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 30 for “"Degree of Branching"”.
-
Synthesis and Characterization of Multiphase, Highly Branched Polymers
… for hyperbranched polymers. However, the high degree of branching in these polymers restricts entanglement and the resultant mechanical properties suffer. Longer distances between branch points may allow entanglements. Highly branched polymers, where linear units are incorporated between branch …
-
Synthesis and Characterization of Branched Macromolecules for High Performance Elastomers, Fibers, and Films
An A2 + B3 polymerization for the synthesis of hyperbranched polymers was altered using oligomeric precursors in place of either one or both of the monomer pairs to synthesize highly branched macromolecules. Unique topologies that are intermediates between long-chain branched and hyperbranched …
-
Structure and dynamics of confined chain molecules
… they have no methyl side-branches. As the amount of branching increased, the layering was disrupted so that no oscillatory surface forces were measured. On the other hand, molecules with low degree of branching showed a weakly ordered structure, yet layering persisted. Curiously, all of these …
-
"Part A. Functional Modular Phenylacetylene Units: A ""Molecular Turnstile."" Part B. Progress Towards an Electrochemically Active 9-Phenylcarbazole Hyperbranched Polymer"
Part B. Progress towards a new family of hyperbranched polymers based on the condensation of an AB$\sb2$ 9-phenylcarbazole monomer 169 has been described. Initial condensation reactions have provided material of greater than 100,000 mw as determined by GPC. No estimate of the degree of branching …
-
Diffusion and Relaxometry Studies in Mesoporous Systems using Nuclear Magnetic Resonance
The role of diffusion plays a crucial part in catalytic reactions by facilitating the transport of reactants to the catalysts' active sites. Numerous chemical processes involve species with branches, such as the hydroisomerisation of fuels, Low-Density Polyethylene (LDPE) production, and the …
-
Polyhydroxyethers synthesis, analysis and crosslinking
… the "Taffy Process" which involves the reaction of 4,4′ isopropylidene diphenol (Bis-A) with epichlorohydrin under basic conditions. They may also synthesized from the base catalyzed reaction of diglycidylether of Bis-A and Bis-A, which is referred to as the "Advancement Process". Both processes …
-
Combinatorics and Modelling of Highly Branched Polymers
… hyperbranched polymers have a found a variety of chemical applications owing to their unique structural and functional properties, but in many cases are still lacking sufficient theoretical characterization. This thesis takes marginal steps toward addressing this by firstly studying a …
-
The characterization of starches and maltodextrins by proton nuclear magnetic resonance spectroscopy
A new method to quantify the degree of branching in $\alpha$-glucans using proton nuclear magnetic resonance (NMR) has been developed. Instrument parameters and sample conditions were investigated for their effect on determining the $\alpha$-(1,4)/$\alpha$-(1,6) linkage ratios of starches. Two …
-
Production of mid-chain branched detergent-range olefins over shape-selective acid catalysts
For the purpose of producing mid-chain mono-methyl branched olefins, a range of acid catalysts (MFI, BEA, TON and amorphous silica-alumina) were screened for the dimerization of 1-hexene, under generally mild conditions, viz. 150 - 170°C, 20 - 40 bar and 1 - 4h-1 WHSV. It was postulated that …
-
Chemical characterization of dissolved organic matter (DOM) in seawater : structure, cycling, and the role of biology
The goal of this thesis is to investigate three different areas relating to the characterization of dissolved organic matter (DOM): further determination of the chemical compounds present in high molecular weight DOM (HMWDOM), the cycling of individual compounds within the HMWDOM pool, and the …
-
Definierte Synthese hyperverzweigter Copolyester und Copolyether mit kontrolliertem Verzweigungsgrad
… verschiedener analytischer Methoden (NMR, MALDI-TOF MS, VPO, GPC, LALLS, Viskosimetrie, Rheologie, DSC). Durch Copolymerisationen aktivierter Dihydroxybenzoesäure als AB2-Monomer mit Monohydroxybenzoesäuren als AB-Monomere konnte eine Kontrolle des Verzweigungsgrads nachgewiesen werden (NMR). Die …
-
Branched Glycopolymers
Linear and branched glycopolymers of a sugar-carrying acrylate monomer, 3-O-acryloyl-1,2:5,6-di-O-isopropylidene-alpha-D-glucofuranose (AIGlc), were synthesized via atom transfer radical polymerization (ATRP). Self-condensing vinyl copolymerization (SCVCP) via ATRP was employed for the synthesis of …
-
Influence of basicity in Fischer-Tropsch synthesis over supported iron-based catalysts
… is a well-established process for the production of synthetic fuels, waxes and high-value chemicals, such as α-olefins. A draw-back of the currently used iron-based catalysts is their short lifetime, caused by sintering and particle break-up. These disadvantages might be overcome by utilizing a …
-
The characterisation and cetane number determination of synthetic diesel fuels
… synthetic fuel plants produce large quantities of lower alkenes which can be catalytically oligomerized to liquid transportation fuels. In the screening of experimental catalysts for the production of diesel-range fuels, it is important to measure the quality, as well as the quantity, of the …
-
Chemical characterization of dissolved organic matter (DOM) in seawater : structure, cycling, and the role of biology
The goal of this thesis is to investigate three different areas relating to the characterization of dissolved organic matter (DOM): further determination of the chemical compounds present in high molecular weight DOM (HMWDOM), the cycling of individual compounds within the HMWDOM pool, and the …
-
Synthesis and characterization of hyperbranched poly(urea-urethane)s
… (DEA) or diisopropanolamine (DIPA). Conditions of polymerisation reactions were optimised. Complete structural analysis using 1H and 13C NMR for the obtained aromatic polymers was carried out. Degree of branching up to 70% was calculated. Aliphatic polymers have spectra with overlapped signals …
-
N-Vinylcaprolactam based Bulk and Microgels: Synthesis, Structural Formation and Characterization by Dynamic Light Scattering
… methods were used for characterization of properties and formation of networks of different dimension, based on N-vinylcaprolactam (VCL). Formation of PVCL microgels in presence of poly(vinyl alcohol) as stabilizer was studied. Size of resulting microgels strongly depends on the …
-
Topology and Telechelic Functionality Control in Polyester Design
Research efforts have focused on synthesis of linear, long-chain branched, and novel crosslinked polyesters for applications spanning from pressure sensitive adhesives to biomedical applications. Altering polymer topology and functionality using different synthetic strategies was enabled tailoring …
-
Synthesis and applications of core functional hyperbranched polyglycerol
This dissertation details the synthesis of a new alkyne core functional hyperbranched polyglycerol and describes their use as potential monomolecular imprinting materials and increasing the photostability of fluorescent dyes. The first chapter describes two methods for the synthesis of the polymers …
-
Upcycling of Polystyrene, Polyolefin, and Polyvinyl Chloride Waste into Chemicals, Surfactants, and Lubricants
… (PVC), and polystyrene (PS), account for >60% of annual plastic production owing to their excellent physicochemical and mechanical performance in many applications. As a consequence of widespread use, addition polymerization plastics contribute significantly to plastic pollution. Unfortunately, …
Page 1 of 2