Long‐chain branched random polyethylene via acyclic diene metathesis (ADMET) copolymerization

Abstract

Five types of ethylene/α‐alkene model copolymers containing 21‐carbon alkyl branches have been synthesized via acyclic diene metathesis (ADMET) copolymerization. The overall branch content is controlled by varying the feedstock ratio of the long‐chain branched symmetrical α, ω‐diene and 1,9‐decadiene. Well‐defined melting transitions are present at low branch incorporation, followed by the broadening of the endotherms as the branch contents increase. However, instead of making the material amorphous, further increasing of the branch contents leads to the retrieval of the semi‐crystalline material creating a new crystalline domain, branches that co‐crystallize. Detailed IR spectra analyses suggest a crystal morphology transformation from orthorhombic to hexagonal phase as the branch content increases in these polymers. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018

Effect of Long-Chain Branch of Poly(methyl acrylate-co-1-octene) on the Vulcanization and Mechanical Properties

“…The ρ of LCB copolymer shown in Table is less than that of UL copolymer shown in Table , indicating that the molecular topological structure of the LCB copolymer is closer to solid spheres . The branching densities for LCB copolymers can be controlled by varying the feedstock ratios of the 1,7-octadiene or by controlling MA conversions …”

“…41 The branching densities for LCB copolymers can be controlled by varying the feedstock ratios of the 1,7-octadiene or by controlling MA conversions. 32 In Figure 5, the intrinsic viscosity ([η], from TD-GPC) of LCB copolymer (M n = 80200, PDI = 3.37) is lower than that UL copolymer (M n = 70200, PDI = 2.96) at a certain M w , indicating a constringent conformation of LCB copolymer. 42 And the slope of the Mark−Houwink−Sakurada curve for the LCB copolymer is less than that for UL copolymer, because the dendritic topology for LCB copolymer is more inclined to form solid sphere conformation.…”

“…The different properties [stress–strain behavior, elastic moduli ( G ′), and loss moduli ( G ″)] of vulcanized linear and branched polymers have been noticed in previous research. − It is significant to comparatively study the effects of long-chain branch (LCB) on cross-link network and then on mechanical properties of the vulcanite, which have not been reported yet. On the basis of the funded technology in our previous research for synthesizing copolymer of polar monomer (e.g., methyl acrylate) with nonpolar monomer (e.g., 1-octene), in this work, two copolymers, i.e., copolymer (with unsaturated linear chain structure, UL copolymer) of methyl acrylate, 1-octene, and allyl glycidyl ether , and copolymer (with long-chain branch structure, LCB copolymer) of methyl acrylate, 1-octene, and 1,7-octadiene, − will be synthesized and then comparatively studied on their vulcanization and mechanical properties to reveal the effects of the long-chain branch on vulcanization reactions, vulcanite topologies and mechanical properties of vulcanite by differential scanning calorimetry, dynamic mechanical analyzer, and stress–strain test to develop elastomers with advanced mechanical properties.…”

Competition of Lamellar Crystal and Smectic Liquid Crystal in Precise Polyethylene Derivative Bearing Mesogenic Side-Chains

“…[13][14][15] Advanced polymer chemistry endows the accurate placement of the branching points along the backbone; namely, one could precisely adjust the spacing between the two adjacent side-chains, and thus, the grafting density. [16][17][18][19][20][21][22][23][24][25] Enlarged side-chain spacing would enable the recovery of at least part of the backbone flexibility of SCLCPs, thereby affording more possibilities of hierarchical self-organization. 18,19,23,[26][27][28][29][30] It has been demonstrated that, in addition to the coil conformation, when side-chain spacing is large enough, the backbones could even fold to form crystalline packing.…”