Phase separation in polymer solutions. II. Determination of thermodynamic parameters of poly (2,6-dimethyl-1,4-phenylene oxide) toluene mixtures

In liquid systems where it is possible to perform light scattering experiments at the melting points of polymer solutions without nucleation taking place because of undercooling, the thermodynamic parameters necessary to calculate the correction parameter g in the Flory-Huggins equation as modified by Koningsveld can be determined. In the system poly(2,6-dimethyl 1,4-phenylene oxide)-toluene crystallization will be induced by liquid-liquid phase separation at temperatures below the melting points. The Huggins interaction parameter x, calculated from light scattering data, shows negative values for solutions up to 24.5 weight per cent of polymer. This indicates specific interactions between polymer and solvent molecules. A combination of data from light scattering and from calculations based on the theory of melting point depression affords the values necessary for calculating the free enthalpy of mixing ΔG

Differential scanning calorimetry of poly(2,6 dimethyl-1,4 phenylene-oxide)-toluene solutions

A study has been made by differential scanning calorimetry of the phase separation phenomena of solutions of poly(2,6 dimethyl-1,4 phenylene-oxide) (PPO) in toluene. Upon cooling a homogeneous solution, liquid-liquid phase separation always precedes crystallization effects. By assuming the correction parameter g (in the expression for the chemical potential difference of the solution) to be temperature-dependent, the value of the heat of fusion is calculated to be 8·2 cal g−1 for PPO toluene crystals

Phase separation of polymer solutions. The calculation of the cloudpoint curve with a concentration and temperature-dependent free energy correction parameter

The free enthalpy correction parameter g in the Flory-Huggins equation for the Gibbs free enthalpy of mixing in polymer solutions is considered generally as a concentration- and temperature-independent parameter. It has been extended here with linear concentration- and temperature-dependent terms. With these parameters, six different types of cloudpoint curves can be predicted. Using the experimental cloudpoint curve for solutions of poly(2,6-dimethyl-1,4-phenylene oxide) in toluene up to about 70 per cent by weight of polymer, a set of g-parameters is obtained, accounting for concentration and temperature dependence. With the parameters thus obtained, the melting point curve has been calculated which agrees very well with the experimental melting points for this system

Liquid-liquid phase separation by nucleation and growth in solutions of poly(2,6 dimethyl-1,4 phenylene oxide) in toluene

In solutions of poly(2,6 dimethyl-1,4 phenylene oxide) in toluene, the nucleation of the newly formed phase during liquid-liquid phase separation takes place after induction periods which vary between several minutes (at temperatures close to the spinodal) and several hours (at temperatures close to the cloudpoint). The growth of the nuclei in the initial stages is diffusion controlled. The diffusion coefficients and the activation energy of diffusion were calculated. From these values, together with the calculated volume free energies and the experimental induction times, an estimate could be made of the size of a critical nucleus and of the surface free energy of the nuclei

Phase separation in polymer solutions. I. Liquid-liquid phase separation of PPO poly (2, 6-dimethyl 1, 4-phenylene oxide) in binary mixtures with toluene and ternary mixtures with toluene and ethyl alcohol

In the system poly(2, 6-dimethy1-1, 4-phenylene oxide) (PPO)-toluene three phase separation lines can be detected: the melting point curve, the cloud point curve, and the spinodial. Because crystallization of PPO occurs very slowly, a phase transition will always be initiated by liquid-liquid phase separation. Depending upon the experimental circumstances two mechanisms are possible, either nucleation and growth (extremely slowly in this system) or the spinodial decomposition mechanism. In the system PPO-toluene-ethanol, liquid-liquid phase separation occurs leading to two bulk liquid fractions. Only in mixtures containing very small concentrations of alcohol can three phase separation curves be detected from which the position of the cloud point curve of the system PPO-toluene can be confirmed

Liquid-Liquid phase separation in concentrated polymer solutions studied by electron microscopy

Depending upon quenching temperature and composition, liquid-liquid phase separation in polymer solutions will occur either by nucleation and growth or by the spinodal decomposition. Both mechanisms occur in the system poly(2,6-dimethyl-1,4-phenylene oxide)-toluene and can be made visible by electronmicroscopy using the freeze-etching method as sample preparation technique

Revelation: the emergence of the euphonium from the traditional brass and wind band culture and its modern day acceptance in solo, chamber and orchestral genres

The thesis presents new research concerning aspects of the euphonium and its repertoire, including both new and historical compositions that have never before been documented or recorded. The thesis discusses the historical context of the euphonium, and demonstrates new ways of using the euphonium and combinations of instruments that work with it. Each chapter of this thesis aims to expand on basic information regarding to the euphonium. Chapter one is a literature review covering various books relating directly to the euphonium and the tuba. Chapter two covers the historical origins of the euphonium and where the instrument was mainly used in its early years. Chapters three and four cover the euphoniums traditions, current social status and the relationship between the euphonium, cello and the orchestra. Chapter five covers the euphoniums repertoire in the wind band genre and chapter six looks at the euphonium in the orchestral context. Finally chapter seven covers the euphonium and its solo repertoire over the past 150 years and the thesis closes with the final conclusion in chapter 8. Performance of the works discussed has formed an integral part of the research process, and has both informed, and been informed by the historical and analytical material presented here. In support of the thesis, two CDs are provided which have been recorded specifically to give the reader an audible example of the changes in repertoire and the development in compositional styles for the euphonium. The first CD - ’Neath Austral Skies - showcases the Australian repertoire for the euphonium accompanied by brass band. The music on this CD has never before been recorded, and the enclosed programme notes and information on the music document influences on the composers. The second CD - Utaki, The Sacred Grove - demonstrates a variety of alternative uses for the euphonium outside the band context. This CD does not focus on orchestral repertoire, but demonstrates the instrument in alternative roles, including in chamber music and as concerto soloist in music of varying styles, including several newly commissioned works, thus revealing a new direction and repertoire for the euphonium. This second CD projects the euphonium into a new and completely different sound world, effectively demonstrating some of the more romantic qualities of the euphonium, while capturing the versatility of its voice by utilising accompaniments such as a string quartet, string duo, piano and chamber brass - all of which complement the distinctive tessitura and vocal qualities of the euphonium. For more information about Matthew please visit his personal website: www.matthewvanemmerik.co

Ethical Reflexivity, Care, and Slippery Data: Lessons From Working With the Mass Observation Project

As part of a research project on the lived and everyday temporal experiences of British people in the Covid-19 pandemic, a Mass Observation directive was commissioned that asked volunteers about their changing rhythms, feelings, and imagined futures. The responses were rich and raw. Some of these reflections, however, expressed a risk of harm that raised ethical issues that were not anticipated beforehand. These issues were complicated by the interstitial character of the data, being not primary and not quite secondary. This Sociology in Action paper reflects on one diary that expressed risk of harm to think through the slipperiness of the data as well as the ethical responsibility researchers have towards the well-being of participants and that of their own. I suggest a proactive ethical framework for such interstitial data that includes an ethics of care towards the participants and stimulates ethical reflexivity that prepares the researcher for potential emotional ties and investments

Improving Balance and Mobility in People with Multiple Sclerosis

Impaired balance and gait function are highly prevalent and associated with reduced quality of life in those with Multiple Sclerosis (MS). Recent evidence implicates the somatosensory system as a major contributor to balance dysfunction in this population. As part of the mini-symposium entitled Advanced Computational and Technological Approaches to Mitigating Mobility Dysfunction in People with Multiple Sclerosis, this presentation will review current intervention and rehabilitation methods aimed at improving balance and mobility in people with MS. Particular focus will be on the effects of Tai Chi training, which integrates coordination, strength and flexibility in enhancing adaptive postural control and physical function