Effect of Mesophase Separation on the Crystallization Behavior of Olefin Block Copolymers

Abstract

This paper investigates the effect of mesophase separation on the crystallization behavior of olefin block copolymers (OBCs) with different octene contents, which were synthesized by chain shuttling technology. Crystallization always occurs simultaneously but competitively with mesophase separation in OBCs. Because of the reason that the crystallization temperature is lower than the mesophase separation temperature for the OBCs, the mesophase separation can start first; large portions of the crystallizable hard blocks are confined in the mesophase-separated domains and could not contribute to the formation of radial lamellar stacks. In addition, the mesophase separation creates a stereo-hindrance effect; crystal lamellae could only grow through the interstitial space between the dispersed domains. As a result, large and compact crystals could not be formed. As the octene content increased in the sample, mesophase separation becomes more and more dominant, and the crystal morphology degrades sharply from spherulites to fragmentary lamella structures. It is found that increasing the annealing time during development of the mesophase-separated structure has a similar effect to increasing the octene content in the sample. However, all of the OBCs can form nearly the same crystalline morphology if the mesophase separation is suppressed, from which we can postulate that the nature of crystallization due to the crystallizable hard blocks in OBCs should be similar.

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.…”

Regulation of crystalline morphologies and mechanical properties of olefin multiblock copolymers by blending polymer with similar architecture of constituent blocks

“…[29,31] The lamellae can be arranged into space-filling spherulites even when the crystallinity is as low as 7%, and the impinged spherulites show straight boundaries, which indicates that OBC experiences heterogeneous nucleation with nuclei of similar activity. [29,31,32] This morphology resembles crystallization from a miscible melt, and the phenomenon is distinct from that of traditional block copolymers. During crystallization, the aggregation of hard blocks forces segregation of the noncrystallizable soft blocks into the interlamellar regions.…”

“…Investigations have found that the block length, octene content as well as the ratio between hard and soft blocks is closely correlated to the apparent properties of this M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 5 promising elastomer. [33][34][35][36][37][38][39][40] In consideration of the difficulty of altering block architecture during synthesizing, we aim to adjust the apparent properties by blending with PE, which possesses architecture similar to hard blocks of OBC. Based on our exploration, we found that PE chains were inclined to cocrystallize with OBC, which made it possible to increase strength without great depression of tenacity.…”

Synthesis of statistical PET/PEN random block copolymers and their crystallizability in the bulk and at the surface

“…Where only one of the monomers is crystallizable, such as in a study of poly(butylene terephthalate) (PBT)/poly(tetramethylene ether glycol), the other component may be rejected from crystals for small (in this case up to 17%) mole fraction, after which crystallization is suppressed . Other copolymer systems have shown crystallization by rejection of one component from the crystalline phase . However, in some cases of two, similar, crystallizing monomers, such as poly(ethylene terephthalate) (PET)/poly(ethylene 2,6‐naphthalate) (PEN) copolymers, crystallization involving both monomers may occur.…”