Andrew Hebb | University of Greenwich (original) (raw)

Papers by Andrew Hebb

Research paper thumbnail of Synthesis and Processing of Porous Polymers Using Supercritical Carbon Dioxide

Progress in Rubber Plastics and Recycling Technology, Nov 1, 2002

Research paper thumbnail of Synthesis of Structured Polymeric Materials Using Compressed Fluid Solvents

Acs Symposium Series, Jul 23, 2003

Research paper thumbnail of Synthesis and Processing of Porous Polymers Using Supercritical Carbon Dioxide

Progress in Rubber, Plastics and Recycling Technology, 2002

Research paper thumbnail of Synthesis of Well-defined Monolithic Porous Polymers Using Compressed Fluid Solvents

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Research paper thumbnail of Synthesis of Structured Polymeric Materials Using Compressed Fluid Solvents

ACS Symposium Series, 2003

Research paper thumbnail of Direct Synthesis of Nanosized NiCo 2 O 4 Spinel and Related Compounds via Continuous Hydrothermal Synthesis Methods

Industrial & Engineering Chemistry Research, 2007

A series of crystalline homometallic and heterometallic cobalt and nickel hydroxides and oxides w... more A series of crystalline homometallic and heterometallic cobalt and nickel hydroxides and oxides were prepared using a continuous hydrothermal flow synthesis system. In all syntheses, the relevant metal salt solutions were pumped under high pressure to meet pH or other chemical modifiers (H 2 O 2 or PVP) before the mixture was brought into contact with a feed of superheated (or supercritical) water, whereupon precipitation and particle growth occurred. The resulting nanoparticle (typically less than 100 nm in diameter) suspensions were collected from the outlet of the back-pressure regulator of the hydrothermal system. The collected suspensions were centrifuged, and the washed solids were freeze-dried prior to analyses. The nanopowders were characterized by a number of analytical methods including X-ray powder diffraction, Brunauer-Emmett-Teller (BET) surface area measurements, and simultaneous thermogravimetric analysis/differential scanning calorimetry.

Research paper thumbnail of Formation of porous natural-synthetic polymer composites using emulsion templating and supercritical fluid assisted impregnation

Polymer Bulletin, 2007

Porous natural-synthetic polymer composites were prepared using an alginate emulsion templating s... more Porous natural-synthetic polymer composites were prepared using an alginate emulsion templating step followed by supercritical carbon dioxide (sc-CO2) assisted impregnation (and subsequent polymerisation) of synthetic monomer mixtures. In the impregnation step, an initiator and either 2-hydroxyethylmethacrylate (HEMA), butylmethacrylate (BMA), ethyleneglycoldimethacrylate (EGDMA) or trimethylolpropanetrimethacrylate (TRIM) monomers, respectively, were used. After impregnation into the porous alginate foam, the synthetic monomer(s) were polymerised in situ, forming porous composites with increased stiffness. A number of methods were used to assess the effects of the impregnation/polymerisation process including uniaxial compression testing, scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), helium pycnometry and Fourier transform infra-red (FTIR) spectroscopy. Our results suggest that alginate foams impregnated with HEMA show higher weight gains and are stiffer than those impregnated with BMA. Such stiffer porous composites are potentially better suited than the unmodified materials in applications such as tissue engineering (cell-seeded) scaffolds, where mechanical conditioning is desired to stimulate cells for development of neo tissue growth.

Research paper thumbnail of Synthesis of porous cross-linked polymer monoliths using 1,1,1,2-tetrafluoroethane (R134a) as the porogen

Composites Science and Technology, 2003

In this paper, we describe the synthesis of porous, cross-linked polymethacrylate monoliths by fr... more In this paper, we describe the synthesis of porous, cross-linked polymethacrylate monoliths by free radical polymerization using 1,1,1,2-tetrafluoroethane (R134a) as the porogenic solvent. Solvent separations were simple (boiling point R134a=−26.5 °C) and the reactions were carried out at relatively low pressures (<20 bar). It was found that the surface area and the median pore diameter of the materials could be varied over a wide range (5–320 m2/g and 15 nm–5 μm, respectively) by varying the monomer concentration. By contrast, pressure had little influence on the structure of the materials due to the relatively incompressible nature of liquid R134a.

Research paper thumbnail of Structural Control in Porous Cross-Linked Poly(methacrylate) Monoliths Using Supercritical Carbon Dioxide as a “Pressure-Adjustable” Porogenic Solvent

Chemistry of Materials, 2003

The synthesis of permanently porous, highly cross-linked, poly(methacrylate) resins using supercr... more The synthesis of permanently porous, highly cross-linked, poly(methacrylate) resins using supercritical CO 2 is described. The pressure-adjustable solvent properties associated with supercritical fluid solvents are exploited to fine-tune the average pore size and surface area of the materials. It was found that the materials' properties varied in a discontinuous manner with respect to the CO 2 pressure. A minimum in the BET surface area (and a maximum in the pore diameter) was observed at a reaction pressure of approximately 2600 psi. These trends were rationalized by the fact that the mechanisms of nucleation, aggregation, and pore formation are highly sensitive to the nature of the porogenic solvent environment.

Research paper thumbnail of Synthesis and Processing of Porous Polymers Using Supercritical Carbon Dioxide

Progress in Rubber Plastics and Recycling Technology, Nov 1, 2002

Research paper thumbnail of Synthesis of Structured Polymeric Materials Using Compressed Fluid Solvents

Acs Symposium Series, Jul 23, 2003

Research paper thumbnail of Synthesis and Processing of Porous Polymers Using Supercritical Carbon Dioxide

Progress in Rubber, Plastics and Recycling Technology, 2002

Research paper thumbnail of Synthesis of Well-defined Monolithic Porous Polymers Using Compressed Fluid Solvents

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Research paper thumbnail of Synthesis of Structured Polymeric Materials Using Compressed Fluid Solvents

ACS Symposium Series, 2003

Research paper thumbnail of Direct Synthesis of Nanosized NiCo 2 O 4 Spinel and Related Compounds via Continuous Hydrothermal Synthesis Methods

Industrial & Engineering Chemistry Research, 2007

A series of crystalline homometallic and heterometallic cobalt and nickel hydroxides and oxides w... more A series of crystalline homometallic and heterometallic cobalt and nickel hydroxides and oxides were prepared using a continuous hydrothermal flow synthesis system. In all syntheses, the relevant metal salt solutions were pumped under high pressure to meet pH or other chemical modifiers (H 2 O 2 or PVP) before the mixture was brought into contact with a feed of superheated (or supercritical) water, whereupon precipitation and particle growth occurred. The resulting nanoparticle (typically less than 100 nm in diameter) suspensions were collected from the outlet of the back-pressure regulator of the hydrothermal system. The collected suspensions were centrifuged, and the washed solids were freeze-dried prior to analyses. The nanopowders were characterized by a number of analytical methods including X-ray powder diffraction, Brunauer-Emmett-Teller (BET) surface area measurements, and simultaneous thermogravimetric analysis/differential scanning calorimetry.

Research paper thumbnail of Formation of porous natural-synthetic polymer composites using emulsion templating and supercritical fluid assisted impregnation

Polymer Bulletin, 2007

Porous natural-synthetic polymer composites were prepared using an alginate emulsion templating s... more Porous natural-synthetic polymer composites were prepared using an alginate emulsion templating step followed by supercritical carbon dioxide (sc-CO2) assisted impregnation (and subsequent polymerisation) of synthetic monomer mixtures. In the impregnation step, an initiator and either 2-hydroxyethylmethacrylate (HEMA), butylmethacrylate (BMA), ethyleneglycoldimethacrylate (EGDMA) or trimethylolpropanetrimethacrylate (TRIM) monomers, respectively, were used. After impregnation into the porous alginate foam, the synthetic monomer(s) were polymerised in situ, forming porous composites with increased stiffness. A number of methods were used to assess the effects of the impregnation/polymerisation process including uniaxial compression testing, scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), helium pycnometry and Fourier transform infra-red (FTIR) spectroscopy. Our results suggest that alginate foams impregnated with HEMA show higher weight gains and are stiffer than those impregnated with BMA. Such stiffer porous composites are potentially better suited than the unmodified materials in applications such as tissue engineering (cell-seeded) scaffolds, where mechanical conditioning is desired to stimulate cells for development of neo tissue growth.

Research paper thumbnail of Synthesis of porous cross-linked polymer monoliths using 1,1,1,2-tetrafluoroethane (R134a) as the porogen

Composites Science and Technology, 2003

In this paper, we describe the synthesis of porous, cross-linked polymethacrylate monoliths by fr... more In this paper, we describe the synthesis of porous, cross-linked polymethacrylate monoliths by free radical polymerization using 1,1,1,2-tetrafluoroethane (R134a) as the porogenic solvent. Solvent separations were simple (boiling point R134a=−26.5 °C) and the reactions were carried out at relatively low pressures (<20 bar). It was found that the surface area and the median pore diameter of the materials could be varied over a wide range (5–320 m2/g and 15 nm–5 μm, respectively) by varying the monomer concentration. By contrast, pressure had little influence on the structure of the materials due to the relatively incompressible nature of liquid R134a.

Research paper thumbnail of Structural Control in Porous Cross-Linked Poly(methacrylate) Monoliths Using Supercritical Carbon Dioxide as a “Pressure-Adjustable” Porogenic Solvent

Chemistry of Materials, 2003

The synthesis of permanently porous, highly cross-linked, poly(methacrylate) resins using supercr... more The synthesis of permanently porous, highly cross-linked, poly(methacrylate) resins using supercritical CO 2 is described. The pressure-adjustable solvent properties associated with supercritical fluid solvents are exploited to fine-tune the average pore size and surface area of the materials. It was found that the materials' properties varied in a discontinuous manner with respect to the CO 2 pressure. A minimum in the BET surface area (and a maximum in the pore diameter) was observed at a reaction pressure of approximately 2600 psi. These trends were rationalized by the fact that the mechanisms of nucleation, aggregation, and pore formation are highly sensitive to the nature of the porogenic solvent environment.