Star topology increases ballistic resistance in thin polymer films

Published on Nov 1, 2020in Extreme Mechanics Letters4.806
· DOI :10.1016/J.EML.2020.101038
Andrea Giuntoli4
Estimated H-index: 4
(NU: Northwestern University),
Nitin K. Hansoge4
Estimated H-index: 4
(NU: Northwestern University),
Sinan Keten34
Estimated H-index: 34
(NU: Northwestern University)
Abstract Polymeric films with greater impact and ballistic resistance are highly desired for numerous applications, but molecular configurations that best address this need remain subject to debate. We study the resistance to ballistic impact of thin polymer films using coarse-grained molecular dynamics simulations, investigating melts of linear polymer chains and star polymers with varying number ( 2 ≤ f ≤ 16 ) and degree of polymerization ( 10 ≤ M ≤ 50 ) of the arms. We show that increasing the number of arms f or the length of the arms M both result in greater specific penetration energy within the parameter ranges studied. Greater interpenetration of chains in stars with larger f allows energy to be dissipated predominantly through rearrangement of the stars internally, rather than chain sliding. During film deformation, stars with large f show higher energy absorption rates soon after contact with the projectile, whereas stars with larger M have a delayed response where dissipation arises primarily from chain sliding, which results in significant back face deformation. Our results suggest that stars may be advantageous for tuning energy dissipation mechanisms of ultra-thin films. These findings set the stage for a topology-based strategy for the design of impact-resistant polymer films.
📖 Papers frequently viewed together
34 Citations
#1Andrea Giuntoli (Wesleyan University)H-Index: 4
#2Francesco Puosi (UniPi: University of Pisa)H-Index: 16
Last. Jack F. Douglas (NIST: National Institute of Standards and Technology)H-Index: 91
view all 5 authors...
We examine the influence of steady shear on structural relaxation in a simulated coarse-grained unentangled polymer melt over a wide range of temperature and shear rates. Shear is found to progressively suppress the α-relaxation process observed in the intermediate scattering function, leading ultimately to a purely inertially dominated β-relaxation at high shear rates, a trend similar to increasing temperature. On the basis of a scaling argument emphasizing dynamic heterogeneity in cooled liqui...
10 CitationsSource
#1Jinpeng Fan (Wesleyan University)H-Index: 1
#2Hamed Emamy (Columbia University)H-Index: 6
Last. Francis W. Starr (Wesleyan University)H-Index: 54
view all 5 authors...
While glass formation of linear chain polymer melts has widely been explored, comparatively little is known about glass formation in star polymer melts. We study the segmental dynamics of star polymer melts via molecular dynamics simulations and examine the cooperative nature of segmental motion in star melts. In particular, we quantify how the molecular architecture of star polymers, i.e., the number of arms and the length of those arms, affects the glass transition temperature Tg, the non-Gaus...
15 CitationsSource
#1Andrea Giuntoli (Wesleyan University)H-Index: 4
#2Alexandros Chremos (NIST: National Institute of Standards and Technology)H-Index: 1
Last. Jack F. Douglas (NIST: National Institute of Standards and Technology)H-Index: 91
view all 3 authors...
We investigate how varying molecular topology of polymers influences crystallization in thin polymer films. In particular, we simulate linear and star polymers of fixed mass having a progressively increasing number of arms (f ≤ 16) in a system where the linear polymer exhibits crystallization in a thin film geometry, but no apparent crystallization in the corresponding bulk material. The degree of crystallization of the polymer film at long times decreases progressively with increasing f, and no...
2 CitationsSource
#1Kenneth S. Schweizer (UIUC: University of Illinois at Urbana–Champaign)H-Index: 39
#1Kenneth S. Schweizer (UIUC: University of Illinois at Urbana–Champaign)H-Index: 79
Last. David S. Simmons (USF: University of South Florida)H-Index: 17
view all 2 authors...
The nature of alterations to dynamics and vitrification in the nanoscale vicinity of interfaces—commonly referred to as “nanoconfinement” effects on the glass transition—has been an open question for a quarter century. We first analyze experimental and simulation results over the last decade to construct an overall phenomenological picture. Key features include the following: after a metrology- and chemistry-dependent onset, near-interface relaxation times obey a fractional power law decoupling ...
16 CitationsSource
#1Edwin P. Chan (NIST: National Institute of Standards and Technology)H-Index: 23
#2Wanting XieH-Index: 8
Last. Christopher L. Soles (NIST: National Institute of Standards and Technology)H-Index: 38
view all 5 authors...
The fracture behavior of glassy polymers is strongly coupled to molecular parameters such as entanglement density as well as extrinsic parameters such as strain rate and test temperature. Here we use laser-induced projectile impact testing (LIPIT) to study the extreme strain rate (≈107 s–1) puncture behavior of free-standing polycarbonate (PC) thin films. We demonstrate that changes to the PC molecular mass and the degree of plasticization can lead to substantial changes in the specific puncture...
12 CitationsSource
#1Xin Qin (NU: Northwestern University)H-Index: 7
#2Benjamin C. Marchi (NU: Northwestern University)H-Index: 1
Last. Sinan Keten (NU: Northwestern University)H-Index: 34
view all 4 authors...
The Bouligand structure features a helicoidal (twisted plywood) layup of fibers that are uniaxially arranged in-plane and is a hallmark of biomaterials that exhibit outstanding impact resistance. Despite its performance advantage, the underlying mechanisms for its outstanding impact resistance remain poorly understood, posing challenges for optimizing the design and development of bio-inspired materials with Bouligand microstructures. Interestingly, many bio-sourced nanomaterials, such as cellul...
6 CitationsSource
#1Zhaoxu Meng (NU: Northwestern University)H-Index: 13
#2Sinan Keten (NU: Northwestern University)H-Index: 34
10 CitationsSource
#1Wengang Zhang (Wesleyan University)H-Index: 7
#2Jack F. Douglas (NIST: National Institute of Standards and Technology)H-Index: 91
Last. Francis W. Starr (Wesleyan University)H-Index: 54
view all 3 authors...
There is significant variation in the reported magnitude and even the sign of T g shifts in thin polymer films with nominally the same chemistry, film thickness, and supporting substrate. The implicit assumption is that methods used to estimate T g in bulk materials are relevant for inferring dynamic changes in thin films. To test the validity of this assumption, we perform molecular simulations of a coarse-grained polymer melt supported on an attractive substrate. As observed in many experiment...
22 CitationsSource
#1Ankit Malik (MOD: United Kingdom Ministry of Defence)H-Index: 4
#2Balasubramanian Kandasubramanian (MOD: United Kingdom Ministry of Defence)H-Index: 30
ABSTRACTThe miniaturization of electronics has been following Moore's Law for decades and has resulted in the development of sequentially evolutionized multifunctional nanoengineered devices. The conventional electronic devices are processed over planar hierarchically nanopatterned substrates having mechanical rigidity and stiffness which limit the degree of utility due to its inability to interface with soft curvilinear morphology, brittle nature, and inferior optical transparency. However, fle...
31 CitationsSource
#1Emmanouil Glynos (FORTH: Foundation for Research & Technology – Hellas)H-Index: 21
#2Kyle Johnson (UM: University of Michigan)H-Index: 8
Last. Peter F. GreenH-Index: 56
view all 7 authors...
: The surface relaxation dynamics of supported star-shaped polymer thin films are shown to be slower than the bulk, persisting up to temperatures at least 50 K above the bulk glass transition temperature T_{g}^{bulk}. This behavior, exhibited by star-shaped polystyrenes with functionality f=8 arms and molecular weights per arm M_{arm}
14 CitationsSource
Cited By1
#1Andrew L Bowman (ERDC: Engineer Research and Development Center)
#2Edwin P. Chan (NIST: National Institute of Standards and Technology)H-Index: 23
Last. John K. Newman (ERDC: Engineer Research and Development Center)H-Index: 3
view all 4 authors...
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 (Ep*) versus impact velocity predicts t...