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Variability of rainfall in East Africa has major impacts on lives and livelihoods. From floods to droughts, this variability is important on short daily time‐scales to longer decadal time‐scales, as is apparent from the devastating effects of droughts in East Africa over recent decades. Past studies have highlighted the Congo airmass in enhancing East African rainfall. Our detailed analysis of the feature shows that days with a westerly moisture flow, bringing the Congo airmass, enhance rainfall by up to 100% above the daily mean, depending on the time of year. Conversely, there is a suppression of rainfall on days with a strong easterly flow. Days with a westerly moisture flux are in a minority in all seasons but we show that long rains with more westerly days are wetter, and that during the most‐recent decade which has had more frequent droughts (associated with the “Eastern African climate paradox”), there has been few days with such westerlies. We also investigate the influence of the Madden–Julian Oscillation (MJO) and tropical cyclones, and their interaction with the westerly flow. We show that days of westerly moisture flux are more likely during phases 3 and 4 of the MJO and when there are one or more tropical cyclones present. In addition, tropical cyclones are more likely to form during these phases of the MJO, and more likely to be coincident with westerlies when forming to the east of Madagascar. Overall, our analysis brings together many different processes that have been discussed in the literature but not yet considered in complete combination. The results demonstrate the importance of the Congo airmass on daily to climate time‐scales, and in doing so offers useful angles of investigation for future studies into prediction of East African rainfall.

Visible-light photocatalysts that degrade organic pollutants in an efficient and recyclable way are highly desirable for water treatment. In this study, UiO-66, a zirconium-based metal-organic framework, was conjugated with AgI to obtain a composite for use as photocatalyst. The AgI/UiO-66 composites with different composition ratios were synthesized by a simple solution method and exhibited remarkable activity for the degradation of rhodamine B (RhB) under visible-light irradiation. The scanning electron microscopy and X-ray diffraction results confirmed the outstanding structural stability of the AgI/UiO-66 photocatalysts. The photocatalytic stability of the AgI/UiO-66 composite was further examined by reusing AgI/UiO-66 for long-term dye degradation. The good stability of the AgI/UiO-66 composite can be attributed to the outstanding stability of the UiO-66 framework material, as well as the good interaction between AgI and the UiO-66 framework. The mechanism of the photocatalytic RhB degradation by AgI/UiO-66 was investigated by introducing different scavengers to compete for the possible reactive species involved in the degradation process.

Three new topology-varied rod-coil block copolymers, comprising the same oligo(p-phenyleneethynylene) (OPE) rod components and the same coil components, were synthesized by atom-transfer radical polymerization. Their photophysical properties were systematically studied and compared in consideration of their solid-state structures and self-assembly abilities. These copolymers have similar intrinsic photophysical properties to the OPE rods, as reflected in dilute solution. However, their photophysical properties in the solid state are manipulated to be dissimilar by supramolecular organization. Wide-angle X-ray diffraction (WAXD) and atomic force microscopy (AFM) data demonstrate that these copolymers possess different self-assembly abilities due to the molecular-architecture-dependent pi-pi interactions of the rods. Hence, the aggregates in the solid state are formed with a different mechanism for these copolymers, bringing about the discrepancy in the solid-state luminescent properties.

A novel series of well-defined alternating poly[2,7-(9,9-dihexylfluorenyl)-alt-pyridinyl] (PDHFP) with donor-acceptor repeat units were synthesized using palladium (0)-catalyzed Suzuki cross-coupling reactions in good to high yields. In this series of alternating polymers, 2, 7-(9,9-dihexylfluorenyl) was used as the light emitting unit, and the electron deficient pyridinyl unit was employed to provide improved electron transportation. These polymers were characterized by 1 H-NMR and 13 C-NMR, gel permeation chromatography (GPC), thermal analyses, and UV-vis and fluorescence spectroscopy. The glass transition temperature of copolymers in nitrogen ranged from 110 to 148 °C, and the copolymers showed high thermal stabilities with high decomposition temperatures in the range of 350 to 390 °C in air. The difference in linkage position of pyridinyl unit in the polymer backbone has significant effects on the electronic and optical properties of polymers in solution and in film phases. Meta-linkage (3,5- and 2,6-linkage) of pyridinyl units in the polymer backbone is more favorable to polymer for pure blue emission and prevention of aggregation of polymer chain than para-linkage (2,5-linkage) of the pyridinyl units.

Department of Chemistry, National University of Singapore, Singapore 119260 E-mail: chmcsoh@nus.edu.sg A number of series of fluorescent and conducting polymers containing alternating 3-functionalized thienylene/ bithienylene and phenylene/ pyridyl/ biphenylene units were synthesized from a number of central symmetric high oligomers and characterized using UV-Vis, photoluminescence, conductivity measurement, thermal analysis, electrochemistry, XRD and XPS. Structural variation of the polymers was realized by both side chain and polymer backbone modifications. Close structure-property correlation of the polymers was observed. This paper mainly reports the results of two families of them, those substituted by alkyl pendant chains and electro-withdrawing and donating groups.

A novel chiral sensor based on quartz crystal microbalance (QCM) with a self-assembled monolayer of permethylated β-cyclodextrin as the enantioselective coating has been derived which exhibit improved enantioselectivity and excellent long-term environmental stability when used in gas phase sensing.

The electrochemical and optical properties of poly(3-substituted-2,2'-bithiophene)s with bromo, alkyl, alkoxy and alkylthio pendants obtained by electrochemical polymerisation were investigated. As 3-alkylthiothiophenes, 3-alkylthio-2,2'-bithiophenes cannot be electropolymerised although the polymer can be successfully generated via a chemical oxidative approach. Other monomers were successfully electropolymerised to afford uniform polymer films on the anodic electrodes by adopting either Bu 4 NBF 4 -CH 3 CN or boron trifluoride diethyl etherate (BF 3 -OET 2 ) as the electrolytic media. These two media exhibit contrasting effects on the film formation behaviour and optoelectronic properties in some of these polybithiophenes with differen pendants. The oxidation potentials of monomers in Bu 4 NBF 4 -CH 3 N follow the trend: 3-methoxy-2,2'-bithiophenes < 3-octylthio-2,2'-bithiophenes < 2,2'-bithiophenes < 3 octyl-2,2'-bithiophenes < 3-bromo-2,2'-bithiophenes while those of the polymers are poly(3-methoxy-2,2'-bithiophene)s < poly(3-octyl-2,2'-bithiophene)s < poly(2,2'-bithiophene)s < poly(3-bromo-2,2'-bithiophene)s. However, in BF 3 OEt 2 the tend of oxidation potentials for monomers is 3-octylthio-2,2'-bithiophenes < 2,2'-bithiophenes < 3-bromo-2,2'-bithiophenes < 3-octyl-2,2'-bithiophenes < 3-methoxy-2,2'-bithiophenes while that for polymers is poly(3-octyl-2,2'-bithiophenes) < poly(3-methoxy-2,2'-bithiophenes) < poly(2,2'-bithiophenes) < poly (3-bromo-2,2'-bithiophenes). The facile and stable p- and n-dopability of poly(3-alkyl-2,2'-bithiophene) was also investigated.

Five polymers comprising alternating electron-donating thiophene and electron-withdrawing oxadiazole units have been synthesised by polycondensation reaction. The optical and charge transporting properties of the polymers were investigated by UV-Vis absorption spectroscopy, fluorescence emission spectroscopy and cyclic voltammetry. Thermal stability of the polymers has also been studied. All polymers depicted blue fluorescence and high fluorescence quantum efficiency. The influence of the introduction of an electron-donating alkoxy group to both the 3- and 4-positions of the thiophene ring and the length of the alkoxy side chain on properties of the polymers were discussed.

The synthesis and electropolymerization of 3-alkylthiophenes functionalized with a terminal amino group and its protected forms are reported. As expected, due to the strong electronic interference of the amino group, the electropolymerization of the unprotected monomer is fully inhibited. After protection of the amino group the polymerizability of the corresponding monomers is considerably improved; however, the successful polymerization process clearly depends on the nature of the used protective group. Only such monomers in which the nucleophilic character of the amino group is strongly suppressed by a suitable proctective group undergo electropolymerization to form the corresponding electroactive polymers. The obtained polymers are electrochemically stable and, besides the typical properties such as redox behavior and electrochromism, they exhibit a distinct solvatochromic behavior. Electrical conductivity measurements on their oxidized forms by means of the two-probe method give values in the range of 10 -3 to 10 -2 S . cm -1 . The feasibility of using the resulting polymers as conducting carrier materials was demonstrated by the removal of the protecting groups and the subsequent attachment of a redox active ferrocene compound. Electrochemical and spectroscopic experiments confirmed that after the polymer analogous reaction the used redox active ferrocene model compound is covalently immobilized onto the polymer surface and the electroactivity of the bonded redox groups as well as the carrier materials is retained.

Polyaniline (PANI) was doped with p-phenolsulfonic acid (PSA) or 5-sulfosalicylic acid (SSA). The PANI salts were blended with poly(N-vinyl-2-pyrrolidone), poly (N-methyl- N-vinylacetamide), poly (N,N-dimethylacrylamide), or poly ( 2-methyl-2-oxazoline) by solution casting from dimethyl sulfoxide. Blends containing up to 50% by weight of PANI salt were homogeneous and each exhibited a single glass transition temperature, indicating miscibility. Fourier transform infrared spectroscopic studies indicated that the carbonyl groups of the tertiary amide polymers interacted with the PANI salt as evidenced by the development of a shoulder at a lower frequency in the carbonyl stretching band. Electrical conductivities of the blends are in the range 10 -5 to 10 -3 S/cm, depending on the blend composition.

HCl-doped poly(o-anisidine ) (PANIS-HCl) and undoped poly(o-anisidine) (PANIS-base) were blended with poly(2-methyl-2-oxazoline) ( PMOx) or poly(2-ethyl-2-oxazoline) (PEOx) by solution casting from dimethyl sulfoxide. Blends containing 50 wt % or less of PANIS-HCI or PANIS-base were flexible and homogeneous. The glass transition temperature of the blend continuously shifted away from that of PMOx or PEOx with increasing PANIS-HCI or PANIS-base content, indicating miscibility. The shift in the T g value was larger for the PMOx blend than for the corresponding PEOx blend, suggesting a stronger interpolymer interaction in the former blend. Fourier transform infrared spectroscopic studies indicated the presence of specific interactions in the blends as evidenced by the changes of C=O and NH bands. Blends containing 50 wt % of PANIS-HCI showed conductivity of about 10 -4 S/cm.

Wood–polymer composites (WPC) of Geronggang (GE; Cratoxylon arborescens), a light tropical hardwood, impregnated with methyl methacrylate (MMA), styrene-co-acrylonitrile (3: 2; STAN), methyl methacrylate-co-bis (2-chloroethyl) vinyl phosphonate (3 : 1; MVP) and methyl methacrylate-co-bis (chloropropyl)-2-propene phosphonate (3:1;MPP), were prepared by in situ polymerization using γ-radiation or catalyst-heat treatment. Thermal characterization of these WPC by limiting oxygen index measurements (LOI), thermogravimetry (TG), and differential scanning calorimetry (DSC) showed that the impregnants greatly modified the wood properties. The LOI values of the GE–MVP and GE–MPP composites were much higher than that for GE and the other composites, indicating the effectiveness of the phosphonates as flame retardants. Concomitantly, the flaming characteristics also compared favorably against that for GE and the other composites. The decomposition temperature and maximum rate of weight loss determined by TG for GE–MVP and GE–MPP were substantially reduced, whereas the char yields were greatly higher. These observations again indicate that phosphonates imparted flame-retarding properties to their composites. The thermal properties of GE–MMA and GE–STAN composites were not vastly different from that of untreated GE. Flame retardancy in the phosphonate-containing composites was effected through both the condensed- and gaseous-phase mechanisms due to the presence of phosphorus and chlorine, respectively. Indication of grafting of polymer to wood was found for GE–STAN, GE–MVP, and GE–MPP composites, but not for GE–MMA. Composites prepared by γ-radiation or by the catalyst-heat treatment had similar thermal characteristics.