Type of Document Thesis Author Rmaile, Amir Hussein Author's Email Address email@example.com URN etd-07152007-022451 Title Characterization of Polyelectrolyte Multilayers and Complexes: Towards Bio-Implant Applications Degree Master of Science Department Chemistry and Biochemistry, Department of Advisory Committee
Advisor Name Title Joseph Schlenoff Committee Chair Alan G. Marshall Committee Member Andre Striegel Committee Member Rufina Alamo Committee Member Sanford Safron Committee Member Keywords
- Mechanical Testing
- Polyelectrolyte Complex
- Polyelectrolyte Multilayer
- Attentuated Total Reflectance
Date of Defense 2007-05-09 Availability unrestricted AbstractA self assembled multilayer technique based on alternating deposition of oppositely charged polyelectrolytes onto charged solid substrates is described in this thesis. The main principles and methodologies of this technique are explained in details in an effort to develop new technologies that would be beneficial for making new products or enhancing the quality of existing ones.
In this thesis, fundamental studies to characterize the water content, swelling by different salts, annealing effect, viscoelastic and mechanical properties of polyelectrolyte multilayers and complexes are illustrated and conducted.
Using the attenuated total reflectance Fourier Transform Infrared, ATR-FTIR, spectroscopy it is possible to probe the bulk of the PDADMA/PSS and P4VMP/PSS multilayers thus gaining valuable information about their water and counter-ion content. The multilayer resembles a polymeric network comprising regions of varying intensities of polyion-polyion interactions the extent and distribution of which are sensitive to the type of the polyelectrolyte used and to the type and concentration of the salt in the surrounding medium.
A distinction is afforded in terms of the swelling and doping abilities of 14 different salts based on their hydration state. For both PDADMA/PSS and P4VMP/PSS multilayers, one can cautiously generalize that hydrophobic ions are more effective dopers than hydrophilic ions.
Water content of those two multilayers was studied extensively using a range of different experiments conducted by ATR-FTIR technique. Osmotic pressure experiment is a good approach to characterize the water content inside a PEMU. Polyethylene glycol, PEG, a highly water-soluble polymer, was used as an osmotic stressing agent. Unlike salt solutions, PEG does not diffuse inside the PEMU from solution. It rather creates enough osmotic pressure to pull water out from the PEMU. A good estimate of the number of water molecules inside a multilayer was achieved using PEG.
Ion-pairing and water content are key factors influencing permeability of molecules into polyelectrolyte multilayers. They are also important in controlling the multilayer mechanical properties which are especially important when considering the use of PEMUs in biomaterials applications.
Layer by layer buildup of polyelectrolyte multilayers on a germanium crystal and ATR-FTIR measurements of ratios of water to sulfonate and azide to sulfonate peaks allowed us to monitor the annealing of PDADMA-PSS multilayers of different thicknesses in different ionic strength solutions. The film loses extrinsic sites as it anneals.
PDADMA/PSS complexes were produced and their mechanical and thermal properties were characterized using different analytical methods. Dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), and mechanical stretching machines were used to conduct different experiments on those complexes. Swelling of the PDADMA/PSS complexes was investigated. We were able to get preliminary data about both the elastic modulus and the shear modulus of those complexes. Their water content, mechanical properties, thermal properties, and swelling behavior all encourage us to apply them in the biomedical field, in particular as bio-implants to replace intervertebral disc in the spinal cord. We are still investigating the different properties of those complexes and working on enhancing their structure and biocompatibility. We are synthesizing PAA-co-PAEDAPS and PDADMA-co-PAEDAPS for that purpose. The synthesis of those two polyzwetterions PZs is one of many steps taken towards producing biocompatible complexes that can be used as bio-implants
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