End-grafted polystyrene "brushes" of various thickness and grafting density on silica surfaces were synthesized by surface-initiated polymerization. The "brushes" were studied by contact angle measurements, ellipsometry, and scanning force microscopy (SFM). Wetting behavior of thin polystyrene film on the top of the grafted layers was investigated using optical microscopy and SFM. The film stability was strongly dependent on the grafting amount. We identified three grafting density regimes with respect to stability of the top polystyrene films: at small and very large grafting density the top film dewets "brushes", while at moderate grafting density the polystyrene film was stable after 80 h of annealing time at 155°C.

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Soybean oil (SBO) was modified with polystyrene via a radical graft polymerization reaction for use as a processing oil in tire tread compounds. Poly(styrene-butadiene)/polybutadiene rubber compounds with silica and carbon black, containing different processing oils including naphthenic oil (NO), aromatic oil (AO), SBO, and polystyrene-modified SBO (SBO-PS), were formulated, vulcanized, and tested. The curing behavior, mechanical properties, and dynamic properties were investigated. The cure test results showed that all SBO-based rubbers had a shorter scorch time and cure window than the NO- and AO-based rubbers. The tensile tests demonstrated that partial and complete replacement of NO with SBO led to reduced tensile modulus but increased elongation of rubber. For the rubbers compounded with SBO-PS and with a 50/50 mixture of NO/SBO-PS, tensile strength and elongation were higher than for the NO-based rubber. The same tendency was observed when SBO-PS–based rubbers were compared with SBO- and AO-based rubbers. SBO-PS–based rubbers demonstrated better tensile properties than AO-based rubbers and far better properties than SBO-based rubbers. In the tear resistance test and durometer hardness test, SBO-PS contained rubbers that showed similar properties to NO-containing rubber. The dynamic mechanical analysis of SBO-PS–containing rubbers demonstrated that use of this compound in tire treads is expected to improve both rolling resistance and wet traction when compared with an AO-based rubber. The modification of SBO with grafted PS is a promising method of making processing oil, which can replace petroleum-based processing oils with bio-based renewable oils in tire tread compounds while improving their properties.

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The adsorption features of two peroxide macroinitiators (PMIs) with various functionalities from their semi-dilute solutions on the silica surface were thoroughly investigated in the present work. These investigations include the study of the adsorption kinetics of PMI in diverse solvents and a detailed examination of the adsorbed layer structure with the aid of ellipsometry, scanning force microscopy (SFM), and contact angle measurements. Rearrangements of PMI macromolecules at the solid surface are supposed to be the main reason for the appearance of extremes on the kinetic curves and, besides, have a more pronounceable effect on adsorption rate than their diffusion rate to the surface even at the initial stage of the process. Both island-like and densely packed structures of absorbed layers were revealed by combining contact angle measurements and SFM. Surprisingly, even in the case when saturation of the adsorbed layer is reached, PMI does not completely occupy the substrate surface which is at least particularly reachable for the wetting liquids. PMIs adsorbed at the solid surface are intended for the formation of tethered polymer "brushes" via the initiation of "grafting from" polymerization.