Unusual Memory Effect of Crystallization Raised by 4-Phenyl-1-butene and 4-Anthryl-1-butene Comonomers in 1-Butene-Based Copolymers

Shen, Jiazheng; Yang, Fei; Liao, Yilong; Ma, Zhe; Li, Yuesheng

doi:10.1021/acs.macromol.4c00721

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“…These authors reported that the self-seeded melts exhibited rheologically complex behavior that failed to follow the classic time–temperature superposition principle of polymer melts, demonstrating that melt heterogeneity provided recrystallization self-nuclei. Considering the substantial impact of self-nucleated heterogeneity on recrystallization, a rapidly increasing number of studies have explored the initiation of self-nucleation in various polymer systems, aiming to establish the correlation between self-nucleation and macromolecular architecture. − The pioneering work of Reid et al first disclosed with the ethylene/butene-1 random copolymers that the strong memory effect associated with the heterogeneously partitioning sequences appeared even well above the equilibrium melting temperature . Wang et al investigated the influence of segregated long crystallizable sequences on crystallization under quiescent conditions.…”

Section: Introductionmentioning

confidence: 99%

Flow-Induced Crystallization Coupled with Strong Memory Effect: Revealing Melt Heterogeneity

Zhao,

Liu,

Liu

et al. 2024

Macromolecules

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Herein, the flow-induced crystallization coupled with an intrinsic strong memory effect was investigated via in situ wide-angle X-ray diffraction. A poly(butene-1) random copolymer with 4.3 mol % ethylene co-units was utilized as the model polymorphic material to examine memory effect induced by crystallization kinetics and polymorphism. The quiescent crystallization results clearly demonstrated that the melt-memory effect was able to induce a heterogeneous melt even above the equilibrium melting temperature, in which locally segregated segments comprised the residual domains and effectively facilitated the formation of the most stable phase (trigonal form I′) rather than the kinetically favored phase (tetragonal form II). Form I′ exhibited more pronounced accelerated crystallization kinetics than form II as the melt temperature (T melt ) was decreased, enhancing melt heterogeneity, and became the kinetically favored phase at T melt = 120 °C. Subsequently, the complex mutual effect of flow was explored in the heterogeneous melt, in which crystallization exhibited a dependence on flow strength. For mild flow at 0.3 s −1 , flow mainly accelerated the crystallization of oriented form II while that of form I′ was hardly affected, in contrast to the melt-memory effect observed during the aforementioned quiescent crystallization. The distinct responses to macroscopic flow revealed not only the dependence of tetragonal and trigonal phase formation but also the heterogeneous melt response.

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