Homopolymer and block amphiphilic polymer brushes on silicon wafers have been successfully prepared by combining the self-assembled monolayer of initiator and atom transfer radical polymerization (ATRP). Two methods for self-assembly of initiator monolayer were compared:  One was to treat the silicon surface with 6-((2-bromo-2-methyl)propionyloxy)hexyltrichlorosilane solution (solution method), and the other was to treat it with the vapor of 3-aminopropyl)triethoxysilane, followed by amidization with 2-bromoisobutyric acid (vapor method). While the solution method produced particles due to cross-linked products of the chlorosilane on silicon surface, the vapor method gave a uniform surface. The homopolymer brushes of poly(methyl methacrylate) (PMMA) and poly(acrylamide) (PAAM) were prepared by ATRP on the modified silicon wafer by the initiator. The amphiphilic block copolymer brushes consisting of PAAM and PMMA blocks were obtained by using the homopolymer brush as the macroinitiator for the second ATRP polymerization of another monomer. XPS revealed that the first polymer layer of the surface was partly covered with the second polymer layer after block copolymerized with the second monomer. AFM measurement of the amphiphilic block polymer brush imaged different morphology when they were treated with water and toluene. The amphiphilic polymer brush was stretched out from the surface and the individual polymer chains have sufficient free volume to permit the conformational change in different solvents.

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Soil erosion by water is one of the main environmental concerns in the drought‐prone Eastern Africa region. Understanding factors such as rainfall and erosivity is therefore of utmost importance for soil erosion risk assessment and soil and water conservation planning. In this study, we evaluated the spatial distribution and temporal trends of rainfall and erosivity for the Eastern Africa region during the period 1981–2016. The precipitation concentration index, seasonality index, and modified Fournier index have been analysed using 5 × 5‐km resolution multisource rainfall product (Climate Hazards Group InfraRed Precipitation with Stations). The mean annual rainfall of the region was 810 mm ranging from less than 300 mm in the lowland areas to over 1,200 mm in the highlands being influenced by orography of the Eastern Africa region. The precipitation concentration index and seasonality index revealed a spatial pattern of rainfall seasonality dependent on latitude, with a more pronounced seasonality as we go far from the equator. The modified Fournier index showed high spatial variability with about 55% of the region subject to high to very high rainfall erosivity. The mean annual R‐factor in the study region was calculated at 3,246 ± 1,895 MJ mm ha−1 h−1 yr−1, implying a potentially high water erosion risk in the region. Moreover, both increasing and decreasing trends of annual rainfall and erosivity were observed but spatial variability of these trends was high. This study offers useful information for better soil erosion prediction as well as can support policy development to achieve sustainable regional environmental planning and management of soil and water resources.

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