Papers by Melissa Pasquinelli
Macromolecular Rapid Communications, Nov 1, 2016
Journal of Chemical Physics, Sep 28, 2020
The mechanical properties of physical gels generated by selectively swelling a homologous series ... more The mechanical properties of physical gels generated by selectively swelling a homologous series of linear multiblock copolymers are investigated by quasistatic uniaxial tensile tests. We use the slip-tube network model to extract the contributions arising from network crosslinks and chain entanglements. The composition dependence of these contributions is established and considered in terms of simulations that identify the probabilities associated with chain conformations. Dynamic rheology provides additional insight into the characteristics and thermal stability of the molecular networks.
Journal of Physical Chemistry B, Jul 1, 2010
The goal of this study is to explore the interface between single-walled carbon nanotubes (SWCNTs... more The goal of this study is to explore the interface between single-walled carbon nanotubes (SWCNTs) and polymer chains with semiflexible and stiff backbones in vacuum via molecular dynamics (MD) simulations, which complements our previous work with flexible backbone polymers. These simulations investigate the structural and dynamical features of interactions with the SWCNT, such as how the polymers prefer to interface with the SWCNT and how the interfacial interaction is affected by the chemical composition and structure of the polymer. The simulations indicate that polymers with stiff and semiflexible backbones tend to wrap around the SWCNT with more distinct conformations than those with flexible backbones. Aromatic moieties along the backbone appear to dictate the adsorption conformation, which is likely due to the preference for optimizing pi-pi interactions, although the presence of bulky aliphatic side chains can hinder those interactions. Moment of inertia plots as a function of time indicate that the adsorption of polymers with stiff backbones tends to be a two-step process, in contrast to flexible backbones.
ACS Applied Materials & Interfaces, Nov 13, 2017
In the presence of a midblock-selective solvent, triblock copolymers not only self-organize but a... more In the presence of a midblock-selective solvent, triblock copolymers not only self-organize but also form a molecular network. Thermoplastic elastomer gels constitute examples of such materials and serve as sealants and adhesives, as well as ballistic, microfluidic, and electroactive media. We perform Monte Carlo and dissipative particle dynamics simulations to investigate the phase behavior and network characteristics of these materials. Of particular interest is the existence of a truncated octahedral morphology that resembles the atomic arrangement of various inorganic species. Both simulation approaches quantify the midblock bridges responsible for network development and thus provide a detailed molecular picture of these composition-tunable soft materials.
Journal of Physical Chemistry B, Feb 10, 2012
Conductive polymers have several applications such as in flexible displays, solar cells, and biom... more Conductive polymers have several applications such as in flexible displays, solar cells, and biomedical sensors. An inclusion complex of a conductive polymer and cyclodextrin is desired for some applications such as for molecular wires. In this study, different orientations of β-cyclodextrin rings on a single polyaniline (PANI) chain in an alternating emeraldine form were simulated using molecular dynamics. The simulations were performed in an implicit solvent environment that corresponds to experimental conditions. When the larger opening of the β-cyclodextrin toroids face the same direction, the cyclodextrins tend to repel each other. Alternating the orientation of the β-cyclodextrins on the chain causes the β-cyclodextrin rings to be more attractive to one another and form pairs or stacks of rings. These simulations explain how the β-cyclodextrins can be used to shield the polyaniline from outside chemical action by analyzing the PANI/cyclodextrin interactions from a molecular perspective.
Bulletin of the American Physical Society, Mar 18, 2010
ACS Omega, 2021
To understand the properties of polyaniline (PANI), aim gas, and the interaction between them in ... more To understand the properties of polyaniline (PANI), aim gas, and the interaction between them in PANI-based gas sensors and help us to design sensors with better properties, direct calculations with molecular dynamics (MD) simulations were done in this work. Polyamide 6/polyaniline (PA6/PANI) nanofiber ammonia gas sensors were studied as an example here, and the structural, morphological, and ammonia sensing properties (to 50−250 ppm ammonia) of PA6/PANI nanofibers were tested and evaluated by scanning electron microscopy, Fourier transform infrared spectroscopy, and a homemade test system. The PA6/PANI nanofibers were prepared by in situ polymerization of aniline with electrospun PA6 nanofibers as templates and hydrochloric acid (HCl) as a doping agent for PANI, and the sensors show rapid response, ideal selectivity, and acceptable repeatability. Then, complementary molecular dynamics simulations were performed to understand how ammonia molecules interact with HCl-doped PANI chains, thus providing insights into the molecular-level details of the ammonia sensing performances of this system. Results of the radial distribution functions and mean square displacement analysis of the MD simulations were consistent with the dedoping mechanism of the PANI chains.
ACS Omega, 2018
Soft, wearable or printable strain sensors derived from conductive polymer nanocomposites (CPNs) ... more Soft, wearable or printable strain sensors derived from conductive polymer nanocomposites (CPNs) are becoming increasingly ubiquitous in personal-care applications. Common elastomers employed in the fabrication of such piezoresistive CPNs frequently rely on chemically cross-linked polydiene or polysiloxane chemistry, thereby generating relatively inexpensive and reliable sensors that become solid waste upon application termination. Moreover, the shape anisotropy of the incorporated conductive nanoparticles can produce interesting electrical effects due to strain-induced spatial rearrangement. In this study, we investigate the morphological, mechanical, electrical, and electromechanical properties of CPNs generated from thermoplastic elastomer (TPE) triblock copolymer systems containing vapor-grown carbon nanofiber (CNF). Modulus-tunable TPE gels imbibed with a midblock-selective aliphatic oil exhibit well-behaved properties with increasing CNF content, but generally display nonlinear negative piezoresistance at different strain amplitudes and stretch rates due to nanofiber mobility upon CPN strain-cycling. In contrast, a neat TPE possessing low hard-block content yields a distinctive strain-reversible piezoresistive response, as well as low electrical hysteresis, upon cyclic deformation. Unlike their chemically cross-linked analogs, these physically cross-linked and thus environmentally benign CPNs are fully reprocessable by thermal and/or solvent means.
Soft matter, Jan 8, 2017
Nanocomposites prepared by incorporating functionalized polyhedral oligomeric silsesquioxane (POS... more Nanocomposites prepared by incorporating functionalized polyhedral oligomeric silsesquioxane (POSS) into polymer matrices afford a wide range of versatile hybrid materials for use in technologies ranging from cosmetics and pharmaceuticals to sensors and batteries. Here, we investigate the phase behavior of nanocomposites composed of poly(ethylene oxide) (PEO) and monosubstituted isobutyl POSS (iPOSS) modified with different functional moieties. Microscopic analyses of blends containing these iPOSS variants reveal the existence of different macroscopic morphologies and surface topologies. In the presence of octa-iPOSS, a POSS-rich surface cell motif reminiscent of breath patterns develops, whereas addition of allyl-iPOSS promotes the formation of surface plates. While aminopropyl-iPOSS forms dispersed aggregates, maleamic acid-iPOSS disperses in PEO with little effect on PEO crystal morphology. We perform rotational isomeric state Monte Carlo simulations to discern the effect of mono...
Lecture Notes in Computer Science, 2009
Research domains that deal with complex molecular systems often employ computer-based thermodynam... more Research domains that deal with complex molecular systems often employ computer-based thermodynamics simulations to study molecular interactions and investigate phenomena at the nanoscale. Many visual and analytic methods have proven useful for analyzing the results of molecular simulations; however, these methods have not been fully explored in many emerging domains. In this paper we explore visual-analytics methods to supplement existing standard methods for studying the spatial-temporal dynamics of polymer-nanotube interface. Our methods are our first steps towards the overall goal of understanding macroscopic properties of the composites by investigating dynamics and chemical properties of the interface. We discuss a standard computational approach for comparing polymer conformations using numerical measures of similarities and present matrix-and graph-based representations of the similarity relationships for some polymer structures.
Proceedings of the IEEE SoutheastCon 2010 (SoutheastCon), 2010
We are using molecular simulations to investigate the interface between the polymer matrix and th... more We are using molecular simulations to investigate the interface between the polymer matrix and the carbon nanotube reinforcement, which is the key aspect of the bulk properties of nanocomposites. These simulations are typically analyzed with standard techniques like graphs and animations; however, existing methods are limited for certain exploratory tasks for analyzing the interfacial domains. We present a supplemental exploratory approach that employs standard effective visualanalytical techniques to analyze spatial and temporal properties of the polymer-carbon nanotube interfaces. Our approach is based on a computational method that uses a numerical measure of similarity to compare multiple molecular conformations. We discuss some numerical measures for exploring the behavior of polymer molecules in interfacial domains and present a matrixbased visualization to display and explore local and global similarity relationships of the polymer structures, including dynamical aspects. These methods constitute our initial efforts for using visual-analytical tools to relate the interfacial dynamics to macroscopic properties of the nanocomposite interfaces.
The Journal of Physical Chemistry B, 2010
The goal of this study is to explore the interface between single-walled carbon nanotubes (SWCNTs... more The goal of this study is to explore the interface between single-walled carbon nanotubes (SWCNTs) and polymer chains with semiflexible and stiff backbones in vacuum via molecular dynamics (MD) simulations, which complements our previous work with flexible backbone polymers. These simulations investigate the structural and dynamical features of interactions with the SWCNT, such as how the polymers prefer to interface with the SWCNT and how the interfacial interaction is affected by the chemical composition and structure of the polymer. The simulations indicate that polymers with stiff and semiflexible backbones tend to wrap around the SWCNT with more distinct conformations than those with flexible backbones. Aromatic moieties along the backbone appear to dictate the adsorption conformation, which is likely due to the preference for optimizing pi-pi interactions, although the presence of bulky aliphatic side chains can hinder those interactions. Moment of inertia plots as a function of time indicate that the adsorption of polymers with stiff backbones tends to be a two-step process, in contrast to flexible backbones.
The Journal of Physical Chemistry B, 2010
The goal of this study is to explore the interface between single-walled carbon nanotubes (SWCNTs... more The goal of this study is to explore the interface between single-walled carbon nanotubes (SWCNTs) and polymer chains with flexible backbones in vacuo via molecular dynamics (MD) simulations. These simulations investigate whether the polymers prefer to wrap the SWCNT, what the molecular details of that interface are, and how the interfacial interaction is affected by the chemical composition and structure of the polymer. The simulations indicate that polymers with flexible backbones tend to wrap around the SWCNT, although not in any distinct conformation; no helical conformations were observed. PAN with the cyano side group showed a preference for transversing the length of the SWCNT rather than wrapping around its diameter, and the cyano group prefers to align parallel to the SWCNT surface. Flexible backbone polymers with bulky and aromatic side groups such as PS and PMMA prefer intrachain coiling rather than wrapping the SWCNT. Moment of inertia plots as a function of time quantify the interplay between intrachain coiling and adsorption to the SWCNT surface.
Nanocomposites that have increased surface area at the interface between the reinforcement and th... more Nanocomposites that have increased surface area at the interface between the reinforcement and the matrix only need a little amount of reinforcement to achieve a significant enhancement in the overall desired property1. Thus, carbon nanotubes (CNTs), with their high surface area, are an attractive option for a composite reinforcement material. CNTs have a very high modulus, ranging up to 1 TPa, and thus can greatly enhance the modulus of nanocomposites to several GPa2. In addition, some studies have shown that ...
Interest in bicomponent fibers have grown mainly with the objective that properties of two differ... more Interest in bicomponent fibers have grown mainly with the objective that properties of two different polymer components can be utilized in a single fiber. Choice of the two components can be diverse and can result in many different cross-sectional geometry–such as, side by side, sheath-core, islands-in-the-sea, etc [1]. These different cross-sections are mostly governed by the manufacturing process and their applications. In the present study we focus on single bicomponent fibers with sheath-core cross-sectional geometry, where one ...
Polymer Preprints, 2010
Carbon nanotubes have emerged as one of the most interesting materials since their discovery by I... more Carbon nanotubes have emerged as one of the most interesting materials since their discovery by Ijima1. The high aspect ratio and excellent mechanical and electrical properties exhibited by CNTs make them materials of choice as toughening reinforcements in polyamide based nanocomposites2. However poor dispersion of nanotubes3 and the severe dependence of properties on the orientation of fillers4 in the bulk material require proper engineering of the interface between the CNTs and the polymer matrix. Several ...
Bulletin of the American Physical Society, Mar 17, 2010
The goal of this work is to supplement existing methods for analyzing spatial-temporal dynamics o... more The goal of this work is to supplement existing methods for analyzing spatial-temporal dynamics of polymer conformations derived from molecular dynamics simulations by adapting standard visual-analytics tools. We intend to use these tools to quantify conformational dynamics and chemical characteristics at interfacial domains, and correlate this information to the macroscopic properties of a material. Our approach employs numerical measures of similarities and provides matrix-and graph-based representations ...
Bulletin of the American Physical Society, Mar 18, 2010
Molecular dynamics simulations were used to study the noncovalent interactions between a zig-zag ... more Molecular dynamics simulations were used to study the noncovalent interactions between a zig-zag single-walled carbon nanotube (SWCNT) and polymer chains with varying degrees of saturation, aromaticity, and aliphaticity. The simulations indicate that polymers with both flexible and rigid backbones tend to wrap around the SWCNT, although in different conformations. Flexible backbones wrap in random conformations, which are dependent upon the aliphatic lengths along the backbone and the presence of chemical groups like carbonyls. Polymers with ...
The Journal of Physical Chemistry B
ACS Applied Polymer Materials
Uploads
Papers by Melissa Pasquinelli