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Ryan Waletzko Chemical Engineering Grad Student |
The target of the project is to create extremely tough synthetic polymers. This could be achieved by introducing reinforcements in the soft segment in the form of either nanofillers or by incorporating a stiffer component within the soft segment covalently. The nanoparticles we are investigating are mostly SiO2-based, as they tend to preferentially associate with the polyether soft segments. The purpose of the stiff component within the soft segment is to create a tri-phase material where there is a reinforcing phase within the soft segment in addition to the amorphous matrix and the hydrogen bonded hard segment. With this sort of morphology, novel mechanical properties can result, yielding high-modulus materials that still possess a great deal of extensibility.
A series of custom-made polyurethane elastomers with varying hard segment contents is the current area being investigated. Pluronic-based soft segment (1900 g/mol PEO-PPO-PEO) polyurethanes have shown a higher degree of microphase segregation compared to PEO soft segment polyurethanes at comparable soft segment compositions. When longer PEO (~4600 g/mol) was used as the soft segment, a lamellar morphology was seen. This is a likely result of the high level of crystallinity in the hard and soft domains. As the hard segment content is increased, the polymer morphology transitions from a soft segment matrix morphology to a hard segment continuous one.
Thermal behavior of polyurethane series shows strong microphase segregation in pluronic series (PU-1-26 to PU-1-47). Bottom two are for PEO homopolymer soft segments (1000 g/mol, black and 4600 g/mol, purple). All others, except for top, are of pluronic-based soft segment polyurethanes. (From L. Korley, PhD Thesis 2005)
Transition from soft segment continuous matrix to hard segment continuous morphology. Increasing hard segment content from left to right. (From L. Korley, PhD Thesis, 2005)
