Atomic force microscopy (AFM) is used to study the morphology evolution upon thermal treatment of a thin composite film typically used for polymer solar cells application. This film consists of poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) and 1-(3-methoxycarbonyl)propyl-1-phenyl-[6,6]-methanofullerene (PCBM) with 80 wt % of PCBM in the composite. AFM topographic images clearly demonstrate that PCBM crystal clusters grow up out of the film, and the areas surrounding the crystals become thinner due to the depletion of PCBM material, which causes the phase separation in the composite film upon annealing. Volume quantification analysis on these sequential AFM topographic images in-situ recorded during annealing shows that the volumes of both PCBM crystals and depletion zones are significantly increased during the initial annealing times, followed by a stable period indicating the occurrence of equilibrium state. The different morphology evolution kinetics between the depletion zones and PCBM crystals is mostly due to the asynchronism between the move out of PCBM from its original position and collapse down of the film wherein. The global equilibrium state is finally achieved as most of the PCBM in the whole film has been depleted for crystal growth.

SUMMARYA novel flame retardant (DVN) containing silicon, phosphorus, and nitrogen has been synthesized from the reaction of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), vinylmethyldimethoxy silane (VMDMS) and N --(aminoethyl)--aminopropyle methyl dimethoxy silane (NMDMS), then incorporated into polycarbonate/acrylonitrile butadiene styrene (PC/ABS) alloy. The flame retardancy of PC/ABS/DVN is evaluated by cone calorimeter and limited oxygen index (LOI) and the thermal degradation behavior is investigated by thermogravimetric analysis under nitrogen and air. The PC/ABS/DVN sample was thermally degraded at 400 • C for different amounts of time and studied by Fourier transform infrared spectroscopy to better understand the mechanism of flame retardancy. The results show that the thermal stability and flame retardancy of PC/ABS are improved by incorporation of DVN. Scanning electric microscopy results show that the outer surface of the char layer of PC/ABS/DVN after the LOI test is smooth and the internal structure is like swollen cells, which benefits the flame retardancy of PC/ABS.

Novel halogen‐free compounds [9,10‐dihydro‐9‐oxa‐10‐phosphaphanthrene‐10‐oxide/vinyl methyl dimethoxysilane/N‐β‐(aminoethyl)‐γ‐aminopropyl methyl dimethoxysilane (DOPO–VMDMS–NMDMS)] that simultaneously contain phosphorus, nitrogen, and silicon have been synthesized through the reaction of 9,10‐dihydro‐9‐oxa‐10‐phosphaphanthrene‐10‐oxide (DOPO), vinyl methyl dimethoxysilane (VMDMS), and N‐β‐(aminoethyl)‐γ‐aminopropyl methyl dimethoxysilane (NMDMS). The chemical structure and properties of DOPO–VMDMS–NMDMS have been investigated with Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, phosphorous nuclear magnetic resonance, and thermogravimetric analysis (TGA). These synthesized flame retardants have been blended with a poly[2,2‐propane‐(bisphenol) carbonate]/acrylonitrile butadiene styrene (PC/ABS) alloy. The flame‐retardant properties of these mixture samples have been estimated with the limiting oxygen index (LOI), and the thermal stability has been characterized with TGA. The LOI value of PC/ABS/DOPO–VMDMS–NMDMS is enhanced up to 27.2 vol % from 21.2 vol %, and the char yield is also improved slightly (from 12 to 17%) with 2.8 wt % phosphorus, 3.0 wt % silicon, and 0.5 wt % nitrogen (at a 30 wt % loading of DOPO–VMDMS–NMDMS). The results show that there is a synergistic effect of the elements phosphorus, silicon, and nitrogen on the flame retardance. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1542–1551, 2007