energy (w max ) values were determined using equation 2. Table 7. Weight average molecular weight (M w ), dispersity (Ɖ), and specific energy (w max ) data for sonications of PAA SPP at 2.5% w/v. See FIG. 5. Table 8. Maximum power (P max ) consumed during sonication for PAA SPP at 5.0% w/v. Maximum specific energy (w max ) values were determined using equation 2. Table 9. Weight average molecular weight (M w ), dispersity (Ɖ), and specific energy (w max ) data for sonications of PAA SPP at 5.0% w/v. See FIG. 6. 1.8 Effect of Time on Sonicating PAA P&G 1.8.1 Decrosslinking – A batch of 5.0% w/v decrosslinked PAA P&G solution was prepared by stirring PAA P&G (10 g) in aq. NaOH (0.3 M, 200 mL) in a 500 mL glass bottle at 80 °C for 24 h. 1.8.2 Sonication – Portions of the decrosslinked PAA P&G solution (50 mL) were poured into jacketed beakers equipped with stir bars. The PAA solutions were sonicated while collecting 0.50–1.0 mL aliquots at 1, 2, 3, 5, and 10 min. The aliquots were diluted with DI H 2 O (5 mL) and dialyzed overnight in DI water to remove NaOH. The aliquots were diluted (to 1–1.5 mg/mL) with 0.1 M aq. NaNO 3 /ethylene glycol (99:1 v/v) and analyzed via SEC. See FIG. 7. Table 10. Maximum power (P max ) consumed during sonication for PAA P&G . Maximum specific energy (w max ) values were determined using equation 2. Table 11. Weight average molecular weight (M w ), dispersity (Ɖ) and specific energy (w max ) data for sonications of decrosslinked PAA P&G at 5.0% w/v. See FIG. 8. 1.9. Chain-shortening of PAA to fragments for esterification PAA SIGMA1 and PAA SIGMA2 were used for esterification without chain-shortening. PAA SPP and PAA P&G were chain-shortened to shorter fragments respectively before esterification. 1.9.1 PAA SPP – PAA SPP solution (5.0% w/v) was prepared by dissolving PAA SPP (12.5 g) with DI H 2 O (250 mL) in a 500 mL glass bottle equipped with a stir bar. NaCl (0.30 g, 5.13 mmol) was added to lower the solution viscosity. The PAA solution was stirred at 300 rpm for 10 h at rt, and then divided into 50 mL portions, which were sonicated in jacketed beakers for either 2, 5, 10, or 20 min. The sonicated polymer solutions were freeze-dried and ground using a mortar and pestle to achieve fine powders which were labeled PAA SPP-2min, PAA SPP-5min , PAA SPP-10min , and PAA SPP-20min , respectively. Specifically, while wearing cryogenic gloves, the freeze-dried polymer is ground with the mortar immersed in a liquid nitrogen bath. After grinding the polymer into a fine powder, the polymer is immediately (to avoid water from condensing) transferred into a vial and dried under high vacuum for 5–10 min. 1.9.2 PAA P&G – PAA P&G solution (5.0% w/v) was prepared by adding PAA P&G (10.00 g) over 5 min into a 500 mL glass bottle with aq. NaOH (300 mM, 200 mL). The solution was stirred at 80 °C for 24 h for decrosslinking. The decrosslinked PAA P&G solution was divided into 50 mL portions which were sonicated in jacketed beakers for either 2, 5, or 10 min. The polymers were dialyzed to remove the NaOH using DI water (1 gallon), which was changed three times (i.e., every 3–4 h). Then, the polymer solution was protonated by passing through a column of DOWEX ion exchange resin (15–20 g). The protonated polymer solutions were freeze-dried and ground using a mortar and pestle to achieve fine powders which were labeled PAA P&G-2min , PAA P&G-5min , and PAA P&G-10min , respectively. 1.7 Fischer Esterifications In general, commercial PAAs (i.e., PAA SIGMA1 and PAA SIGMA2 ) come fine powder form and low molecular weight (< 450 kg/mol) relative to the chain-shortened PAA SPP and PAA P&G . Consequently, the chain-shorted PAAs needed longer esterification time (8 h versus 3–5 h for commercial PAAs). High degrees of esterification were qualitatively confirmed when the white heterogenous reaction mixture became clear and homogenous (see FIG. 10). Recoveries were difficult to measure due to the stickiness of the sythesized adhesives. 1.7.1 Effect of alcohol equivalents on conversion Reactions were run under identical conditions except for the amounts of 2- ethylhexanol (2-EHOH) (3, 5, 10, 15 equiv.) used relative to PAA. 2-EHOH (12.6 mL, 16.7 mmol, 3.00 equiv.; 4.30 mL, 27.8 mmol, 5.0 equiv.; 8.70 mL, 55.5 mmol, 10.0 equiv.; 13.0 mL, 83.3 mmol, 15.0 equiv.) was added to seperate 20 mL vials equipped with stir bars. p-TsOH (527 mg, 2.80 mmol, 0.500 equiv.) was added to each vial and stirred until dissolved. The vials were subsequently heated to 120 °C, then PAA SIGMA2 (400 mg, 5.60 mmol, 1.0 equiv.) was added. The vials were capped and stirred for 3–5 h at 120 °C. Thereafter, the vials were cooled in a rt water bath. The poly(2-ethylhexyl acrylate) SIGMA2 (P(2-EHA)) SIGMA2 ) was isolated by precipitating into MeOH (10 mL) and removing the supernatent. Then, the polymer was purified by dissolving in minimal amounts of THF (1 mL), precipitating into MeOH (10 mL) and removing the supernatent repeated three times. The resulting solid was dried under high vacuum at 60 °C for 3 h. See FIG. 11 and FIG. 12. 1.7.2 Effect of water (byproduct) on conversion Reactions were run under the same conditions except for equiv.alents (1.5 and 2 equiv.) of 2-EHOH used relative to PAA.To two 15 mL pressure tubes, 2-EHOH (0.980 mL, 6.24 mmol, 1.50 equiv.; 1.30 mL, 8.33 mmol, 2.00 equiv.) and H 2 SO 4 (0.0550 mL, 1.04 mmol, 0.250 equiv.) were added and stirred at 120 °C. While stirring, PAA SIGMA1 (300 mg, 4.20 mmol, 1.0 equiv.) was subsequently added and the vessel was sealed and stirred for 3–5 h at 120 °C. Thereafter, the vessels were cooled in a rt water bath. The poly(2-ethylhexyl acrylate) SIGMA1 (P(2-EHA)) SIGMA1 ) was isolated by precipitating into MeOH (10 mL) and removing the supernatent. Then, the polymer was purified by dissolving in minimal amounts of THF (1 mL), precipitating into MeOH (10 mL) and removing the supernatent repeated three times. The resulting solid was dried under high vacuum at 60 °C for 3 h. See FIG. 13 and FIG. 14. 1.7.3 Effect of adding water on conversion To a 15 mL pressure tube, 2-EHOH (1.95 mL, 12.5 mmol, 3.00 equiv.), DI H 2 O (0.220 mL, 12.5 mmol, 3.00 equiv.) and H 2 SO 4 (0.0550 mL, 1.04 mmol, 0.250 equiv.) were added and stirred at 120 °C. While stirring, PAA SPP-20min (300 mg, 4.20 mmol, 1.0 equiv.) was subsequently added and the vessel was sealed and stirred for 8 h at 120 °C. Thereafter, the vessels were cooled in a rt water bath. The poly(2-ethylhexyl acrylate) SPP- 20min (P(2-EHA)) SPP-20min ) was isolated by precipitating into MeOH (10 mL) and removing the supernatent. Then, the polymer was purified by dissolving in minimal amounts of THF (1 mL), precipitating into MeOH (10 mL) and removing the supernatent repeated three times. The resulting solid was dried under high vacuum at 60 °C for 3 h. See FIG. 15. 1.7.4 Effect of adding a second alcohol on conversion To a 15 mL pressure tube, 2-EHOH (1.95 mL, 12.5 mmol, 3.00 equiv.), 3- bromopropanol (3-BrPrOH) (1.13 mL, 12.5 mmol, 3.00 equiv.), and H 2 SO 4 (0.0550 mL, 1.04 mmol, 0.250 equiv.) were added and stirred at 120 °C. While stirring, PAA SPP-20min (300 mg, 4.20 mmol, 1.0 equiv.) was subsequently added and the vessel was sealed and stirred for 8 h at 120 °C. Thereafter, the vessel was cooled in a rt water bath. The poly(2- ethylhexyl acrylate-co-3-bromopropyl acrylate) SPP-20min (P(2-EHA-co-3-BPA) SPP-20min ) was isolated by precipitating into MeOH (10 mL) and removing the supernatent. Then, the polymer was purified by dissolving in minimal amounts of THF (2 mL), precipitating into MeOH (10 mL) and removing the supernatent repeated three times. The resulting solid was dried under high vacuum at 60 °C for 3 h. See FIG. 16. To a 15 mL pressure tube, 2-EHOH (1.95 mL, 12.5 mmol, 3.00 equiv.), EtOH (0.74 mL, 12 mmol, 3.0 equiv.) and H 2 SO 4 (0.0550 mL, 1.04 mmol, 0.250 equiv.) were added and stirred at 120 °C. While stirring, PAA SPP-20min (300 mg, 4.20 mmol, 1.0 equiv.) was subsequently added and the vessel was sealed and stirred for 8 h at 120 °C. Thereafter, the vessel was placed in a water bath at rt to cool. The poly(2-ethylhexyl acrylate-co-ethyl acrylate) SPP-20min (P(EHA-co-EA) SPP-20min ) was isolated by precipitating into MeOH (10 mL) and removing the supernatent. Then, the polymer was purified by dissolving in minimal amounts of THF (2 mL), precipitating into MeOH (10 mL) and removing the supernatent repeated three times. The resulting solid was dried under high vacuum at 60 °C for 3 h. See FIG. 17. 1.7.5 Effect of adding water on conversion for small molecule carboxylic acids The experiment was run in duplicate. To two 15 mL pressure tubes equipped with stir bars, EtOH (1.5 mL, 26 mmol, 5.1 equiv.), H 2 SO 4 (0.0670 mL, 1.25 mmol, 0.245 equiv.) and acetic acid (0.29 mL, 5.1 mmol, 1.0 equiv.) were added. Then, DI H 2 O (0.45 mL, 25 mmol, 4.9 equiv.) was added to one vessel and both vessels were sealed and stirred at 120 °C for 8 h. Thereafter, the vessels were cooled in a rt water bath and aliquots (0.1 mL) were diluted with 2:1 CDCl 3 /pyridine-d5 (0.4 mL) for 1 H NMR spectroscopic analysis. See FIG. 18 and FIG. 19. To two 15 mL pressure tubes equipped with stir bars, 2-EHOH (1.8 mL, 12 mmol, 5.2 equiv.), H 2 SO 4 (0.031 mL, 0.58 mmol, 0.25 equiv.) and decanoic acid (400 mg, 2.32 mmol, 1.00 equiv.) were added. Then, DI H 2 O (0.21 mL, 12 mmol, 5.2 equiv.) was added to one vessel and both vessels were sealed and stirred at 120 °C for 8 h. Thereafter, the vessels were cooled in a rt water bath and aliquots (0.1 mL) were diluted with 2:1 CDCl 3 /pyridine-d5 (0.4 mL) for 1 H NMR spectroscopic analysis. See FIG. 20. To two 15 mL pressure tubes equipped with stir bars, 2-EHOH (1.8 mL, 12 mmol, 5.0 equiv.), H 2 SO 4 (0.031 mL, 0.58 mmol, 0.25 equiv.) and undecanoic acid (433 mg, 2.30 mmol, 1.0 equiv.) were added. Then, DI H 2 O (0.21 mL, 12 mmol, 5.0 equiv.) was added to one vessel and both vessels were sealed and stirred at 120 °C for 8 h. Thereafter, the vessels were cooled in a rt water bath and aliquots (0.1 mL) were diluted with 2:1 CDCl 3 /pyridine-d5 (0.4 mL) for 1 H NMR spectroscopic analysis. See FIG. 21.
1.8 Free-energy Calculations 1.8.1 Background on free energy calculations The calculation of free-energy differences between two states is a common and widely adopted method in computational chemistry. Christ et al., 2010. To assess the difference between two states, the states must have a configurational overlap large enough for a comparison to be made. In practice, most end states do not have such an overlap, necessitating the use of bridge states that are a mix of both systems of interest. Herein the degree of perturbation is denoted as l. 1.8.2 System Construction Nonamers AA 9 , BA 8 AA 1 , AA 8 BA 1 , and BA 9 were constructed using Avogadro, Hanwell et al., 2012, and then solvated in a 3:1 butanol:water cuboid using PACKMOL, Martinez et al., 2009, providing a 12 Å buffer between the nonamer and the edge of the cuboid. This resulted in a 41.841x44.981x45.167 Å box with 480 butanols and 160 waters for BA 8 AA 1 and BA 9 , and a 37.678x40.876x35.483 Å box with 333 butanols and 111 waters for AA 9 and AA 8 BA 1 . All of the nonamers studied were isotactic. TIP3P parameters, Jorgensen et al., 1983, were used for water, and parameters for butanol and the nonamers were derived from CGenFF, Vanommeslaeghe et al., 2009, using MATCH. Yesselman et al., 2012. 1.8.3 Molecular Dynamics Molecular dynamics studies were performed using the CHARMM molecular mechanics platform (developmental version 44a1), Brooks et al., 2009, with the domain decomposition (DOMDEC) computational kernels on graphics processing units (GPUs). Hynninen and Growley, 2014. Molecular dynamics were performed using the canonical ensemble (NVT) at 298.15 K using a Langevin thermostat. The Leapfrog Verlet integrator was used with an integration time of 2 fs. Electrostatic interactions were modeled using a particle-mesh Ewald method, Darden and Pedersen, 1993; Essmann et al., 1995; Huang et al., 2016, with a grid spacing of 1 Å, interpolation order of 6, and a k- value of 0.32 Å -1 . Van der Waals interactions were modelled using a 9 Å switching radius, 10 Å cutoff radius, and a 12 Å neighbor list. See FIG. 22. 1.8.4 Calculating the difference in free energy of esterification (DDA) The difference in free energy of esterification (DDA) was calculated using the Multistate Bennet Acceptance Ratio method, Shirts and Chodera, 2008, using a dual topology approach. Both AA 9 and BA 8 AA 1 were perturbed to AA 8 BA 1 and BA 9 , respectively, using 11 discrete l states, 0 ® 1, in steps of Dl = 0.1. Perturbation of l was achieved using the block module of CHARMM, l values held constant using the MSlD ffix keyword. Vilseck et al., 2019. Non-bonding interactions were scaled by l using a soft-core potential. Hayes et al., 2017. Prior to molecular dynamics simulations, a system was subjected to 200 steps of steepest descent minimization. Each l state was subjected to 200 steps of steepest descent minimization, followed by equilibration for 5 ns. Production runs consisted of 50 ns of simulation, with trajectory frames saved every 2,500 timesteps (yielding 10,000 frames total). 1.8.5 Energy Calculation Results The free energy difference between the l=0 and other lambda states (0.1 to 1.0) for the AA 9 and BA 8 AA 1 systems are shown in Table 1. From the DA value for when l=1 for both systems, the DDA of esterification is calculated to be 0.7 ± 0.1 kcal/mol. As the consumption of butanol and the evolution of water is expected to be identical in AA 8 BA 1 and BA 9 , the DA of butanol consumption and water formation during the process of esterification was ignored, as it those terms would cancel out in the calculation of DDA of esterification (FIG. 1). Table 12. Values for the difference in free energy between l=0 and other l values for the AA 9 and BA 8 AA 1 systems.
1.9 Esterification Reactions to Synthesize Pressure Sensitive Adhesives 1.9.1 Esterifying PAA SPP fragments To a 100 mL pressure tube, 2-EHOH (8.14 mL, 52.0 mmol, 5.0 equiv.) and H 2 SO 4 (0.140 mL, 2.60 mmol, 0.250 equiv.) were added and stirred at 120 °C. While stirring, PAA SPP-20min (750 mg, 10.4 mmol, 1.0 equiv.) was subsequently added and the vessel was sealed and stirred for 8 h at 120 °C. Thereafter, the vessel was cooled in a rt water bath. The poly(2-ethylhexyl acrylate) SPP-20min (P(2-EHA)) SPP-20min ) was isolated by precipitating into MeOH (20 mL) and removing the supernatent. Then, the polymer was purified by dissolving in minimal amounts of THF (5 mL), precipitating into MeOH (20 mL) and removing the supernatent repeated three times. The resulting solid was dried under high vacuum at 60 °C for 3 h. A portion of the P(2-EHA) SPP-20min (650 mg) was used for frequency sweep measurements. See FIG. 23-FIG. 24. To a 100 mL pressure tube, 2-EHOH (8.14 mL, 52.0 mmol, 5.0 equiv.) and H 2 SO 4 (0.140 mL, 2.60 mmol, 0.250 equiv.) were added and stirred at 120 °C. While stirring, PAA SPP-10min (750 mg, 10.4 mmol, 1.0 equiv.) was subsequently added and the vessel was sealed and stirred for 8 h at 120 °C. Thereafter, the vessel was cooled in a rt water bath. The poly(2-ethylhexyl acrylate) SPP-10min (P(2-EHA)) SPP-10min ) was isolated by precipitating into MeOH (20 mL) and removing the supernatent. Then, the polymer was purified by dissolving in minimal amounts of THF (5 mL), precipitating into MeOH (20 mL) and removing the supernatent repeated three times. The resulting solid was dried under high vacuum at 60 °C for 3 h. A portion of the P(2-EHA) SPP-10min (650 mg) was used for frequency sweep measurements. See FIG. 25-FIG. 26. To a 15 mL pressure tube, 2-EHOH (8.68 mL, 55.5 mmol, 5.0 equiv.) and H 2 SO 4 (0.150 mL, 2.80 mmol, 0.250 equiv.) were added and stirred at 120 °C. While stirring, PAA SPP-2min (800 mg, 11.1 mmol, 1.0 equiv.) was subsequently added and the vessel was sealed and stirred for 8 h at 120 °C. Thereafter, the vessel was cooled in a rt water bath. The poly(2-ethylhexyl acrylate) SPP-2min (P(2-EHA)) SPP-2min ) was isolated by precipitating into MeOH (20 mL) and removing the supernatent. Then, the polymer was purified by dissolving in minimal amounts of THF (5 mL), precipitating into MeOH (20 mL) and removing the supernatent repeated three times. The resulting solid was dried under high vacuum at 60 °C for 3 h. A portion of the P(2-EHA) SPP-2min (650 mg) was used for frequency sweep measurements. See FIG. 27.
1.9.2 Esterifying PAA P&G fragments To a 100 mL pressure tube, 2-EHOH (8.14 mL, 52.0 mmol, 5.0 equiv.) and H 2 SO 4 (0.140 mL, 2.60 mmol, 0.250 equiv.) were added and stirred at 120 °C. While stirring, P(2-EHA) P&G-10min (750 mg, 10.4 mmol, 1.0 equiv.) was subsequently added and the vessel was sealed and stirred for 8 h at 120 °C. Thereafter, the vessel was cooled in a rt water bath. The poly(2-ethylhexyl acrylate) P&G-10min (P(2-EHA)) P&G-10min ) was isolated by precipitating into MeOH (20 mL) and removing the supernatent. Then, the polymer was purified by dissolving in minimal amounts of THF (5 mL), precipitating into MeOH (20 mL) and removing the supernatent repeated three times. The resulting solid was dried under high vacuum at 60 °C for 3 h. A portion of the P(2-EHA) P&G-10min (650 mg) was used for frequency sweep measurements. See FIG. 29-FIG. 30. To a 100 mL pressure tube, 2-EHOH (8.68 mL, 55.5 mmol, 5.0 equiv.), and H 2 SO 4 (0.150 mL, 2.80 mmol, 0.250 equiv. ) were added and stirred at 120 °C. While stirring, PAA P&G-5min (800 mg, 11.1 mmol, 1.0 equiv.) was subsequently added and the vessel was sealed and stirred for 8 h at 120 °C. Thereafter, the vessel was cooled in a rt water bath. The poly(2-ethylhexyl acrylate) P&G-5min (P(2-EHA)) P&G-5min ) was isolated by precipitating into MeOH (20 mL) and removing the supernatent. Then, the polymer was purified by dissolving in minimal amounts of THF (5 mL), precipitating into MeOH (20 mL) and removing the supernatent repeated three times. The resulting solid was dried under high vacuum at 60 °C for 3 h. A portion of the P(2-EHA) P&G-5min (650 mg) was used for frequency sweep measurements. See FIG. 31-FIG. 32. To a 100 mL pressure tube, 2-EHOH (8.68 mL, 55.5 mmol, 5.0 equiv.), and H 2 SO 4 (0.150 mL, 2.80 mmol, 0.250 equiv. ) were added and stirred at 120 °C. While stirring, PAA P&G-2min (800 mg, 11.1 mmol, 1.0 equiv.) was subsequently added and the vessel was sealed and stirred for 8 h at 120 °C. Thereafter, the vessel was cooled in a rt water bath. The poly(2-ethylhexyl acrylate) P&G-2min (P(2-EHA)) P&G-2min ) was isolated by precipitating into MeOH (20 mL) and removing the supernatent. Then, the polymer was purified by dissolving in minimal amounts of THF (5 mL), precipitating into MeOH (20 mL) and removing the supernatent repeated three times. The resulting solid was dried under high vacuum at 60 °C for 3 h. A portion of the P(2-EHA) P&G-2min (650 mg) was used for frequency sweep measurements. See FIG. 33-FIG. 34. REFERENCES All publications, patent applications, patents, and other references mentioned in the specification are indicative of the level of those skilled in the art to which the presently disclosed subject matter pertains. 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Although the foregoing subject matter has been described in some detail by way of illustration and example for purposes of clarity of understanding, it will be understood by those skilled in the art that certain changes and modifications can be practiced within the scope of the appended claims.
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