Modeling Random Methyl Branching in Ethylene/ Propylene Copolymers Using Metathesis Chemistry:  Synthesis and Thermal Behavior

Abstract

The structure of random ethylene/propylene (EP) copolymers has been modeled using step polymerization chemistry. Six ethylene/propylene model copolymers have been prepared via acyclic diene metathesis (ADMET) polymerization and characterized for primary and higher level structure using in-depth NMR, IR, DSC, WAXD, and GPC analysis. These copolymers possess 1.5, 7.1, 13.6, 25.0, 43.3, and 55.6 methyl branches per 1000 carbons. Examination of these macromolecules by IR and WAXD analysis has demonstrated the first hexagonal phase in EP copolymers containing high ethylene content (90%) without the influence of sample manipulation (temperature, pressure, or radiation). Thermal behavior studies have shown that the melting point and heat of fusion decrease as the branch content increases. Further, comparisons have been made between these random ADMET EP copolymers, random EP copolymers made by typical chain addition techniques, and precisely branched ADMET EP copolymers.

Synthesis of poly(sulfonate ester)s by ADMET polymerization

“…20,53 A comparison of the literature data suggests that an increase of the fraction of methyl groups has a more significant influence on the melting point of the corresponding polymer than an increase of the ester content. In addition, an increase of the methyl content was found to cause a change of the morphology from an orthorhombic to a hexaganol crystal structure, 53 whereas the orthorhombic structure was maintained in long-chain polyesters.…”

“…20,53 A comparison of the literature data suggests that an increase of the fraction of methyl groups has a more significant influence on the melting point of the corresponding polymer than an increase of the ester content. In addition, an increase of the methyl content was found to cause a change of the morphology from an orthorhombic to a hexaganol crystal structure, 53 whereas the orthorhombic structure was maintained in long-chain polyesters. 10 Mecking and coworkers propose two possible explanations for this effect; the decreased steric hindrance of the ester moiety versus the methyl group, and the influence of dipole-dipole interactions between ester groups on the packing.…”

gem‐Dimethyl Effects in the Thermal Behavior of Polyethylene

“…The 1 H NMR (300 MHz) and 13 C NMR (75 MHz) spectra were recorded on a Varian Associates Gemini 300 or VXR-300 superconducting spectrometer system. Chemical shifts for 1 H NMR were referenced to TMS and those for 13 C NMR were referenced to residual signals from CDCl 3 solvent.…”

“…This alternative approach is founded on equilibrium polycondensation chemistry (acyclic diene metathesis (ADMET) reaction) to precisely insert branches within polyethylene. [13,14] The course of this work has led to identifying parameters needed to render polyethylene completely amorphous.…”

Fractionation and characterization of an ethylene–propylene copolymer produced with a MgCl2/SiO2/TiCl4/diester‐type ziegler–natta catalyst

“…[11][12][13] Beyond this range, long crystallizable ethylene or propylene sequences are present in the backbone, and the copolymers are more similar to their homopolymers, which behave as thermoplastic materials. More recently, plenty of experimental results have proved that propylene units can enter the lattice of orthorhombic polyethylene (PE) crystals, [14][15][16][17] whereas ethylene units can also be partially incorporated into PP lattices. 18 Unfortunately, most of the research has been focused on ethylene-rich or propylene-rich EP copolymers, and the structure-property relationship of copolymers with intermediate compositions has been scarcely reported.…”