CONTACT Hamid Reza Pourianfar pourianfar@acecr.ac.ir ray diffraction pattern The XRD results showed clear diffraction line at low angles, ie 30 -80 ( Figure 5). The Bragg reflections at angles 2u of 38.18 , 44.35 , 64.4 and 77.3 corresponded to 111, 200, 220 and 311 sets of lattice planes, respectively. This band pattern confirmed the structure 132 B. BAHRAMI-TEIMOORI ET AL.

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Due to having a short half-life and novel site of action, the herbicidal potential of natural compounds are lionized. Coumarin is a secondary metabolite from Lavandula sp., family Lamiacae. The impact of eight concentrations of coumarin (0, 100, 200, 400, 800, 1600, 3200 and 6400 ppm) were separately used as a pre-plant incorporated into soil on six plant species under greenhouse conditions. Generally, coumarin had phytotoxic effect against all plant species. The phytotoxic effect was concentration-dependent. The high concentrations could inhibit the emergence of seedlings (probably by stopping germination of seeds). Based on ED50 parameter, the ranking of plant species for tolerance to coumarin was S. halepense > Z. mays > C. album > A. retroflexus > E. cruss-gali > P. oleracea. Based on selectivity index, coumarin at a concentration of 365.69 ppm can control P. oleracea without damaging Z. mays, whereas any concentration it cannot control other weeds without damaging Z. mays.

In a conventional semi‐batch seeded emulsion copolymerization of vinyl acetate/butyl acrylate (VA/BA) using hybrid surfactants namely, dioctyl sulfosuccinate (DOSS) as an anionic surfactant, nonylphenol ethoxylate (KENON 30) as a non‐ionic type, and polydimethylsiloxane surfactant (having hydrophilic silanol‐terminated, called PDMS). The effect of PDMS on the properties of the latex synthesized was investigated by measuring solid content, viscosity, colloidal stability, particle size distributions of the base latex, viscosity average molecular weight (M¯v) of the copolymer, latex particle morphology, glass transition temperature (Tg) of a copolymer and thermal gravimetric analysis (TGA). Particle size of the base latex decreases (Z‐average from 246.48 to 143.69 nm) upon increasing the amount of PDMS surfactant in the recipe (up to 6 wt%). The presence of PDMS surfactant in the hybrid surfactants led to a significant increase in the solid content (from 48.71 to 51.31 wt%), viscosity (from 334 to 806 centipoise, cp) and M¯v (from 1.91 × 105 to 2.34 × 105 g mol−1). Thermal stability and Tg of the copolymer were increased with addition of PDMS surfactant (thermal stability from 344.77 to 389.81 °C and Tg from −20.7 to 21.7 °C). The colloidal stability evaluated using the electrolyte addition method was improved with addition of PDMS surfactant. The uniform morphological structure of the final particle is the main effect of using PDMS in the hybrid surfactants.

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