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Morphology Formation (morphology + formation)
Selected AbstractsEffects of addition of acrylic compatibilizer on the morphology and mechanical behavior of amorphous polyamide/SAN blendsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010D. Becker Abstract Amorphous polyamide (aPA)/acrylonitrile-styrene copolymer (SAN) blends were prepared using methyl methacrylate-maleic anhydride copolymer MMA-MA as compatibilizer. The aPA/SAN blends can be considered as a less complex version of the aPA/ABS (acrylonitrilebutadiene-styrene) blends, due to the absence of the ABS rubber phase in the SAN material. It is known that acrylic copolymer might be miscible with SAN, whereas the maleic anhydride groups from MMA-MA can react in situ with the amine end groups of aPA during melt blending. As a result, it is possible the in situ formation of aPA-g-MMA-MA grafted copolymers at the aPA/SAN interface during the melt processing of the blends. In this study, the MA content in the MMA-MA copolymer and its molecular weight was varied independently and their effects on the blend morphology and stress,strain behavior were evaluated. The morphology of the blends aPA/SAN showed a minimum in the SAN particle size at low amounts of MA in the compatibilizer, however, as the MA content in the MMA-MA copolymer was increased larger SAN particle sizes were observed in the systems. In addition, higher MA content in the compatibilizer lead to less ductile aPA/SAN blends under tensile testing. The results shown the viscosity ratio also plays a very important role in the morphology formation and consequently on the properties of the aPA/SAN blends studied. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Core,shell structure and segregation effects in composite droplet polymer blendsAICHE JOURNAL, Issue 4 2003Joël Reignier Core,shell morphology formation within the dispersed phase was studied for composite droplet polymer-blend systems comprising a high-density polyethylene matrix, polystyrene shell and different molecular weights of poly(methyl methacrylate) core material. The blends were prepared in the melt using an internal mixer, and the morphology was analyzed by electron microscopy. Changing the viscoelastic properties of the core in the dispersed phase dramatically affects PS-PMMA segregation within the dispersed composite droplet itself. A high-molecular-weight-PMMA core contains a large quantity of occluded PS inclusions, while the low-molecular-weight PMMA results in a perfectly segregated PS shell and PMMA core. These phenomena were attributed to the viscosity of the PMMA. Using the latter system, a direct microscopic study of the shell formation process demonstrates unambiguously that under conditions of perfect segregation, the onset of complete shell formation corresponds to a shell thickness that is close to two times the radius of gyration of polystyrene. Thus, the thinnest possible shell in such a system possesses a molecular-scale thickness. The system with the high-molecular-weight-PMMA core demonstrates an onset of complete shell formation that is displaced to higher concentrations due to the poor segregation effect. By counterbalancing the effects of viscosity ratio and interfacial effects on the composite droplet size, it is possible to generate perfectly segregated core,shell dispersed-phase morphologies of almost identical size with a controlled shell thickness ranging from 40 to 300 nm. [source] Salmonella enterica phage-resistant mutant colonies display an unusual phenotype in the presence of phage Felix 01LETTERS IN APPLIED MICROBIOLOGY, Issue 6 2007G. O'Flynn Abstract Aims:, To investigate irregular colony morphology formation in Salmonella enterica serovar Typhimurium DPC6046 in the presence of a lytic phage, Felix 01. Methods and Results:, Phage-resistant derivatives of the parent strain DPC6046 were isolated which exhibited an irregular colony morphology. These were subjected to viability studies by using confocal scanning laser microscopy and live/dead BacLight stain to evaluate the cell viability within the colony. The phenomenon was also observed with other S. enterica serotypes tested which were normally sensitive to phage Felix. In the case of strain DPC6046, dead cells were clearly evident at the irregular edges of the phage-resistant colonies in locations where the cell density was lower. This colony morphology was not apparent with two other Salmonella phages tested. Conclusions:, These findings support the hypothesis that the unusual morphology is due to reversion to phage sensitivity and consequent cell death within the colony as it forms. Significance and Impact of the Study:, The irregular colony morphology observed is peculiar to phage Felix. The confocal scanning laser microscopy methodology allowed the basis for the irregular morphology to be elucidated. [source] Synthesis and Self-Assembly of Novel Amphiphilic Six-Armed Star Copolymers TP[PDMAEMA -b- PSt]6MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 6 2009Kang Tao Abstract A triphenylene (TP)-based hexafunctional initiator was prepared and used in successive ATRP of DMAEMA and St. Well-defined six-armed star block copolymers TP[PDMAEMA -b- PSt]6 bearing hydrophilic backbones inside and hydrophobic blocks outside were successfully synthesized. The self-assembly behaviors of the novel amphiphilic copolymer were further investigated. Co-existing spherical and bowl-shaped aggregates were observed from their neutral aqueous solution, while large spherical structures with different dimensions were obtained from their diluted HCl and CF3COOH aqueous solution, respectively. Dynamic light scattering in different aqueous solutions were conducted to give further confirmation. The possible mechanism of the morphology formation was proposed. [source] | ||||||||||