This thesis describes the use of bisphenol a carbonate cyclic oligomers (BPACY) as novel building blocks for polymer blends. The objective of the initial phase of this research is to determine whether the thermodynamics of mixing are affected by changes in the topology of a mixture's components. The second phase of this research involves the in-situ polymerization of BPACY in miscible thermoplastic matrices. The thermodynamics of mixing have been shown to be quite sensitive to changes in the topology of blend components. Cyclic bisphenol a carbonate cyclic oligomers are miscible with a wider range of polystyrene molecular weights than are chemically equivalent linear oligomers. The Flory-Huggins mean field theory predicts the shape of phase boundaries quite well for linear polystyrene (PS) /linear polycarbonate (PC) blends as well as for linear polystyrene/cyclic polycarbonate blends. However, the interaction parameter was determined to be strongly dependent upon topology with $\rm\chi\sb{PS\sb{L}/PC\sb{C}}<\chi\sb{PS\sb{L}/PC\sb{L}}.$ This result has been explained in terms of a topological interaction unique to ring polymers which is expected to be quite general. The in-situ polymerization of BPACY/styrene-acrylonitrile copolymer (SAN) blends has been demonstrated to yield PC/SAN blends with morphologies unattainable via conventional melt blending. Extremely fine phase dispersion can be obtained by this method of blend preparation. The domain coarsening kinetics have been shown to be quite sensitive to the volume fraction of the dispersed phase. The "pinning" of domain coarsening, unique to polymer systems, can be attributed to the extreme barriers to diffusive coarsening mechanisms in these systems. Thus, phase coarsening is arrested when percolation ceases or domains no longer form local clusters. The dispersed phase size has been shown to have a dramatic effect on high stress deformation in systems where a brittle phase is dispersed in a more compliant ductile matrix. The increased ductility of blends with finer phase dispersions has been rationalized based on a lower tendency for smaller brittle phases to craze/crack in addition to the influence of complex local stress fields in heterogeneous materials.
| Identifer | oai:union.ndltd.org:UMASS/oai:scholarworks.umass.edu:dissertations-8662 |
| Date | 01 January 1993 |
| Creators | Nachlis, Warren L |
| Publisher | ScholarWorks@UMass Amherst |
| Source Sets | University of Massachusetts, Amherst |
| Language | English |
| Detected Language | English |
| Type | text |
| Source | Doctoral Dissertations Available from Proquest |
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