ABSTRACT:Oxidative degradation of epoxidized natural rubber (ENR) was effectively performed in latex phase by using periodic acid at 30°C. The ENR was prepared from the epoxidation of natural rubber in latex phase using performic acid generated in situ by the reaction of hydrogen peroxide and formic acid. The prepared ENR latex was subsequently treated with periodic acid. It was found that the higher the amount of the periodic acid employed the faster the molecular weight of the ENR decreased. Different epoxidation levels of the ENR had no significant effect on the degradation reaction. Based on 1 H NMR analysis, the epoxide content in the epoxidized liquid natural rubber (ELNR) obtained was about the same as that observed in the ENR before degradation. FT-IR analysis showed an increase in carbonyl signal after prolonged reaction time or when higher amounts of periodic acid were employed. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 6 -15, 2005

Summary: Norbornenylazlactone (NBAz) was prepared by a Diels‐Alder cycloaddition between cyclopentadiene and 2‐vinyl‐4,4‐dimethyl‐5‐oxazolone. The stereoselectivity of this pericyclic reaction was in favour of endo isomers. The ring‐opening metathesis polymerization (ROMP) of NBAz was carried out in presence of ruthenium catalysts [(PCy3)2(Cl)2RuCHPh 1; (SIMes)(PCy3)(Cl)2RuCHPh 2 (SIMes: 1,3‐dimesityl‐4,5‐dihydroimidazol‐2‐ylidene); (PiPr3)2(Cl)2RuCHSPh 3; (PiPr3)(Cl)2RuCH(CH2)2C, N‐2‐C5H4N 4]. It was found that the exo isomer is much more reactive than the corresponding endo isomer. Some hypotheses of mechanism are suggested to justify the low polymerization rate of endo isomer using the results of NBAz derivatives as the hydrolyzed NBAz, 5, and the coupling product between NBAz and glycine methyl ester hydrochloride, 6. For exo‐NBAz, the propagating rate constant, kp, was determined with the four Ru‐initiators and their activity decreases in the order 2 > 1 > 3 > 4. Complementary kinetic measurements with 1 and 2 were given as kp/ki ratio. The ROMP of exo isomer was faster with 2 than 1 in spite of a worse control of the chains size. The azlactone ring survived intact during the polymerization and may be used for further reactions with nucleophiles.ROMP of NBAz by ruthenium initiators.magnified imageROMP of NBAz by ruthenium initiators.

SYNOPSISSurface grafting of polymeric materials, such as films and fibers, may improve their reactive surface properties. Polypropylene active sites that should initiate a surface postgrafting can be formed by either nitrogen cold plasma or an electron-beam irradiation. The plasmamodified polymer surface is cross-linked and functionalized with primary amino groups and with oxidized groups, and it is almost not degraded. Electron-beam-modified polypropylene is also functionalized through an aging reaction, emphasized by a high radical concentration. In both cases, active surface films are susceptible to react with monomers in a postgrafting reaction. The grafting yield and rate of acrylic acid were shown to be dependent on the formed amino group concentration: The hydrophilic character of the modified polypropylene surface enhances the acrylic acid approach. The electron-beam treatment leads also to a reactive surface that can initiate a grafting reaction. But its yield and rate are dependent on the radical concentration: radicals formed during the irradiation. 0 1994 John Wiley & Sons, Inc.