Simon Butler

Neutron reflectivity of polymer interfaces

Abstract Neutron reflectivity (NR) measurements have been used to investigate the interfacial composition profile between immiscible semi-crystalline polymers, from which values for the Flory–Huggins χ parameter and interfacial tension can be obtained. In addition, measurements of small molecule ingress into high molecular weight polymers, have successfully been performed in-situ in real time. In both cases, special sample environment equipment has been used.

Early stages of oligomer–polymer diffusion

Abstract We present results of neutron reflectivity measurements of plasticiser diffusion into high molecular weight deuterated poly(methyl methacrylate) (dPMMA). These measurements were made in situ and in real time, enabling the interfacial profile to be studied in detail in situations where the normal ‘anneal–quench’ procedure is impossible. From the velocity of the diffusion front, the diffusion coefficients for two molecular weights of oligo-methyl methacrylate (OMMA) have been determined. Oligo-poly(ethylene glycol) (PEG) diffusing into dPMMA has also been measured and limited solubility of PEG observed.

Partial observability during predictions of the opponent's movements in an RTS game

In RTS-style games it is important to be able to predict the movements of the opponents forces to have the best chance of performing appropriate counter-moves. Resorting to using perfect global state information is generally considered to be ‘cheating’ by the player, so to perform such predictions scouts (or observers) must be used to gather information. This means being in the right place at the right time to observe the opponent. In this paper we show the effect of imposing partial observability onto an RTS game with regard to making predictions, and we compare two different mechanisms that decide where best to direct the attention of the observers to maximise the benefit of predictions.

Predicting the Movements of Robot Teams Using Generative Models

When a robot plans its actions within an environment containing multiple robots, it is often necessary to take into account the actions and movements of the other robots to either avoid, counter, or cooperate with them, depending on the scenario. Our predictive system is based on the biologically-inspired, simulationtheoretic approach that uses internal generative models in single-robot applications. Here, we move beyond the single-robot case to illustrate how these generative models can predict the movements of the opponent’s robots, when applied to an adversarial scenario involving two robot teams. The system is able to recognise whether the robots are attacking or defending, and the formation they are moving in. It can then predict their future movements based on the recognised model. The results confirm that the speed of recognition and the accuracy of prediction depend on how well the models match the robots’ observed behaviour.

Effect of mechanical confinement on an immiscible polymer-polymer interface

The interfacial width formed between two immiscible polymers when they are subject to mechanical confinement has benn studied using the neutron reflection technique. Deuterated polystyrene (dPS) and high-density polyethylene (HDPE) of high molecular weight were used in this study. The measurements were performed in situ at 175°C using a melt cell where the thickness of the dPS layer, coating the silicon substrate, was varied and was held onto a thick HDPE plate. The interfacial roughness extracted from the reflectivity curves was around 1.5 nm for thicker dPS films and decreased to around 1.1 nm for thinner film. In contrast to the prediction that long range van der Waals forces would destabilise the system, particularly for the thinner dPS films, it is stable within the time scal of the measurements. This could indicate a possible mechanical confinement effect on the stability of thin polymer films.

Neutron reflectivity investigations of semi-crystalline polymer interfaces

Abstract Neutron reflectivity measurements have been made on immiscible amorphous-crystalline and crystalline-crystalline polymer interfaces in the melt. Using a special reflectivity cell the macroscopic roughness and waviness associated with the crystalline polymer can be removed. From the measurement of the interfacial width between the two polymers the Flory-Huggins interaction parameter, χ, and interfacial tension, γ 0 , have been extracted. The measured interfacial width has to be deconvoluted into the real and capillary wave component contributions to interfacial broadening. Interaction parameters and interfacial tension values for both dPS-PE and dPP-PE systems have been evaluated.