Thesis (Ph. D.)--Johns Hopkins University, 1915. / Biography.

Thesis (Ph. D.)--University of Rhode Island, 2006. / Includes bibliographical references (leaves 99-105).

The work in this thesis relates to the transport of salt species in polymer electrolytes, which are solid ionic conductors in which mass transport is similar to that in liquids, rather than in ion-conducting glasses. A brief examination of some of the experimental techniques which have been used to study polymer electrolytes is given before examining in more detail the processes involved when these materials are polarised between non-blocking electrodes. A theoretical treatment is given for various models of polymer electrolytes, in particular polymer electrolytes containing free ions and polymer electrolytes containing free ions and ion-pairs. Non-ideality has been considered for the free ion model. Computer simulations of the free ion and ion-pair model predict that the steady-state current that these materials pass may be proportional to the applied potential difference for many tens of volts, in contrast with the free ion model, where the potential difference limit is of the order of millivolts. The use of the terms "transference number" and "transport number" is discouraged, because of the effect of the motion of uncharged species in practical systems. A new parameter, the current fraction, is defined for steady-state polarisation experiments. An experimental study of amorphous polymer electrolytes is described, in which electrolytes were polarised to steady-state using non-blocking electrodes. The application of the Hittorf technique to these materials has been demonstrated, with true transference numbers determined for some electrolytes. Conductivity and neutron scattering experiments suggest that the reported unusual conductivity behaviour of lithium triflate-based electrolytes does not exist or is not generally displayed.

A knowledge of structure is crucial to the understanding of inorganic solids and polymers. Neutron and X-ray powder diffraction are two powerful complementary techniques which can be used in the structural characterisation of a variety of crystalline materials. Chemical and electrochemical oxygen intercalation techniques involving both aqueous and non-aqueous systems, have been investigated for a number of crystalline inorganic oxides. The pyrochlore structure has been discovered to be a new class of host for the chemical intercalation of oxygett and the interstitial solid solution of Ce2Zr2O7+x based on this structure-type has been investigated. Intercalation in this system is found to involve an unusual mechanism of oxygen displacement. The structures of other complex metal oxides have also been elucidated using a combination of X-ray and neutron powder diffraction, including those of Li29Zr9Nb3O40 and Li29Zr9.6Ta2.4O40. The doping behaviour of magnesium into the technologically important material lithium niobate has also been studied using these techniques. Polymer electrolytes are a class of ionically conducting solid phases formed by the dissolution of salts in ion co-ordinating macromolecules. The relationship between the crystalline and amorphous phase of the polymer-salt complex PEO3.LiCF3SO3 has been examined by variable-temperature powder X-ray diffraction. This has shed new light on the relationship between the crystalline and amorphous structures of polymer electrolytes. Finally, the crystal structure of the polymer-salt complex PEO4:RbSCN has been determined.

The electrochemical, thermal and structural properties of polyethylene oxide (PEO) based polymer electrolytes containing multivalent ions were investigated. The phase diagram for the PEO:Ca(CF3SO3)2 system was determined by x-ray diffraction and differential scanning calorimetry techniques. Precipitation of the salt from the system at high temperatures was directly observed by variable temperature x- ray diffraction. This was ascribed to a negative entropy of dissolution of the salt in the polymer. A new crystalline complex PEO6Ca(CF3SO3)2, which exhibits a phase transition between two polymorphic forms was observed. The temperature dependence of ionic conductivity was related to the phase diagram. Redox behaviour of the PEO:Nil2 system was probed. Motion of the Ni(II) species through the system was extremely slow as evidenced by the low effective diffusion coefficient (1.82 x 10 11 cm 2s−1) and cationic current fraction (F+ < 0.1). Deposition of nickel from the polymer was characterised by instantaneous nucleation followed by three dimensional diffusion controlled growth. Investigation of the redox behaviour of the PE0:Eu(CF3SO3)3 system indicated that reduction of Eu3+ followed an ec mechanism. Evidence was obtained for extremely slow diffusion of Eu3+ containing species (D[sub]eff ~ 3.66 x 10 −16cm2s−1) through the system and slow kinetics of electron transfer. Thermal studies of the PEO:Co(SCN)2 system indicated that the glass transition temperature (Tg) was grossly elevated by the presence of Co(SCN)2 in the polymer. The absence of a crystalline PEO:Co(SCN)2 complex was ascribed to the high Tg which leads to slow crystallisation kinetics. UV-visible spectra indicated that the Co2+ ion was tetrahedrally coordinated in the system at low salt concentrations. The structure of the PEO3NaClO4 crystalline complex was reported as a subsidiary study.

The ion-polymer and ion-ion interactions in polymer electrolytes based on high molecular weight, amorphous methoxy-linked PEO (PMEO) and lithium salts have been investigated by conductivity measurement, magic-angle spinning NMR (mas NMR) and pulsed field gradient NMR (pfgNMR) techniques. In the very dilute salt concentration region, ion pairing effects are dominant in these polymer electrolytes. Ion association is found to increase with temperature and salt concentration. Ion transport for these electrolytes is controlled both by segmental motion of the polymer and activation process, in which the former is important for the dilute concentration samples while the latter is important for the concentrated samples. The mass transport process in polymer electrolytes based on a zinc salt has been investigated by steady state dc polarisation and Hittorf techniques. Zinc ion constituents in these electrolytes are mobile with a limiting current fraction of about 0.2 at 80°C, and the transference number measured by the Hittorf method is less than 0.1. The main species in these electrolytes are proposed to be neutral mobile triples. The electrode-electrolyte interfaces in polymer electrolytes based on calcium and magnesium salts have been studied. Dc polarisation experiments for these polymer electrolytes were carried out using two electrode cells with the metal anode and mercury film amalgam cathode. The results of dc polarisation experiments suggest that calcium species are mobile in high molecular weight electrolytes, while magnesium species are immobile. The influence of the molecular weight of the polymer on the dynamics of cation constituents has been studied based on the experimental results of dc polarisation and pfg NMR, and on the theoretical analyses of the reptation theory and the Rouse model. It is found that the transport of the gravity centre of the polymer will influence the ion transport in polymer electrolytes based on PEO in a manner described by the Rouse model when the molecular weight of PEO is less than 3200.

The thesis details studies relating to polymer electrolytes; the solid ionic conductors farmed by the dissolution of salts in suitable high molecular weight polymers. An outline of polymer electrolyte study is presented with respect to current understanding of the phase behaviour, morphology and conductance behaviour of the electrolyte materials. (In particular, those based upon the linear homopolymer poly(ethylene oxide), PEO.) An electrochemical study has been undertaken (298 K) involving a low molecular weight PEO analogue, PEO(400)e = CH3C02(CH2CH20) CO CH3 (n = 8 - 9 ), containing LiCF3SO3 or LiClO4. The study has shown that at low to medium salt concentrations in polyether media ion - ion interactions are important and are realized as ion association. The conductance vs. concentration behaviour has been modelled according to an equilibrium between single, ion pair and triple ion species where the concentration of simple (single) ions are small and decreasing, and above a total salt concentration of about 0.01 mol kg−1, the majority of the current is carried by triple ion species of the form Li2X- LiX2 (X = CF3SO3 , CIO4). Equilibrium constant data were obtained for single and triple ion formation (from neutral ion pairs). Determination of triple ion formation constants vs. temperature has shown that the triple ion formation process for LiCF3SO3 in PEO(400)e is an exothermic process, negative, whereas for LiClO4 AH = 0 kJinal−1. Using nuclear magnetic resonance (nmr), diffusion coefficients have been obtained for the oligomer chain in PEO(400)e and PEO(400)e.LiCF3SO3 solutions. The chain diffusion coefficients have been shown to give good agreement with those for salt diffusion, determined from conductance measurements via the Nernst - Einstein relation. An in - depth nmr investigation of the PEO.LICF3SO3 system (high molecular weight PEO) has shown that there is partition of lithium environments, probably within the salt rich crystalline phase (EQ/Li - 3.5/1). Significant numbers of lithium nuclei are not observed with the nmr technique because they occupy environments of law symmetry. This was reinforced by other nmr measurements which suggested cation - anion proximity in the crystalline phase. A mixed salt system has been studied, PEO. LiCF3SO3. Nal, and it has been shown that the mixing of salts gave materials with superior conductivities to the relevant single salt systems (PEO. LiCF3SO3 and PEO.Nal) of the same overall salt content. Nmr has shown that the mixed salt effect was due to a larger amorphous (conducting) polymer phase and more potential charge carriers for the mixed salt in comparison to the single salt materials. A marked effect upon lithium motion was observed for PEO.LiCF3SO3 Nal system in comparison to PEO.LiCF3SO3 and it has been proposed that this was due to the observed lithium species becoming mobile at notably lower temperatures for the mixed salt system.

(1) Developments in a.c. conductance techniques during the past ninety years have been reviewed, and a brief outline is given of the older theories regarding electrolytic polarisation. (2) A conductance bridge - incorporating the double heterodyne principle - has been constructed, capable of giving resistance readings to an accuracy of 0.01% over a range of frequencies covering the best part of 100 kc/s. It has also been found possible to calibrate the oscillator so that frequency settings can be guaranteed to an accuracy of , at least, 0.1% in the range: 2 kc/S to 50 kc/S. (3) The Wheatstone Bridge Network has been slightly modified to enable measurements at the high frequencies. (4) Resistances in the measuring arm of the bridge have been calibrated 'in situ' by the method of intercomparison. (5) A brief description is given of the modern theories regarding electrode processes and modern methods of eliminating electrode effects. (6) Two types of conductance cells, with bright Pt electrodes, have been used to carry out measurements on potassium chloride solutions: (a) Thomas- Gledhill Cell (b) Nichol-Fuoss Cell. The latter incorporates concentric, cylindrical electrodes with the lead to the outer electrode acting as an electrical shield for the lead to the inner electrode. This cell was constructed and used for the first time in this laboratory. (7) From resistance-frequency graphs plotted, it is shown that the Jones and Christian extrapolation procedure cannot be applied (with any degree of confidence) to obtain the true resistance, when measurements are effected over an extended range of frequencies. (8) The method of resistance-reactance diagrams is discussed and applied to various networks of resistances and capacitances. (9) By drawing resistance-reactance diagrams for the experimental readings obtained, equivalent circuits have been derived - for all the solutions investigated in the N-F cell, and for the approx. O.OlD solution in the T-G cell - which approximate to cell behaviour in the range: 500 c/s to 75 kc/s. The less concentrated solutions in the T-G cell show peculiar behaviour at the high frequencies. (10) Probable reasons are advanced for deviations from linearity on resistance-frequency graphs. (11) A new method is proposed for determining the true resistance of solutions measured in cells of the N-F type. Summary, p. 166-167.

No description available.

The effect of age and some environmental factors, especially light, on the vertical migration and distribution of Chaoborus flavicans larvae were studied both in the field and in the laboratory at Corbett Lake, British Columbia during the summer of 1963. Distribution and migration of Chaoborus larvae were studied largely by frequent horizontal Clarke-Bumpus plankton tows made at 1 metre intervals from the surface almost to the maximum depth of the lake. Marked differences were noted in daytime vertical distribution and diel migration of 5 size (or age) classes of larvae. These size classes probably corresponded approximately to larval instars. Class 0 and 1 larvae inhabited the epilimnion in the daytime throughout the summer, while class 4 larvae were largely confined to the hypolimnion during the day. Class 2 and 3 larvae occupied the epi-, meta-, and hypolimnion in the daytime during June and July, but were found chiefly in the hypolimnion during August and September. Only the older larvae (class 2, 3 and 4) underwent marked diel vertical migration which consisted of 4 phases: 1) daydepth, 2) ascent from day-depth to the surface, 3) gradual descent from surface, 4) rapid descent during dawn. The ascent occurred when subsurface light was rapidly diminishing at dusk, while the descent took place during darkness and was most marked when light started to penetrate the subsurface layers during dawn. Seasonal changes in timing of ascent and descent appeared to be correlated to seasonal changes in time of disappearance of subsurface light intensity during dusk. The rates of ascent and descent calculated from the analysis of echo traces were 13.6 and 1.1 m/hr respectively. Further analysis of the echo traces revealed that the Chaoborus scattering layer was in contact with the lake basin during daytime and descent, but not during ascent. Results from observations of larval migration in experimental tubes housed in a dark room corroborated those of the field. Class 2 larvae having similar daytime vertical distribution (surface and 5 m) as class 0 and 1 larvae underwent virtually no diel vertical migration in the tubes, while class 2 and 3 larvae taken from the deeper layers (10-14 m) of the lake did. The diel migration consisted of the same 4 phases observed in the field, as well as a "dawn rise" phase which was particularly evident for class 3 larvae. Complete migration cycles were induced by artificially changing the natural light intensity over an experimental tube during the period of relatively constant light (0900-1900 hours); the larvae responded most markedly to changes in light intensity at the 0-1000 lux range. Experiments indicated that the diel vertical migration of Chaoborus larvae is an exogenous rhythm controlled by light. / Science, Faculty of / Zoology, Department of / Graduate