Copolymers of ethene and 1-octene, 1-dodecene, 1-octadecene, and 1-hexacosene were carried out with [Ph 2 C(2,7-ditert BuFlu)(Cp)]ZrCl 2 /methylalumoxane as a catalyst to obtain short-chain branched polyethylenes with branch lengths of 6-26 carbon atoms. This catalyst provided high activity and a very good comonomer and hydrogen response. In this study, the influence of the length and number of the side chains on the mechanical properties of the materials was investigated. The crystalline methylene sequence lengths of the copolymers and lamellar thicknesses were calculated after the application of a differential scanning calorimetry/successive self-annealing separation technique. By dynamic mechanical analysis, the storage modulus as an indicator of the stiffness and the loss modulus as a measure of the effect of branching on the a and b relaxations were studied. The results were related to the measurements of the polymer density and tensile strength to determine the effect of longer side chains on the material properties. The hexacosene copolymers had side chains of 24 carbons and remarkable material properties very different from those of conventional linear low-density polyethylenes. The side chains of these copolymers crystallized with one another and not only parallel to the backbone lamellar layer, depending on the hexacosene concentration in the copolymer. The side chains crystallized even at low hexacosene concentrations in the copolymer. A transfer of these results to 16 carbons

No abstract

No abstract

No abstract

The atom transfer radical polymerization of methyl methacrylate (MMA) and n-butyl methacrylate (n-BMA) was initiated by a poly(ethylene oxide) chloro telechelic macroinitiator synthesized by esterification of poly(ethylene oxide) (PEO) with 2-chloro propionyl chloride. The polymerization, carried out in bulk at 90 8C and catalyzed by iron(II) chloride tetrahydrate in the presence of triphenylphosphine ligand (FeCl 2 Á 4H 2 O/PPh 3 ), led to A-B-A amphiphilic triblock copolymers with MMA or n-BMA as the A block and PEO as the B block. A kinetic study showed that the polymerization was first-order with respect to the monomer concentration. Moreover, the experimental molecular weights of the block copolymers increased linearly with the monomer conversion, and the molecular weight distribution was acceptably narrow at the end of the reaction. These block copolymers turned out to be water-soluble through the adjustment of the content of PEO blocks (PEO content >90% by mass). When the PEO content was small [monomer/macroinitiator molar ratio (M/I) ¼ 300], the block copolymers were water-insoluble and showed only one glass-transition temperature. With an increase in the concentration of PEO (M/I ¼ 100 or 50) in the copolymer, two glass transitions were detected, indicating phase separation. The macroinitiator and the corresponding triblock copolymers were characterized with Fourier transform infrared, proton nuclear magnetic resonance, size exclusion chromatography analysis, dynamic mechanical analysis, and differential scanning calorimetry. V V C 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: [5049][5050][5051][5052][5053][5054][5055][5056][5057][5058][5059][5060][5061] 2005