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Macrophase Separation (macrophase + separation)
Selected AbstractsBlends of high density polyethylene and ethylene/1-octene copolymers: Structure and properties,JOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2007Rameshwar Adhikari Abstract The morphology formation in the blends comprising a high density polyethylene (HDPE) and selected ethylene/1-octene copolymers (EOCs) was studied with variation of blend compositions using atomic force microscopy (AFM). The binary HDPE/EOC blends studied showed well phase-separated structures (macrophase separation) in consistence with individual melting and crystallization behavior of the blend components. For the blends comprising low 1-octene content copolymers, the lamellar stacks of one of the phases were found to exist side by side with that of the another phase giving rise to leaflet vein-like appearance. The formation of large HDPE lamellae particularly longer than in the pure state has been explained by considering the different melting points of the blend components. The study of strain induced structural changes in an HDPE/EOC blend revealed that at large strains, the extensive stretching of the soft EOC phase is accompanied by buckling of HDPE lamellar stack along the strain axis and subsequent microfibrils formation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1887,1893, 2007 [source] Thermoresponsive brush copolymers with poly(propylene oxide- ran -ethylene oxide) side chains via metal-free anionic polymerization "grafting from" techniqueJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2010Junpeng Zhao Abstract Thermoresponsive brush copolymers with poly(propylene oxide- ran -ethylene oxide) side chains were synthesized via a "grafting from" technique. Poly(p -hydroxystyrene) was used as the backbone, and the brush copolymers were prepared by random copolymerization of mixtures of oxyalkylene monomers, using metal-free anionic ring-opening polymerization, with the phosphazene base (t -BuP4) being the polymerization promoter. By controlling the monomer feed ratios in the graft copolymerization, two samples with the same side-chain length and different compositions were prepared, both of which possessed high molecular weights and low molecular weight distributions. The results from light scattering and fluorescence spectroscopy indicated that the brush copolymers in their dilute aqueous solutions were near completely solvated at low temperature and underwent slight intramolecular chain contraction/association and much more profound intermolecular aggregation at different stages of the step-by-step heating process. Above 50 °C, very turbid solutions, followed by macrophase separation, were observed for both of the samples, which implied that it was difficult for the brush copolymers to form stable nanoscopic aggregates at high temperature. All these observations were attributed, at least partly, to the distribution of the oxyalkylene monomers along the side chains and the overall brush-like molecular architecture. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2320,2328, 2010 [source] The Effect of Nanofiller on the Thermomechanical Properties of Polyimide/Clay NanocompositesMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 6 2008Khine Yi Mya Abstract The interaction between PI and partially exfoliated clay nanofillers is investigated by studying the thermomechanical properties of the resulting nanocomposites by NMR, XPS, XRD, TEM, TGA, TMA, and DMA. XRD and TEM showed more exfoliated structure at ,2.5 wt.-% clay and a macrophase separation above 2.5 wt.-% clay. Td and the storage modulus increased with increasing clay content. A decrease in CTE was observed for clay content ,2.5 wt.-% because of the good dispersion of the clay in the polymer and the reduced segmental motion of polymer matrix. NMR confirmed the quality of clay dispersion, and XPS exhibited that the interaction in PI/2.5 wt.-% clay is much stronger than that in PI/5 wt.-% clay. [source] Monte-Carlo Study of Triblock Copolymer/Homopolymer Blend FilmsMACROMOLECULAR THEORY AND SIMULATIONS, Issue 1 2007Yongmin Huang Abstract The morphologies of triblock copolymer/homopolymer blend films confined between two neutral hard walls were studied via MC simulations on a simple cubic lattice. For ABA/A and ABA/B blend films, the effects of ,h (the volume fraction of the homopolymer) and Mh/Mb (the ratio of the molecular mass of the homopolymer to that of the corresponding blocks) on the morphologies were investigated in detail. For both ABA/A and ABA/B blend films, a higher ,h or Mh/Mb would result in stronger macrophase separation between the triblock copolymer and homopolymer. For ABA/C blend films, Mh/Mb hardly influences the morphologies of homopolymer domains regardless of whether the homopolymer C is more compatible with block A or with block B. Compared to AB/A and AB/C blend films, the morphologies of ABA/A (or ABA/B) and ABA/C blend films are much more irregular. The simulated results in this work show good consistency with experiments and other simulations. [source] Preparation and mechanical properties of waterborne polyurethane/carbon nanotube compositesPOLYMER COMPOSITES, Issue 5 2009Cai-Xia Zhao Waterborne polyurethane (WBPU) and multiwalled carbon nanotubes (CNTs) composite films with 0,4.0 wt% CNTs were prepared by ultrasonic dispersion of carboxylic acid-functionalized CNTs in WBPU followed by emulsion casting process. The elongations at break of the WBPU/CNTs composites increase with the incorporation of CNTs. The tensile strength and crystallinity of the nanocomposite films with lower CNTs contents (<2 wt%) increase obviously; while the tensile strengths of the composites with more CNTs (,2 wt%) decrease, in contrast to the pure PU film. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations indicated that the CNTs are uniformly dispersed in the composites incorporated with lower CNTs contents (,1.5 wt%). However, aggregation of CNTs increased with increasing CNTs content in the WBPU/CNTs composites, causing the macrophase separation. The dispersion state of the CNTs affects the crystallinity of the PU matrix and the phase separation of the composites, which are two key factors to influence the mechanical properties of the WBPU/CNTs composites. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source] | ||||||||||