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The advantages of the Maxwell–Stefan (MS) formulation over Fick’s law to describe multicomponent mass transfer are well recognized. However, in its original form, the MS equations are written in terms of mole fractions, which are ill-defined if one of the components is a polymer. To overcome this problem, a revised formulation of the MS equations written in terms of volume fractions is proposed. The...
Poly(monochloro-p-xylylene) (Parylene C) coatings are commonly used in a number of applications due to their robust properties and unique ability to be deposited directly from the vapor phase. Recently, Parylene C has been used in new medical devices, where an accurate assessment and understanding of liquid transport and its relationship to the polymer structure is critical in design and evaluation...
The miniemulsion polymerization of styrene mediated by N-(2-methyl-2-propyl)-N-(1-diethylphosphono-2,2-dimethylpropyl)-N-oxyl (SG1) at 396 K is modeled up to high conversion as a function of the targeted chain length (TCL) and particle diameter. Thermal self-initiation and diffusional limitations are explicitly accounted for. The importance of the compartmentalization of nitroxide, initiator and macroradicals...
Gravimetry was used to study the diffusion of a homologous series of linear carboxylic acids (C n , with n=2, 6–16) in amorphous polystyrene at temperatures from 35°C to 165°C, that is, both below and above the polymer glass transition temperature of 100°C. All the mass uptake results are well described by a simple Fickian model (for t<t 1/2 ) and were used to calculate the corresponding...
The strength development and healing of symmetric and asymmetric interfaces of amorphous cyclic olefin copolymers (COC) was studied by assessment of diffusion and lap-shear strength measurement of samples bonded at different temperatures, pressures and healing times. Amorphous COCs comprise copolymers of norbornene and ethylene whereby COCs with differing norbornene content have different glass transition...
Water transport in polymer coatings is a key process in their failure. Mostly, such systems are composed of multiple layers to meet the required specifications. Understanding water transport requires a model that relates the kinetics with the properties of the layers. In this article a theoretical model for water transport in two-layered coatings is formulated and verified. The model considers systems...
The simultaneous ingress of acetone and water into dried PVOH-clay nanocomposites containing 2.5 wt% or 5 wt% of well dispersed Na-Cloisite, using FTIR-ATR, has been compared with that into pure PVOH films. The rate at which water and acetone moved through the PVOH films is significantly reduced (i) at high acetone concentrations and (ii) when clay is incorporated in the PVOH film. For example, it...
Presented with an elevated level of aqueous salt, a polyelectrolyte multilayer (PEM) swells and subsequently can undergo large mass uptake when exposed to a salt solution containing the capping polyelectrolyte. Features of the uptake depend on the properties of polyelectrolyte (molecular weight, polydispersity, concentration), solvent (salt concentration and ion identities), and PEM (number of layers,...
CO 2 sorption in molten poly(ε-caprolactone) (PCL) has been investigated by temporally resolved Raman line imaging, which is introduced here as a new technology for the direct measurement of gas mass fraction profiles inside polymers during transient sorption experiments. Molten PCL was exposed to pressurized carbon dioxide in an optically accessible pressure cell at 80 °C and pressures up...
Dissipative particle dynamics (DPD) combined with Monte Carlo (MC) tracer diffusion calculations are used to study phase separation and diffusion within hydrated (amphiphilic) alternating multi block co-polymer membranes. The co-polymers are composed of hydrophobic (A) and hydrophilic (C) fragments. The hydrophobic A block length is alternating short (x A fragments) and long (y A fragments). One repeat...
The present work is concerned with the effect of cation exchange, with calcium, aluminum and cupric cations, on the permeation kinetics of dimethyl methylphosphonate (DMMP) in a pentablock ionomer (Nexar™) and a perfluoroionomer (Nafion™). The diffusion constant was determined by matching a Fickian solution to early time data, with a zero-time shift, initially attributed to the effect of immobilization...
A new and non-invasive technique based on confocal laser scanning microscopy (CLSM) that allows the visualization of penetrant diffusion in-situ has been developed and was applied to quantify local solute dynamics in polymeric films. The effectiveness of the proposed technique was demonstrated using a model penetrant, rhodamine-6G (Rh-6G), and a system of polyvinyl alcohol (PVA) films with different...
Di(2-ethylhexyl) phthalate (DEHP) is a commonly employed plasticizer for poly(vinyl chloride) (PVC). Diffusion of di(2-ethylhexyl) phthalate (DEHP) takes place when plasticized PVC is immersed in hexane. Rather than determining DEHP concentration in the immersion solvent, an IR window for PVC from 1500 to 1900 cm−1 enabled direct measurement of HADD (hexane assisted DEHP diffusion) using ATR-IR by...
Governing equations for evolution of concentration and temperature in three-component systems were derived in the framework of classical irreversible thermodynamics using Onsager’s variational principle and were presented for solvent/solvent/polymer and solvent/polymer/polymer systems. The derivation was developed from the Gibbs equation of equilibrium thermodynamics using the local equilibrium hypothesis,...
The kinetics of stepwise polymerization in the diffusion-controlled regime was investigated using dynamic Monte Carlo simulation and scaling analysis. In analogy to Flory’s expression, a concise expression of reaction kinetics in diffusion controlled regime was proposed, where the number average degree of polymerization was related to the initial concentration and reaction time through a power law...
Polymer gel electrolytes (PGEs) have been prepared using lithium tetrafluoroborate (LiBF4), propylene carbonate (PC) and poly (vinylidene fluoride) (PVDF). Self diffusion coefficients have been measured using pulse field gradient nuclear magnetic resonance (PFG-NMR) for the lithium cation, BF4 anion and solvent molecules using 7Li, 19F and 1H nuclei, respectively. It was found that lithium ion diffusion...
The diffusion of polymer in long cylindrical tubes is investigated by using Monte Carlo simulations. Two kinds of cylindrical tubes are taken into account: (1) a homogeneous tube where the polymer-tube interaction is independent of monomer position along the longitudinal direction of the tube, and (2) a periodic one where the interaction is periodically changed along the tube. In the homogeneous tube,...
There are few studies of the impact of membrane charge on ion and organic uncharged solute transport in polymers. This study was aimed at addressing the lack of such fundamental information in the literature. Liquid methanol sorption, diffusion and permeation in water swollen, cross-linked, uncharged poly(ethylene glycol) diacrylate (XLPEGDA) and in charged membranes were investigated. Membrane water...
New polyampholyte linear polymers and hydrogels based on N-acryloyl-N′-ethyl piperazine (AcrNEP) and maleic acid (MaA) were prepared by free-radical solution polymerization. The microstructure of copolymers was statistically estimated by the terminal copolymerization model. A maximum tendency (80%) of alternating sequence of monomers units occurred at about 85 mol % of AcrNEP in the reaction feed...
The interdiffusion of the C8, the C9 and the C10 aldehyde molecules into a glassy uncrosslinked polymer film composed of four components is studied by using coarse-grained (CG) molecular dynamics simulations. Effects of the aldehyde molecule size, water and temperature on the interdiffusion processes are probed. It is found that (i) the interdiffusion generally follows the smaller-the faster rule...
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