The diterpenoids are fairly widely distributed in nature. The best known members are the resin acids obtained from the non-volatile portion of many oleoresins, especially those obtained fram conifers. Diteppenoid acids, alcohols, lactones, phenols, and alkaloids have been obtained from a variety of sources. The hydrocarbons are more restricted in occurrence; all are found in New Zealand and all but two (camphorene and cupressene) in endemic species. Their reported occurrences are almost solely limited to countries bordering on the Pacific.

The chemistry of the amidoximes (a) has long been of interest because of the possibility of tautomerism with hyroxyamidines (b)

Whole document restricted, see Access Instructions file below for details of how to access the print copy. / Attempts have been made to transform lanosterol, by both chemical and microbial means, into compounds of potential pharmacological importance. In part I some compounds with heterocyclic rings (pyrazoles, isoxazoles, and furazans) fused to ring-A have been synthesized by chemical methods. These have been tested for cytotoxic properties against lymphoid leukemia L-1210. The equilibria and n.m.r. spectra of some formyl ketones have also been studied. In part II attempts have been made to oxidize some lanosterol derivatives with microbial cultures in pursuit of synthetically useful intermediates. 3β-Hydroxy-11-keto-4, 4, 14α-trimethyl-5α-chol-8-enic acid methyl ester (35e) has been synthesized from lanosterol and transformed by Trichotecium roseum to a dihydroxy-5α-cholenic acid derivative. Extensive chemical transformations have been carried out on lanosterol to prepare substrates for microbial transformation. In particular a new efficient method for the mild degradation of the lanosterol side chain to a 17β-acetyl group has been developed.

This thesis investigated the formation of compositional gradients across 0.5 – 1 cm of porous silicon layers which had thicknesses of 2 – 10 μm. These compositional gradients were then characterised, and their potential use as vapour sensors was probed. Surface composition gradients have been reported on flat surfaces, but this is the first time that they have been reported on a three-dimensional material with controlled pore geometry. Chemical gradients have been generated across the surface of porous silicon by performing electrochemical attachment of organohalides with an asymmetric electrode arrangement, and by chemical hydrosilylation of alkenes in the presence of a diffusion gradient of diazonium salts across the porous silicon surface. Samples with electrochemical gradients of methyl, pentyl acetate, and decyl and using chemical hydrosilylation with gradients of undecanoic acid and decyl groups. The latter four gradient-modified porous silicon types have been ‘endcapped’ with methyl groups to give improved stability and greater hydrophobicity. The pentyl acetate and undecanoic groups have been converted into pentanol and undecanoate groups respectively to increase the hydrophilicity of these porous silicon surfaces. The gradients have been characterised using two-dimensional FTIR microspectrophotometry and water contact angle measurements. The interaction of these gradient porous silicon samples with ethanol, heptane, toluene and 2-hexanol vapours have been monitored either by UV-Vis reflectance spectroscopy at selected points across the surface or more globally using a digital camera. The undecanoate gradient porous silicon sample showed a large difference in optical response between the undecanoate end and the methyl end of the gradient when exposed to water vapour, showing that imposition of a chemical gradient can alter the sensing character of porous silicon in a controllable manner.

This thesis examines the preparation and chemistry of osmium and ruthenium complexes with ligands featuring the group 14 donor atoms carbon and silicon, and the group l5 donor atom phosphorus. Aryl, alkenyl, and alkynyl complexes of osmium and ruthenium, prepared via mercury reagents, are discussed in Chapter One. 5-Coordinate 2-halophenyl complexes M(C6H4X-2)CI(CE)(PPh3)2 (M = Os; X = C1, Br; E = O, S; M = Os; X = I E = O; M = Ru; X = CI, Br, E = O) were synthesised by reaction of organomercury reagents Hg(C6H4X-2)2 (X = C1, I, Br) with MHC1(CO)(PPh3)3: (M = Os, Ru). Os(C6H4X-2)C1(CO)(PPh3)2 (M = Os; X = C1, I, Br) were characterised structurally and the interaction between X and M examined. Attempted benzyne syntheses using these complexes were not successful. 6-Coordinate complexes M(C6H4X-2)C1(CO)(CE)(PPh3)2 (M = Os, X = C1, E = O, S; Br, E = O, S; M = Os, E = O, X = I; M = Ru, E = O, X = C1, Br) were prepared by the addition of carbon monoxide to the corresponding 5-coordinate precursors. Approaches towards reduction of these complexes are discussed. The structure of Os(C6H4C1-2)C1(CS)(CO)(PPh3)2 revealed that the thiocarbonyl and the aryl halide ligands were cis and therefore in an ideal geometry to rearrange and form a substituted thioacyl ligand. Indeed, on heating Os(C6H4X-2)C1(CS)(CO)(PPh3)2 (X = C1, Br) the corresponding thioacyl complexes Os(η2-CS{C6H4X-2})C1(CO)(PPh3)2 (X = C1, Br) were formed. The decreased electron density in the halo aryl rings of these thioacyl complexes, combined with the fact that the halide substituents were no longer bonded to the metal, enabled facile lithiation of the aryl rings, even at low temperature. Quenching the appropriate lithiated intermediate with Bu3SnC1 gave Os(η2-CS{C6H4SnBu3-2})C1(CO)(PPh3)2. These results suggested that M(C6H4{CH2X}-2)C1(CO)(PPh3)2 (M = Os, Ru) were worthwhile target complexes for lithiation studies. To this end, Hg(C6H4{CH2OH}-2)C1 was prepared but attempts to convert the alcohol into a tosylate (for subsequent reaction with LiX) were unsuccessful and so this chemistry was not pursued further. Hg(C6H4{CH2OH}-2)C1 transferred the benzylic alcohol groups to osmium and ruthenium, albeit in low yields. Oxidation of Hg(C6H4{CH2OH}-2)C1 with PCC provided the benzaldehyde-containing mercury complex Hg(C6H4{CHO}-2)C1, symmetrization of which gave Hg(C6H4{CHO}-2)2. The latter compound was used to prepare aldehyde complexes of osmium and ruthenium, as well as mercury(II) benzaldoxime and benzaldimines. The aldehyde oxygen atoms in the osmium and ruthenium complexes were bound to the metals and were unaffected by amines, and by attempts to displace them from the metals. The addition of dimethyldithiocarbamate to Ru(C6H4{CHO}-2)C1(CO)(PPh3)2 displaced a triphenylphosphine ligand and Ru(C6H4{CHO}-2)(CO)({CH3}2NCS2)(PPh3) was formed. Transfer of the benzaldoxime ligand, and various benzaldimine ligands [C6H4{C[H]=NR] R = Me, CH2CH2NEt2, CH2CH2NMe2], to osmium or ruthenium gave M(C6H4{C[H]=NR}-2)C1(CO)(PPh3)2 (M = Ru, R = OH; M = Os, Ru; R = Me, CH2CH2NEt2;M= Ru, R = CH2CH2NMe2). The derived cationic complexes Ru(C6H4{C[H]=NCH2CH2NHR2}-2)C1(CO)(PPh3)2]BF4 (R - Me, Et) were prepared by protonation of the benzaldimine complexes with HBF4+ and Ru(C6H4{C[H]=NCH2CH2NR2}-2)(Co)(PPh3)2]BF4(R = Me, Et)were prepared by addition of AgBF4. Bromination of Ru(C6H4{C[H]=NMe}-2)C1(Co)(PPh3)2 gave Ru(C6H3{C[H]=NMe}-2, Br-4)C1(Co)(PPh3)2 which was lithiated at low temperature. The aryllithium was quenched with Bu3SnC1 to give Ru(C6H3 { C[H]=NMe}-2,SnBu3-4)C1(CO)(PPh3)2. The reaction of alkynylmercury reagents with osmium and ruthenium complexes are discussed in the following sections. Treatment of RuHCI(CO)(PPh3)2 with Hg(C≡CPh)2 has been reported previously, the result being formation of an α-phenylethynyl-trans-β-styryl ligand. However, the corresponding reaction with OsHCI(CO)(PPh3)3 resulted in catalysed coupling of the alkyne. This reaction was re-examined and the 6-coordinate α-phenylethynyl-trans-β-styryl osmium complex was prepared by direct reaction of the 5-coordinate complex with acetate ion. A dicarbonyl complex containing the α-phenylethynyl-trans-β-styryl ligand, Os(C{C≡Ph}=CHPh)CI(CO)2(PPh3)2, was prepared by the addition of carbon monoxide in the presence of LiC1 to the acetate complex. Thiocarbonyl complexes containing an α-phenylethynyl-trans-β-styryl ligand were prepared. Addition of carbon monoxide to solutions containing these complexes gave the thioacyl analogues M(η2-CS{C[C≡CPh]=CHPh})C1(CO)(PPh3)2 (M = Os, Ru). The remaining sections in Chapter One examine the reactions of mercury(II) reagents with the osmium(O) complexes Os(CO)2(PPh3)3 and OsCI(NO)(PPh3)3. Oxidative addition of the mercury-carbon bond of HgR2 (R = C6H4CH34, C≡CPh, trans-CH=CHPh) to Os(CO)2(PPh3)3 gave OsR(HgR)(CO)2(PPh3)2. Reaction of the acetylide or styryl complexes with iodine resulted in cleavage of the osmium-mercury bond and yielded either Os(C≡CPh)I(CO)2(PPh3)2 or Os(trans-CH=CHPh)I(CO)2(PPh3)2. Similar complexes were not accessible from reaction of the osmium(II) complex OsHC1(CO)(PPh3)3 with the appropriate mercury reagent. Whereas the mercury reagents reacted with Os(CO)2(PPh3)3 to give the simple oxidative addition products, the corresponding reactions of OsC1(NO)(PPh3)3 with HgR2 did not always give the analogous products OsR(HgR)C1(NO)(PPh3)2. Addition of Hg(C6H4CH3-4)2 to OsC1(NO)(PPh3)3 gave a mixture of the bis(p-tolyl) complex Os(C6H4CH3-4)2C1(NO)(PPh3)2 and the mono(p-tolyl) complex Os(C6H4CH3-4)CI2(NO)(PPh3)2. The structure of the bis(p-tolyl) complex revealed that the p-tolyl ligands were trans and the metal-carbon(aryl) bond lengths were extremely long. Addition of pyridine to the bis(p-tolyl) complex gave Os(C6H4CH3-4)2(C5H5N)CI(NO)(PPh3), which contained two cis p-tolyl ligands. The reactions of Hg(C6H4C1-2)2 and Hg(C≡CPh)Ph with OsCI(NO)(PPh3)3 gave complexes containing a single organic ligand. In contrast, treatment of OsCI(NO)(PPh3)3 with either Hg({C4H4S-2})2 or Hg([C4H4SMe-5]-2})2 gave the dithienyl complexes OsR2CI(NO)(PPh3)2 [R = (C4H4S)-2, ({C4H4SMe-5})-2. Furthermore, the reaction of Hg(CF3)2 with OsC1(NO)(PPh3)3 gave Os(CF3)(Hg{CF3})CI(NO)(PPh3)2. Treatment of OsCI(NO)(PPh3)3 with Hg(trans-CH=CHPh)2 gave Os(trans-CH=CHPh)CI2(NO)(PPh3)2 and an osmaindene complex, Os(C6H4CH=CH)H(NO)(PPh3)2, which in turn gave Os(C6H4CH=CH)Cl(No)(PPh3)2 on treatment with HCl. Chapter Two examines osmabenzene chemistry. Spectroscopic data were collected for the known complexes Os(η2-C[S]CH=CHCH=CH)(CO)(PPh3)2, and Os(C[SH]CH=CHCH=CH)(cis-CI)(CO)(PPh3)2. Oxidation of the osmabenzene thiol to a sulfinic acid was attempted. Methylation of the parent complex, Os(η2-C[S]CH=CHCH=CH)(CO)(PPh3)2, gave the product of kinetic control as Os(C[SMe]CH=CHCH=CH)(cis-I)(CO)(PPh3)2, reported previously, which rearranged on heating to give the trans isomer, Os(C[SMe]CH=CHCH=CH)(trans-I)(CO)(PPh3)2. Approaches to auration of the sulphur in Os(η2-C[S]CH=CHCH=CH)(CO)(PPh3)2, are described. Although the metallabenzenes reported previously have physical properties comparable with those of benzene itself, little evidence has been reported to suggest that the chemical reactivity of metallabenzenes is similar to that of benzene. The research described in this chapter provides the first example of a metallabenzene complex that undergoes aromatic electrophilic substitution. Thus, the metallabenzene complex Os(C[SMe]CH=CHCH=CH)(cis-I)(Co)(PPh3)2was brominated, chlorinated, and even iodinated. Crystal structure determinations and NMR studies showed that C5, which was activated by the thioether functionality, was the preferred site of electrophile attack. Even more significantly, Os(C[SMe]CH=CHCH=CH)(cis-I)(Co)(PPh3)2 was nitrated with either Cu(NO3)2/acetic anhydride, or with the more potent reagent NO2CF3SO3.CF3SO3H. The site of nitration was identical with that of halogenation, namely, C5. Previous syntheses of metallabenzenes had reported the use of the simplest alkyne, ethyne. This chapter describes the first metallabenzene complex prepared from propyne, giving the metallabenzene Os(η2-C[S]C{CH3}=CHCH=C{CH3})(CO)(PPh3)2 and the oxidative addition product Os(C≡CCH3)H(CO)(CS)(PPh3)2. Ten of the metallabenzene complexes were characterised structurally and the significance of the carbon-carbon bond lengths in the metallacyclic rings are discussed. The complete characterisation of these complexes by NMR spectroscopy revealed that the ring protons in the metallabenzene complexes, excepting H6, were at chemical shifts similar to those expected for normal aromatic carbons. Chapter Three examines the coordination of the strongly ח-accepting tris(N-pyrrolyl)phosphine ligand to osmium. Two tris(N-pyrrolyl)phosphine complexes of Os(II), OsHCI(CO)(PPh3)2(P{NC4H4}3) and OsH(C6H4CH3-4)(CO)(PPh3)2(P{NC4H4}3), were prepared. Both of these showed significantly higher infrared carbonyl stretching absorptions than the analogous triphenylphosphine complexes, reflecting the ח-acceptor nature of the tris(N-pyrrolyl)phosphine ligand. The osmium(O) complexes Os(CE)(CO)(PPh3)2P(NC4H4)3 (E = O, S) were prepared and the carbonyl complex was characterised structurally. The osmium-phosphorus(pyrrolyl) bond length of this complex was relatively short. The tris(N-pyrrolyl)phosphine ligand was in the equatorial plane as were the two carbonyl ligands. Chapter Four examines silyl and siloxane complexes of osmium and ruthenium. Although triethoxysilyl complexes of ruthenium have been prepared previously through ethanolysis of the coordinated SiCl3 group, the osmium analogues could not be prepared this way. It was found that Os(Si{OEt}3)CI(CO)(PPh3)2 could be prepared successfully by direct treatment of Os(Ph)Cl(CO)(PPh3)2 with triethoxysilane. Addition of carbon monoxide to the 5-coordinate triethoxysilyl complex afforded the dicarbonyl complex. The triethoxysilyl nitrosyl complex, OsH(Si{OEt}3)CI(NO)(PPh3)2, was prepared by oxidative addition of triethoxysilane to OsCI(NO)(PPh3)3, and the siloxane nitrosyl complex, Os(O[Si{OEt}3])CI2(NO)(PPh3 )2 was also characterised fully. Prior to this work only a single silatranyl complex was known. This chapter reports fifteen new silatranyl complexes and examines the unique properties conferred upon the silatrane by coordination to the metal. The silatranyl-containing complexes OsH(Si{OCH2CH2}3N)CI(No)(pph3)2 and OsH(Si{OCH2CH2}3N)(CO)2(pph3)2 were formed by oxidative addition of silatrane to the appropriate osmium(O) complex. Neither was suitable for further research because the chloro nitrosyl complex ejected silatrane in the presence of oxygen, and the dicarbonyl complex was isolated as a mixture of three isomers. In contrast, the unsaturated complexes M(Si{OCH2CH2}3N)C1(CO)(PPh3)2 (M = Os, Ru) were excellent materials for further study. The crystal structures of both of these complexes reveal typical metal-silyl distances with atypical silatranyl N→Si bond lengths. In both cases the N→Si bond length is elongated, the nitrogen is planar, and the cage is best described as quasi-silatranyl. The unsaturated nature of the metal in Os(Si{OCH2CH2}3N)CI(CO)(PPh3)2 offered access to derived complexes. The ח-acid carbon monoxide added to the vacant site forming Os(Si{OCH2CH2}3N)C1(co)2(pph3)2. Methylation of the 5-coordinate silatranyl complexes, gave [M(Si{OCH2CH2}3NMe)CI(CO)(PPh3)2]CF3SO3(M = Os, Ru). This reaction has not been achieved previously for silatrane derivatives. These methylated complexes have the longest recorded N→Si distances for any silatrane derivatives, and display a tetrahedral bridgehead nitrogen which points out of the cage at the methyl substituent. Protonation of the 5-coordinate silatranyl complexes gave [M(Si{OCH2CH2}3NH)CI(CO)(PPh3)2]CF3SO3 (M = Os, Ru). The thiocarbonyl-containing derivatives Os(Si{OCH2CH2}3N)CI(CS)(PPh3)2 and [Os(Si{OCH2CH2}3NMe)CI(CS)(PPh3)2]CF3S03 were prepared and these complexes showed spectroscopic properties similar to those observed for the carbonyl-containing analogues. The 5-coordinate silatranyl-thiocarbonyl complex rearranged in the presence of carbon monoxide to form Os(η2-C{S}Si{OCH2CH2}3N))CI(CO)(PPh3)2, which did not contain a metal-silicon bond. The silatranyl cage in the structure of this complex showed a very short N→Si bond with the nitrogen centre tetrahedral and pointing into the cage and towards the silicon atom. The osmium(IV) complex OsH3(Si{OCH2CH2}3N)(pph3)2 was prepared from OsH4(PPh3)2 and silatrane. The structure of this complex showed that the hydride ligands were oriented trans to a single triphenylphosphine in each case. Treatment of this complex with methyl iodide gave the quaternary salt [OsH3(Si{OCH2CH2}3NMe)(PPh3)3]I, and protonation gave [OsH3(Si{OCH2CH2}3NH)(PPh3)3]CF3SO3.

A theoretical analysis of the Be9(pd)Be8 reaction at a proton energy of 333kev assuming compound nucleus formation of a 1- state in B10 predicts that if protons are unpolarised the deuterons have zero vector but maximum possible tensor polarisation i.e. the magnetic substate population ration is 1:0:1 and Pzz =1. furthermore it predicts that both the polarization and the angular distribution of these deutrerons are isotropic. The polarization of these deuterons emitted at 30 in the lab. has been measured by allowing them to initiate the reaction He3 (dp)He4 at 430 kev and determining the angular distribution of the resulting protons. / Note: parts of this thesis have since been published in Nuclear Physics A 95 663-673 http://dx.doi.org/10.1016/0375-9474(67)90859-7

This thesis describes the crystal structure determinations of ten minor groove binding ligands complexed to the DNA oligonucleotides d(CGCGAATTCGCGh and d(CGCAAATTTGCGh. The ligands are all based on bisbenzimidazole or bisquatemary ammonium heterocycles (BQAH) and some have additional DNA interacting functional groups. Two of the ligands presented in chapter 4 are models for DNA alkylators (nitrogen mustard and pyrrole diol) and their DNA bound structures confirm the reaction mechanisms for the true alkylating analogues. The other two ligands in this chapter are a carborane substituted bisbenzimidazole ligand and a BQAH molecule which contains no hydrogen bonding functionality. Neither ligand could be located in the crystal structures. yet the well defined DNA conformations showed that the ligands can bind in the minor groove of DNA.

The density and shear viscosity of mixtures of tert-Butyl alcohol (ButOH) and tert-Butylamine (ButNH2) with water have been determined for various temperatures (288.15 K to 318.15 K for H2O+ButOH and 288.15 K to 308.15 K for H2O+ButNH2) over the whole composition range. Excess molar volumes and apparent molar volumes of the components of each system were calculated from the density data. In both systems the apparent molar volume of the organic component passes through a minimum in the water-rich region. Both systems exhibit large negative excess molar volumes which are essentially independent of temperature at all compositions. The two systems show pronounced maxima in their shear viscosity isotherms. The empirical solvent polarity parameters ENR and ET for the solvatochromic compounds Nile Red and pyridinium-N-phenoxide betaine respectively, have been determined as a function of composition for water + tert-Butyl alcohol and water + tert-Butylamine binary mixtures, over the whole composition range at 298.15 K. For both systems the two parameters vary with composition in a strongly nonlinear fashion, and the polarity of the mixture decreases with increasing proportion of the organic cosolvent. The nonlinear variation of the polarity parameters is attributed to water-cosolvent hydrophobic interactions at low cosolvent contents, and hydrogen bonding interactions at higher cosolvent contents. Permittivity and refractive index have also been measured at 298.15 K for both systems, and both properties are strongly nonlinear functions of composition. The self-diffusion coefficients of water and of the organic component have been measured for H2O+t-butyl alcohol and H2O+t-butylamine mixtures over the whole composition range at 301.15 K, using the NMR spin-echo technique. In the water-rich region below 20 mole % of cosolvent, the self-diffusion coefficients of both components for each binary solvent system decrease rapidly with increasing cosolvent content. In cosolvent-rich mixtures with more than 50 mole % cosolvent, motions of water are evidently strongly correlated with those of cosolvent molecules. The semiempirical equation proposed by Albright relating the shear viscosity of a mixture to the diffusion coefficients of its components successfully predicts the general shape of the viscosity curve for each binary system. For the composition region above 50 mole % cosolvent the Albright equation gives calculated viscosities which agree well with observed values, but in the water-rich region there are significant deviations between the observed and calculated viscosities. Volume ratios have been measured with a bellows volumometer for t-Butylamine and six water + t-Butylamine mixtures at 278.15, 288.15, 298.15 and 313.15 K, at pressures up to about 200 MPa or at a lower pressure slightly below the freezing pressure at the temperature of measurement. From densities measured at 0.1 MPa together with the volume ratios at higher pressures, excess molar volumes, and isothermal compressibilities have been evaluated. The compressibility is a relatively simple function of pressure, temperature, and composition. Hydroxyl-proton chemical shifts for water and t-Butyl alcohol in water + t-Butyl alcohol mixtures with ≥8 mol% t-Butyl alcohol, and the averaged hydroxyl and amino proton chemical shift for water + t-Butylamine mixtures, have been determined at 200 MHz for four temperatures (263.15, 278.15, 298.15 and 313.15 K) as a function of composition. Further measurements have been made for water + t-Butyl alcohol + t-Butylamine ternary mixtures at 310.15 K over the complete mole fraction range at 60 MHz. Variations in solvent composition have little effect on the resonance for the methyl protons of the cosolvent, but the signal for the hydroxylic protons is substantially influenced. The water proton resonance initially shifts to higher frequencies (low fields) as the cosolvent is added to water, and the shift to higher frequency in the water proton resonance induced by the hydrophobic cosolvent is strongly temperature dependent, the effect being greatly enhanced at lower temperatures. As the proportion of cosolvent increases the hydroxyl proton signals in the water + t-Butyl alcohol system and the averaged proton signal in water + t-Butylamine mixtures shift to lower frequency (high field). Raman and FT-IR absorption spectra of aqueous t-Butyl alcohol and t-Butylamine in the region of O-H and NH2 stretching and bending modes have been measured at 298.15 K as a function of organic cosolvent concentration in the whole cosolvent mole fraction region. Vibrational intensities of some bands show definite trends with varying concentrations of the solutions. In the concentration dependence study unusual linewidth changes of certain bands were observed. Conductivities, densities and viscosity B-coefficients from the Jones-Dole equation were determined for NaI, KI, Bu4NI, LiCl and KCl at 298.15 K in various mixtures of water with t-Butyl alcohol and t-Butylamine. The limiting molar conductances and the corresponding Walden products have been computed. Values of the partial molar volumes of the electrolytes at infinite dilution in the various solvent mixtures were obtained from the density measurements.

Whole document restricted, see Access Instructions file below for details of how to access the print copy. / The literature on polymer gels and hydrogels since the beginning of last century has been reviewed, and the properties of polymers and gels based on 2-acrylamido-2-methylpropanesulphonic acid (AMPS) summarized. Copolymer gels were synthesised, using gamma radiation initiation, from aqueous solutions of the comonomers acrylamide and AMPS. The progress of copolymerisation and crosslinking was followed by measuring the viscosity of reaction mixtures that had been irradiated for different times and hence had received different doses. The variation of viscosity with dose has been interpreted in terms of main chain growth and the onset of crosslinking and gelation. It was observed that the viscosity of irradiated reaction mixtures decreased substantially on standing at ambient temperature. That behaviour has been attributed to breaking of non-permanent bonds formed during irradiation and subsequently broken over the ageing period. The environmental responsiveness of the gels formed by gamma radiation initiation was assessed by observation of the volume phase transition triggered by increasing the proportion of acetone in aqueous acetone media in which the gels were immersed. Free-radical copolymerisation of aqueous solutions of comonomer AMPS and Nisopropylacrylamide (NIPA) was initiated with ammonium persulphate at 70°C. Reaction times that varied with comonomer mixture composition gave a series of copolymers corresponding to low conversion. The copolymer composition data set was used in conjunction with the Kelen-Tϋdos and Finemann-Ross methods, assuming the terminal model to be valid, to give the monomer reactivity ratios r(AMPS)=0.24 and r(NIPA)=1.12. The reactivity ratios show that copolymers made from comonomer mixtures with more than 25 mol% AMPS consist of relatively short monomer sequences. The dependence of glass transition temperature on copolymer composition was determined using differential scanning calorimetry and the experimental data compared with Tg predicted from the Fox equation. High-field (400 MHz) 1H-NMR spectroscopy was used to probe the early stages of polymerisation and gelation at 70°C in a D2O solution of AMPS and NIPA, crosslinker N,N1-methylenebisacrylamide (MBAA) and poly(ethylene glycol) (PEG). The change in signal intensity of vinyl protons of the monomers and crosslinkers, and the methylene proton signals from PEG were recorded as a function of reaction time. The relative initial rates of reactant consumption showed that the crosslinking monomer was consumed more rapidly than either AMPS or NIPA, so that crosslinking of the copolymer chains took place predominantly in the early stages of copolymer chain growth. The PEG signal was found to be invariant with time, confirming that PEG did not participate in the polymerization reaction but acted as the linear interpenetrating component in semi-interpenetrating network gels. The kinetics of gel formation and other rheological properties of copolymer and SIPN pregel solutions were analysed using parallel plate rheometry. The variation of shear moduli and other rheological parameters during reaction under dynamic shear was interpreted in terms of chain growth and crosslinking reactions. In relation to the sol-gel transition, viscosity, tan(δ), G' and G" were used to assess the kinetics of gelation. The densities of copolymer and SIPN dried gels were measured for a range of copolymer chain compositions and found to be similar in magnitude (within about 10%) for gels with the same copolymer chain composition. The surface morphology of both types of gel, in dried form, was examined using scanning electron microscopy. The swelling ratio of SIPN gels in water was found, in general, to be proportional to the AMPS content of the copolymer chains. The influence of initiator and crosslinker concentrations in the pregel solutions on the rheological properties of gels was investigated in detail. G', G", tan(δ) and critical strain were correlated to initiator concentration, but the crosslink density of the gel was essentially independent of initiator concentration. As expected, the effect of crosslinker concentration, hence crosslink density in the gels, on rheological properties, was significant. With increasing crosslinker concentration, the critical strain (at gel rupture) and tan(δ) decreased markedly. The surface roughness of dried gels also decreased with increasing crosslinker concentration. Effects of comonomer mixture and copolymer chain composition for copolymer and SIPN systems on the initiation temperature of pregel solutions and rheological properties of gels were compared. A feature of the data is that the copolymer gels exhibited much larger values of G' and G" than the corresponding SIPN gels, whereas the SIPN gels had larger equilibrium storage modulus (G'e), indicating that stronger covalent or physical crosslinks may exist in the SIPN gels. Copolymer and SIPN gels examined at constant frequency and shear stress exhibited a phase transition associated with the water in the gels. Both types of gels were found to have an ice-dominant structure at -6°C with G' smaller than that of ice at -5°C, and there was an ice phase to gel phase transition induced by shear strain at -6°C, which was not found in gels at -4°C. Temperature-time effects on gel formation kinetics and post-gel properties were determined and appear to be correlated to rates of gel formation as well as the final gel microstructure. As expected, the induction time for gel formation is greater at lower reaction temperature, and PEG enhances this effect and reduces the viscosity compared to the corresponding PEG-free system. The post gel microstructure has been examined in terms of G', angular frequency, reaction temperature and time. The most significant effect is that increasing reaction temperature for a fixed time builds a more complete gel network. Creep and stress relaxation of gels were investigated. Both copolymer and SIPN gels show a high degree of elasticity, and at specific frequencies the gels behave as ideal elastic solids. SIPN and copolymer gels were characterized using spectroscopic, thermal and morphological techniques (DSC, TG, FTIR, XPS, XRD and SEM). Interactions between PEG and copolymer network were found to markedly influence the properties of SIPNs. Thermal analysis revealed that the PEG component of the SIPNs showed melting behaviour that was similar to that of pure PEG, but modified by interactions between PEG and the copolymer network. Composition and temperature effects on thermal and morphological properties were investigated in detail. Protonation of a substantial proportion of the amide groups in the dried SIPN gets was detected by X-ray photoelectron spectroscopy, and mainly attributed to proton transfer from the sulphonic acid groups of AMPS units to the amide groups of NIPA units. Sodium diclofenac was used as a model drug in design of a drug encapsulation/release system based on use of PEG/poly(AMPS-co-NIPA) SIPN hydrogels. The thermal stability of the drug and the SIPN gel used for its encapsulation was determined as a prerequisite to the development of a direct drug loading technique whereby the drug was encapsulated during accelerated formation of the SIPN matrix in a suspension polymerisation system at 100°C. Direct loading of the drug was found to be superior, in terms of the distribution of the drug in the gel matrix, to the conventional diffusion loading technique. Drug release in pH7.4 phosphate buffer solutions and in pHl.0 simulated gastrointestinal liquid was determined as a function of time.

The work has been divided and abstracted under three headings: (1) The Absorption of Sulphur Dioxide by Aqueous Solution. The rate of absorption of low concentrations of SO2 (~ 500 µg.m-3) was examined, varying a number of parameters. The results were expressed as deposition velocities (Vg = flux/gas concentration). Vg did not vary with relative humidity. Deposition into acid solutions (pH <3) was controlled by diffusion processes in the liquid film while under more alkaline conditions (pH >4) the process was governed by the rate at which SO2 could diffuse to the interface through the gas boundary layer. Oxidizing agents (e.g. H2O2) were found to increase the rate of diffusion in the liquid boundary layer. Salts generally exerted a more complex effect on liquid phase diffusion. Vg for SO2 deposition into aqueous solution under calm conditions and at pH values expected in the atmosphere was calculated to be about 0.7 cm.s-1 from these experiments. Efflux of SO2 from solution was examined at low pH values under boundary conditions similar to the deposition work. At high S(IV) concentrations in solution (~10-3N) the half lives for SO2 desorption from solution were 600, 1020, 3300 s for pH values 2.0, 2.5, 3.0 respectively. The consequences of the experimental results are discussed with respect to the atmosphere at large and to scrubbing of flue gases. Poor absorption rates for SO2 at low pH values suggested that sea water with its high pH would be an excellent scrubbings agent and its buffering ability was investigated. Experiments showed 10-3M S(IV) could be absorbed with the pH dropping only as far as pH 5.5. (2) The Oxidation of Sulphur Dioxide in Aqueous Solution The rate of oxidation in 10-5M of SO2 solutions was examined. The results showed the reaction to be very sensitive to traces of metallic ions, which made it impossible to determine the uncatalysed rate. The half life for oxidation of S(IV) in (10-5M) in triply distilled water was 36, 8, 5 hours at pH 4.6, 5.2, and 6 respectively. The rate increased upon addition of traces (10-6M) of Fe(III) and Mn(II) ions (pH 4 – 5) while Cu(II) seemed to act as an inhibitor. In solutions of ammonium sulphate Fe(III) was found to be an excellent catalyst. The reaction appeared to have a variable order with respect to S(IV) being 1st order at pH <4 and 2nd order at pH >5. Results in potassium sulphate were similar, but the reactions somewhat slower. At pH >5 the reaction was sensitive to the alkali used for neutralization, the oxidation rate being much greater if ammonium hydroxide was used rather than sodium hydroxide. Solutions of ammonium chloride and sodium bicarbonate showed a second order dependence on S(IV) concentration at high pH values. The Fe(III) catalysed oxidation was faster in 'Chloride' solutions than in 'sulphate' solutions at pH <4. A radical mechanism previously proposed by a number of workers was found to give considerable insight into the complex experimental results. (3) The Dissolution of Iron from Ferric Oxide and Pulverized Fuel Ash The aqueous oxidation of SO2 requires the presence of a catalytic metal ion. The most abundant catalyst in the atmosphere would appear to be iron. However, it would have to be present in solution to be an effective homogeneous catalyst. The rates of dissolution of iron from Fe2O3 were investigated and found to be extremely slow even in the presence of H2SO4 or 'H2SO3'. The dissolution of iron from pulverised fuel ash (a possible atmospheric source of iron in polluted areas) is quite rapid even under only Moderately acid conditions (pH 3.5) where solutions 1.9 x 10-4 M in Fe(III) can be reached in a matter of 20 minutes. The high rate of dissolution is thought to arise from the fusing of iron oxides with other alkaline oxides in the furnace.