Coupled length and time scales determine the dynamic behavior of polymers underlie their unique viscoelastic properties. To resolve long-time dynamics it is imperative to which must be correctly modeled. Here we probe degree coarse graining required simultaneously retain significant atomistic details access large scales. The in turn sets minimum scale instrumental defining polymer properties dynamics. Using linear polyethylene as a model system, how affects measured Iterative Boltzmann...

Large-scale simulations of thermal welding polymers are performed to investigate the rise mechanical strength at polymer-polymer interface with time ${t}_{w}$. The process is core integrating polymeric elements into devices as well in induced healing polymers, processes that require development interfacial equal bulk. Our show saturates bulk shear long before diffuse by their radius gyration. Along increase, dominant failure mode changes from chain pullout scission formation sufficient...

The structure and proton conductivity of sulfonated styrene−ethylene copolymers have been studied. Conductivities in excess 0.1 S/cm are obtained depending upon copolymer composition sulfonation level. dependence on humidity has measured compared with that Nafion a partially block copolymer. X-ray neutron scattering studies suggest the presence bicontinuous network hydrophilic hydrophobic domains water-swollen samples.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTBirefringence detection of the order-to-disorder transition in block copolymer liquidsN. P. Balsara, D. Perahia, C. R. Safinya, M. Tirrell, and T. LodgeCite this: Macromolecules 1992, 25, 15, 3896–3901Publication Date (Print):July 1, 1992Publication History Published online1 May 2002Published inissue 1 July 1992https://doi.org/10.1021/ma00041a011RIGHTS & PERMISSIONSArticle Views554Altmetric-Citations99LEARN ABOUT THESE METRICSArticle Views are...

Self-healing of polymer films often takes place as the molecules diffuse across a damaged region, above their melting temperature. Using molecular dynamics simulations we probe healing and compare results with those obtained for thermal welding homopolymer slabs. These two processes differ from each other in interfacial structure since damage leads to increased polydispersity more short chains. A sample was cut into separate that were then held together melt state. The recovery film followed...

The distinctive viscoelastic behavior of polymers results from a coupled interplay motion on multiple length and time scales. Capturing the broad scales polymer remains challenge. Using polyethylene (PE) as model macromolecule, we construct coarse-grained (CG) models PE with three to six methyl groups per CG bead probe two critical aspects technique: pressure corrections required after iterative Boltzmann inversion (IBI) generate potentials that match reference fully atomistic melt...

Ionic assemblies, or clusters, determine the structure and dynamics of ionizable polymers enable their many applications. Fundamental to attaining well-defined materials is controlling balance between van der Waals interactions that govern backbone behavior forces drive formation ionic clusters. Here, using small-angle neutron scattering fully atomistic molecular simulations, a model ionomer, sulfonated polystyrene in toluene solutions, was investigated as cluster cohesion tweaked by...

We have measured simultaneously both the normal forces F⊥(D) and shear F∥(D) that act between compressed polymer-bearing mica surfaces, a distance D apart, as they slide past each other. find for surface-attached polystyrene (PS) brushes in good solvent toluene are extremely weak, over wide range of velocities at loads correspond to 2L < ⅙(2L), where L is height brush. Compared with required bare surfaces immersed simple liquids (toluene or cyclohexane) under comparable loads, reduce...

The association of ionizable polymers strongly affects their motion in solutions, where the constraints arising from clustering groups alter macroscopic dynamics. interrelation between on multiple length and time scales is fundamental to a broad range complex fluids including physical networks, gels, polymer–nanoparticle complexes long-lived associations control structure Using neutron spin echo fully atomistic, multimillion atom molecular dynamics (MD) simulations carried out times...

Neutron reflectometry is used to obtain a direct measurement of the monomer distribution weakly bound end-grafted polystyrene layer in equilibrium with bulk solution, as function polymer concentration and temperature. We report for first time two new regions density profile polymers, an excess near surface wetting on top brush. The physical properties are strongly affected by between free molecules.

Hexa-peri-hexabenzocoronene (HBC) derivatives possess many interesting properties ranging from liquid crystallinity, to hole transport, variable emission behavior, yet are plagued by insolubility and general accessibility of polymerizable substituents. The first synthesis trifluorovinyl ether-substituted hexabenzocoronene its polymerization perfluorocyclobutyl (PFCB) polymers copolymers is shown. Unlike hydrocarbon ethers, fluoro vinyl ethers stable under HBC oxidation conditions. Discrete...

The structure of rigid sulfonated polyphenylene ionomers was investigated in bulk and dilute organic solutions. uniqueness lies their backbone which prevents folding therefore affects the partition into hydrophilic ionic domains hydrophobic regions. This segregation dominates flexible polymers. Small-angle neutron scattering studies these have demonstrated that bundles polymer molecules are formed clustered building block persists dry hydrated states ionomers. Hydration membranes results to...

The liquid-vapor interfacial properties of semifluorinated linear alkane diblock copolymers the form F(3)C(CF(2))(n-1)(CH(2))(m-1)CH(3) are studied by fully atomistic molecular dynamics simulations. chemical composition and conformation molecules at interface identified correlated with energies. A modified Optimized Parameter for Liquid Simulation All-Atom (OPLS-AA) force field Jorgensen co-workers [J. Am. Chem. Soc. 106, 6638 (1984); 118, 11225 (1996); J. Phys. 105, 4118 (2001)], which...

While nearly all theoretical and computational studies of entangled polymer melts have focused on uniform samples, synthesis routes always result in some dispersity, albeit narrow, distribution molecular weights (${\DJ{}}_{M}={M}_{w}/{M}_{n}\ensuremath{\sim}1.02--1.04$). Here, the effects dispersity chain mobility are studied for entangled, disperse using a coarse-grained model polyethylene. Polymer with lengths set to follow Schulz-Zimm same average ${M}_{w}=36\text{ }\text{...

Ionic clusters control the structure, dynamics, and transport in soft matter. Incorporating a small fraction of ionizable groups polymers substantially reduces mobility macromolecules melts. These ionic often associate into random melts, where distribution morphology impact these materials. Here, using molecular dynamic simulations we demonstrate clear correlation between cluster size with polymer melts sulfonated polystyrene. We show that low dielectric media ladderlike are lower energy...

We have extended earlier work on the reduction of friction by polymer brushes between moderately-compressed sliding surfaces to case shear forces brush-bearing as they slide past each other at high compressions, against much larger frictional forces. Our results reveal that compression ratios β= (2L/D)≳8, where L is unperturbed thickness brush and D surface separation, rise rapidly. At sufficiently compressions (β≳10) we observe stick—slip behavior, well clear indications detachment chains...

Supermolecular structures of lamellae folded into rodlike features were observed in thin films dialkylpoly(p-phenyleneethynylene)s (R = 2-ethylhexyl, 2,5,5-trimethylhexyl, nonyl, dodecyl). The polymers have been melted onto oxidized silicon wafers and spontaneously wetted the to form thin, micrometer thick films. These investigated by AFM microscopy wide- small-angle X-ray scattering. In all cases, spontaneous self-assembly PPEs occurs. process takes place on two length scales leading...

A transition from a fluid to constrained phase, in dilute solutions of rodlike molecule, poly(2,5-dinonylparaphenylene ethynylene)s (PPE) toluene has been studied, exploring the dynamics and structure PPE molecules solvent both phases. The is characterized by visual changes viscosity system its color, where transparent liquid transforms into yellow glassy phase. Nuclear magnetic resonance relaxation measurements indicated that significant restriction motion polymeric molecule take place as...

The dynamics of water within ionic polymer networks formed by sulfonated poly(phenylene) (SPP), as revealed quasi-elastic neutron scattering (QENS), is presented. These polymers are distinguished from other macromolecules their rigidity and therefore in network structure. QENS measurements a function temperature the fraction groups humidity were varied have shown that molecules immobile while absorbed remain dynamic. occupy multiple sites, either bound or loosely constrained, bounce between...