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Tuning Properties of Surfaces and Nanoscopic Objects using Dendronization and Controlled PolymerizationsÖstmark, Emma January 2007 (has links)
In this study, dendronization and grafting via controlled polymerization techniques, atom transfer radical polymerization (ATRP) and ring-opening polymerization (ROP), have been explored. Modification of surfaces and cellulose using these techniques, which enable grafting of well-defined polymer architectures, has been investigated. The interest in using cellulose stems from its renewability, biocompatibility, high molecular weight, and versatile functionalization possibilities. Dendronization was performed using disulfide-cored didendrons of 2,2-bis(methylol)propionic acid (bis-MPA) on gold surfaces, for the formation of self-assembled monolayers. It was found that the height of the monolayer increased with increasing dendron generation and that the end-group functionality controlled the wettability of the modified surface. Superhydrophobic cellulose surfaces could be obtained when a ‘graft-on-graft’ architecture was obtained using ATRP from filter paper after subsequent post-functionalized using a perfluorinated compound. The low wettability could be explained by a combination of a high surface roughness and the chemical composition. Biobased dendronized polymers were synthesized through the ‘attach to’ route employing dendronization of soluble cellulose, in the form of hydroxypropyl cellulose (HPC). The dendronized polymers were studied as nanosized objects using atomic force microscopy (AFM) and it was found that the dendron end-group functionality had a large effect on the molecular conformation on surfaces of spun cast molecules. ATRP of vinyl monomers was conducted from an initiator-functionalized HPC and an initiator-functionalized first generation dendron, which was attached to HPC. The produced comb polymers showed high molecular weight and their sizes could be estimated via AFM of spun cast molecules on mica and from dynamic light scattering in solution, to around 100-200 nm. The comb polymers formed isoporous membranes, exhibiting pores of a few micrometers, when drop cast from a volatile solvent in a humid environment. HPC was also used to initiate ROP of ε-caprolactone, which was chain extended using ATRP to achieve amphiphilic comb block copolymers. These polymers could be suspended in water, cross-linked and were able to solubilize a hydrophobic compound. / QC 20100826
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Synthesis and electrochemistry of novel conducting dendrimeric star copolymers on poly(propylene imine) dendrimerBaleg, Abd Almonam Abd Alsalam January 2011 (has links)
<p>One of the most powerful aspects of conducting polymers is their ability to be nanostructured through innovative, synthetically manipulated, transformations, such as to tailor-make the polymers for specialized applications. In the exponentially increasing wide field of nanotechnology, some special attention is being paid to innovative hybrid dendrimer-core based polymeric smart materials. Star copolymers are a class of branched macromolecules having a central core with multiple linear polymer chains extending from the core. This intrinsic structural feature yields a unique 3D structure with extended conjugated linear polymer chains, resulting in star copolymers, which have higher ionic conductivities than their corresponding non-star conducting polymer counterparts. In this study an in-depth investigation was carried out into the preparation and characterization of specialized electronic &lsquo / smart materials&rsquo / . In particular, the preparation and characterization of novel conducting dendrimeric star copolymers which have a central poly(propylene imine) (PPI) dendrimer core with conducting polypyrrole (PPy) chains extending from the core was carried out. This involved, first, the preparation of a series of dendrimeric polypyrrole poly(propylene imine) star copolymers (PPI-co-PPy), using generations 1 to 4 (G1 to G4) PPI dendrimer precursors. The experimental approach involved the use of both chemical and electrochemical synthesis methods. The basic procedure involved a condensation reaction between the primary amine of a diamino functional PPI dendrimer surface and 2-pyrrole aldehyde, to afford the pyrrole functionalized PPI dendrimer (PPI-2Py). Polymerization of the intrinsically contained monomeric Py units situated within the dendrimer backbone was achieved via two distinctly different routes: the first involved chemical polymerization and the second was based on potentiodynamic oxidative electrochemical polymerization. The star copolymers were then characterized using various sophisticated analytical techniques, in-situ and ex-situ. Proton nuclear magnetic resonance spectroscopy (1HNMR) and Fourier transform infrared spectroscopy (FTIR) were used to determine the structures. Scanning electron microscopy (SEM) was used to determine the morphology. Themogravimetric analysis (TGA) was used to study the thermal stability of the prepared materials. X-ray diffraction analysis (XRD) was used to study the structural make-up of phases, crystallinity and amorphous content. Hall effect measurements were carried out to determine the electrical conductivity of the chemically prepared star copolymers. The PPI-co-PPy exhibited improved thermal stability compared to PPI-2Py, as confirmed by TGA. SEM results showed that the surface morphology of the functionalized dendrimer and star copolymer differed. The surface morphology of the chemically prepared star copolymers resembled that of a flaky, waxy material, compared to the ordered morphology of the electrochemically grown star copolymers, which resembled that of whelk-like helixes. In the case the electrochemically grown star copolymers, SEM images recorded at higher magnifications showed that the whelk-like helixes of the star copolymers were hollow tubes with openings at their tapered ends, and had an average base diameter of 2.0 &mu / m. X-ray diffraction analysis of the first generation star copolymer G1PPI-co-PPy revealed a broadly amorphous structure associated with PPy, and crystalline peaks for PPI. Cyclic voltammetry (CV), square wave voltammetry (SWV) and electrochemical impedance spectroscopy (EIS) techniques were used to study and model the electrochemical reactivity of the star copolymer materials. Electrochemical impedance spectroscopy data showed that the G1PPI-co-PPy exhibited slightly higher ionic conductivity than pristine PPy in lithium perchlorate. The second generation star copolymer G2PPI-co-PPy electrochemically deposited on a platinum (Pt) electrode had a lower electrochemical charge transfer resistance compared to electrodeposited polypyrrole (PPy) on a Pt electrode, and bare Pt. The decrease in charge transfer resistance was attributed to an increase in the conjugation length of the polymer as a result of the linking of the highly conjugated PPy to the PPI dendrimer. Bode impedimetric analysis indicated that G2PPI-co-PPI was a semiconductor, with a maximum phase angle shift of 45.3° / at 100 MHz. The star copolymer exhibited a 2- electron electrochemistry and a surface coverage of 99%. Results of Hall effect measurements showed that the star copolymer is a semiconducting material, having a conductivity of 0.7 S cm-1, in comparison to the 1.5 S cm-1 of PPy. To the best of my knowledge, these new star copolymers have not been reported in the open literature. Their properties make them potentially applicable for use in biosensors.</p>
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Synthesis of top coat surface treatments for the orientation of thin film block copolymersChen, Christopher Hancheng 08 October 2013 (has links)
Block copolymer self-assembly has demonstrated sub-optical lithographic resolution . High values of chi, the block copolymer interaction parameter, are required to achieve next-generation lithographic resolution . Unfortunately, high values of chi can lead to thin film orientation control difficulties , which are believed to be caused by large differences in the surface energy of each block relative to the substrate and the free surface. The substrate-block interface can be modified to achieve a surface energy intermediate to that of each individual block ; the air-polymer interface, however, presents additional complications. This thesis describes the synthesis of polymers for top coat surface treatments, which are designed to modify the surface energy of the air-block copolymer interface and enable block copolymer orientation control upon thermal annealing. Polymers with β-keto acid functionality were synthesized to allow polarity switching upon decarboxylation. Syntheses of anhydride containing polymers were established that provide another class of polarity switching materials. / text
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Design, synthesis, and engineering of advanced materials for block copolymer lithographyDurand, William John 18 September 2015 (has links)
Block copolymers (BCPs) are an attractive alternative for patterning applications used to produce next-generation microelectronic devices. Advancements require the development of high interaction parameter χ BCPs that enable patterning at the sub-10 nm length scale. Several organosilicon BCPs were designed to both enhance χ and impart an inherent etch selectivity that facilitates pattern transfer processes. Increasing the BCP silicon content both increases χ and bolsters the etch resistance, providing a pathway to designing new high-χ materials. Unfortunately, the BCPs investigated are not amenable to thermal annealing because the organosilicon block preferentially segregates to an air/vacuum interface and drives orientation parallel to the surface. A series of spin-coatable, polarity-switching top coats (as well as other strategies) were developed to provide a “neutral” top interface and promote the perpendicular orientation of BCP domains. In addition, a methodology for evaluating the neutral condition, relying on thickness quantization and the corresponding wetting behavior (i.e. island/hole topography) of lamellae. The top coat strategy was demonstrated for several BCP systems, and perpendicular structures can successfully be etched on commercial tools and be transferred into underlying substrates. The interaction parameter χ was evaluated using two methods to compare the performance of several BCPs: the order-disorder transition (ODT) of symmetric diblock copolymers, and the absolute scattering profile of a disordered BCP melt. Both methods, while severely limited for quantitative comparison, indicate trends towards higher χ with additional appended polar and organosilicon functional groups. Furthermore, the pattern fidelity is shown to be a function of the overall BCP segregation strength. The free energy of confined lamella was modeled algebraically to produce response surface plots capable of identifying process conditions favorable for perpendicular orientation. Thickness independent perpendicular orientation is only favorable using two neutral interfaces. Incommensurate film thicknesses are the most favorable, with commensurability conditions dependent on the wetting behavior at each interface. The modeling was supplemented with an extensive body of thin film experimental work that qualitatively agrees well with the above conclusions.
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Study on RAFT polymerization and nano-structured hybrid system of POSS macromersDeng, Yuanming 08 June 2012 (has links) (PDF)
This work is generally aimed to synthesize POSS based BCPs via RAFT polymerization, to study their self-assembly behaviors, to research on the effect of POSS self-assembly structure on the bulk properties and to prepare nanostructured hybrid epoxy via self-assembly of POSS based copolymer. In Chapter1, We studied the RAFT polymerization of POSS macromers and capable to synthesize well defined POSS based BCPs with high POSS fraction and different topology such as AB,BAB and (BA)3. The vertex group and the morphology effect on thermo-mechanical properties of POSS based BCPs as well as the structure-property relationship was investigated. Dispersion RAFT polymerization in apolar solvent was applied and various aggregates with different morphology in Chapter2. Cooling induced reversible micelle formation and transition was found and the pathway selection in vesicle formation was investigated. Nano-construction of O/I hybrid epoxy materials based on POSS based copolymers was investigated in Chapter4. The effect of functional group content on miscibility of POSS based statistic copolymer and epoxy was investigated. A novel method to nanostructure epoxy hybrid involving self-assembly of POSS based BCPs in epoxy was presented. High homogeneity and well size/morphology control of core-corona structure containing rigid POSS core and soluble PMMA corona in networks were obtained.
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Synthesis and electrochemistry of novel conducting dendrimeric star copolymers on poly(propylene imine) dendrimerBaleg, Abd Almonam Abd Alsalam January 2011 (has links)
<p>One of the most powerful aspects of conducting polymers is their ability to be nanostructured through innovative, synthetically manipulated, transformations, such as to tailor-make the polymers for specialized applications. In the exponentially increasing wide field of nanotechnology, some special attention is being paid to innovative hybrid dendrimer-core based polymeric smart materials. Star copolymers are a class of branched macromolecules having a central core with multiple linear polymer chains extending from the core. This intrinsic structural feature yields a unique 3D structure with extended conjugated linear polymer chains, resulting in star copolymers, which have higher ionic conductivities than their corresponding non-star conducting polymer counterparts. In this study an in-depth investigation was carried out into the preparation and characterization of specialized electronic &lsquo / smart materials&rsquo / . In particular, the preparation and characterization of novel conducting dendrimeric star copolymers which have a central poly(propylene imine) (PPI) dendrimer core with conducting polypyrrole (PPy) chains extending from the core was carried out. This involved, first, the preparation of a series of dendrimeric polypyrrole poly(propylene imine) star copolymers (PPI-co-PPy), using generations 1 to 4 (G1 to G4) PPI dendrimer precursors. The experimental approach involved the use of both chemical and electrochemical synthesis methods. The basic procedure involved a condensation reaction between the primary amine of a diamino functional PPI dendrimer surface and 2-pyrrole aldehyde, to afford the pyrrole functionalized PPI dendrimer (PPI-2Py). Polymerization of the intrinsically contained monomeric Py units situated within the dendrimer backbone was achieved via two distinctly different routes: the first involved chemical polymerization and the second was based on potentiodynamic oxidative electrochemical polymerization. The star copolymers were then characterized using various sophisticated analytical techniques, in-situ and ex-situ. Proton nuclear magnetic resonance spectroscopy (1HNMR) and Fourier transform infrared spectroscopy (FTIR) were used to determine the structures. Scanning electron microscopy (SEM) was used to determine the morphology. Themogravimetric analysis (TGA) was used to study the thermal stability of the prepared materials. X-ray diffraction analysis (XRD) was used to study the structural make-up of phases, crystallinity and amorphous content. Hall effect measurements were carried out to determine the electrical conductivity of the chemically prepared star copolymers. The PPI-co-PPy exhibited improved thermal stability compared to PPI-2Py, as confirmed by TGA. SEM results showed that the surface morphology of the functionalized dendrimer and star copolymer differed. The surface morphology of the chemically prepared star copolymers resembled that of a flaky, waxy material, compared to the ordered morphology of the electrochemically grown star copolymers, which resembled that of whelk-like helixes. In the case the electrochemically grown star copolymers, SEM images recorded at higher magnifications showed that the whelk-like helixes of the star copolymers were hollow tubes with openings at their tapered ends, and had an average base diameter of 2.0 &mu / m. X-ray diffraction analysis of the first generation star copolymer G1PPI-co-PPy revealed a broadly amorphous structure associated with PPy, and crystalline peaks for PPI. Cyclic voltammetry (CV), square wave voltammetry (SWV) and electrochemical impedance spectroscopy (EIS) techniques were used to study and model the electrochemical reactivity of the star copolymer materials. Electrochemical impedance spectroscopy data showed that the G1PPI-co-PPy exhibited slightly higher ionic conductivity than pristine PPy in lithium perchlorate. The second generation star copolymer G2PPI-co-PPy electrochemically deposited on a platinum (Pt) electrode had a lower electrochemical charge transfer resistance compared to electrodeposited polypyrrole (PPy) on a Pt electrode, and bare Pt. The decrease in charge transfer resistance was attributed to an increase in the conjugation length of the polymer as a result of the linking of the highly conjugated PPy to the PPI dendrimer. Bode impedimetric analysis indicated that G2PPI-co-PPI was a semiconductor, with a maximum phase angle shift of 45.3° / at 100 MHz. The star copolymer exhibited a 2- electron electrochemistry and a surface coverage of 99%. Results of Hall effect measurements showed that the star copolymer is a semiconducting material, having a conductivity of 0.7 S cm-1, in comparison to the 1.5 S cm-1 of PPy. To the best of my knowledge, these new star copolymers have not been reported in the open literature. Their properties make them potentially applicable for use in biosensors.</p>
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Homo-polymers with balanced hydrophobicity translocate through lipid bilayers and enhance local solvent permeabilityWerner, Marco, Sommer, Jens-Uwe, Baulin, Vladimir A. 07 April 2014 (has links) (PDF)
Recent experimental studies indicate that polymeric structures with a well-adjusted balance of amphiphilic parts may translocate through self-assembled phospholipid bilayers and enhance the passive trans-membrane transport of smaller molecules. Using a coarse grained lattice Monte Carlo model with explicit solvent we investigate self-assembled lipid bilayers interacting with a linear polymer chain under variation of the hydrophobicity of the chain. Here, we focus on the relationship between the chain's hydrophobicity and its translocation behavior through the membrane as well as induced membrane perturbations. We show, that there is an adsorption transition of the polymer at the bilayer interface, where effectively the solvent phase and the tail phase of the bilayer are equally repulsive for the polymer. Close to this adsorption threshold of the polymer both the translocation probability of the polymer as well as the permeability of the membrane with respect to solvent are enhanced significantly. The frequency of polymer translocation events can be understood quantitatively assuming a simple diffusion along a one-dimensional free energy profile, which is controlled by the effective lipophilicity of the chain and the tail-packing in the bilayer's core. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
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Morphology Control of Copolymer Thin Films by NanoparticlesShagolsem, Lenin Singh 04 March 2014 (has links) (PDF)
Diblock-Copolymers (DBCs), created by covalently joining two chemically distinct polymer blocks, spontaneously form various nanoscale morphologies such as lamellae, cylinders, spheres, etc. due to the chemical incompatibility of its constituent blocks. This effect is called microphase separation in the literature. Because of this self-organizing property DBCs find applications in many areas e.g. in creating selective membranes, and in polymer based modern electronic devices like organic photovoltaics where the internal morphology plays an important role in determining the performance of the device. Many such modern devices are based on thin film technologies and uses copolymer nanocomposites as it exhibits advantageous electrical, optical, and mechanical properties. Also, DBC can direct the spatial distribution of nanoparticles (NPs) in the polymer matrix via microphase separation. Generally, two types of NPs are distinguished with respect to their monomer affinity: selective NPs which prefer one component of DBC, and non-selective NPs which interact equally with both components of DBC. In this work, using molecular dynamics simulations and analytical calculations, we explore the effect of adding both types of NP in the copolymer matrix considering a thin film (or confined) geometry.
We consider a cylinder forming DBC melt confined by purely repulsive walls in slit geometry and study the behavior of the system upon adding non-selective NPs. Two models of non-selective interactions between the monomers and NPs are applied, i.e repulsive and weakly attractive interactions (athermal and thermal cases respectively). Spatial distribution of NPs in the copolymer matrix is sensitive to the NP-monomer interaction behavior. We focus on the thermal case and discuss, in particular, the following points: (1) role of diblock and polymer-wall interfaces, (2) spatial distribution of NPs, and (3) NP segregation and uptake behavior by the copolymer film. The uptake of NPs by the copolymer film in the thermal case displays a non-monotonic dependence on temperature which can be explained qualitatively using a mean-field model. In general, addition of non-selective NPs do not affect the copolymer morphology and the NPs are preferentially localized at the interface between microphase domains.
Morphological transitions are observed when adding selective NPs to the copolymer matrix. By varying the amount of selective NPs and diblock composition we systematically explore the various structures formed by the nanocomposites under confinement and constructed the corresponding phase diagram in diblock composition and NP concentration. We also discuss the NP induced orientation transition of lamellar structure and study the stability of lamellar phases formed by the nanocomposites.
To study the commensurability and wetting transition of horizontally oriented lamellar phase formed by the nanocomposites we have developed a mean field model based on the strong segregation theory. Our model predicts that it is possible to reduce the frustration in a film of fixed thickness by properly tuning the NP-monomer interaction strength. Furthermore, the model predicts a discontinuous transition between the non-wetted phase (where a dense NP layer is present in the polymer-substrate interface) and wetted phase (where the substrate is covered by polymers).
Finally, we extend our study to non-equilibrium where we apply a shear flow field to copolymer thin films. Here, we study the flow behavior, lamellae deformation and change of pair-wise interaction energy, and macroscopic response like kinetic friction coefficient and viscosity of the copolymer thin film with and without NPs. / Lösungen von Diblock-Copolymeren (DBC), welche durch die kovalente Bindung zweier chemisch unterschiedlicher linearer Polymerblöcke entstehen, können spontan mikroskopische Strukturen ausbilden, welche je nach dem Grad der chemischen Kompatibiliät der Blöcke beispielsweise lamellen-, zylinder- oder kugelartige Formen zeigen. Dieses Phänomen wird meist als Mikrophasenseparation bezeichnet. Aufgrund dieser selbstorganisierenden Eigenschaft finden DBCs Anwendungen in vielen Bereichen der Forschung und der Industrie. Beispielsweise zur Erzeugung selektiver Membranen oder in moderner polymerbasierter Elektronik, wie organischen Solarzellen, wo die innere Struktur eine wichtige Rolle spielt um die Leistungsfähigkeit zu erhöhen. Viele moderne Geräte basieren auf der Technologie dünner Schichten und nutzen Copolymer-Nanokomposite um elektrische, optische oder mechanische Eigenschaften zu verbessern.
In Folge der Mikrophasenseparation kann man mit Hilfe von DBC die räumliche Verteilung von Nanopartikeln (NP) in der Polymermatrix kontrollieren. Man unterscheidet im Allgemeinen zwischen zwei Arten von NP: selektive NP, welche eine der beiden Komponenten der DBC bevorzugen und nicht-selektive NP, welche mit beiden Komponenten gleichartig wechselwirken. In der vorliegenden Arbeit nutzen wir molekulardynamische Simulationen und analytische Rechnungen um den Eigenschaften zu studieren, welche eine Zugabe von selektiven und nicht-selektiven NP auf eine dünnschichtige Copolymermatrix hat.
Wir betrachten eine zylinderformende Schmelze aus DBC, welche in einem dünnen Film, zwischen zwei harten Wänden eingeschränkt ist, und untersuchen das Verhalten des Systems unter Zugabe nicht-selektiver NP. Zwei Modelle nicht-selektiver Wechselwirkungen werden angenommen: ausschließlich repulsive (athermische) Wechselwirkungen und schwach anziehende (thermische) Wechselwirkungen. Die räumliche Verteilung der NP ist abhängig von dem jeweiligen Wechselwirkungsverhalten. Wir konzentrieren uns hierbei auf den thermischen Fall und diskutieren speziell folgende Schwerpunkte: (1.) die Rolle der sich ausbildenden Grenzschichten, (2.) die räumliche Verteilung der NP und (3.) die Abscheidung der NP, sowie die Aufnahmefähigkeit derselben durch die Polymermatrix. Im thermische Fall zeigt die Aufnahme der NP durch die Copolymerschicht eine nicht-monotone Abhängigkeit von der Temperatur, was mit Hilfe eines Mean-Field Modells erklärt werden kann. Die Zugabe nicht-selektiver NP hat keinen Einfluss auf die Struktur der Copolymermatrix und die NP werden vorzugsweise an der Grenzschicht der jeweiligen Mikrophasen gefunden.
Im Gegensatz dazu kann man durch die Zugabe selektiver NP eine Strukturveränderung in der Copolymermatrix feststellen. Durch Veränderung der Menge der NP und der Zusammensetzung der DBC können wir systematisch unterschiedliche Strukturen des räumlich eingeschränkten Nanokomposits erzeugen und ein entsprechendes Phasendiagram bezüglich der NP Konzentration und der DBC Zusammensetzung erstellen. Wir untersuchen auch die durch NP induzierte Orientierung der Lamellenstruktur und analysieren ihre Stabilität.
Um den sogenannten Kommensurabilitäts- und Benetzungsübergang in horizontal orientierten Lamellenstrukturen zu untersuchen haben wir ein Mean-Field Modell entwickelt, welches auf der Annahme der 'starken Segregation' basiert. Unser Modell macht die Vorhersage, dass es möglich ist die Frustration in einem Kompositfilm zu reduzieren, indem man die NP-Monomer-Wechselwirkung entsprechend anpasst. Zusätzlich sagt das Modell einen diskontinuierlichen Übergang zwischen der unbenetzten Phase (Ausbildung einer dichten NP Konzentration an der Polymer-Substrat Grenzschicht) und der benetzten Phase (das Substrat ist ausschließlich vom Polymerkomposit bedeckt) voraus.
Abschließend weiten wir unsere Untersuchungen auf Nicht-Gleichgewichtszustände aus und induzieren durch Scherung der Substratwände einen Strömungprofil im Kompositfilm. Dabei analysieren wir das Strömungsverhalten, die Lamellendeformation und die Änderung der paarweisen Wechselwirkungsenergie. Wir untersuchen auch makroskopische Größen, wie den kinetischen Reibungskoeffizienten und die Viskosität, je in An- und Abwesenheit von Nanopartikeln.
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Rational Design of Drug Formulations using Computational ApproachesHuynh, Loan 24 July 2013 (has links)
Theory has been used to complement experiment in the development of both drugs and delivery systems. Theoretical methods are capable of identifying the molecular basis of drug formulation inadequacies and systematic theoretical studies may suggest fruitful avenues for material modification. This thesis highlights the utility of computer-based theoretical calculations for guiding the design of drug formulations and enhancing material-drug compatibility and stability. Specifically, the present work explores the applications of semi-empirical methods and atomistic molecular dynamics (MD) simulations to enhance the performance of nano-emulsions and polymer micelle formulations for the delivery of hydrophobic drugs. This work includes three separate studies preceded by an introductory summary of available theoretical techniques.
The first study evaluates the accuracy and reliability of semi-empirical methods and MD simulations as means to select suitable excipients to formulate the anti-cancer drug docetaxel in an emulsion. Here, simulations accurately predict the rank order of drug solubility in various excipients, suggesting that simulation is useful for library enrichment.
In the second study, a drug conjugation approach is used to further improve the stability and solubility of docetaxel in a triglyceride-based nano-emulsion. Here, optimal conjugates are identified with computer-based theoretical calculations and conjugates with formulation-compatible moieties are synthesized. As predicted, the conjugates exhibit enhanced solubility and loading efficiency in a nano-emulsion.
The goal of the third study is to rationally design a stable unimolecular star copolymer that, as a unimer, does not disassemble upon the dilution that accompanies intravenous injection. Here, MD simulation is used to systematically investigate the solution properties of differently composed star copolymers. Overall, star copolymers with a hydrophobic PCL core ≤ 2 kDa and hydrophilic PEG blocks approaching 14.6 kDa per arm are predicted to form unimolecular micelles that remain unimeric at high concentrations.
The studies presented in this thesis demonstrate that theoretical approaches are useful for fast pre-screening of drug formulation materials and for the development of delivery systems and drug derivatives.
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Rational Design of Drug Formulations using Computational ApproachesHuynh, Loan 24 July 2013 (has links)
Theory has been used to complement experiment in the development of both drugs and delivery systems. Theoretical methods are capable of identifying the molecular basis of drug formulation inadequacies and systematic theoretical studies may suggest fruitful avenues for material modification. This thesis highlights the utility of computer-based theoretical calculations for guiding the design of drug formulations and enhancing material-drug compatibility and stability. Specifically, the present work explores the applications of semi-empirical methods and atomistic molecular dynamics (MD) simulations to enhance the performance of nano-emulsions and polymer micelle formulations for the delivery of hydrophobic drugs. This work includes three separate studies preceded by an introductory summary of available theoretical techniques.
The first study evaluates the accuracy and reliability of semi-empirical methods and MD simulations as means to select suitable excipients to formulate the anti-cancer drug docetaxel in an emulsion. Here, simulations accurately predict the rank order of drug solubility in various excipients, suggesting that simulation is useful for library enrichment.
In the second study, a drug conjugation approach is used to further improve the stability and solubility of docetaxel in a triglyceride-based nano-emulsion. Here, optimal conjugates are identified with computer-based theoretical calculations and conjugates with formulation-compatible moieties are synthesized. As predicted, the conjugates exhibit enhanced solubility and loading efficiency in a nano-emulsion.
The goal of the third study is to rationally design a stable unimolecular star copolymer that, as a unimer, does not disassemble upon the dilution that accompanies intravenous injection. Here, MD simulation is used to systematically investigate the solution properties of differently composed star copolymers. Overall, star copolymers with a hydrophobic PCL core ≤ 2 kDa and hydrophilic PEG blocks approaching 14.6 kDa per arm are predicted to form unimolecular micelles that remain unimeric at high concentrations.
The studies presented in this thesis demonstrate that theoretical approaches are useful for fast pre-screening of drug formulation materials and for the development of delivery systems and drug derivatives.
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