Syntheses, Polymerization, and Characterization of Novel Semifluorinated Methacrylates, Including Novel Liquid Crystalline Materials
Polymers and High Performance Materials
Ethyl alpha-(chloromethyl)acrylate was converted to a variety of new ether derivatives using triethylamine-catalyzed reaction with commercially available fluoroalkyl alcohols. Rapid, high-conversion polymerization of neat monomers occurred with 2,2'-azobis(isobutyronitrile) at 50-70-degrees-C. Monomers and polymers were characterized by FTIR, both solution- and solid-state C-13 NMR spectroscopy, differential scanning calorimetry, optical microscopy, viscosity, gel permeation chromatography (GPC), and X-ray analysis. Weight-average molecular weights (M(w)) estimated by GPC ranged from 3.02 x 10(5) to 7.59 x 10(5). Additionally, tert-butyl alpha-(hydroxymethyl)acrylate (tBHMA) was converted to alpha-(chloromethyl)acryloyl chloride in one step. This reactive intermediate allows incorporation of identical ester and ether moieties (e.g., trifluoroethyl) or mixed ester-ether units consisting of, for example, perfluoroalkyl ether units with either hydrophilic esters (based on oligomers of ethylene oxide) or lipophilic esters such as longer alkyl and tert-butyl derivatives. Polymers containing longer alkyl and tert-butyl ester units had M(w)(GPC) values ranging from 3.98 x 10(4) to 6.0 x 10(4). Monomers with a semifluorinated ether group containing ten CF2 units were found to form highly ordered smectic B-like mesophases, which were confirmed by optical microscopy and X-ray analysis. Especially interesting was the persistence of the order in polymers obtained by polymerization in the mesophase. For example, the ethyl ester polymer showed much sharper X-ray peaks when obtained by in situ polymerization (in the monomer liquid crystal phase) than polymer reprecipitated from solution. Analogous diacrylates were synthesized by reacting the chloromethyl acid chloride with various diols followed by ether formation with fluoroalcohols. Most interesting was the ability of the mono- and diacrylate compounds incorporating ethylene oxide ester units to form liquid crystalline phases similar to that of the ethyl ester monomer. All the polymers containing ten CF2 units in the side chain exhibited a single first-order transition by DSC (48-58-degrees-C) which corresponds to melting of the side chain crystals independent from the main chain behavior.
Jariwala, C. P.,
Mathias, L. J.
(1993). Syntheses, Polymerization, and Characterization of Novel Semifluorinated Methacrylates, Including Novel Liquid Crystalline Materials. Macromolecules, 26(19), 5129-5136.
Available at: http://aquila.usm.edu/fac_pubs/6653