Features of structural relaxation in diblock copolymers

Ma, Mingchao; Xue, Tianju; Chen, Shenyue; Guo, Yunlong; Chen, Yujie; Liu, Hezhou

doi:10.1016/j.polymertesting.2017.02.027

Cited by 5 publications

(8 citation statements)

References 25 publications

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“…The aging rate R a , obtained by FSC and classical DSC, was R a ¼ 1.6 ± 0.1 and R a ¼ 0.7 ± 0.1 J/decade respectively, R a being defined from the enthalpy of recovery variations with aging time ( Figure SI.4 in Supplementary Information). R a was already used to compare the physical aging kinetics of various polymer glasses [15,53,54], polymer nanoparticles [55], nanocomposites [40], freeestanding films [25,36,56], stacked films [38], coeextruded multilayers [44,57]. In Fig.…”

Section: Resultsmentioning

confidence: 99%

Reduced physical aging rates of polylactide in polystyrene/polylactide multilayer films from fast scanning calorimetry

Monnier

Nassar

Domenek

et al. 2018

Polymer

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The physical aging behavior of amorphous polylactide constrained against polystyrene in layers of 300 nm, thanks to the layeremultiplying coeextrusion process, was investigated by fastescanning calorimetry (FSC). By cooling down the sample from the liquid state to the glassy one at very fast scanning rates, it was possible to investigate the structural relaxation of the polymer glass at high temperatures for which the time needed to reach the equilibrium was shortened. Therefore it was possible to perform the study of physical aging in experimental conditions providing an expanded view of the structural relaxation for short aging times. Taking benefit of this property, it was highlighted that the aging kinetics of polylactide occurred significantly slower in the multilayer film, in comparison with a bulk amorphous film. The process of recovery in the multilayer system was found to occur at similar rates, or even slower, than in a threeelayer film in which polylactide reached its maximum extent of crystallinity. This was attributed to mobility hindrance that might be inherent to the extrusion conditions or associated with the presence of capped interfaces with polystyrene.

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Section: Resultsmentioning

confidence: 99%

Reduced physical aging rates of polylactide in polystyrene/polylactide multilayer films from fast scanning calorimetry

Monnier

Nassar

Domenek

et al. 2018

Polymer

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“…The materials above are the same as what we used in our previous work. 32 Enthalpy Relaxation Test. Enthalpy relaxation measurements were performed by a Shimadzu DSC-60 plus differential scanning calorimeter (DSC) under a nitrogen atmosphere.…”

Section: Methodsmentioning

confidence: 99%

Enthalpy Relaxation and Morphology Evolution in Polystyrene-b-poly(methyl methacrylate) Diblock Copolymer

Huang

Guo

2018

Macromolecules

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Desirable patterns formed by microphase separation in block copolymers make these materials attractive for miniaturization of functional devices in which formation of nanostructures is highly demanded. The microphase separation forms microdomains under three-dimensional confinement for each component and thus substantially changes physical properties such as structural relaxation of the polymer blocks. In this article, we report enthalpy relaxation and morphology evolution in polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) during isothermal physical aging, measured by calorimetry and atomic force microscopy (AFM). Under nanoconfinement formed by microphase separation, the PS blocks have higher relaxation rate and amount of relaxed enthalpy compared with the corresponding homo-PS, while the PMMA blocks have lower relaxation rate and relaxed enthalpy than the homo-PMMA. The in situ morphology evolution shows that the characteristic distribution profiles of the AFM phase angle become lower and wider with increasing aging time for both the blocks, and the average distance between the central phase angles of the two blocks increase during aging. As large AFM phase angle of PMMA representing higher modulus, it demonstrates that the PS blocks under hard confinement exhibit greater enthalpy change with enhanced relaxation rate from the bulk. In contrast, PMMA blocks under soft confinement show the opposite trend.

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“…A Shimadzu DSC-60 Plus differential scanning calorimeter (DSC) with the environment of nitrogen gas was used to perform enthalpy relaxation experiments, as described in our previous work. 45 In aging testing, a sample of 3-5 mg was sealed in an aluminum pan. The sample was first heated to 160 C with a heating rate of 20 C/min, and was held for 10 min at the end, in order to remove residual stress.…”

Section: Enthalpy Relaxation Testmentioning

confidence: 99%

“…The temperature protocol for aging test was presented in our previous work. 45 From the experiments, heat capacity curves can be obtained for both aged or unaged (without annealing at T a ) samples.…”

Section: Enthalpy Relaxation Testmentioning

confidence: 99%

Physical aging of polystyrene blocks under three‐dimensional soft confinement in PS‐b‐poly(n‐butyl methacrylate) diblock copolymer: Two equilibrations on the way

Guo

2021

Journal of Polymer Science

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Polystyrene‐block‐poly(n‐butyl methacrylate) (PS‐b‐PnBMA) was used to investigate three‐dimensional (3D) soft confinement effect on physical aging of the PS block therein. The soft confinement is constructed by phase‐separated PnBMA domains, as PnBMA is liquid on the aging temperatures of PS blocks due to its low glass transition temperature. In enthalpy recovery, aging response of PS blocks is represented by a low and broad heat capacity peak associated with an enhanced aging rate with respect to homo‐PS, when the aging temperature is relatively low. However, the aging response exhibits opposite characteristics at relatively high temperatures, compared with the results of homo‐PS. The phase‐separated morphology and thus the soft confinement on PS blocks was confirmed by atomic force microscope imaging using the Peak Force quantitative nanomechanical mapping (QNM) technique. Two local maximums of recovered enthalpy versus aging temperature indicate that two equilibration processes exist during aging of confined PS blocks, within a substantially shorter timescale to the bulk. The 3D soft confinement effect on aging of PS blocks is attributed to dual equilibration mechanisms: one dominates at higher aging temperatures, leading to a restrained aging rate, while the other plays a key role at lower aging temperatures, resulting in accelerated physical aging.

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Features of structural relaxation in diblock copolymers

Cited by 5 publications

References 25 publications

Reduced physical aging rates of polylactide in polystyrene/polylactide multilayer films from fast scanning calorimetry

Reduced physical aging rates of polylactide in polystyrene/polylactide multilayer films from fast scanning calorimetry

Enthalpy Relaxation and Morphology Evolution in Polystyrene-b-poly(methyl methacrylate) Diblock Copolymer

Physical aging of polystyrene blocks under three‐dimensional soft confinement in PS‐b‐poly(n‐butyl methacrylate) diblock copolymer: Two equilibrations on the way

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