230 S.McGrother,G.Goldbeck-Wood,and Y.M.Lam The effect of temperature on self-assembled structures of amphiphilic block copolymers in aqueous solution has been recently studied with Meso- Dyn [11.17].While,according to Flory-Huggins theory,the interaction pa- rameter has a simple inverse dependence on temperature(x~1/T),it is well known that corrections need to be applied for most polymer blends and solu- tions.A more appropriate relationship for polymer solutions is the following 6 x=a+T (11.4) In simple term,a represents a non-combinatorial entropic contribution,and B represents the enthalpic contribution.This expression was fitted to exper- imental data of interaction parameters between poly (ethylene oxide)and water,as well as poly (propylene oxide)and water,respectively.Typically, these data are determined experimentally by vapour pressure measurements. The resulting x(T)could then be used in MesoDyn simulations of Pluronic P85 (triblock copolymer of ethylene oxide,propylene oxide,ethylene oxide, with certain chain lengths)in water for a range of temperatures. The experimental phase diagram [11.18 shows the striking range of phases exhibited by such a relatively simple system.In particular,it shows that at polymer concentrations above about 20%,a micellar phase is observed at low temperatures,and rods or cylinders are formed above about 60C. MesoDyn simulations were performed at these temperatures,and the re- sulting morphologies are show in Fig.11.3(a)and 11.3(b).They are extremely encouraging,with definite evidence of the correct phase evolving at the cor- rect temperature and composition. 11.4 Multiscale Modeling 11.4.1 From the Molecular to the Mesoscale In order to integrate the molecular level and the mesoscale,the atomistic simulation results can be used to parameterise mesoscale simulation by pro- viding sensible coarse-graining methods and effective interactions between species[11.17,11.19]. One such example is the work by Vergelati and Spyriouni [11.19].Their aim was to investigate the compatibility of a polyamide with a poly (vinyl acetate),where the acetate was systematically hydrolyzed towards the poly vinyl alcohol.The authors started on the atomistic level,using Discover Molecular Dynamics with the COMPASS force-field to determine cohesive energy densities of the various mixtures.The Flory-Huggins interaction pa- rameters of the blends could then be calculated and used as input to Meso- Dyn simulations.The bead size parameters for MesoDyn were determined from the molecular weight and characteristic ratios of the polymers.Encour- agingly,the length scale and morphology of the phase separation observed230 S. McGrother, G. Goldbeck-Wood, and Y.M. Lam The effect of temperature on self-assembled structures of amphiphilic block copolymers in aqueous solution has been recently studied with Meso￾Dyn [11.17]. While, according to Flory-Huggins theory, the interaction pa￾rameter has a simple inverse dependence on temperature (χ ∼ 1/T), it is well known that corrections need to be applied for most polymer blends and solu￾tions. A more appropriate relationship for polymer solutions is the following χ = α + β T (11.4) In simple term, α represents a non-combinatorial entropic contribution, and β represents the enthalpic contribution. This expression was fitted to exper￾imental data of interaction parameters between poly (ethylene oxide) and water, as well as poly (propylene oxide) and water, respectively. Typically, these data are determined experimentally by vapour pressure measurements. The resulting χ(T) could then be used in MesoDyn simulations of Pluronic P85 (triblock copolymer of ethylene oxide, propylene oxide, ethylene oxide, with certain chain lengths) in water for a range of temperatures. The experimental phase diagram [11.18] shows the striking range of phases exhibited by such a relatively simple system. In particular, it shows that at polymer concentrations above about 20%, a micellar phase is observed at low temperatures, and rods or cylinders are formed above about 60◦C. MesoDyn simulations were performed at these temperatures, and the re￾sulting morphologies are show in Fig. 11.3(a) and 11.3(b). They are extremely encouraging, with definite evidence of the correct phase evolving at the cor￾rect temperature and composition. 11.4 Multiscale Modeling 11.4.1 From the Molecular to the Mesoscale In order to integrate the molecular level and the mesoscale, the atomistic simulation results can be used to parameterise mesoscale simulation by pro￾viding sensible coarse-graining methods and effective interactions between species [11.17, 11.19]. One such example is the work by Vergelati and Spyriouni [11.19]. Their aim was to investigate the compatibility of a polyamide with a poly (vinyl acetate), where the acetate was systematically hydrolyzed towards the poly vinyl alcohol. The authors started on the atomistic level, using Discover Molecular Dynamics with the COMPASS force-field to determine cohesive energy densities of the various mixtures. The Flory-Huggins interaction pa￾rameters of the blends could then be calculated and used as input to Meso￾Dyn simulations. The bead size parameters for MesoDyn were determined from the molecular weight and characteristic ratios of the polymers. Encour￾agingly, the length scale and morphology of the phase separation observed