Crew-cut micelle-like aggregates of various morphologies prepared from polystyrene-b-poly(acrylic acid), PS-b-PAA, diblock copolymers under near-equilibrium conditions, were studied by transmission electron microscopy (TEM). The insoluble block (PS) contents in the copolymers ranged from 80 to 98 wt %. In spherical micelles, the micelle cores, formed by aggregation of the PS blocks, were generally monodisperse. A comparison between star and crew-cut micelles showed that the latter are distinguished by a low density of corona chains on the core surface and a low degree of stretching of the PS blocks in the cores. As the PAA content in block copolymer decreased, the morphology of the aggregates changed progressively from spheres to cylinders, to bilayers (both vesicles and lamellae), and eventually to compound micelles consisting of an assembly of inverted micelles surrounded by a hydrophilic surface. The compound micelles are believed to be a new morphology for block copolymers. The addition of homopolysty...

Multiple Morphologies and Characteristics of “Crew-Cut” Micelle-like Aggregates of Polystyrene-b-poly(acrylic acid) Diblock Copolymers in Aqueous Solutions

The melt-state phase behavior of isotactic polypropylene (i-PP) blended with a series of poly(ethylene/ethylethylene) random copolymers has been investigated using small-angle neutron scattering (SANS). These PEExx copolymers, where xx is the percentage of ethylethylene (EE) units, were prepared by hydrogenation of anionically polymerized polybutadienes with controlled amounts of 1,2 addition. Random phase approximation (RPA) fits to the scattering data for blends of i-PP with a deuterated, low molecular weight PEE90 at 180 °C indicate a statistical segment length for i-PP that is 10% less than that reported previously. Scattering from blends of i-PP with higher molecular weight PEE90 and PEE73 at 180 °C can be quantitatively fit using the RPA theory with χ as the only adjustable parameter, indicating melt miscibility. PEE46 and PEE62 are strongly and marginally immiscible, respectively, with i-PP at 180 °C. These results establish a “window” in EE content in which these random copolymers can form single ...

Phase Behavior of Isotactic Polypropylene−Poly(ethylene/ethylethylene) Random Copolymer Blends

A systematic approach was used to study and compare the bonding of an ethylene-octene random copolymer and a low-density polymer, injection molded over polypropylene homopolymer. Wide ranges of overmolding and cooling interface temperatures and packing pressures were explored. Standard peeling tests were conducted at room temperature on overmolded samples, to measure the bonding strength. Large differences were found for bonding strength for both ethylene-based polymers, which are explained on a molecular basis. The analysis of the experimental results gives strong indications about the bonding mechanism and the temperatures and time scaleinvolved in the process. Simple, reliable rules to design the overmolding process parameters for these polymers pairs are developed. Polym. Eng. Sci. 44:2110–2116, 2004. © 2004 Society of Plastics Engineers.

Sequential injection overmolding of an elastomeric ethylene-octene copolymer on a polypropylene homopolymer core

“Crew-cut” aggregates of polystyrene-b-poly(acrylic acid) block copolymers can be prepared by dissolving the copolymers in N,N-dimethylformamide (DMF) and adding water to the solution to induce aggregation of the styrene segments of the copolymer chains. The aggregates are formed at near-equilibrium conditions, and their structures are subsequently frozen by isolating them into aqueous solution by dialysis. Aggregates of a number of different morphologies have been prepared. The morphologies, identified by transmission electron microscopy, consist of spheres, rods, vesicles, lamellae, large compound vesicles, large compound micelles, etc. The formation of aggregates of different morphologies can be controlled by varying the copolymer composition, by changing the initial copolymer concentration in DMF, by adding ions (e.g. NaCl, CaCl2, HCl and NaOH, etc), or by adding homopolystyrene.

Structures of “crew-cut” aggregates of polystyrene-b-poly(acrylic acid) diblock copolymers

The invention relates to melt-miscible polyolefin blends, and a process for preparing the melt-miscible blends, of two or more polyolefins. Matching of the segment length of a modifying polyolefin with the segment length of a primary polyolefin, such as polypropylene or an ethylene/alpha-olefin copolymer, provides polyolefin blends heretofore unknown to be melt-miscible. A broad range of polyolefin blend compositions, and of polyolefin blends containing other polymers made compatible with the polyolefin blend compositions, are defined, all of the blend compositions having at least one melt-miscible polyolefin phase.

Miscible blend of polyolefin and polyolefin block copolymer

Isotactic polypropylene-compatible block copolymer

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Isotactic polypropylene-compatible block copolymer