Dissertation > Excellent graduate degree dissertation topics show

Study of pH/Temperature Dually Responsive of Polymer Microspheres with Interpenetrating Polymer Network Structure

Author: GuoHui
Tutor: ChaLiuSheng
School: Donghua University
Course: Materials Science
Keywords: poly(N-isopropylacrylamide) poly(acrylic acid) pH and temperature dual responsiveness interpenetrating polymer network structure intelligent polymer microspheres phase transition Fourier transform infrared spectrum(FTIR) dynamic rheological property
CLC: O631.3
Type: Master's thesis
Year: 2011
Downloads: 114
Quote: 0
Read: Download Dissertation

Abstract


As pH and temperature are two environmental conditions, which are very common and changed very easily in biological and chemical systems, the intelligent polymer microspheres which can respond to both pH and temperature stimuli have potential applications in many fileds, such as biological sensor, drug release, biomass separation, enzyme carrier, etc. In this thesis, the pH/temperature dually responsive polymer microspheres with interpenetrating polymer network (IPN) structure were synthesized, which overcame the drawbacks of the pH/temperature dually responsive polymer microspheres prepared by random copolymerization method, core/shell structure method or graft copolymerization method. Then, the microenvironment change of macromolecular chains of pH/temperature dually responsive IPN polymer microspheres during their phase transition were investigated by temperature-variable Fourier transform infrared (FTIR) spectrscopy. Finally, the dynamic rheological properties of the pH/temperature dually responsive IPN polymer microspheres latexes were studied. The main results obtained are as follows:(1) The pH/temperature dually responsive polymer microspheres with interpenetrating polymer network (IPN) structure based on poly(N-isopropylacrylamide) (PNIPAM) and poly(acrylic acid) (PAA) were synthesized by seed-emulsion polymerization using redox initiator at room temperature. The polymer microspheres were determined to be composed of PNIPAM and PAA by Fourier transform infrared spectrometer(FTIR). The content of PAA in the polymer microspheres increased with the used amount of acrylic acid (AA) monomer in feed recipe. The IPN structure in the microspheres was confirmed by transmission electron microscopy (TEM). The results obtained by dynamic laser light scattering (DLLS) under different pH and temperature conditions showed that the polymer microspheres had good pH and temperature stimuli responsiveness with little interference. The pH stimuli responsiveness of the microspheres was enhanced by the increase in PAA content within them.(2) The microenvironment change of macromolecular chains of pH/temperature dually responsive PNIPAM/PAA IPN polymer microspheres in D2O media during their phase transition were investigated by temperature variable Fourier transform infrared (FTIR) spectroscopy under different temperatures and pH values. The results indicated that, with the increase of pH value of D2O media, the COOH groups of PAA chains in the microspheres dissociated into COO-, leading to the phase transition induced by pH variation. However, the microenvironment of PNIPAM chains within the microspheres was not evidently changed with the pH variation, showing that the PNIPAM network holds relative independence. The redshift of the amideⅡbands and the blueshift of the amideⅠbands of PNIPAM component after temperature induced phase transition of the microspheres exhibited that the hydrogen bond between amide groups and water was broken, and the number of free amide groups was increased. In addition, the redshift of the C-H stretching bands for the isopropyl groups of PNIPAM component may be due to the breakdown of water cage structure around the groups.(3) The effect of temperature and pH on the dynamic rheology of PNIPAM/PAAIPN polymer microspheres aqueous dispersions were investigated by rotation viscometer. When the pH value of the dispersion was 7.0, the viscoelastic properties of polymer microspheres dispersion exhibited viscosity of liquid predominately. As the temperature increased and exceeded 32℃, their viscoelastic properties exhibited elastic property of soild, and the polymer microsphere dispersion became thicker and even underwent sol-gel transition. When the pH value of the aqueous dispersion was 3.0, the loss moduli G" of the dispersions was always larger than the storage moduli G’over the entire temperature range studied. The loss tangents (tan8) measured under different temperatures indicated the gelation temperature for the polymer microsphere dispersion was 33℃, which was in accordance with the VPTT of PNIPAM polymer microspheres.

Related Dissertations

  1. Study of the Temperature Distribution Model and Designing Method for Efficient Shell-and-Tube Heat Exchangers,TQ051.5
  2. Low phase transition temperature VO 2 Films,TN304.055
  3. Multi-layer multi sublattice study the physical properties of thin film materials,TB383.2
  4. Voltage current-limiting fuses pre-arcing time current characteristic simulation,TM563.1
  5. The Spin-wave Excitations of the Collinear Antiferromagnetic Phase in Iron Pnictides,O469
  6. Study on the Melting Transition and Creep Motion of Two-Dimensional Vortex Lattice Using Computer Simulation,O511
  7. Thermoelectric properties of nano - PbTe under high pressure,O469
  8. Phase Transformation Research of Crystal Silicon Induced by Axial Compress and Nanoindentation,TB302.3
  9. La, Ce doped iron oxide nanoparticles and surface adsorption phase transition behavior of,TB383.1
  10. The Mass-radius Relation of Rotating Neutron Star under Color Superconductivity Phase and Latent Heat from Spin One Color Superconductivity Phase Transitions,P145.6
  11. Study on Optical Properties of Some Cholesteric Liquid-Crystalline Polymers,O753.2
  12. Monte Carlo Simulation on the Magnetic Properties of a Honeycomb Monolayer Film,O482.5
  13. Analytically Study of Kinetic Ising Model within an Effective-field Theory with Correlations,O313
  14. The Research on Forecasting System of High Speed Wire Rod’s Temperature and Microstructure,TG335.6
  15. The Research on Low-carbon 800MPa Cold Heading Steel,TG335
  16. An Effective-field Theoretical Study on Ising Metamagnet,TB34
  17. Phenomenological Theoretical Study of Ferroelectric Phase Transitions in Epitaxial Perovskite Thin Films,TB383.2
  18. The High-pressure Phase Transition of FeCr2O4 and Density-Functional Theory Investigation on Each Phase of FeCr2O4,O614.8
  19. Study on Preparation and Performance of PNIPAM/CS Microgels,O648.17
  20. Study of Infrared Optical Properties in Perovskite Manganese Oxide La1-xCaxMnO3,P575
  21. Noise-Induced Phase Transition: Zero-Dimensiona Brownian Particles Subjected to a Time Derivative Noise,O552.1

CLC: > Mathematical sciences and chemical > Chemistry > Polymer chemistry ( polymer ) > Polymer physics and physical chemistry of polymers > The chemical nature of polymers
© 2012 www.DissertationTopic.Net  Mobile