Diblock copolymers (DBCs) are fascinating materials which, under the correct conditions, self-assemble into periodically ordered structures with nanometre sized domains. The majority of theoretical and experimental studies of DBCs have concentrated on the monodisperse melt, where all of the polymers are identical. Although these ideal molecules have allowed for detailed understanding of the phase behaviour of the materials by removing the effects of polydispersity, they are costly and time consuming to manufacture. More recently, however, a range of techniques have emerged that allow chemists to synthesise DBCs more cheaply, albeit with higher levels of polydispersity. These methods will be more attractive to industry providing that the novel material properties remain. Self consistent field theory (SCFT) has made good progress in predicting the effects of polydispersity in DBC melts, such as increasing domain size and shifting of order-order phase boundaries - effects which are observed in experiments. However, whereas SCFT predicts that polydispersity shifts the order-disorder transition (ODT) to higher temperatures, recent experiments have found that this is not always the case and we suspect that this failure is due to the lack of fluctuation effects in the theory. In this study, Monte Carlo simulations are used to investigate DBC melts since the technique includes fluctuation effects. A detailed study of the monodisperse system is performed, providing a benchmark to which the results from polydisperse melts are compared. The simulations are also contrasted with SCFT and experiments in order to resolve the disagreement between them.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:553661 |
| Date | January 2010 |
| Creators | Beardsley, Thomas Mark |
| Publisher | University of Reading |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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