THERMODYNMICS AND STRUCTURE OF POLY(ETHYLENE OXIDE) IN MIXTURES OF WATER AND ETHANOL

Poly(ethylene oxide) (PEO) is one of the most researched synthetic polymers due to the complex behavior which arises from the interplay of the hydrophilic and hydrophobic sites on the polymer chain. PEO in ethanol forms an opaque gel-like mixture with a partially crystalline structure. Addition of a small amount of water disrupts the gel: 5 wt % PEO in ethanol becomes a transparent solution with the addition of 4 vol % water. The phase behavior of PEO in mixed solvents have been studied using small-angle neutron scattering (SANS). PEO solutions (5 wt % PEO) which contain 4 vol % - 10 vol % (and higher) water behave as an athermal polymer solution and the phase behavior changes from UCST to LCST rapidly as the fraction of water is increased. 2 wt % PEO in water and 10 wt % PEO in ethanol/ water mixtures are examined to assess the role of hydration. The observed phase behavior is consistent with a hydration layer forming upon the addition of water as the system shifts from UCST to LCST behavior. At the molecular level, two or three water molecules can hydrate one PEO monomer (water molecules form a sheath around the PEO macromolecule) which is consistent with the suppression of crystallization and change in the mentioned phase behavior as observed by SANS. The clustering effect of aqueous PEO solution (M.W of PEO = 90,000 g/mol) is monitored as an excess scattering intensity at low-Q. Clustering intensity at Q = 0.004 Å^-1 is used for evaluating the clustering effect. The clustering intensity is proportional to the inverse temperature and levels off when the temperature is less than 50 ˚C. When the temperature is increased over 50 ˚C, the clustering intensity starts decreasing. The clustering of PEO is monitored in ethanol/ water mixtures. The clustering intensity increases as the fraction of water is increased. Based on the solvation intensity behavior, we confirmed that the ethanol/ water mixtures obey a random solvent mixing rule, whereby solvent mixtures are better at solvating the polymer that any of the two solvents. The solution behavior of PEO in ethanol was investigated in the presence of salt (CaCl2) using SANS. Binding of Ca2+ ions to the PEO oxygens transforms the neutral polymer to a weakly charged polyelectrolyte. We observed that the PEO/ethanol solution is better solvated at higher salt concentration due to the electrostatic repulsion of weakly charged monomers. The association of the Ca2+ ions with the PEO oxygen atoms transforms the neutral polymer to a weakly charged polyelectrolyte and gives rise to repulsive interactions between the PEO/Ca2+ complexes. Addition of salt disrupts the gel, which is consistent with better solvation as the salt concentration is increased. Moreover, SANS shows that the phase behavior of PEO/ethanol changes from UCST to LCST as the salt concentration is increased.

Tracing Neoclassical Influences in selected solo and chamber music for the clarinet

The musical period of Neoclassicism began in the 1920's, between the first and second world wars. It was initiated by French composers and eventually spread to other countries. One of the most important themes to emerge from the movement was to escape from the formless, rather emotional music of the Romantic era and instead, emphasize balance, order, objectivity and clarity in musical form. Many popular clarinet repertoires are enjoyed by performers and listeners because the music is enjoyable to play and easy to listen to. In particular, classically influenced clarinet music is quite interesting because it features musical elements from both the past and contemporary musical styles. For instance, some composers have integrated preexisting, more traditional styles of composition with lighter styles of modern culture such as popular music and Jazz. It is difficult to discover purely neoclassical clarinet repertoires even though many composers created their pieces during the neoclassical era. What we most commonly find are both neoclassical and non-neoclassical influences in compositions from that time period. Thus, I aim to trace the influence of neoclassicism in selected clarinet repertoires that exist today. It is my hope that increased awareness and knowledge about accessible clarinet music may encourage the general public to develop a deeper interest in a wider sphere of clarinet music, beyond what is considered popular today. The works performed and discussed in this dissertation are the following: (Recital I) Duo Concertante by Darius Milhaud; Sonata by Leonard Bernstein; Sonata for Two Clarinets by Francis Poulenc; Duos for Flute and Clarinet, Op. 34 by Robert Muczynski; Dance Preludes by Witold Lutoslawski, (Recital II) Sonatine by Arthur Honegger; Time pieces by Robert Muczynski; Suite for Clarinet, Violin and Piano by Darius Milhaud; Sonate for Clarinet, Flute and Piano by Maurice Emmanuel; Tarantelle for Flute, Clarinet and Piano, Op. 6 by Camille Saint-Saëns, (Recital III) Sonatina by Joseph Horovitz; Suite from L'histoire du Soldat for Clarinet, Violin and Piano by Igor Stravinsky; Contrasts for Clarinet, Violin and Piano by Béla Bartók The recitals that took place on December 1, 2012 and on April 25, 2013 were performed in the Ulrich Recital Hall of the Clarice Performing Arts Center in College Park, Maryland. The recital that took place on November 2, 2013 was performed at the Gildenhorn Recital Hall of the same performing arts center.