Biomedical subjects

Kenneth B Wagener

Publications and source records attributed to Kenneth B Wagener.

3 recordsLinked to original sources

PubMed2006

Functionality dependent olefin activity in acyclic diene metathesis polymerization: mass spectrometry characterization of amino acid functionalized olefins.

Mass spectrometry has become an essential tool in delineating the structural properties of a new series of amino acid functionalized acyclic diene metathesis (ADMET) polymers known as bioolefins. These measurements, coupled with the measurement of the polymers chemical and physical properties, assist in the determination of their utility as biomaterials. In the present study, a set of five polymers with different bulk size and electronic properties were chosen for structural analyses by MALDI-TOF, MALDI-FTICR, and DIOS-TOF. The obtained data show that due to the competing metathesis and isomerization during ADMET, depending on their structural properties, the olefins display different selectivity toward main metathesis or isomerized products.

Acids, Acyclic↗

PubMed2004

Modeling branched polyethylene: copolymers possessing precisely placed ethyl branches.

A structural investigation of precise ethylene/1-butene (EB) copolymers has been completed using step polymerization chemistry. The synthetic methodology needed to generate four model copolymers is described; their primary and higher level structure is characterized. The copolymers possess an ethyl branch on every 9th, 15th, and 21st carbon along the backbone of linear polyethylene. Melting points and heats of fusion decrease with increased branch frequency. Differential scanning calorimetry and infrared spectroscopy show highly disordered crystal structures favoring ethyl branch inclusion. On the other hand, the EB copolymers contain high concentrations of kink and gauche defects independent of branch frequency. These model copolymers are compared with random copolymers produced using traditional chain chemistry and previously synthesized ADMET EP copolymers.

Journal Article↗

PubMed2003

Modeling random methyl branching in ethylene/ propylene copolymers using metathesis chemistry: synthesis and thermal behavior.

The structure of random ethylene/propylene (EP) copolymers has been modeled using step polymerization chemistry. Six ethylene/propylene model copolymers have been prepared via acyclic diene metathesis (ADMET) polymerization and characterized for primary and higher level structure using in-depth NMR, IR, DSC, WAXD, and GPC analysis. These copolymers possess 1.5, 7.1, 13.6, 25.0, 43.3, and 55.6 methyl branches per 1000 carbons. Examination of these macromolecules by IR and WAXD analysis has demonstrated the first hexagonal phase in EP copolymers containing high ethylene content (90%) without the influence of sample manipulation (temperature, pressure, or radiation). Thermal behavior studies have shown that the melting point and heat of fusion decrease as the branch content increases. Further, comparisons have been made between these random ADMET EP copolymers, random EP copolymers made by typical chain addition techniques, and precisely branched ADMET EP copolymers.

Journal Article↗