Synthesis and Properties of Amphiphilic Poly(1,4-Phenylene Ethynylene)S Bearing Alkyl and Semifluoroalkyl Substituents

New poly(1,4-phenylene ethynylenes)s (PPEs), in which each phenylene unit is substituted with both semifluoroalkoxy(-O(CH2)m(CF2)nF) and dodecyloxy (-O(CH2)(12)H) groups, are amphiphilic by virtue of the self-aggregating properties fo the dissimilar side chains. Sonogashira polymerization of 4-iodophenylacctylenes bearing semifluoroalkox y and alkoxy groups in the 2- and 5-positions, respectively, alfords polymers with regular relative placement of the dissimilar side chains (i.e., "regioregular" materials containing only "head-to-tail" drads) This provides a Janus type structure The assembly of these polymers was studied as a function of the length of the fluoroalkyl segment in the side chain by X-ray diffraction, differential scanning calorimetry, and UV-vis spectroscopy. The properties of these polymers were compared to analogues with random relative placement of side chains (i.e., materials containing a mixture of "head-to-head", "tail-to-tail" and "head-to-tail" drads), and to a nonfluorinated analogue. In contrast to the highly ordered and oriented solid phases formed by alkyl/semifluoroalkyl substituted poly(bithiophene)s, and despite their defined molecular structure, the amphiphilicity of the new semifluoro PPEs impedes their crystallization. While the overall structure of the regioregular polymer is amphiphilic, in which the dissimilar side chains are expected to segregate, we ascribe the lack of crystallinity to the disruption of side chain crystallization by virtue of having the alkyl and fluoroalkyl segments withing a single side chain. These side chain cannont pack in an interdigitated fashion by virtue of the disparate segments, thereby leading to poorly ordered, or amorphous, solid materials.