Crystal growth and morphology of hindered phenol AO-60

Cao, Yunyun; Wang, Shaolei; Mou, Haiyan; Xu, Hongyao; Wu, Chifei

doi:10.1016/j.jcrysgro.2010.02.002

Cited by 2 publications

(2 citation statements)

References 15 publications

(22 reference statements)

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“…Two issues remain to be addressed: , one is to provide direct evidence showing that the hydrogen bonding between the phenolic hydroxyl group of the small molecule and the carbonyl group of acrylic resins is the determining factor for promoting the damping performance and the other is to achieve stabilization of these novel damping materials for long-term application. The dispersed small molecules may diffuse and migrate to self-aggregate and subsequently crystallize because of the high cohesive energy density and the existence of intramolecular hydrogen bonding interactions between the hydroxyl groups. − Thus, the damping properties during service are ultimately degraded. − …”

Section: Introductionmentioning

confidence: 99%

β_fast Relaxation Governs the Damping Stability of Acrylic Polymer/Hindered Phenol Hybrids

Shi

Liu

2020

Macromolecules

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Hindered phenols remarkably enhance the sound attenuation and vibration damping of acrylic polymers. However, this novel damping material suffers from gradual degradation during long-term use because of potential self-aggregation and crystallization of small molecules. In this work, the effects of small molecule size, hydrogen bonding strength, and mobility of the pendant group of acrylic matrices on the long-term damping stability were investigated. The results were correlated to the hierarchical relaxation of acrylic mixtures. We were surprised by the findings that the damping degradation dynamics appears to be governed by βfast relaxation instead of α and/or βJG relaxation of the polymer matrix. Further experiments revealed that the long-distance diffusion of small molecules to self-aggregation and subsequent crystallization is regulated by βJG relaxation, but dissociation of the intermolecular hydrogen bonding between the hydroxyl group of phenols and the carboxyl group of acrylates during physical aging plays the decisive role in damping degradation. We supposed that the small molecule’s fluctuation-induced dissociation of hydrogen bonding is limited within a sub-Å amplitude and therefore couples with the cage-breaking motion of βfast relaxation. These results clarify the mechanism of small-molecule-enhanced damping and provide a strategy for the rapid evaluation of the service life of novel damping materials and a thermodynamic criterion k 0 for the future design of small molecules and long-term stable damping materials.

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Section: Introductionmentioning

confidence: 99%

β_fast Relaxation Governs the Damping Stability of Acrylic Polymer/Hindered Phenol Hybrids

Shi

Liu

2020

Macromolecules

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“…Rare cases are known in metals such as bismuth . To the best of our knowledge, the only report of hopper structure in an organic crystal is of a highly hindered alcohol; there have been no investigations of materials relevance in the context of molecular hopper crystals. From a fundamental crystal growth perspective, it is interesting to explore potential small molecules and their assembly that can provide a lead to the development of hopper morphologies.…”

Section: Introductionmentioning

confidence: 99%

Molecular Hopper Crystals and Electron Beam-Triggered Reversible Actuation

Senthilnathan

Radhakrishnan

2020

Chem. Mater.

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Molecular crystals with unusual morphologies characteristic of "hopper crystals" have rarely been explored; such structures are potentially useful for eliciting specific responses to external fields or stimuli. Upon simple reprecipitation and controlled growth, select members of a family of strongly zwitterionic molecules, assembling in non-centrosymmetric lattices, are shown to form microcrystals with novel "hopper" morphology. The molecular aggregation is monitored by their characteristic fluorescence enhancement; X-ray diffraction, microscopy, and surface potential mapping provide insight into the development of the unique morphology. Under optimized conditions of electron beam irradiation in a scanning electron microscope, the prototype microcrystal is found to exhibit smooth, prominent, and reversible actuation. Even though electrically triggered macromolecular actuators as well as mechanically responsive and photo/ thermosalient molecular crystals are known, controlled bending/folding induced by electron beams are rare and have been demonstrated only in specialized nanostructures. The current observations with a simple small-molecule-based hopper microcrystal are analyzed by a detailed examination of the crystal lattice structure and asymmetric dipole distribution, together with the simulations of the electron beam interactions. An empirical model developed for the responses in the local electrostatic field provides a mechanistic understanding of the actuation process.

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Crystal growth and morphology of hindered phenol AO-60

Cited by 2 publications

References 15 publications

β_fast Relaxation Governs the Damping Stability of Acrylic Polymer/Hindered Phenol Hybrids

β_fast Relaxation Governs the Damping Stability of Acrylic Polymer/Hindered Phenol Hybrids

Molecular Hopper Crystals and Electron Beam-Triggered Reversible Actuation

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Crystal growth and morphology of hindered phenol AO-60

Cited by 2 publications

References 15 publications

βfast Relaxation Governs the Damping Stability of Acrylic Polymer/Hindered Phenol Hybrids

βfast Relaxation Governs the Damping Stability of Acrylic Polymer/Hindered Phenol Hybrids

Molecular Hopper Crystals and Electron Beam-Triggered Reversible Actuation

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β_fast Relaxation Governs the Damping Stability of Acrylic Polymer/Hindered Phenol Hybrids

β_fast Relaxation Governs the Damping Stability of Acrylic Polymer/Hindered Phenol Hybrids