Star topology increases ballistic resistance in thin polymer films

Giuntoli, Andrea; Hansoge, Nitin K.; Keten, Sinan

doi:10.1016/j.eml.2020.101038

Cited by 12 publications

(14 citation statements)

References 24 publications

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“…2,3 In addition, the prevalence of internal interactions and molecular rearrangements in star polymers compared to their linear counterparts contributes to enhanced energy dissipation of solvent-free thin films composed of star polymers during ballistic impact. 4,5 Moreover, star polymer architecture is also advantageous for the development of novel drug and gene delivery systems. 6−10 In particular, star polymers have been demonstrated to have higher dye/drug trapping efficiency 11,12 and lower cytotoxicity 13,14 than linear polymers.…”

Section: ■ Introductionmentioning

confidence: 99%

“…The resulting compact molecular architecture differentiates the behavior of star polymers from that of their linear counterparts. For example, polymer branching results in a lowering of intrinsic viscosity, which is desirable in developing novel additives for lubricants. , In addition, the prevalence of internal interactions and molecular rearrangements in star polymers compared to their linear counterparts contributes to enhanced energy dissipation of solvent-free thin films composed of star polymers during ballistic impact. , Moreover, star polymer architecture is also advantageous for the development of novel drug and gene delivery systems. − In particular, star polymers have been demonstrated to have higher dye/drug trapping efficiency , and lower cytotoxicity , than linear polymers.…”

Section: Introductionmentioning

confidence: 99%

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Impact of Star Polyacid Branching on Polymer Diffusion within Multilayer Films

2022

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A series of linear and star poly(acrylic acids) (LPAA and star PAAs) were synthesized to explore the effect of molecular architecture on the stratification and polymer dynamics of electrostatic layer-by-layer (LbL) films. Studies of LbL deposition of LPAA and star PAAs with poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) at acidic pH showed an ∼30% increase in film dry thickness with increased polymer branching. Consistent with a greater mass of star polymer deposited within the films, in situ ellipsometric measurements of PAA uptake from solution revealed ∼3.5-fold greater diffusion coefficients for 8-arm PAA in comparison to linear PAA. For comparison, the dynamics of the linear PDMAEMA partner was explored via neutron reflectometry (NR) studies of stacked multilayers containing hydrogenated and deuterated polycations, hPDMAEMA and dPDMAEMA. The stacked multilayers deposited from low-ionic-strength solutions were stratified, exhibiting interfacial widths between hydrogenated and deuterated stacks of ∼15 and 10 nm for films constructed with star and linear PAAs, respectively, suggesting relatively low mobility of the polycation in both assemblies. Further exposure of these films to 0.5 M sodium chloride solutions enhanced the mobility of PDMAEMA, revealing an order magnitude faster diffusion of PDMAEMA in films of 8-arm PAA relative to linear PAA. The faster diffusion of polymers within films of star polyacids was correlated not only with the compactness of star polymers but also with an ∼2-fold lower ionization of assembled 8-arm PAA as determined by Fourier transform infrared spectroscopy and thus a lower number of polycation–polyacid ionic contacts in the case of star polymers as compared to their linear counterparts. The significant influence of molecular architecture on the number of polymer–polymer contacts was further confirmed by isothermal titration calorimetry studies of polyelectrolyte complexes in solution.

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Section: ■ Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Impact of Star Polyacid Branching on Polymer Diffusion within Multilayer Films

2022

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“…The acceleration arises from the decrease in the total number of atoms, the use of a larger time step for the evolution of molecular dynamics, and the smoothing of the interatomic potential energy landscape. CG polymer models have been developed by using different schemes − and employed to simulate the dynamics and rheological properties − ,− of polymers above the glass transition temperature T g as well as the mechanical properties − of glassy polymers below T g . The CG simulations have fostered the understanding of microscopic mechanisms underlying the macroscopic properties of polymers, which are otherwise difficult to explore with fully atomistic simulations.…”

Section: Introductionmentioning

confidence: 99%

Effects of Coarse-Graining on Molecular Simulation of Craze Formation in Polymer Glass

et al. 2022

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Crazing precedes the crack propagation in polymer glass and greatly increases the fracture toughness. We perform molecular dynamics simulations to study craze formation in glassy polystyrene (PS). The use of a structure-based coarse-grained (CG) model allows us to create and equilibrate a large-scale sample (≈ 71 nm × 71 nm × 71 nm) of well-entangled PS chains with molecular weight 10 times the entanglement threshold. The back-mapping of the CG sample to the united-atom (UA) representation generates a PS sample with fine atomistic details. The structural features of the craze fibrils in the CG and UA simulations are almost the same, and both correlate with the underlying entanglement network as in the traditional theoretical description, reflecting the preservation of structural correlations during the coarse-graining. The stress level in the CG simulation is reduced compared with the UA simulation, as the coarse-graining with fine atomistic details removed leads to a smoother potential energy landscape for craze formation. In both CG and UA simulations, the same large fraction (70%−80%) of the stress during craze formation is dissipative stress, suggesting the coarse-graining preserves the relative contributions of the energetic and dissipative components to the overall stress. The constant drawing stress is related to the surface tension and the average spacing between craze fibrils in the simulations, as in the traditional models of crazing. We also demonstrate a scale-bridging simulation protocol where the CG simulation is used to accelerate the craze formation, and the subsequent back-mapping to the UA simulation is used to recover the stress level.

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“…MD simulations of high-velocity impacts on carbon-based materials are rather limited, but a few fundamental works exists, mostly involving impacts on graphene sheets − or polymer thin films. − For example, the ballistic penetration was studied for poly(methyl methacrylate) (PMMA) to compare E p * and local failure mechanisms of polymers, graphene, and metals . However, bond scission was not accounted for in PMMA.…”

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confidence: 99%

“…Although rupture of individual bonds does not dissipate high amounts of energy (see SI Figure S4), bond rupture promotes chain mobility as the tension in highly stressed chains is relieved along the backbone. Impact simulations by Giuntoli et al confirm that bond energy has a small direct role in the total energy dissipation and interchain frictional forces dominate.…”

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confidence: 99%

Supersonic Impact Response of Polymer Thin Films via Large-Scale Atomistic Simulations

et al. 2021

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Recent nanoscale ballistic tests have shown the applicability of nanomaterials for ballistic protection but have raised questions regarding the nanoscale structure−property relationships that contribute to the ballistic response. Herein, we report on multimillion-atom reactive molecular dynamics simulations of the supersonic impact, penetration, and failure of polyethylene (PE) and polystyrene (PS) ultrathin films. The simulated specific penetration energy (E p *) versus impact velocity predicts to within 15% the experimentally determined E p * for PS. For impact velocities less than 1 km s −1 , a crazing/petalling failure mode is observed due to chain disentanglement, transitioning to fragmentation coupled with large amounts of adiabatic heating at velocities greater than 1 km s −1 . Interestingly, the high entanglement density of PE provides enhanced penetration resistance at low velocities, whereas increased adiabatic heating in PS promotes greater penetration resistance at elevated velocities. By understanding nanoscale mechanisms of energy absorption, nanomaterials can be designed to provide superior penetration resistance.

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Star topology increases ballistic resistance in thin polymer films

Cited by 12 publications

References 24 publications

Impact of Star Polyacid Branching on Polymer Diffusion within Multilayer Films

Impact of Star Polyacid Branching on Polymer Diffusion within Multilayer Films

Effects of Coarse-Graining on Molecular Simulation of Craze Formation in Polymer Glass

Supersonic Impact Response of Polymer Thin Films via Large-Scale Atomistic Simulations

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