Melt and Solid-State Structures of Polydisperse Polyolefin Multiblock Copolymers

Abstract

Crystallization in polydisperse ethylene–octene multiblock copolymers, polymerized via chain shuttling chemistry, is examined using two-dimensional synchrotron small- and wide-angle X-ray scattering on flow-aligned specimens. The multiblocks are composed of alternating crystalline (hard) blocks of low 1-octene content and amorphous (soft) blocks of high 1-octene content; the block lengths and the number of blocks per chain are characterized by most-probable distributions. These polymers self-assemble into lamellar domain morphologies in the melt, and the melt morphology is retained in the solid state. Despite extensive mixing between hard and soft blocks, the high crystallinity (>50%) of the hard blocks leads to an alignment of the crystallites within the domain structure, with the orthorhombic polyethylene c-axis generally perpendicular to the lamellar domain normal. The interlamellar domain spacings exhibited by the multiblocks, which exceed 100 nm, are estimated to be 5 times larger than those in near-monodisperse block copolymers having a similar chemical composition and a number-average molecular weight equivalent to the multiblock’s “constituent diblock” repeating unit. This swelling factor exceeds the value of 3 previously reported for analogous polydisperse olefin diblock copolymers, due to the lower segregation strength and enhanced phase mixing of the multiblocks studied here.

Phase diagrams of block copolymer melts by dissipative particle dynamics simulations

“…Concerning possible future applications of DPD to studying the phase behavior of block copolymers we would like to mention, first of all, Markovian (random correlated) multiblock copolymers, a model that was deeply studied in theory since the seminal paper by Milner, Fredrickson, and Leibler 79 and recently attracted the attention of experimentalists [80][81][82] due to the progress in the controlled synthesis of multiblock polyolefins. 83 Comprehensive simulation techniques 84 reveal only short-range order in the disordered phase (microemulsion), which, however, possesses interesting mechanical characteristics, and it would be interesting to search for long-range ordered structures with the help of DPD.…”

Intelligent Monte Carlo: A New Paradigm for Inverse Polymerization Engineering

“…The trans‐metallation reaction occurs via a chain shuttling agent (CSA). The resulting products, olefinic block copolymers (OBCs), are recently developed representatives of macromolecules with a complex, fine‐tuned microstructure composed of blocks of statistical copolymers with two different compositions, one being crystallizable and the other amorphous …”

“…The resulting products, olefinic block copolymers (OBCs), are recently developed representatives of macromolecules with a complex, fine-tuned microstructure composed of blocks of statistical copolymers with two different compositions, one being crystallizable and the other amorphous. [34] We previously reported on microstructural changes in the semibatch chain shuttling polymerization of ethylene and 1-octene using KMC simulation. [35][36][37][38] The KMC simulation was able to quantify many signature distributional characteristics of ethylene/1-octene copolymerization, such as the block composition, referred to as C8%, the block length represented by the number-average degree of polymerization DPn, the relative proportion of the blocks described via the hard block content (HB%), the number of linking points between blocks Macromol.…”

Molecular Architecture of Multi‐Block Polymer Synthesized in a Dual‐Catalyst Single CSTR

“…They investigated the effect of CSA concentration on the system. Li et al studied the crystallization in polydisperse ethylene−octene multi‐block copolymers polymerized via chain‐shuttling chemistry. They concluded that the block lengths and the number of blocks per chain were characterized by most‐probable distributions.…”