Andrew I. Cooper

Synthesis of cross-linked polymer microspheres in supercritical carbon dioxide

SUMMARY: Herein we report the synthesis of highly cross-linked polymers based on divinylbenzene by heterogeneous polymerization in supercritical CO2 (scCO2). The polymers were isolated in the form of discrete microspheres (diameter = 1.5 ‐ 5 lm) in good yields (F 90%), in the absence of any stabilizers. In the presence of a CO2-soluble polymeric stabilizer, much smaller particles (diameter a 0.5 lm) were formed in high yields (F 95%) by emulsion polymerization in scCO2.

Polymer synthesis and characterization in liquid / supercritical carbon dioxide

Abstract The use of carbon dioxide as an inert solvent has emerged recently as an important development in polymer chemistry. The past year has seen major advances in the synthesis of a variety of polymeric materials in carbon dioxide. At the same time complementary studies have successfully elucidated the physical behavior of a range of polymers in carbon dioxide solution. Herein we review both synthetic and physical studies that are defining the scope of this approach.

High-pressure reactions in polyethylene films, a new development in matrix isolation. The photochemical reaction of Fe (CO)5 with N2 and the thermal reaction of Fe (CO)4 (N2) with H2

A new miniature high-pressure cell has been developed for the spectroscopic study of reactions between organometallic compounds impregnated into polymer films and gases such as N 2 or H 2 at any temperature between ambient and 20 K. The use of the cell is illustrated by the photochemical reactions of Fe(CO) 5 in polyethylene film (PE) with N 2 and H 2 at 190 K to form Fe (CO) 4 (N 2 ) and Fe (CO) 4 H 2 respectively. IR spectra suggest that the N 2 group may occupy an equatorial rather than an axial position. Once formed, Fe (CO) 4 (N 2 ) is shown to react thermally with H 2 at ≈ 210 K to yield the dihydride compound, Fe (CO) 4 H 2 .

Supercritical fluid impregnation of polyethylene films, a new approach to studying equilibria in matrices; the hydrogen bonding of fluoroalcohols to (η5-C5Me5)Ir(CO)2 and the effect on CH activation

Abstract Polyethylene (PE) film is used as a matrix for studying temperature-dependent equilibria by IR spectroscopy; the film is impregnated with Cp*Ir(CO)2 (Cp*=η5-C5Me5) using supercritical CO2 and subsequently saturated with HORF (RF=(CF3)2CH or (CF3)3C). At 200 K, the equilibrium between Cp*Ip(CO)2 and the hydrogen-bonded complex, Cp*Ir(CO)2…HORF, is frozen out and can be disturbed photochemically, because Cp*Ir(CO)2 is more efficient than Cp*Ir(CO)2…HORF for CH activation of polyethylene.

Spectroscopic probes for hydrogen bonding, extraction impregnation and reaction in supercritical fluids

Spectroscopy is used for monitoring a number of processes relevant to solution, extraction and impregnation in supercritical CO2(scCO2). Examples include: a combined infrared (IR) and ultraviolet study of the interaction between para-hydroquinone (HQ) and tributyl phosphate in scCO2, which reveals hydrogen bonding, detected by the characteristic v(O–H) IR bands; IR measurement of the solubility of CpMn(CO)3(Cp =η5–C5H5) in scCO2 as a function of temperature and pressure; an investigation of the uniformity of supercritical impregnation of CpMn(CO)3 into 4 mm diameter pellets of polyethylene (PE) using Fourier-transform infrared (FTIR) microscopy and FTIR depth profiling by photoacoustic detection; and an IR study of the photochemical reaction of CpMn(CO)3 with N2 with PE film.