Polymer replica method

Porous ZrB -Based Components Prepared by the Polymer Replica Method... 

In both cases an expression for the free energy results which is identical with tq. (37) derived by the replica method From the congruent results obtained by different theoretical methods for physically equivalent models, it can be concluded that Eq. (37) is representative for network models with harmonic constraining potentials. Equation (37) will be used extensively in all further discussions concerning the properties of the tube model of polymer networks. 

Averaging over disorder The replica trick The numerical results in the previous section reveal that a polymer in a random potential can be viewed as a glassy system. In order to develop this point of view, wc apply the replica method, which has been successfully applied in the study of glassy systems [21]. The replica approach was invented in order to compute quenched averages such as as given in Eq. (10), which is difflcult since it entails averaging a ratio of the... 

Oliver and Mason [292] have used replica methods to assess the effect of surface roughness on the spreading of liquids and to measure contact angles. For stationary studies, small beads of poly(methyl methacrylate) (PMMA) were melted and the molten droplets spread and solidified on the surfaces. Dynamic studies involved polymer melts mounted on a remotely controlled hot stage stub in the SEM and the experiments were video recorded. 

The general replica method for SEM of fibers or other polymers is as follows. 

The removal of direct carbon replicas is dependent upon the polymer. Boiling xylene vapor was used to remove drawn PE from replicas [296] in work on drawn polymer morphology. Hobbs and Pratt [297] described a direct carbon replica method for replication of a PBT impact fracture surface by evaporation of platinum at 20° and PBT removal in hexafluor-oisopropanol (HFIP). Latex film coalescence in poly(vinyl acrylate) homopolymer and vinyl acrylic copolymer latexes was studied using direct replicas [298]. As the latex films have a low glass transition temperature, they were cooled by liquid nitrogen to about -150°C in the vacuum evaporator and shadowed with Pt/ Pd at 45° followed by deposition of a carbon support film at 90° to the specimen surface. The latex films were dissolved in methyl acetate/ methanol. TEM micrographs of the latex films show the difference between films aged for various times (Section 5.5.2). 

Suh et al. also reported a direct method for molding of PEG polymers [40], which involves the placement of a patterned PDMS mold on top of a drop-dispensed or spin-coated PEG solution typically dissolved in water or ethanol, leaving behind a polymer replica after solvent evaporation followed by mold removal. In comparison with qCP, the technique generates features varying in height with precise control over cell migration and interconnection of cell arrays. 

One increasingly popular method which lead to non-dynamical trajectories is replica-exchange MC or MD [11-13], which employs parallel simulations at a ladder of temperatures. The "trajectory" at any given temperature includes repeated visits from a number of (physically continuous) trajectories wandering in temperature space. Because the continuous trajectories are correlated in the usual sequential way, their intermittent — that is, non-sequential — visits to the various specific temperatures produce non-sequential correlations when one of those temperatures is considered as a separate ensemble or "trajectory" [14]. Less prominent examples of non-dynamical simulations occur in a broad class of polymer-growth algorithms (e.g., refs. 15-17). 

A case of application of fractional replica 27-3 of a full factorial experiment on studying adhesion of thermoplastic polymer and fiber has been analyzed earlier in Example 2.33. Tensile strength of adhesion has been measured as the system response. The experiment included seven factors, with the nature of fiber being a qualitative-categorical factor. The regression coefficient values and method of steepest ascent are shown Table 2.188. 

This replica-trick method was used in the Refs. [60,61] for the polymer network free energy calculation. For averaging of Z"-value over the ensemble of realizations the probability distribution should be chosen. The authors of Refs. [60,61] have used the condition of the thermodynamical equilibrium for the Gibbs probability distribution corresponding to the conditions of network preparation. To our mind, it is a beautiful idea but it should be considered more deeply because not all the types of networks can be described in such a way - many networks cannot be prepared under any equilibrium conditions. Using some additional tube-like approximations, the authors have obtained rather simple results for network elastic constants and for some other parameters. 

Brittain et al. describe a series of soft lithographic methods that may be suited to the patterning of organic layers [82]. A pattern-transfer element is formed by pouring a liquid polymer, such as poly(dimethylsiloxane), onto a master made from silicon. The polymer is allowed to cure to form an elastomer, which can then be removed from the master. This replica can be used subsequently as a stamp to transfer chemical ink, such as a solution of an alkanethiol, to a surface. Features with dimensions of 40-100 nm can be produced with the technique of near-field, phase-shift photolithography [82]. 

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