Systematic Studies of Morphological Changes of Precision Polyethylene

Abstract

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.

Effect of Short Chain Branching on the Interlamellar Structure of Semicrystalline Polyethylene

“…Interestingly, at a relatively low co-monomer content, authors found branches to be uniformly distributed between the interphase and amorphous phases for both LLDPEs, while at high co-monomer content branches were found to be more populous in the amorphous phase than in the interphase for the ZN-LLDPE; the latter was attributed to the non-uniform distribution of co-monomer among chains of different length produced by the ZN catalyst. Experiments [11][12][13] have also shown that the regu-5 lar unit cell structure of the crystal can be distorted by the presence of branches. Incorporation of methyl branches and, to a lesser extent, ethyl branches into the crystal causes distortion of the unit cell.…”

Recent developments in the synthesis of sequence controlled polymers

“…These monomers underwent ADMET to afford model polyethylene (after hydrogenation) with precisely located side groups ( Figure 16). The crystallization behavior of the products was remarkably influenced by the precisely spaced "defects" along the polyethylene backbone [68].…”

The chemistry of the carbon-transition metal double and triple bond: Annual survey covering the year 2014

“…(10) preparation of stereoregular polymers via ROMP [37]; (11) preparation of self-assembled supramolecular polymers [38]; (12) combining ROMP and thiol-ene coupling chemistry for preparation of linear and nonlinear macromolecules [39]; (13) synthesis of cyclo-polyolefins through ring expanding metathesis polymerization [40]; (14) precision polymers through ADMET polymerization [41,42]; (15) systematic studies of morphological changes of ADMET-derived precision polyethylene [43]; (16) concurrent cross metathesis and enzymatic oxidation reactions [44]; (17) rhenium oxide based olefin metathesis [45]; and (18) olefin metathesis over molybdenum-exchanged zeolites [46]. Additional reviews in languages other than English include: (1) olefin metathesis in complex synthesis [47]; (2) Z-selective olefin metathesis catalysts and their applications [48]; (3) modification of biodiesel using olefin metathesis [49]; (4) cyclic aminocarbene complexes (Bertrand carbene complexes) in olefin metathesis reactions [50]: (5) progress in ROMP of dicyclopentadiene [51]; and (6) the role MgO in WO 3 / SiO 2 catalyzed olefin metathesis [52].…”