Control and modification of the structure and properties of associative network polymer hydrogels
Polymeric systems that have a 'sticky' functional group along their backbone tend to physically associate in solution leading to formation of interesting self-assembled structures. Continued association between these self assembled domains eventually leads to formation of a three-dimensional network structure. This dissertation describes our study of the structure-property-activity relationship of such an associative network structure formed by triblock copolymers of poly (lactide)-poly(ethylene oxide)-poly(lactide) (PLA-PEO-PLA). The relationship between the chemistry of the starting polymer, the nano- and micro-scale structure of the polymer in solution and gel state and the macroscopic properties of the associative network solutions and hydrogels formed by the polymer was obtained by using a combination of various characterization techniques such as light scattering, small angle neutron/X-ray scattering, ultra small angle neutron/X-ray scattering and dynamic mechanical rheology. The rheological properties and drug release characteristics of these polymers were seen to be very closely dependent upon the nanoscale structure of the materials which in turn can be directly controlled by modifying the chemistry of the starting polymer. Based upon our understanding of the relationship as described above, we further modified the nanoscale structure and thereby the properties of the polymer gels by addition of small amounts of specific inorganic nanoparticles that act as new 'sticky' domains in the polymer network. In particular, the mechanical properties of the hydrogels were seen to be significantly enhanced by addition of nanoparticles.