Papers by Daniele Cangialosi
Macromolecules, Aug 27, 2019
Conditions of rapid processing often drive polymers to adopt nonequilibrium molecular conformatio... more Conditions of rapid processing often drive polymers to adopt nonequilibrium molecular conformations, which, in turn, can give rise to structural, dynamical, and mechanical properties that are significantly different from those in thermodynamic equilibrium. However, despite the possibility to control the desired nonequilibrium properties of polymers, a rigorous microscopic understanding of the processing−property relations is currently lacking. In an attempt to stimulate progress along this topical direction, we focus here on three prototypical and apparently different cases: spin-coated polymer films, rapidly drawn polymer fibers, and sheared polymer melts. Inspired by the presence of common observations in the chosen cases, we search for order parameters as, for example, topological correlations and heterogeneities, which may allow characterizing the processing-induced behavior of polymers. We highlight that such approaches, necessitating concerted efforts from theory, simulations, and experiments, can provide a profound understanding leading to predictable and tunable properties of polymers.
Polymer, Jun 1, 2021
Abstract The origin of “annealing peaks” in semicrystalline polymers, obtained with aging thermal... more Abstract The origin of “annealing peaks” in semicrystalline polymers, obtained with aging thermal protocols at temperatures between the glass transition and the melting temperature, and revealed by calorimetry as small endotherms preceding the main melting peak, has been recently debated in the literature. On the one side it is claimed that these small endotherms are related to the melting of defective/thinner crystals, on the other side it is proposed that they can be associated to the enthalpy relaxation of the rigid amorphous fraction (RAF), i.e., that part of the amorphous region directly coupled to the crystalline stems. With this work we aim to contribute to the debate, by exploiting the different thermal properties of the RAF coupled with different crystal modifications of polymorphic poly(butene-1) (PB-1). In this polymer the RAF mobilizes at largely different temperatures when it is coupled with crystals of trigonal Form I, or tetragonal Form II. By exploiting this peculiarity, we performed isochronous aging experiments with differential scanning calorimetry (DSC) on both crystalline phases, in a wide temperature range between the glass transition of the mobile (bulk) amorphous fraction and the onset of crystal melting. An endothermic peak above the aging temperature was typically observed. The trend of the enthalpy of this annealing peak with temperature can be described by a bell-shaped curve, approaching zero recovered enthalpy at temperatures of 100-110 °C, and 40-50 °C for Form I and Form II, respectively. These temperatures coincide with previous literature report about mobilization of PB-1 RAF and are thus identified as the upper limit of the RAF glass transition for the two polymorphs. Isothermal aging experiments as a function of time suggest that the enthalpy recovery of Form I RAF show the typical signature of glassy dynamics, similarly to what occurs for Form II RAF after short aging times. At longer times, the superposition of the polymorphic phase transition and RAF aging changes the kinetics of the recovered enthalpy for the latter polymorph, possibly due to the increased stress at the crystal-amorphous interface and creation of additional RAF in parallel with Form II to Form I transformation. Overall, our results demonstrate that for PB-1, at least within the investigated temperature range, the annealing peaks can be related to the RAF strive to attain thermodynamic equilibrium in its glassy state.
Macromolecules, Feb 12, 2021
The concept of free volume underpins the variations in polymer dynamics. Annihilation of free-vol... more The concept of free volume underpins the variations in polymer dynamics. Annihilation of free-volume holes through diffusion to surfaces has been proposed to determine the vitrification of the conf...
RSC soft matter series, 2019
DC acknowledges financial support from the project MAT2015-63704-P, (MINECO/FEDER, UE) and PGC201... more DC acknowledges financial support from the project MAT2015-63704-P, (MINECO/FEDER, UE) and PGC2018-094548-B-I00 (MICINN-Spain and FEDER-UE), and the Basque Government (Grant No. IT-654-13 (GV)). AN acknowledges financial support from the Spanish Ministry of Economy (Grant No. MAT2014-59187-R).
Resumen del trabajo presentado a la 10th Conference on Broadband Dielectric Spectroscopy and its ... more Resumen del trabajo presentado a la 10th Conference on Broadband Dielectric Spectroscopy and its Applications (BDS) celebrada en Bruselas (Belgica) del 26 al 31 de agosto de 2018.
Bulletin of the American Physical Society, Mar 15, 2017
A decade ago ultra-stable small molecule glass formers were discovered. Since then a significant ... more A decade ago ultra-stable small molecule glass formers were discovered. Since then a significant amount of research has been devoted to traverse down the energy landscape of such glass formers via physical vapor deposition (PVD). Matrix assisted pulsed laser evaporation (MAPLE) has the known ability to produce vapour deposited nanostructured polymer glass with exceptional kinetic stability. We explored the role of deposition temperature/ growth rate on thermodynamic and kinetic stabilities of poly (methyl methacrylate) (PMMA) films, deposited over a fast-scanning calorimetry sensor. We found in general any MAPLE deposited glass is kinetically more stable than bulk polymer and its spin-coated film. Moreover slow growth rate and optimum temperature during MAPLE deposition can additionally lead to thermodynamically stable (low-energy) glass. The role of interfaces formed through dramatic nanostructuring and packing of nanoglobules (removal of void space) may have additional role on such ultrastability.
Polymer Engineering and Science, Jul 4, 2022
Recent efforts, fostered by a pioneering work by us, have shown the of multiple steps in the reco... more Recent efforts, fostered by a pioneering work by us, have shown the of multiple steps in the recovery of equilibrium of glasses. Jin and McKenna raise concerns regarding the validity of such scenario alleging that the multiple recovery steps would be an artifact arising from poor temperature control in the oven used for isothermal glass equilibration. We critically discuss Jin and McKenna arguments from both the viewpoints of scrutinizing previous literature data and that of the temperature control in the oven. In doing so, we provide compelling arguments that Jin and McKenna conjectures are unjustified and point out the need for efforts to describe glass dynamics significantly below the glass transition temperature, T g , by accounting for the presence of different relaxation mechanisms active in glass equilibration.
Acs Symposium Series, 2021
Macromolecules, Oct 28, 2021
Irreversible adsorption at polymer/substrate interfaces has been reported to influence glassy pro... more Irreversible adsorption at polymer/substrate interfaces has been reported to influence glassy properties in thin films. However, consideration has yet to be extended to the nanocomposite geometry, wherein a large interfacial area and high processing temperatures afford especially favorable conditions for irreversible adsorption at the polymer/nanoparticle interface. Here, we present an approach for directly measuring the site-specific glassy properties at the polystyrene (PS)-adsorbed layer interface in PS−silica nanocomposites. We achieved this using a stepwise assembly approach to localize fluorescent dyes within the nanocomposite adsorbed layer, subsequently measuring the glass transition temperature (T g) via fluorescence. We found that PS adsorption within nanocomposites strongly influenced the local T g. By measuring the thickness of the PSadsorbed layers atop nanoparticles via transmission electron microscopy, we found a correlation between adsorbed layer T g and thickness. Our results provide compelling evidence that adsorbed layer formation within polymer nanocomposites can have a profound impact on local interfacial properties.
Macromolecules, Aug 30, 2019
Advanced Materials, 2020
The relation of phase morphology and solid‐state microstructure with organic photovoltaic (OPV) d... more The relation of phase morphology and solid‐state microstructure with organic photovoltaic (OPV) device performance has intensely been investigated over the last twenty years. While it has been established that a combination of donor:acceptor intermixing and presence of relatively phase‐pure donor and acceptor domains is needed to get an optimum compromise between charge generation and charge transport/charge extraction, a quantitative picture of how much intermixing is needed is still lacking. This is mainly due to the difficulty in quantitatively analyzing the intermixed phase, which generally is amorphous. Here, fast scanning calorimetry, which allows measurement of device‐relevant thin films (<200 nm thickness), is exploited to deduce the precise composition of the intermixed phase in bulk‐heterojunction structures. The power of fast scanning calorimetry is illustrated by considering two polymer:fullerene model systems. Somewhat surprisingly, it is found that a relatively smal...
Reference Module in Materials Science and Materials Engineering, 2016
Physical aging is ubiquitous in glassy materials and originates from their out-of-equilibrium nat... more Physical aging is ubiquitous in glassy materials and originates from their out-of-equilibrium nature. This phenomenon is of great technological and fundamental interest and it is especially relevant in glassy polymers. Here, we summarize the main aspects of the phenomenology of physical aging: (1) its connection to the glass transition temperature (T g ); (2) its nonlinear and nonexponential nature; and (3) the effect on the glass structure and molecular mobility. Furthermore, some new features of physical aging, emerged in recent studies, are discussed. These are the nonmonotonous behavior of equilibrium recovery and the acceleration of equilibrium recovery in polymer under geometrical confinement.
Polymer, Apr 1, 2003
The mobility of small molecules in a glassy polymer is largely determined by the amount of free v... more The mobility of small molecules in a glassy polymer is largely determined by the amount of free volume present in the material. The amount of free volume can be altered by changing the physical state of the polymer. Physical ageing reduces this amount, whereas the thermal rejuvenation increases it. The change in free volume was monitored by oxygen permeation and antioxidant sorption experiments. A clear correlation was found between the physical ageing on the one hand and oxygen permeability on the other. Since the mobility of antioxidants and oxygen are important parameters for the stabilisation of a polymer against oxidation, the physical state of the polymer can have a significant influence on the service life of the product.
Macromolecules, Dec 13, 2002
ABSTRACT
Polymer Degradation and Stability, Mar 1, 2003
The mobility of small molecules in a glassy polymer is largely determined by the amount of free v... more The mobility of small molecules in a glassy polymer is largely determined by the amount of free volume present in the material. The amount of free volume can be altered by changing the physical state of the polymer. Physical ageing reduces this amount, whereas the thermal rejuvenation increases it. The change in free volume was monitored by oxygen permeation and antioxidant sorption experiments. A clear correlation was found between the physical ageing on the one hand and oxygen permeability on the other. Since the mobility of antioxidants and oxygen are important parameters for the stabilisation of a polymer against oxidation, the physical state of the polymer can have a significant influence on the service life of the product.
Journal of Physics: Condensed Matter, Mar 22, 2012
We report a joint analysis of positron annihilation lifetime spectroscopy (PALS), dielectric spec... more We report a joint analysis of positron annihilation lifetime spectroscopy (PALS), dielectric spectroscopy (BDS), and nuclear magnetic resonance (NMR) on cis-trans-1,4-poly(butadiene) (c-t-1, 4-PBD). Phenomenological analysis of the orthopositronium lifetime τ 3 − T dependence by linear fitting reveals four characteristic PALS temperatures: T G b1 = 0.63T PALS g
Reducing the sample size can profoundly impact properties of bulk metallic glasses. Here, we syst... more Reducing the sample size can profoundly impact properties of bulk metallic glasses. Here, we systematically reduce the length scale of Au and Pt-based metallic glasses and study their vitrification behavior and atomic mobility. For this purpose, we exploit fast scanning calorimetry (FSC) allowing to study glassy dynamics in an exceptionally wide range of cooling rates and frequencies. We show that the main α relaxation process remains size independent and bulk-like. In contrast, we observe pronounced size dependent vitrification kinetics in micrometer-sized glasses, which is more evident for the smallest samples and at low cooling rates, resulting in more than 40 K decrease in fictive temperature, Tf, with respect to the bulk. We discuss the deep implications on how this outcome can be used to convey glasses to low energy states.
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Papers by Daniele Cangialosi