K. E. Russell

Peroxide‐initiated grafting of maleic anhydride onto linear and branched hydrocarbons

The structural features of the grafting of maleic anhydride onto low-molecular-weight compounds have been elucidated using several spectroscopic and analytical techniques. Conclusive evidence for the occurrence of singly grafted anhydride residues in multiply grafted products has been established using 2,3-13C2 labeled maleic anhydride. In homogeneous solution, at the low concentrations of maleic anhydride employed, there is little evidence for oligomeric or polymeric grafts to dodecane, pristane, or squalane. The results suggest that isothermal grafting of maleic anhydride to hydrocarbon polymers should also lead to a predominance of single grafts.

Crystallization of side chains in copolymers of ethylene and 1‐alkenes

The phase structure of random copolymers of ethylene and ethylene-d4 with 1-octadecene and other 1-alkenes has been investigated. CPMAS 13C NMR spectra show that a fraction of the central sections of C16H33 side chains in ethylene-d4 copolymers are in ordered environments at 298 K. They give rise to resonances from 32.9 ppm to 33.8 ppm, which show that they are in trans conformations; T1C values for this group of resonances range from 1 s to 7 s. The remaining side chains are in an amorphous environment, the internal methylenes having a chemical shift of 30.8 ppm and a T1C close to 0.4 s. A Raman band at 1062 cm−1 in the spectrum of an ethylene-d4-1-octadecene copolymer is consistent with partial crystallization of side chains. Some side-chain crystallization also occurs in a 1-tetradecene copolymer. X-ray diffraction studies suggest that smaller side chains do not crystallize to a significant extent at 298 K.

Peroxide initiated maleic anhydride grafting: Structural studies on an ester‐containing copolymer and related substrates

Maleic anhydride (MAn) was grafted onto the low molecular weight esters methyl decanoate (MD) and methyl 2-ethylhexanoate (MEH) using the free-radical initiators Lupersol-101 and -130; the esters were used as model compounds for the copolymer poly(ethylene-co-methyl acrylate). The grafted products in both cases were isolated from the unreacted ester and were subjected to extensive analysis using spectroscopic and chromatographic techniques. Analysis of the grafted material indicated the presence of one or more succinic anhydride (SAn) residues grafted to the ester. In the case of the multiply grafted material it has been established conclusively by 13C-NMR using 2,3-13C2 labeled MAn that the multiple grafts exist as single units. A limited number of grafting experiments was performed on the copolymer in the melt and the graft-modified copolymer was characterized spectroscopically. Single graft units were observed.

Polyethylenes revisited: Waxs and the phase structure

Abstract The use of multiple Cauchy/Gauss envelopes to describe crystalline and amorphous reflections in the deconvolution of X-ray diffraction patterns is examined. Crystallinities were estimated for a number of ethylene polymers and copolymers with a variety of sample configurations and of band inputs. These are compared with crystallinities estimated from density and enthalpy of fusion data. The significance of the extra bands required to give an optimum fit with the diffraction pattern is discussed briefly.

Free radical grafting of N-methylmaleimide to hydrocarbons and polyethylene

Abstract N -Methylmaleimide has been grafted to eicosane, squalane and polyethylene using a peroxide initiator at 130–170°. The grafts, consisting of single N -methylsuccinimide units, are concentrated in product containing 6–14 grafts per hydrocarbon molecule. The reaction is of zero order with respect to N -methylmaleimide and of order 0.53 ± 0.06 with respect to peroxide initiator. At these reaction temperatures, the monomer is above its ceiling temperature and propagation occurs by hydrogen abstraction rather than by addition.

The preparation of polyisobutenes and polystyrenes with phenol end-groups

Abstract Polyisobutenes and polystyrenes with phenol end-groups may be prepared by cationic polymerization of isobutene and styrene in the presence of the appropriate phenol. Suitable initiators include stannic chloride and aluminum chloride. High proportions of phenolic end-groups are obtained with 2,6-dialkylphenols at concentrations in reaction mixtures of the order of 0.05 M. The end-groups are characterized by means of 1H and 13C NMR, u.v. and ESR of the phenoxy radicals obtained after oxidation with lead dioxide. In addition to its use in molecular weight determination, gel permeation chromatography with combined refractive index and u.v. detection gives information on the distribution of end-groups as a function of polymer molecular weight.