The syntheses and characterization of three noncentrosymmetric main chain hydrogen bonded macromolecules which incorporate aniline, alkanoic acid, and alkanol hydrogen bond donor units are reported. These macromolecules participate in weak intermolecular hydrogen bonding as demonstrated using attenuated total reflectance (ATR) FTIR. The phase transitions of these macromolecules depend on the identity of the hydrogen bond donor. 1. Introduction Poled organic thin films are technologically useful materials [1–9] which have several advantages over traditional inorganic crystals including ease of processing [10], larger second order susceptibilities [11], an intrinsically low dielectric constant [10], and significantly faster responses [12–15]. Our approach to poled organic films involves surface-induced polar alignment of main chain noncentrosymmetric hydrogen bonded liquid crystalline macromolecules [16]. We have previously synthesized several main chain noncentrosymmetric hydrogen bonded macromolecules (Table 1) [16], and while several of these macromolecules possess liquid crystalline phases, the melting points of these macromolecules are very high and they exhibit poor solubilities in organic solvents [16–20]. Table 1: First generation noncentrosymmetric main chain hydrogen bonded macromolecules. In several of our studies, we found that replacing a benzoic acid hydrogen bond donor group with a weaker hydrogen bond donor (such as a OH group) in our macromolecules resulted in a large melting point depressions and increased solubility in organic solvents [19, 20] presumably due to the weaker donor-acceptor hydrogen bonding. Alkanoic acids, alkanols, and aniline are all weaker hydrogen bond donors than their benzoic acid or phenol analogs [21], therefore incorporating these hydrogen bond donors into our noncentrosymmetric hydrogen bonded macromolecules should result in lower melting points and increased solubility. In this paper, we report the synthesis and characterization of main chain noncentrosymmetric hydrogen bonded macromolecules incorporating alkanoic acid, alkanol, and aniline hydrogen bond donors and stilbazole acceptors. 2. Experimental Section 2.1. Materials All chemicals were purchased from Fisher or Aldrich chemical company and used as received. Tetrahydrofuran (THF) was distilled over sodium-benzophenone under an argon atmosphere. Chromatography was performed using Sorbent Technology 60 angstrom, 63–200？μm mesh silica (10940-25). Thin layer chromatography was performed using Whatman flexible plates with 250？μm layer of fluorescent silica gel
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