Polymer confined

I. Bitsanis, G. Hadziioannou. Molecular dynamics simulations of the structure and dynamics of confined polymer melts. J Chem Phys 92 3827-3847, 1990. 

Luengo, G., Schmitt, R, andHUl, R., Thin Film Rheology and Tribology of Confined Polymer Melts Contrasts with Bulk Properties," Macroniolecules,Vo. 30,1997, pp. 2482-2494. 

Structure and Dynamics of a Confined Polymer Chain Studied by Spatially and Temporally Resolved Fluorescence Techniques... 

Giannelis, E.P., Krishnamoorti, R., Manias, E, Polymer-Silicate Nanocomposites Model Systems for Confined Polymers and Polymer Brushes. VoL 138, pp. 107448. 

Also, because of the constraints imposed by the cavity walls, these confined polymers frequently show no glass transition temperatures or melting points [86,241],... 

Giannelis, E.P., Krishnamoorthy, R. and Manias, E. (1999) Polymer-silicate nanocomposites Model systems for confined polymers and polymer brushes. Advances in Polymer Science, 138, 107-147. 

Galgali and his colleagues [46] have also shown that the typical rheological response in nanocomposites arises from frictional interactions between the silicate layers and not from the immobilization of confined polymer chains between the silicate layers. They have also shown a dramatic decrease in the creep compliance for the PP-based nanocomposite with 9 wt% MMT. They showed a dramatic three orders of magnitude drop in the zero shear viscosity beyond the apparent yield stress, suggesting that the solid-like behavior in the quiescent state is a result of the percolated structure of the layered silicate. 

Computer simulations of confined polymers have been popular for several reasons. For one, they provide exact results for the given model. In addition, computer simulations provide molecular information that is not available from either theory or experiment. Finally, advances in computers and simulation algorithms have made reasonably large-scale simulations of polymers possible in the last decade. In this section I describe computer simulations of polymers at surfaces with an emphasis on the density profiles and conformational properties of polymers at single flat surfaces. 

One of the interests in confined polymers arises from adsorption behavior— that is, the intake or partitioning of polymers into porous media. Simulation of confined polymers in equilibrium with a bulk fluid requires simulations where the chemical potentials of the bulk and confined polymers are equal. This is a difficult task because simulations of polymers at constant chemical potential require the insertion of molecules into the fluid, which has poor statistics for long chains. Several methods for simulating polymers at constant chemical potential have been proposed. These include biased insertion methods [61,62], novel simulation ensembles [63,64], and simulations where the pore is physically connected to a large bulk reservoir [42]. Although these methods are promising, so far they have not been implemented in an extensive study of the partitioning of polymers into porous media. This is a fruitful avenue for future research. 

Finally, a relatively new area in the computer simulation of confined polymers is the simulation of nonequilibrium phenomena [72,79-87]. An example is the behavior of fluids undergoing shear flow, which is studied by moving the confining surfaces parallel to each other. There have been some controversies regarding the use of thermostats and other technical issues in the simulations. If only the walls are maintained at a constant temperature and the fluid is allowed to heat up under shear [79-82], the results from these simulations can be analyzed using continuum mechanics, and excellent results can be obtained for the transport properties from molecular simulations of confined liquids. This avenue of research is interesting and could prove to be important in the future. 

There have been extensive computer simulations and liquid state theories, and a good understanding of these systems is now available. The majority of work has focused on simple hard-chain systems, and the depletion and enhancement effects in these systems are well understood and there are several theories that are in quantitative agreement with computer simulations. In contrast, there has been relatively little attention focused on the effect of wall-fluid and fluid-fluid attractions on the behavior of confined polymers. Only the simplest of DFT approaches has been attempted, and the results are promising although the quantitative performance leaves a lot to be desired. 

Nanocomposite polymers In situ polymerization Nanoscopically confined polymers... 

Muthukumar, M. (2001) Translocation of a confined polymer through a hole. Phys. Rev. Lett., 82, 3188-3191. 

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