Journal of Polymer Science: Polymer Symposia最新文献

Five vinylcatechol precursors have been synthesized by either alcohol dehydration or Wittig coupling techniques. Dehydration of the appropriate sec-phenethyl alcohol is the most efficient synthetic approach: the following monomers (yields) are reported: 5-vinyl-1,3-benzodioxole, I (63%); 3,4-dimethoxystyrene, II (45%); 2,3-dimethoxystyrene, III (85%);6-vinyl-1,4-benzodioxane.IV(65%); and4-vinyl-l,3-benzodioxole, V(50%). The monomers can be converted by free-radical techniques to polymers with molecular weights up to 95,000. Monomers I, II, IV, and V polymerized in the presence of stannic chloride; monomers I, III, and IV yielded polymers upon treatment with butyllithium. With the exception of poly IV, the blocking groups can be removed by treatment with boron trichloride followed by methanolysis to liberate poly(3-vinyl- or 4-vinylcatechol). Suprisingly, the stability of the catechol polymers depends upon the substituent distribution; poly(3-vinylcatechol) is more stable than any polycatechol previously reported. It is soluble in methanol, autooxidizes very slowly, but can be oxidized by ceric ammonium nitrate to poly(3-vinyl-1,2-benzoquinone).

A single-crysial polyethylene-bound palladium catalys: was prepared and used in the synthesis of acelylene-terminated monomers.

A polymeric analogue of crystal violet in which the triarylmethane moiety is pendent from a polyester backbone has been examined as a sensitizer for photoconductivity in poly-N-vinyicarbazole. In both positive and negative surface charging modes, the dark decay rates increase linearly with sensitizer concentration, but are lower than those for monomeric crystal violet sensitization. The photodecay rates, in both modes, show optimal concentration dependence and are higher than those for monomeric crystal violet.

The synthesis and characterization of uracil- and thy mine-containing polynucleotide analogs with a linear polyethylenimine backbone is described. Hypochromicity is observed for these analogs in DMSO and in DMSO/H₂O solutions and found lo increase as the percent water increases. The influence of water on the 240- to 280-nm absorptions of the analogs and their monomer models is correlated with the mobiliiy of the nucleic-acid-base-con tain ing pendant to the polymeric backbone. An impure 5-fluorouracil analog has been prepared, and its increased solubility in water relative to the corresponding uracil analog has been noted. A thy mine-containing analog with a PEI/PEOXZ backbone has been synthesized. The analog consists of water-soluble and insoluble forms characterized by NMR.

The stereoisomeric configurations of poly(2,5-tetraliydrofurandiyl), 1, and poly(2,3-tetrahydrofurandiyl), 2, have been investigated by conformational analysis. Similar results were obtained for 1 and 2, Threodiisotactic (tit) and erythrodisyndiotactic (est) configurations could form low energy helical conformations, whereas erythrodiisotactic (eit) and threodisyndiotactic (tst) configurations generally formed low energy linear conformations. Helical conformations of I placed oxygen atoms at the interior of the helices, but helical conformations of 2 placed oxygen atoms more toward the periphery. The results of ion-binding experiments are interpreted in terms of the results of conformational analysis. Ion-binding experiments are consistent with the suggestion that configurations that can form low energy, helical conformations with oxygen atoms at the interior of the helices could bind cations efficiently. Configurations that can form only low energy linear conformations, or that form helices with oxygen atoms toward the periphery of the helices, should be inefficient in binding cations.

MS analysis was used to identify the cyclic oligomers formed in the polycondensation reactions of dibromoalkanes with dithiols. Cyclic oligomers with only an even number of repeating units are detected among the poly condensation reaction products.

Ozone resistance and high flex life are some of the important features of elastomers needed in the rubber industry. EPDM, a terpolymer of ethylene, propylene, and small amounts of a nonconjugated diene, has a saturated carbon-carbon backbone and therefore shows excellent resistance to ozone and aging, and good flex properties. However, butyl rubber (1IR) has a small amount of unsaturation in its carbon-carbon backbone and consequently does not exhibit as good ozone resistance and aging characteristics as EPDM. We discovered a family of new rubbers named Hexsyn^TM, which were synthesized by copolymerizing higher α-olefins (C₄-C₁₀) with a mixture of 4-methyl- and 5-methyl-1,4-hexadienes. One outstanding Hexsyn™ rubber is a copolymer of 4-hexene and the 5-methyl-1,4-hexadiene. This copolymer uniquely combines the useful properties of EPDM and butyl. Outstanding features are excellent flex life, excellent ozone resistance, good compression set resistance, and high damping.

Due to its excellent flex life, Hexsyn^TM( (hexene copolymer) has been found useful in fabricating experimental pumping diaphragms of air-driven artificial hearts of calves and also for left ventricle assist devices. This rubber has found application as a flexing element in artificial finger joints for damaged or diseased human fingers.