Structurally well-defined C4F9, C7F15, C10F21 and C13F27 end-functionalized polystyrene (RF-PS) and polybutylmethacrylate (RF-PBMA) were prepared by Atom Transfer Radical Polymerization using RF-tagged initiators. Blends (1/1 wt/wt) of these polymers were studied by differential scanning calorimetry (DSC), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), optical transmittance(OT), electron microscopy (TEM) and optical transmittance (OT). The RF-PS/RF-PBMA blends having molecular weights of 20,000 and C7F15 or larger end groups, were optically transparent. The AFM micrographs show crater, necklace and other RF mediated morphologies typically at the submicron scale. TEM images of the corresponding blends show assembly of elongated domains with sizes in the micron or nanometer scales depending on MW and RF size. Thus, above about 3 wt percent RF content only microphases (m) are observed while below 1.8 wt percent only macrophases (M) are seen. A semiquantitative "phase diagram" of the blends shows that lower MWs and longer RF groups improve phase compatibilities. (C) 2013 Elsevier Ltd. All rights reserved.