This article deals with the characterization of high trans‐1,4‐poly(butadiene) (TPBD) prepared by means of an anionic polymerization using an initiator composed of alkyl aluminum, n‐butyl lithium, and barium alkoxide. By controlling both initiator composition and polymerization temperature, a set of TPBD was prepared with well‐known number of 1,4‐trans units, molecular weight distribution, and average molecular weight. Analyses by differential scanning calorimetry and diffraction of wide‐angle X‐rays showed a direct relationship between the microstructure of the polymer and its thermal properties. By increasing the number of 1,4‐trans units (70–90%), the crystallinity of the polymer was increased (10–30%); polymers with less than 65% of 1,4‐trans units were amorphous, whereas TPBD with a number of 1,4‐trans units greater than 80% were polymorphous and presented two endothermic transitions. Summing up, the results presented in this article indicate that cyclohexane solutions of alkyl aluminum, n‐butyl lithium, and barium alkoxide allow produce polybutadienes with enough amount of 1,4‐trans units to display a regular microstructure that makes them susceptible to experience‐induced crystallization, likewise at a reaction rate similar to that observed for the commercial production of poly(butadiene) with n‐butyl lithium. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers

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Development of asphalt modification has been increased because of the need to have asphalt cements with better properties [1]. At low temperatures, asphalt is brittle and at high temperatures it flows. . Modification yields: a) reduction of thermal sensitivity, b) better sensitivity on loading time, c) better deformation strength, and d) better tension and fatigue strength. The styrene-butadiene-styrene (SBS), styrene-isoprene-styrene (SIS), EPDM, atactic polypropylene (APP), ethyl vinyl acetate (EVA) have been used as modification agents in asphalt binders [2,3]. Fluorescence microscopy is much often used in asphalt morphology characterization, although the results are usually poor. The purpose of this paper is to define a simple technique to elucidate morphologies from polymer -modified asphalts using scanning electron microscopy.An asphalt AC-20 Salamanca from Mexico was taken as the asphalt neat. The SBS -modified asphalt was prepared at 180°C, 2500 r.p.m. and 30 minutes in a Ross mixer. Modified asphalt was prepared with 12% by weight of a triblock Styrene-Butadiene-Styrene. The polymermodified asphalt sample was frozen with liquid nitrogen and then it was fractured. A crosssection area of sample was taken and mounted on an aluminum SEM specimen stub. The sample was stained by exposure to the vapor of an aqueous 1% OsO 4 solution overnight at room temperature. Micrographs were obtained using a JEOL JSM-5900 LV-SEM. Low vacuum mode and backscattered electron signal were used. Optical microscopy was performed in a microscope Olympus -Continuum using the fluorescence BX-FLA mode with a blue filter. Figure 1 shows a typical fluorescence microscopy image lt shows the morphology from SBSmodified asphalts. Light regions are rubber which are compatible with the maltenic fraction of asphalt and dark regions are asphaltenic fraction incompatible with polymer. Figure 2 shows an SEM image of the SBS-modified asphalt morphology stained with OsO 4 . Itis clear that SEM gave better contrast, magnification and resolution than fluorescence microscopy. Light regions correspond to the rubber phase and dark regions to the asphalt phase. It is convenient to notice that the morphology of SBS-modified asphalt has been found. It can be divided in three different phases: a SBS-rich phase figure 2a, b and c), an asphaltenic phase figure 2a, b and c) but also a third phase is present. That third phase shows semi-compatibility between asphaltenes and polymer compounds. This is shown in figure 2b and 2c as gray and diffuse regions.It has been established that the OsO 4 staining and backscattered electron signal in SEM-LV yielded better resolution and more details of SBS-modified asphalts than fluorescence microscopy. SEM made possible to detect three different phases in modified asphalt: a polymerrich region, a semi-compatible region and no -compatible region or asphaltenic phase.

Random, diblock, and triblock copolymers of butadiene and styrene, with a well‐defined, high number of 1,4‐trans units (c.a. 80%), were synthesized by anionic living polymerization using an initiator system composed of alkyl aluminum, n‐butyl lithium, and barium alkoxide. The thermal properties of the block copolymers obtained by sequential addition of monomers were basically determined by the 1,4‐trans units of the polybutadiene block. Kinetic data and 1H‐nuclear magnetic resonance analyses showed that simultaneous polymerization of butadiene and styrene provided copolymers with a predominantly random distribution. By increasing the styrene content, the thermal properties of these copolymers were modified; polymers with 80% content of 1,4‐trans units and 5% of styrene presented an endothermic transition at or slightly below room temperature (20°C), corresponding to the crystalline monoclinic form of high 1,4‐trans polybutadiene, whereas copolymers with 25–50% styrene content were amorphous. The glass transition temperature of these copolymers increased significantly as the styrene content was increased. Both the block and random copolymers have a sufficient number of 1,4‐trans units to display a regular distribution of structural units that makes them susceptible to strain‐induced crystallization, which is important for the manufacture of products such as high‐performance tires. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010