Solution acyclic diene metathesis (ADMET) polymerization using Grubbs' fi rst-generation catalyst leads to the direct synthesis of polymers containing hydroxyl groups. Secondary alcohols are placed precisely at specifi c intervals on an unsaturated hydrocarbon backbone. Increasing the number of methylene spacers decreases the frequency of the pendant groups from every 15th carbon to every 21st carbon. The complete hydrogenation of the unsaturated polymers yields model representatives of well-defi ned ethylene-vinyl alcohol copolymers. Despite the decrease in branch frequency in both the homopolymers and randomized versions of such polymers, surprisingly, the precision does not have an infl uence on the thermal properties, and they are all similar in nature. It is concluded that hydrogen bonding dominates the polymer behavior, rather than the precision in hydroxyl-group placement along the polyethylene chain.
The morphological changes of polyethylenes bearing precisely spaced "defects" are reviewed, focusing on the effects of defect frequency, size, and functionality on crystallization and crystalline structure. The precise defect interval is imparted through acyclic diene metathesis polymerization of structurally symmetric diene monomers. Studies have included structural characterization by differential scanning calorimetry, wide-angle X-ray scattering, small-angle X-ray scattering (SAXS), and infrared spectroscopy. The collective results are presented separately for functionalized polyethylenes and for those containing alkyl chain branches, as these two classes of polymers vary greatly in morphology.
Wide-angle X-ray scattering (WAXS) and temperature-dependent Fourier transform infrared spectroscopy (FTIR) spectroscopy are used to study hydrogen bonding interactions of a hydroxyl-functionalized polyethylene (PE) prepared by acyclic diene metathesis (ADMET) chemistry. The hydroxyl polymer exhibits an orthorhombic unit cell structure with characteristic reflection planes at (110) and (200), comparable to pure crystalline PE. These data unequivocally demonstrate that the OH branch is excluded from the PE lamellae. Furthermore, the polymer melts 100 °C higher than all previous analogous polymers possessing precision placed long aliphatic branches that also are excluded from PE lamellae. Temperature-dependent FTIR spectroscopy from ambient to 150 °C, followed by cooling to 125 °C supports exclusion of the hydroxyl group from the crystalline lattice. It is concluded that these hydroxyl groups form stable physical networks in the amorphous region via hydrogen bonding and are important for the overall morphology of such polymers.
2-Bromophenyl salicylate is synthesized from 2-benzyloxybenzoic acid in two steps. The final compound has been characterized by IR, 1H-NMR, 13C-NMR and HRMS. The melting point for 2-bromophenyl salicylate is provided
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