Julian Murphy - Academia.edu (original) (raw)
Papers by Julian Murphy
MRS Proceedings, 2004
ABSTRACTPoly(m-carboranyl-siloxane) elastomers containing a mixture of di-methyl- and methyl(phen... more ABSTRACTPoly(m-carboranyl-siloxane) elastomers containing a mixture of di-methyl- and methyl(phenyl)-silyl units were synthesised using the Ferric Chloride catalysed condensation reaction between di-chloro-di-organosilane and 1, 7-bis(di-methyl(methoxy)silyl)-m-carborane. These prepared polymers were aged either by heating in air at elevated temperature or by λ-irradiation from a 60Co source. Multinuclear (1H, 13C and 11B) solid and solution state nuclear magnetic resonance was used to evaluate degradation. λ-irradiation doses to 1 MGy were found to induce only a small reduction in elastomer properties as evidenced by a reduction in segmental chain dynamics. Ageing at temperatures below 350°C similarly displayed a small reduction in segmental chain dynamics together and a concomitant weight loss as measured by differential scanning calorimetry. Above 350°C degradation of the elastomer was dramatic with a decreased segmental chain dynamics and oxidation of the carborane cage, vide in...
Science and Technology of Advanced Materials, 2008
Reported here is the synthesis and subsequent characterization of the physical and chemical prope... more Reported here is the synthesis and subsequent characterization of the physical and chemical properties of novel polysiloxane elastomers modified with a series of polyhedraloligomericsilsequioxane (POSS) molecular silicas. The physical properties of the formulated nanocomposite systems have been characterized with a combination of dynamic mechanical analysis (DMA), broadband dielectric spectroscopy (BDS) and confocal Raman microscopy. The results of the physical property characterization demonstrate that the incorporation of low levels (1-4% by wt.) of POSS particles into the polysiloxane network leads to significant improvements in the mechanical properties of the elastomer and significantly alters the motional chain dynamics of the system as a whole. The results of studies performed to assess the long-term stability of these novel nanocomposite systems have demonstrated that POSS physical property modifiers can significantly alter the thermal stability of polysiloxane elastomers. Physically dispersed POSS has also been shown in some cases to be both mobile and disruptive within the polysiloxane networks, agglomerating into domains on a micron scale and migrating to the surface of the elastomers. This work demonstrates both the potential of POSS nanoparticles as physical property modifiers and describes the effects of POSS on the physical and chemical stability of polysiloxane systems.
Radiation Physics and Chemistry, 2001
A range of copolymers containing styrene and epoxystyrene, when formulated with a photo-acid gene... more A range of copolymers containing styrene and epoxystyrene, when formulated with a photo-acid generator, undergo a cross-linking reaction by a chain reaction mechanism when exposed to high-energy radiation in an electron beam lithographic writing machine. The sensitivities of the formulations are shown to correlate with a simple kinetic model for the radiation chemistry of the system. Deductions about the nature of the cross-linking species have been made by comparing the behaviour of the epoxystyrene system with that observed for an epoxy novolac.
Radiation Physics and Chemistry, 2002
Irradiation of polymer samples using an accelerated beam of He++ ions passed through a 10μm thick... more Irradiation of polymer samples using an accelerated beam of He++ ions passed through a 10μm thick window of havar foil has been performed. Such an irradiation simulates the effects of large α radiation doses. The experimental set up was designed so that the irradiated material was contained within a small sample chamber, which was isolated from the main vacuum chamber
Polymer Degradation and Stability, 2006
We report in our studies to assess the impact of gamma radiation on silica and on the silicapoly... more We report in our studies to assess the impact of gamma radiation on silica and on the silicapolymer interface in filled polysiloxane rubber. Electron spin resonance (ESR) and solid-state nuclear magnetic resonance (NMR) studies have been performed on samples exposed to gamma ...
Journal of Materials Chemistry, 1997
The version in the Kent Academic Repository may differ from the final published version. Users ar... more The version in the Kent Academic Repository may differ from the final published version. Users are advised to check http://kar.kent.ac.uk for the status of the paper. Users should always cite the published version of record.
Journal of Materials Chemistry, 1997
Radiation chemistry and the lithographic performance of chemical amplification resists formulated... more Radiation chemistry and the lithographic performance of chemical amplification resists formulated from poly(4-epoxystyrene-stat-styrene) and a photoacid generator Richard G. Jones,* Gerard PG. ... 9 RG Jones, Y. Matsubayashi, P. Miller Tate and DR Brambley, J. Electrochem. ...
MRS Proceedings, 2004
ABSTRACTExperimentally investigating ageing caused by irradiation with energetic particles is ver... more ABSTRACTExperimentally investigating ageing caused by irradiation with energetic particles is very difficult. Radioactive sources can be employed but these are difficult to handle and contaminate the material being irradiated precluding subsequent chemical and physical characterisation. The penetration of energetic particles also tends to be small so any change is localised in the near surface region so only a small amount of material is irradiated. Analysing changes in such thin layers causes a number of problems. To simulate ageing induced by particle radiation polymer samples have been exposed to fast He++ ions in an accelerated ion beam. The ions pass through a 10μm thick window of Havar foil before impacting upon the sample. Volatile species evolved from the materials upon bombardment are contained within the irradiation chamber by the foil window. Analysis of such species is shown to be a highly sensitive probe for investigating chemical changes in the exposed materials. A num...
MRS Proceedings, 2004
ABSTRACTPoly(m-carboranyl-siloxane) elastomers containing a mixture of di-methyl- and methyl(phen... more ABSTRACTPoly(m-carboranyl-siloxane) elastomers containing a mixture of di-methyl- and methyl(phenyl)-silyl units were synthesised using the Ferric Chloride catalysed condensation reaction between di-chloro-di-organosilane and 1, 7-bis(di-methyl(methoxy)silyl)-m-carborane. These prepared polymers were aged either by heating in air at elevated temperature or by λ-irradiation from a 60Co source. Multinuclear (1H, 13C and 11B) solid and solution state nuclear magnetic resonance was used to evaluate degradation. λ-irradiation doses to 1 MGy were found to induce only a small reduction in elastomer properties as evidenced by a reduction in segmental chain dynamics. Ageing at temperatures below 350°C similarly displayed a small reduction in segmental chain dynamics together and a concomitant weight loss as measured by differential scanning calorimetry. Above 350°C degradation of the elastomer was dramatic with a decreased segmental chain dynamics and oxidation of the carborane cage, vide in...
Science and Technology of Advanced Materials, 2008
Reported here is the synthesis and subsequent characterization of the physical and chemical prope... more Reported here is the synthesis and subsequent characterization of the physical and chemical properties of novel polysiloxane elastomers modified with a series of polyhedraloligomericsilsequioxane (POSS) molecular silicas. The physical properties of the formulated nanocomposite systems have been characterized with a combination of dynamic mechanical analysis (DMA), broadband dielectric spectroscopy (BDS) and confocal Raman microscopy. The results of the physical property characterization demonstrate that the incorporation of low levels (1-4% by wt.) of POSS particles into the polysiloxane network leads to significant improvements in the mechanical properties of the elastomer and significantly alters the motional chain dynamics of the system as a whole. The results of studies performed to assess the long-term stability of these novel nanocomposite systems have demonstrated that POSS physical property modifiers can significantly alter the thermal stability of polysiloxane elastomers. Physically dispersed POSS has also been shown in some cases to be both mobile and disruptive within the polysiloxane networks, agglomerating into domains on a micron scale and migrating to the surface of the elastomers. This work demonstrates both the potential of POSS nanoparticles as physical property modifiers and describes the effects of POSS on the physical and chemical stability of polysiloxane systems.
Radiation Physics and Chemistry, 2001
A range of copolymers containing styrene and epoxystyrene, when formulated with a photo-acid gene... more A range of copolymers containing styrene and epoxystyrene, when formulated with a photo-acid generator, undergo a cross-linking reaction by a chain reaction mechanism when exposed to high-energy radiation in an electron beam lithographic writing machine. The sensitivities of the formulations are shown to correlate with a simple kinetic model for the radiation chemistry of the system. Deductions about the nature of the cross-linking species have been made by comparing the behaviour of the epoxystyrene system with that observed for an epoxy novolac.
Radiation Physics and Chemistry, 2002
Irradiation of polymer samples using an accelerated beam of He++ ions passed through a 10μm thick... more Irradiation of polymer samples using an accelerated beam of He++ ions passed through a 10μm thick window of havar foil has been performed. Such an irradiation simulates the effects of large α radiation doses. The experimental set up was designed so that the irradiated material was contained within a small sample chamber, which was isolated from the main vacuum chamber
Polymer Degradation and Stability, 2006
We report in our studies to assess the impact of gamma radiation on silica and on the silicapoly... more We report in our studies to assess the impact of gamma radiation on silica and on the silicapolymer interface in filled polysiloxane rubber. Electron spin resonance (ESR) and solid-state nuclear magnetic resonance (NMR) studies have been performed on samples exposed to gamma ...
Journal of Materials Chemistry, 1997
The version in the Kent Academic Repository may differ from the final published version. Users ar... more The version in the Kent Academic Repository may differ from the final published version. Users are advised to check http://kar.kent.ac.uk for the status of the paper. Users should always cite the published version of record.
Journal of Materials Chemistry, 1997
Radiation chemistry and the lithographic performance of chemical amplification resists formulated... more Radiation chemistry and the lithographic performance of chemical amplification resists formulated from poly(4-epoxystyrene-stat-styrene) and a photoacid generator Richard G. Jones,* Gerard PG. ... 9 RG Jones, Y. Matsubayashi, P. Miller Tate and DR Brambley, J. Electrochem. ...
MRS Proceedings, 2004
ABSTRACTExperimentally investigating ageing caused by irradiation with energetic particles is ver... more ABSTRACTExperimentally investigating ageing caused by irradiation with energetic particles is very difficult. Radioactive sources can be employed but these are difficult to handle and contaminate the material being irradiated precluding subsequent chemical and physical characterisation. The penetration of energetic particles also tends to be small so any change is localised in the near surface region so only a small amount of material is irradiated. Analysing changes in such thin layers causes a number of problems. To simulate ageing induced by particle radiation polymer samples have been exposed to fast He++ ions in an accelerated ion beam. The ions pass through a 10μm thick window of Havar foil before impacting upon the sample. Volatile species evolved from the materials upon bombardment are contained within the irradiation chamber by the foil window. Analysis of such species is shown to be a highly sensitive probe for investigating chemical changes in the exposed materials. A num...