INTERFACIAL POLYMERIZATION OF MONOMOLECULAR AND LANGMUIR-BLODGETT-FILMS OF ((BUTOXYCARBONYL)METHYL)URETHANE DIACETYLENES

Monomolecular films of 3-BCMU, 4-BCMU, and 9-BCMU at the air-water interface were studied by measuring their surface pressure (pi) vs surface area per molecule (A) isotherms as well as by the visible absorption spectra of their polymerized Langmuir-Blodgett (L-B) films. The pi-A isotherms of all three n-BCMU monomers displayed a phase transition between an expanded state and a condensed state resembling that of their corresponding polymers. The expanded-state surface areas of 9-BCMU, together with a Corey-Pauling-Koltun (CPK) molecular space-filling model of 9-BCMU, suggest that appreciable diacetylenic-subphase interaction may cause kinking in the looped portions of the side chains. Visible absorption spectra of L-B films of 4-BCMU and 9-BCMU UV polymerized at the air-water interface revealed both a red and a blue form for the former, while the latter was composed of the blue form alone. Horizontally transferring in situ polymerized films of 4-BCMU and 9-BCMU to hydrophobic substrates produced a shift of lambda-max values to longer wavelengths. Polymerization after transfer to solid substrates resulted in only a blue form polymer for both 4-BCMU and 9-BCMU. The reversibility of the conformational coil to rod transition at the air-water interface was shown to depend on the nature of the side group (i.e., the value of n). Poly-4-BCMU showed 100% conversion back to the coil form after expansion to zero surface pressure, poly-3-BCMU showed only partial conversion, and poly-9-BCMU showed essentially no conversion. In situ polymerized 4-BCMU (blue form and red form) converted completely to the red form after expansion to zero surface pressure, while in situ polymerized 9-BCMU essentially remained in its initial blue form. Polymerization of a six-layer multilayer of 4-BCMU was compared to one having five intervening layers of arachidic acid and revealed a significant decrease in the percent polymerization of the latter. A possible explanation is that polymerization is taking place between adjacent layers as well as within a given layer in multilayers of 4-BCMU.