Chemical Structure Drives Memory Effects in the Crystallization of Homopolymers

Sangroniz, Leire; Sangroniz, Ainara; Meabe, Leire; Basterretxea, Andere; Sardón, Haritz; Cavallo, Dario; Müller, Alejandro J.

doi:10.1021/acs.macromol.0c00751

Cited by 50 publications

(98 citation statements)

References 31 publications

(93 reference statements)

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“…T initial is at temperatures where the endothermic melting peak completely disappears in the DSC heating scan. 22,27 We observe that for OEGMA-long the thermal history is erased by annealing at temperatures of about 20 K above the end of the melting event, whereas, interestingly, for OEGMA-short the corresponding critical temperature elevation seems to be higher than 20 K in Fig. 5.…”

Section: Melt Memory Effects In Crystallization Behaviormentioning

confidence: 76%

“…with no ''memory structure''. 22,27 The data in Fig. 5 suggest that melt-memory effects are of comparable strength in the oligomers.…”

Section: Melt Memory Effects In Crystallization Behaviormentioning

confidence: 83%

“…This orientation originates initially from the chain conformations in the crystalline structures or is produced by sticky chain associations of the chains in the melt, due to inter-chain segmental contacts, for example via formation of inter/intramolecular hydrogen bonds or other types of weak forces. 22,26,27 During re-crystallization of the macromolecular chains, an increase in T c (and the crystallization rate) is observed, caused by a self-nucleation process, and the effect is known as the melt memory effect. The strength and specific features of the melt memory effect may offer an additional tool for assessing the degree of complexity in the macromolecular structure and dynamics of various chain architectures due to the existing chain associations and structural constraints.…”

Section: Introductionmentioning

confidence: 99%

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Molecular dynamics and crystallization in polymers based on ethylene glycol methacrylates (EGMAs) with melt memory characteristics: from linear oligomers to comb-like polymers

et al. 2021

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Section: Melt Memory Effects In Crystallization Behaviormentioning

confidence: 76%

“…with no ''memory structure''. 22,27 The data in Fig. 5 suggest that melt-memory effects are of comparable strength in the oligomers.…”

Section: Melt Memory Effects In Crystallization Behaviormentioning

confidence: 83%

Section: Introductionmentioning

confidence: 99%

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Molecular dynamics and crystallization in polymers based on ethylene glycol methacrylates (EGMAs) with melt memory characteristics: from linear oligomers to comb-like polymers

et al. 2021

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“…This can be detected by the increase in the crystallization temperature in comparison with the standard crystallization temperature. The nature of the self-seeds is controversial [313][314][315][316][317][318][319][320][321][322][323][324][325][326][327][328][329]. Our group has proposed a division of Domain II into two sub-Domains [325].…”

Section: Lack Of Sufficiently Active Heterogeneitiesmentioning

confidence: 99%

Fractionated crystallization in semicrystalline polymers

Sangroniz

Wang

et al. 2021

Progress in Polymer Science

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The crystallization of heterogeneously nucleated bulk polymers typically occurs in a single exothermic process, within a narrow temperature range, i.e., a single exothermic peak is detected by Differential Scanning Calorimetry when the material is cooled from the melt. However, when a bulk semicrystalline polymer is subdivided or dispersed into a multitude of totally (or partially) isolated microdomains (e.g., droplets or cylinders), in number comparable to that of commonly available nucleating heterogeneities, several separated crystallization events are typically observed, i.e., fractionated crystallization. This situation is often found for the minor crystallizable component in immiscible blends.When the bulk polymer is dispersed into a number of microdomains that is several orders of magnitude higher than the available number of heterogeneities within it, most microdomains will be heterogeneity-free. In these clean microdomains the nucleation can occur by contact with the interfaces (i.e., surface nucleation) or by homogeneous nucleation inside the microdomain volume. These cases can be easily encountered in cylinders or spheres within strongly segregated block copolymers, or in infiltrated polymers within nanopores of alumina templates.In this work, a comprehensive review of the known cases of fractionated crystallization is provided. The changes upon decreasing microdomain sizes from a dominant single heterogeneous nucleation, through fractionated crystallization, to surface or homogeneous nucleation are critically reviewed. Emphasis is placed on the common features of the phenomenon across the different systems, and thus on the general conclusions that can be drawn from the analysis of representative semicrystalline polymers. The origin of the fractionated crystallization effects and their dramatic consequences on the nucleation and crystallization kinetics of semicrystalline polymers are also discussed.

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“…In [ 26 , 33 , 35 ], a review of these non-trivial problems is given, and general theoretical considerations are outlined showing that near and below the glass transition range the opposite situation can be realized, structural relaxation processes may proceed slowly as compared with crystal nucleation. In such cases, the nucleation kinetics can be significantly affected by structural relaxation processes proceeding in the glass-forming melt as discussed from an experimental point of view in [ 2 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 ]. They result in changes of the state of the liquid in nucleation.…”

Section: The Model: Basic Assumptionsmentioning

confidence: 99%

Effects of Glass Transition and Structural Relaxation on Crystal Nucleation: Theoretical Description and Model Analysis

Schmelzer

Тропин

Fokin

et al. 2020

Entropy

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In the application of classical nucleation theory (CNT) and all other theoretical models of crystallization of liquids and glasses it is always assumed that nucleation proceeds only after the supercooled liquid or the glass have completed structural relaxation processes towards the metastable equilibrium state. Only employing such an assumption, the thermodynamic driving force of crystallization and the surface tension can be determined in the way it is commonly performed. The present paper is devoted to the theoretical treatment of a different situation, when nucleation proceeds concomitantly with structural relaxation. To treat the nucleation kinetics theoretically for such cases, we need adequate expressions for the thermodynamic driving force and the surface tension accounting for the contributions caused by the deviation of the supercooled liquid from metastable equilibrium. In the present paper, such relations are derived. They are expressed via deviations of structural order parameters from their equilibrium values. Relaxation processes result in changes of the structural order parameters with time. As a consequence, the thermodynamic driving force and surface tension, and basic characteristics of crystal nucleation, such as the work of critical cluster formation and the steady-state nucleation rate, also become time-dependent. We show that this scenario may be realized in the vicinity and below the glass transition temperature, and it may occur only if diffusion (controlling nucleation) and viscosity (controlling the alpha-relaxation process) in the liquid decouple. Analytical estimates are illustrated and confirmed by numerical computations for a model system. The theory is successfully applied to the interpretation of experimental data. Several further consequences of this newly developed theoretical treatment are discussed in detail. In line with our previous investigations, we reconfirm that only when the characteristic times of structural relaxation are of similar order of magnitude or longer than the characteristic times of crystal nucleation, elastic stresses evolving in nucleation may significantly affect this process. Advancing the methods of theoretical analysis of elastic stress effects on nucleation, for the first time expressions are derived for the dependence of the surface tension of critical crystallites on elastic stresses. As the result, a comprehensive theoretical description of crystal nucleation accounting appropriately for the effects of deviations of the liquid from the metastable states and of relaxation on crystal nucleation of glass-forming liquids, including the effect of simultaneous stress evolution and stress relaxation on nucleation, is now available. As one of its applications, this theoretical treatment provides a new tool for the explanation of the low-temperature anomaly in nucleation in silicate and polymer glasses (the so-called “breakdown” of CNT at temperatures below the temperature of the maximum steady-state nucleation rate). We show that this anomaly results from much more complex features of crystal nucleation in glasses caused by deviations from metastable equilibrium (resulting in changes of the thermodynamic driving force, the surface tension, and the work of critical cluster formation, in the necessity to account of structural relaxation and stress effects) than assumed so far. If these effects are properly accounted for, then CNT appropriately describes both the initial, the intermediate, and the final states of crystal nucleation.

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Chemical Structure Drives Memory Effects in the Crystallization of Homopolymers

Cited by 50 publications

References 31 publications

Molecular dynamics and crystallization in polymers based on ethylene glycol methacrylates (EGMAs) with melt memory characteristics: from linear oligomers to comb-like polymers

Molecular dynamics and crystallization in polymers based on ethylene glycol methacrylates (EGMAs) with melt memory characteristics: from linear oligomers to comb-like polymers

Fractionated crystallization in semicrystalline polymers

Effects of Glass Transition and Structural Relaxation on Crystal Nucleation: Theoretical Description and Model Analysis

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