Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
Results
Showing 1 to 20 of 41 for “"molecular mobility"”.
-
Investigating the Variations in Molecular Mobility within Amorphous Formulations using Terahertz Spectroscopy
… (THz-TDS) was used to probe variations in molecular mobility within different amorphous systems, with the aim of predicting physical stability based on these changes. The investigation began with a basic polymer-water binary system, representing the simplest case of hygroscopic amorphous …
-
The effect of additives on the molecular mobility, physical stability and dissolution of amorphous solid dispersions
… the determination of the coupling between molecular mobility and crystallization. This approach is especially useful for ASDs with high polymer content where drug crystallization is extremely slow at relevant storage temperature. The ability of several organic acids to stabilize an …
-
Molecular Mobility Characterization of Polymer and Solute Water States as Determined by Nuclear Magnetic Resonance, Rheology and Hydrodynamic Equilibrium (Nmr)
… analytical method which will fully elucidate the mobility and availability of water in food systems is still being sought; both are present in this work.
-
Understanding correlations between secondary relaxations and thermal behaviour of biologically relevant molecules
… current (TSDC) spectroscopy as a probe of molecular mobility in the solid (powdered) state. TSDC spectroscopy has proved useful in understanding the molecular mobility of amorphous materials. However, few investigations have been undertaken in order to understand molecular mobility in …
-
Predicting the Risk of Crystallization for Suspensions of Amorphous Spray Dried Dispersions from Structural, Thermal and Hydrophilicity Properties
… which is attributed to a decrease in molecular mobility. 3 hours was selected as the timeframe between suspension preparation and dosing for the purpose of the present research. For compounds where Tg,dispersion,100% RH is 30 °C, the dispersion is typically free from crystallization …
-
Molecular Origins of Phase Stability in Phase-Change Nano-Emulsions for Thermal Energy Storage by NMR Spectroscopy
… systems.</p> <p>To better understand the molecular origins of phase instability in PCMs nano-emulsions, liquid-state nuclear magnetic resonance (NMR) measurements were applied to a model PCM nano-emulsion. Quantitative <sup>1</sup>H single-pulse NMR measurements established the liquid …
-
Polymer drug dispersions: understanding structure and dynamics
… stable crystalline form. Accurate prediction of molecular level physical stability would be advantageous. Research surrounding stability prediction is evolving; but challenging, including thermodynamic, molecular and kinetic factors. This study focussed on gaining a molecular level understanding …
-
Using NMR to Probe Solute Mobility and Its Relationship to Functionality and Sensory Characteristics of Carbohydrate-Containing Systems
The relationship between molecular mobility and the perceived sweetness of sucrose, fructose, and glucose solutions was investigated. At the same molar concentration, the translational mobility of water was highest in the fructose, followed by the sucrose and glucose solutions. The maximum …
-
Comparison of conventional and super-glassy polymers
… these drawbacks are connected to the internal molecular mobility. In this study, a commonly used non-porous polyimide for gas separation applications, Matrimid, was compared to a microporous, high performance polymer, PIM-1. PIMs are Polymers with Intrinsic Microporosity and were firstly …
-
Temperature-dependent Terahertz Time-domain Spectroscopy as a Tool to Assess the Crystallisation Tendencies of Amorphous Drug-Polymer Systems
… as a sensitive, non-destructive tool to probe molecular mobility and predict the physical stability of amorphous drug-polymer systems. Specifically, the work investigates how molecular properties – such as hydrogen bonding capacity and conformational flexibility – as well as polymer grade and …
-
Characterizing the chemistry of yellow-poplar surfaces exposed to different surface energy environments using DCA, DSC, and XPS
… (XPS) analysis. Results show that the surface molecular orientation of yellow-poplar can be controlled by increasing the temperature above the Tg of lignin with exposure to either an environment of higher (aluminum) or lower (teflon) surface energy. Above the Tg, increases in free volume allows …
-
Rate-dependent deformation behavior of poss-filled and plasticized poly(vinyl chloride)
… polymers change as various primary and secondary molecular mobility mechanisms are accessed. The incorporation of nanoparticles can potentially alter the molecular level structure of polymer, offering the opportunity to tailor the rate-dependent mechanical deformation and failure behavior of the …
-
Terahertz spectroscopy to explore the role of vibrational dynamics in systems with varying structural order and disorder
… an amorphous matrix of suitable small organic molecular glass formers. Degradation mechanisms catalysed by water clusters, the influence of the solvation shell in solution upon reconstitution, and crystallisation processes are important aspects to consider in this context, and this thesis …
-
The cure of and moisture ingress into epoxy resins
… changes are connected to the controlling molecular processes. The dielectric measurements, although sensitive to the cure process, exhibit activation parameters which can be significantly different from those obtained by other methods. The differences observed can be rationalised on the …
-
Influence of Polyolefin Contamination on the Thermal Characteristics of Bottle Grade Recycled Polyethylene Terephthalate
… and that competition between nucleation and molecular mobility was influenced by the variation of cooling rates and repetitive extrusion cycles. As a result, the thermal characteristics were greatly influenced by the inclusion of polyolefin contamination, especially crystallinity, as shown …
-
Physico-chemical properties of polypropylene glycols
Poly(propylene glycol) (PPG) samples of different molecular mass were characterized using differential scanning calorimetry, modulated differential scanning calorimetry, thermogravimetry and thermally stimulated current (TSC) spectroscopy. It was shown, by TSC, that the glass transition temperature …
-
Estudos reológicos de cimentos asfálticos
… behaviour was interpreted at the sight of molecular structure. The obtained results revealed that the selected rheological parameters (viscosity at 25 °c, at shear rate of 0,05 s-1, complex flux grade, temperature at which loss modulus is maximum) correlated well with mechanical properties. …
-
Coarse-Grained Molecular Dynamics Simulations of Macromolecular Complexes
"Molecular dynamics simulations provide critical insights into molecular mechanisms underlying cellular processes. Most such processes, however, remain out of reach, due to large system sizes and long time scales involved. This thesis describes molecular dynamics simulations of large macromolecular …
-
Infrared Study of the Nonequilibrium Glassy State of Polymers (Frequency Shifts)
… deformation (VCD) is proposed as an intramolecular stress associated with the vitrification and aging process. VCD involves the displacement of bond lengths R, bond angles (theta), internal rotation angles (phi) and nonbonded interaction distances q from their equilibrium positions and has …
-
Sub-Tg̳, solid-state, plasticity-induced bonding of polymeric films and continuous forming
… are brought into intimate contact (within molecular proximity) at temperatures well below their glass transition temperature (Tg) negligible adhesion, due to lack of inter-diffusion of macromolecules, will be noted. Because polymer chains are kinetically trapped well below the Tg, the …
Page 1 of 3