Suggested Citation:
Haobo Chen. 2016. Zwitterionic Microgel for Adsorption and Release of Surfactant. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N7R49NS6
Purpose:
The development of advanced multi-responsive and stable zwitterionic microgel dispersions consisting of both cationic and anionic functionalized monomer units has been a subject of significant interest, stemming from their distinctive swelling properties and their ability to “trap” diffused solutes inside governed by complex intrachain electrostatic interactions. This work can be applied towards controlled dispersant systems.
Data Parameters and Units:
PDI_01.xlsx - Sheet1- Temperature (degrees Celcius); zwitterionic microgel 0.29 particles (ZI-MG 0.29); zwitterionic microgel 0.85 particles (ZI-MG 0.85); polydispersity index (PDI); hydrodynamic diameter of particles (d(H) (nm); Sheet2- zwitterionic microgel 0.29 (ZI-MG 0.29); zwitterionic microgel 0.85 (ZI-MG 0.85); N-[3-(dimenthylamino) propyl] methacrylamide % composition (DMAPMA, mol %); acrylic acid % composition (AA, mol %); N-isopropylacrylamid % composition (NIPAm, % mol); SIZE.xlsx - Sheet5- Cationic surfactant cetylpyridinium chloride concentration (CPC, mM); Volume, from stock concentration (A, mL); Volume, water added (B, mL); Absorbance (nm); Average absorbance (nm); Volume, from stock concentration (uL); Sheet1- Cationic surfactant cetylpyridinium chloride concentration (CPC, mM); Volume, from stock concentration (A, mL); Volume, from stock concentration (uL), pH; Official- Cationic surfactant cetylpyridinium chloride concentration (CPC/Input CPC/C1/C2, mM); Absorbance (nm); pH 3, pH 11, Release (sup); Uptake (sup); Uptaken (g); Not uptaken (g); Sheet2- Cationic surfactant cetylpyridinium chloride concentration (CPC, mM); pH 3; pH 11; Sheet3- pH; surfactant absorbed (CPC/MG); Dat files: cetylpyridinium chloride (CPyCl, CPC), surfactant dioctyl sodium sulfosuccinate (DOSS), DOSS concentration (mM), Electrophoretic Mobility (10^-8 m^2 / V s), pH, Surfactant absorbed CPyCl [g] / ZI-MG (0.85) [g] with a fixed initital concentration of 0.412 nM CPyCl, Surfactant absorbed CPyCl [g] / ZI-MG (0.85) [g] with a fixed initital concentration of 0.825 nM CPyCl, Average Hydrodynamic Diameter (nm), Temperature (degrees Celcius), Cationic surfactant cetylpyridinium chloride concentration (CPyCl, mM), Absorbance, nonionic surfactant Trition X-100 concentration (TX-100, mM), % Transmittance Uptake, % Transmittance Release, Surfactant absorbed CPyCl [g] / ZI-MG (0.85) [g]
Methods:
Zwitterionic microgel particles with assorted compositions were synthesized via free radical precipitation polymerization. The synthesis was carried out in a 3-necked (250 mL) round bottom reaction vessel along with 150 mL of water, fitted with a reflux condenser, a magnetic stirrer, a thermocouple and a nitrogen inlet. Overall, the concentrations of NIPAm in the reaction mixtures were controlled at 82.97±0.21 mol% while the molar ratios of DMAPMA/AAc were adjusted. The concentrations of crosslinker and initiator in the reaction mixtures were kept at 2.5-3.0 mol% and 0.8-1.2 mol%, respectively. In a separate vial, the free-radical initiator KPS was dissolved in 5 g water. This initiator solution was slowly added after the monomer mixture was immersed in a water bath set at 70 °C and purged with nitrogen for 30 minutes. The polymerization was left to proceed under nitrogen gas for 8 hours. After polymerization was complete, the microgel dispersion was then allowed to cool to room temperature and was subsequently dialyzed (Spectra/Por Membrane, MWCO: 12-13 kD) against deionized water changed daily for one week at room temperature to remove any residual monomers from the resulting reaction mixture. Zwitterionic microgel aliquots were purified in water via mild centrifugation (Eppendorf 5810-R), followed by decantation and re-dispersion in fresh water solvent to further remove any residual impurities. Each sample was prepared by mixing a known volume of targeted surfactant solution with 0.027±0.003 g of purified microgel particles dispersed in 3 mL of water in an acidic (~pH 3) or basic (~pH 11) medium. Next, these samples were sonicated (VWR Ultrasonic Cleaner) for 15 minutes and left overnight to equilibrate on a mild oscillation desktop shaker (PR-12) at room temperature. The aqueous samples were subsequently collected for additional qualifications. Solution depletion method was utilized to quantify the CPyCl adsorption. Each sample was prepared by following the previously described method. Upon reaching the binding equilibrium CPyCl concentration, the microgel particles were separated from solution by centrifugation at 10,000 rpm for 45 min. The equilibrium surfactant concentrations of the collected supernatants were then obtained from a calibration curve of absorbance versus surfactant concentration performed via Perkin Elmer Lambda 18 UV-Vis spectrometer. The wavelength used was 258 nm, which corresponds to the maximum absorbance peak for CPyCl. When required, the pH was adjusted via gradual addition of 0.1 M HCl or KOH.
Instruments:
The mean hydrodynamic diameter, electrophoretic mobility, and ζ-potential of the particles were determined via dynamic light scattering (DLS) and electrophoretic light scattering techniques using PSS NICOMP 380 ZLS. Scanning electron microscopy (SEM) images of the collapsed microgel particles were obtained using FEI/Philips XL30 Environmental FEG SEM. To further detect DOSS adsorption, 1H nuclear magnetic resonance spectroscopy was used. All solution samples were centrifuged at 10,000 rpm for 45 min to sufficiently sediment the microgel particles in the samples. Afterward, the aqueous supernatants were collected for 1H NMR analysis to quantify residual DOSS amounts. For the preparation of each individual NMR sample, 600 μL supernatant fluid was mixed with 30 μL (4.36 mM) 4,4-dimehtyl-4-silapentane-1-sulfonic acid (DSS) solution and 70 μL D2O in a 5.0 mm NMR tube, giving a total sample volume of 700 μL. All 1H NMR experiments were performed on Varian VNMRS 500 MHz instrument with a triple-resonance probe operating in triple-resonance (1H/13C/15N). Standard water suppression was used and all spectra were collected with spectral width of 16.0 ppm, an acquisition time of 3.0 seconds, a relaxation delay of 3.0 seconds, and 64 scans with the 1H resonance of DSS peak (0 ppm) as reference.
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