Chunggi Baig

The gradient stiffness between stiff epidermis and soft dermis with interlocked microridge structures in human skin induces effective stress transmission to underlying mechanoreceptors for enhanced tactile sensing. Inspired by skin structure and function, we fabricate hierarchical nanoporous and interlocked microridge structured polymers with gradient stiffness for spacer-free, ultrathin, and highly sensitive triboelectric sensors (TESs). The skin-inspired hierarchical polymers with gradient ela

Hierarchical and gradient structures in biological systems with special mechanical properties have inspired innovations in materials design for construction and mechanical applications. Analogous to the control of stress transfer in gradient mechanical structures, the control of electron transfer in gradient electrical structures should enable the development of high-performance electronics. This paper demonstrates a high performance electronic skin (e-skin) via the simultaneous control of tacti

We present detailed results about the structural, conformational, rheo-optical, and topological properties of an entangled of C 400 H 802 linear polyethylene (PE) melt over a wide range of shear rates (covering both the linear and the highly nonlinear viscoelastic regimes) from direct nonequilibrium molecular dynamics (NEMD) simulations of a large system containing 192 chains (corresponding to 79200 interacting atomistic units). We discuss results for (i) the probability distribution of the mean

Biological tissues are multiresponsive and functional, and similar properties might be possible in synthetic systems by merging responsive polymers with hierarchical soft architectures. For example, mechanochromic polymers have applications in force-responsive colorimetric sensors and soft robotics, but their integration into sensitive, multifunctional devices remains challenging. Herein, a hierarchical nanoparticle-in-micropore (NP-MP) architecture in porous mechanochromic polymers, which enhan

Atomistic configurations of model unentangled ring polyethylene (PE) melts ranging in chain length from C 24 up to C 400 have been subjected to detailed molecular dynamics (MD) simulations in the isothermal−isobaric statistical ensemble at temperature T = 450 K and P = 1 atm. Strictly monodisperse samples were employed in all cases. We present and discuss in detail simulation results for a variety of structural, thermodynamic, conformational and dynamic properties of these systems, and their var

We present nonequilibrium molecular dynamics simulations of planar elongational flow (PEF) by an algorithm proposed by Tuckerman et al. [J. Chem. Phys. 106, 5615 (1997)] and theoretically elaborated by Edwards and Dressler [J. Non-Newtonian, Fluid Mech. 96, 163 (2001)], which we shall call the proper-SLLOD algorithm, or p-SLLOD for short. [For background on names of algorithms see W. G. Hoover, D. J. Evans, R. B. Hickman, A. J. C. Ladd, W. T. Ashurst, and B. Moran, Phys. Rev. A 22, 1690 (1980) a

Poly(ethylene glycol) (PEG) has attracted significant interest because of its superior antifouling properties, water solubility, and biocompatibility. However, the translation of its antifouling properties onto target surfaces has been challenging because of its limited functionality. Herein, the superior antifouling properties of PEG-based block copolyethers functionalized with catechol, a mussel-inspired, versatile moiety for coating surfaces, were evaluated within a framework of polyethers ex

We report for the first time rheological and structural properties of liquid decane, hexadecane, and tetracosane using nonequilibrium molecular-dynamics (NEMD) simulations under planar elongational flow (PEF). The underlying NEMD algorithm employed is the so-called p-SLLOD algorithm [C. Baig, B. J. Edwards, D. J. Keffer, and H. D. Cochran, J. Chem. Phys. 122, 114103 (2005)]. Two elongational viscosities are measured, and they are shown not to be equal to each other, indicating two independent vi

We present various rheological and structural properties of three polyethylene liquids, C50H102, C78H158, and C128H258, using nonequilibrium molecular dynamics simulations of planar elongational flow. All three melts display tension-thinning behavior of both elongational viscosities, eta1 and eta2. This tension thinning appears to follow the power law with respect to the elongation rate, i.e., eta approximately epsilon(b), where the exponent b is shown to be approximately -0.4 for eta1 and eta2.

State-of-the-art tube models for the dynamics of entangled polymer melts are usually validated on the basis of the agreement of their predictions for the linear viscoelastic properties (LVE data) of the system against experimentally measured data. We present here a more direct and fundamental test of these models based on their comparison against molecular dynamics (MD) simulation data for the dynamics of primitive paths (PPs) in the system under study. More precisely, we show how one can take a

Abstract In this work, we analyzed the individual chain dynamics for linear polymer melts under shear flow for bulk and confined systems using atomistic nonequilibrium molecular dynamics simulations of unentangled (C 50 H 102 ) and slightly entangled (C 178 H 358 ) polyethylene melts. While a certain similarity appears for the bulk and confined systems for the dynamic mechanisms of polymer chains in response to the imposed flow field, the interfacial chain dynamics near the boundary solid walls

An important objective in polymer science is to manipulate the material properties of polymers by altering their molecular architecture. To this end, understanding of the fundamental role of chain branches along the polymer backbone is crucial. Although the dynamics of linear and long-branched polymers have been thoroughly investigated over the past decades, a comprehensive understanding of branching effects has not yet been obtained, particularly because of a serious lack of knowledge on the ro

We present detailed results on the effect of chain branching on the topological properties of entangled polymer melts via an advanced connectivity-altering Monte Carlo (MC) algorithm. Eleven representative model linear, short-chain branched (SCB), and long-chain branched (LCB) polyethylene (PE) melts were employed, based on the total chain length and/or the longest linear chain dimension. Directly analyzing the entanglement [or the primitive path (PP)] network of the system via the Z-code, we qu

A detailed quantitative analysis on the validity of a coarse-grained (CG) model for nonequilibrium polymeric liquids under flow was reported. The significant features of CG model included the asymptotic behavior of c̃ xx displayed by the atomistic model attributed to finite chain extensibility due to the strong bond-stretching and bond-bending interactions between atoms behind the chain and the chain rotation occurred in shear flow. The large chain deformations exhibited in the CG m

One of the most important nonlinear rheological phenomena in flowing polymeric materials is the stress overshoot under start-up shear at sufficiently high shear rates γ̇, i.e., γ̇ > τ d –1, where τ d is the terminal relaxation time of system. According to the well-known tube theory for entangled polymeric materials, a linear relationship between the anisotropy of the stress and that of the birefringence holds for strain rates in the τ d –1 < γ̇ < τ R –1 range, where τ R is the Rouse time. This i