10 research outputs found
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Process of forming crosslinked copolymer film, crosslinked copolymer film formed thereby, and water purification membrane
Azidoaryl-substituted cyclooctene monomers and synthesized and used in the preparation of various copolymers. Among these copolymers are those prepared from ring-opening metathesis polymerization of cyclooctene, polyethylene glycol-substituted cyclooctene, and azidoaryl-substituted cyclooctene. These copolymers are useful in the formation of crosslinked films that reduce fouling of water purification membranes.Board of Regents, University of Texas Syste
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Synthesis and Interfacial Behavior of Functional Amphiphilic Graft Copolymers Prepared by Ring-opening Metathesis Polymerization
This thesis describes the synthesis and application of a new series of amphiphilic graft copolymers with a hydrophobic polyolefin backbone and pendent hydrophilic poly(ethylene glycol) (PEG) grafts. These copolymers are synthesized by ruthenium benzylidene-catalyzed ring-opening metathesis polymerization (ROMP) of PEG-functionalized cyclic olefin macromonomers to afford polycyclooctene- graft -PEG (PCOE- g -PEG) copolymers with a number of tunable features, such as PEG graft density and length, crystallinity, and amphiphilicity. Macromonomers of this type were prepared first by coupling chemistry using commercially available PEG monomethyl ether derivatives and a carboxylic acid-functionalized cycloctene. In a second approach, macromonomers possessing a variety of PEG lengths were prepared by anionic polymerization of ethylene oxide initiated by cyclooctene alkoxide. This methodology affords a number of benefits compared to coupling chemistry including an expanded PEG molecular weight range, improved hydrolytic stability of the PEG-polycyclooctene linkage, and a reactive hydroxyl end-group functionality for optional attachment of biomolecules and probes. The amphiphilic nature of these graft copolymers was exploited in oil-water interfacial assembly, and the unsaturation present in the polycyclooctene backbone was utilized in covalent cross-linking reactions to afford hollow polymer capsules. In one approach, a bis -cyclooctene PEG derivative was synthesized and co-assembled with PCOE-g-PEG at the oil-water interface. Upon addition of a ruthenium benzylidene catalyst, a cross-linked polymer shell is formed through ring-opening cross-metathesis between the bis -cyclooctene cross-linker and the residual olefins in the graft copolymer. By incorporating a fluorescent-labeled cyclooctene into the graft copolymer, both oil-water interfacial segregation and effective cross-linking were confirmed using confocal laser scanning microscopy (CLSM). In a second approach, reactive functionality capable of chemical cross-linking was incorporated directly into the polymer backbone by synthesis and copolymerization of phenyl azide and acyl hydrazine-functional cyclooctene derivatives. Upon assembly, these reactive polymers were cross-linked by photolysis (in the phenyl azide case) or by addition of glutaraldehyde (in the acyl hydrazine case) to form mechanically robust polymer capsules with tunable degradability ( i.e. non-degradable or pH-dependent degradability). This process permits the preparation of both oil-in-water and water-in-oil capsules, thus enabling the encapsulation of hydrophobic or hydrophilic reagents in the capsule core. Furthermore, the assemblies can be sized from tens of microns to the 150 nm - 1 µm size range by either membrane extrusion or ultrasonication techniques. These novel capsules may be well-suited for a number of controlled release applications, where the transport of encapsulated compounds can be regulated by factors such as cross-link density, hydrolytic stability, and environmental triggers such as changes in pH
Relative Performance of Alkynes in Copper-Catalyzed Azide–Alkyne Cycloaddition
Copper-catalyzed azide–alkyne
cycloaddition (CuAAC) has
found numerous applications in a variety of fields. We report here
only modest differences in the reactivity of various classes of terminal
alkynes under typical bioconjugative and preparative organic conditions.
Propargyl compounds represent an excellent combination of azide reactivity,
ease of installation, and cost. Electronically activated propiolamides
are slightly more reactive, at the expense of increased propensity
for Michael addition. Certain alkynes, including tertiary propargyl
carbamates, are not suitable for bioconjugation due to copper-induced
fragmentation. A fluorogenic probe based on such reactivity is available
in one step from rhodamine 110 and can be useful for optimization
of CuAAC conditions
Encapsidated Atom-Transfer Radical Polymerization in Qβ Virus-like Nanoparticles
Virus-like particles (VLPs) are unique macromolecular structures that hold great promise in biomedical and biomaterial applications. The interior of the 30 nm-diameter Qβ VLP was functionalized by a three-step process: (1) hydrolytic removal of endogenously packaged RNA, (2) covalent attachment of initiator molecules to unnatural amino acid residues located on the interior capsid surface, and (3) atom-transfer radical polymerization of tertiary amine-bearing methacrylate monomers. The resulting polymer-containing particles were moderately expanded in size; however, biotin-derivatized polymer strands were only very weakly accessible to avidin, suggesting that most of the polymer was confined within the protein shell. The polymer-containing particles were also found to exhibit physical and chemical properties characteristic of positively charged nanostructures, including the ability to easily enter mammalian cells and deliver functional small interfering RNA