1,2 A major goal is to devise photodegradable polymers with a tunable onset of degradation and wi... more 1,2 A major goal is to devise photodegradable polymers with a tunable onset of degradation and with a specific degradation rate. In order to design a polymer with such properties, it is necessary to identify the experimental parameters that affect degradation rates and to determine how those parameters affect the degradation mechanism. A typical first step in these studies is to determine the kinetics of the degradation reaction. An interesting observation from these kinetic studies is that the photodegradation rates of solid-state polymers are often biphasic, showing a relatively fast rate constant during the initial period of irradiation but a slower rate constant at longer times. 3,4 This talk reports the results of our investigation into the origin of the biphasic kinetics behavior. Experimental Materials. All manipulations were carried out using standard Schlenk techniques or in a Vacuum Atmospheres Co. glove box under a nitrogen atmosphere. Unless otherwise noted, HPLC grade s...
xxii, 143 p. ; ill. (some col.) A print copy of this title is available through the UO Libraries.... more xxii, 143 p. ; ill. (some col.) A print copy of this title is available through the UO Libraries. Search the library catalog for the location and call number.
... on the polymer project during my tenure in the Tyler lab: Rui Chen, John Harris, Ginger Shult... more ... on the polymer project during my tenure in the Tyler lab: Rui Chen, John Harris, Ginger Shultz, Katherine Klug, and Jennifer Zemke. ... to my education and career development was my involvement in the UO Women in Graduate Science founded by my dear friend Sara J. Staggs. ...
... http://ad. usno. navy. mil/wd s/. Teague, Tom. 2004. Simple techniques of measure-ment. Obser... more ... http://ad. usno. navy. mil/wd s/. Teague, Tom. 2004. Simple techniques of measure-ment. Observing and Measuring Visual Double Stars, ed. Bob Argyle. London: Springer. Chris Estrada is a bio-chemistry major at Allen Hancock College. ...
... on the polymer project during my tenure in the Tyler lab: Rui Chen, John Harris, Ginger Shult... more ... on the polymer project during my tenure in the Tyler lab: Rui Chen, John Harris, Ginger Shultz, Katherine Klug, and Jennifer Zemke. ... to my education and career development was my involvement in the UO Women in Graduate Science founded by my dear friend Sara J. Staggs. ...
A tricyclic ketone is formed from cyclohexanone and cyclohexenone in strong acid solutions. The s... more A tricyclic ketone is formed from cyclohexanone and cyclohexenone in strong acid solutions. The structure is confirmed by X-ray crystallography.
Perhydrophenanthrene-1,5,10-trione (6) was isolated from the reaction of methyl 3-(carboxymethyl)... more Perhydrophenanthrene-1,5,10-trione (6) was isolated from the reaction of methyl 3-(carboxymethyl)cyclohexanone and cyclohexenone in a tandem Michael–Claisen reaction. NMR and X-ray analysis confirmed the structure of the product.
Photochemically degradable polymers and plastics are reviewed with an emphasis on the environment... more Photochemically degradable polymers and plastics are reviewed with an emphasis on the environmental and molecular factors that control the onset of degradation and the rate of degradation. A number of principles are beginning to emerge for the design of viable photochemically degradable plastics. Among the principles discussed are those relating to the effects of chromophores, initiators, antioxidants, temperature, oxygen diffusion into the plastic, polymer crystallinity, tensile and compressive stress, and the absorbed light intensity on the plastic. To obtain a plastic with a controlled lifetime and a specific rate of degradation, many of these parameters can be controlled or adjusted in the design stage of the plastic.
This article outlines the difficulties associated with measuring quantum yields for solid-state s... more This article outlines the difficulties associated with measuring quantum yields for solid-state samples using a high-pressure mercury arc lamp as the irradiation source. Details are given for the conversion of an inexpensive frequency-doubled neodymium-doped yttrium aluminum garnet (Nd:YAG) diode laser pointer module into a viable irradiation source. The modified Nd:YAG laser was incorporated into a computer-controlled system, which allowed for the simultaneous irradiation and spectroscopic monitoring of the sample. The data obtained with the Nd:YAG diode laser system show far less scatter than data obtained with a high-pressure Hg arc lamp, and consequently the degradation rates obtained with the laser system could be calculated with far greater accuracy.
Journal of Inorganic and Organometallic Polymers and Materials, 2009
The effects of time-dependent morphology changes on the photochemical degradation efficiencies of... more The effects of time-dependent morphology changes on the photochemical degradation efficiencies of polymers were investigated using the segmented polyurethane 1. A segmented polyurethane was chosen for this study because segmented polyurethanes have distinct hard (crystalline) and soft (amorphous) morphologies in the solid-state. It is known that, as these polymers cure, the hard and soft domains expand in the days and weeks following preparation. Experiments showed that the quantum yields for degradation of thin films of polymer 1 decreased over a period of about 30 days following preparation of the polymer films. Infrared spectroscopy showed an increase in crystallinity in the polymer during this curing period. These results are consistent with the hypothesis that the rate of photodegradation in polymer systems is controlled by the separation rate of the photogenerated radical pair relative to the rate of radical-radical recombination (Scheme 3). An important factor that controls the ratio of these two rates is the crystallinity of the polymer; an increase in crystallinity favors the radical-radical recombination reaction. The effect of tensile stress on photodegradation efficiencies was also studied. Two samples of the same polymer, one more crystalline than the other, were examined. The quantum yields for degradation of the more crystalline sample were less affected by tensile stress than the less crystalline sample. Tensile stress is known to order polymer chains and the results are again interpreted as being consistent with the idea that crystallinity is an important factor in controlling the efficiency of polymer photodegradation.
Journal of Inorganic and Organometallic Polymers and Materials, 2007
The effect of temperature on the degradation quantum yield of a poly(vinyl chloride) polymer with... more The effect of temperature on the degradation quantum yield of a poly(vinyl chloride) polymer with Cp2Mo2(CO)6 units incorporated into its chains was studied (Cp = cyclopentadienyl). The polymer is photochemically reactive in the absence of oxygen because the CpMo(CO)3 radicals formed by photolysis of the Mo–Mo bonds react with C–Cl bonds to form CpMo(CO)3Cl units. Quantum yields as a function of temperature were obtained for this polymer and for two control systems, Cp′2Mo2(CO)6 dispersed in PVC and Cp′2Mo2(CO)6 in hexane/CCl4 solution (Cp′ = η5-C5H4CH3). The quantum yields of the two control systems showed only slight increases with an increase in temperature. For the reaction in hexane/CCl4, this temperature dependence is attributed to the decrease in viscosity of the solution and the subsequent decrease in the radical-radical recombination efficiency. For the Cp′2Mo2(CO)6 dispersed in PVC, the small temperature dependence is attributed to an increase in free volume as the temperature increases. In contrast to these results, the temperature dependence of the quantum yield of the PVC polymer with Cp2Mo2(CO)6 units along its chains is relatively large. It is proposed that an increase in temperature facilitates the polymer chain relaxation processes (involving recoil and rotation) following photolysis of the Mo–Mo bond. The radical–radical recombination efficiency is subsequently decreased, which leads to a net increase in chain cleavage and degradation efficiency.
1,2 A major goal is to devise photodegradable polymers with a tunable onset of degradation and wi... more 1,2 A major goal is to devise photodegradable polymers with a tunable onset of degradation and with a specific degradation rate. In order to design a polymer with such properties, it is necessary to identify the experimental parameters that affect degradation rates and to determine how those parameters affect the degradation mechanism. A typical first step in these studies is to determine the kinetics of the degradation reaction. An interesting observation from these kinetic studies is that the photodegradation rates of solid-state polymers are often biphasic, showing a relatively fast rate constant during the initial period of irradiation but a slower rate constant at longer times. 3,4 This talk reports the results of our investigation into the origin of the biphasic kinetics behavior. Experimental Materials. All manipulations were carried out using standard Schlenk techniques or in a Vacuum Atmospheres Co. glove box under a nitrogen atmosphere. Unless otherwise noted, HPLC grade s...
xxii, 143 p. ; ill. (some col.) A print copy of this title is available through the UO Libraries.... more xxii, 143 p. ; ill. (some col.) A print copy of this title is available through the UO Libraries. Search the library catalog for the location and call number.
... on the polymer project during my tenure in the Tyler lab: Rui Chen, John Harris, Ginger Shult... more ... on the polymer project during my tenure in the Tyler lab: Rui Chen, John Harris, Ginger Shultz, Katherine Klug, and Jennifer Zemke. ... to my education and career development was my involvement in the UO Women in Graduate Science founded by my dear friend Sara J. Staggs. ...
... http://ad. usno. navy. mil/wd s/. Teague, Tom. 2004. Simple techniques of measure-ment. Obser... more ... http://ad. usno. navy. mil/wd s/. Teague, Tom. 2004. Simple techniques of measure-ment. Observing and Measuring Visual Double Stars, ed. Bob Argyle. London: Springer. Chris Estrada is a bio-chemistry major at Allen Hancock College. ...
... on the polymer project during my tenure in the Tyler lab: Rui Chen, John Harris, Ginger Shult... more ... on the polymer project during my tenure in the Tyler lab: Rui Chen, John Harris, Ginger Shultz, Katherine Klug, and Jennifer Zemke. ... to my education and career development was my involvement in the UO Women in Graduate Science founded by my dear friend Sara J. Staggs. ...
A tricyclic ketone is formed from cyclohexanone and cyclohexenone in strong acid solutions. The s... more A tricyclic ketone is formed from cyclohexanone and cyclohexenone in strong acid solutions. The structure is confirmed by X-ray crystallography.
Perhydrophenanthrene-1,5,10-trione (6) was isolated from the reaction of methyl 3-(carboxymethyl)... more Perhydrophenanthrene-1,5,10-trione (6) was isolated from the reaction of methyl 3-(carboxymethyl)cyclohexanone and cyclohexenone in a tandem Michael–Claisen reaction. NMR and X-ray analysis confirmed the structure of the product.
Photochemically degradable polymers and plastics are reviewed with an emphasis on the environment... more Photochemically degradable polymers and plastics are reviewed with an emphasis on the environmental and molecular factors that control the onset of degradation and the rate of degradation. A number of principles are beginning to emerge for the design of viable photochemically degradable plastics. Among the principles discussed are those relating to the effects of chromophores, initiators, antioxidants, temperature, oxygen diffusion into the plastic, polymer crystallinity, tensile and compressive stress, and the absorbed light intensity on the plastic. To obtain a plastic with a controlled lifetime and a specific rate of degradation, many of these parameters can be controlled or adjusted in the design stage of the plastic.
This article outlines the difficulties associated with measuring quantum yields for solid-state s... more This article outlines the difficulties associated with measuring quantum yields for solid-state samples using a high-pressure mercury arc lamp as the irradiation source. Details are given for the conversion of an inexpensive frequency-doubled neodymium-doped yttrium aluminum garnet (Nd:YAG) diode laser pointer module into a viable irradiation source. The modified Nd:YAG laser was incorporated into a computer-controlled system, which allowed for the simultaneous irradiation and spectroscopic monitoring of the sample. The data obtained with the Nd:YAG diode laser system show far less scatter than data obtained with a high-pressure Hg arc lamp, and consequently the degradation rates obtained with the laser system could be calculated with far greater accuracy.
Journal of Inorganic and Organometallic Polymers and Materials, 2009
The effects of time-dependent morphology changes on the photochemical degradation efficiencies of... more The effects of time-dependent morphology changes on the photochemical degradation efficiencies of polymers were investigated using the segmented polyurethane 1. A segmented polyurethane was chosen for this study because segmented polyurethanes have distinct hard (crystalline) and soft (amorphous) morphologies in the solid-state. It is known that, as these polymers cure, the hard and soft domains expand in the days and weeks following preparation. Experiments showed that the quantum yields for degradation of thin films of polymer 1 decreased over a period of about 30 days following preparation of the polymer films. Infrared spectroscopy showed an increase in crystallinity in the polymer during this curing period. These results are consistent with the hypothesis that the rate of photodegradation in polymer systems is controlled by the separation rate of the photogenerated radical pair relative to the rate of radical-radical recombination (Scheme 3). An important factor that controls the ratio of these two rates is the crystallinity of the polymer; an increase in crystallinity favors the radical-radical recombination reaction. The effect of tensile stress on photodegradation efficiencies was also studied. Two samples of the same polymer, one more crystalline than the other, were examined. The quantum yields for degradation of the more crystalline sample were less affected by tensile stress than the less crystalline sample. Tensile stress is known to order polymer chains and the results are again interpreted as being consistent with the idea that crystallinity is an important factor in controlling the efficiency of polymer photodegradation.
Journal of Inorganic and Organometallic Polymers and Materials, 2007
The effect of temperature on the degradation quantum yield of a poly(vinyl chloride) polymer with... more The effect of temperature on the degradation quantum yield of a poly(vinyl chloride) polymer with Cp2Mo2(CO)6 units incorporated into its chains was studied (Cp = cyclopentadienyl). The polymer is photochemically reactive in the absence of oxygen because the CpMo(CO)3 radicals formed by photolysis of the Mo–Mo bonds react with C–Cl bonds to form CpMo(CO)3Cl units. Quantum yields as a function of temperature were obtained for this polymer and for two control systems, Cp′2Mo2(CO)6 dispersed in PVC and Cp′2Mo2(CO)6 in hexane/CCl4 solution (Cp′ = η5-C5H4CH3). The quantum yields of the two control systems showed only slight increases with an increase in temperature. For the reaction in hexane/CCl4, this temperature dependence is attributed to the decrease in viscosity of the solution and the subsequent decrease in the radical-radical recombination efficiency. For the Cp′2Mo2(CO)6 dispersed in PVC, the small temperature dependence is attributed to an increase in free volume as the temperature increases. In contrast to these results, the temperature dependence of the quantum yield of the PVC polymer with Cp2Mo2(CO)6 units along its chains is relatively large. It is proposed that an increase in temperature facilitates the polymer chain relaxation processes (involving recoil and rotation) following photolysis of the Mo–Mo bond. The radical–radical recombination efficiency is subsequently decreased, which leads to a net increase in chain cleavage and degradation efficiency.
Uploads
Papers by Bevin Daglen