Pulsed-laser polymerization (PLP) in conjunction with polymer analysis by size-exclusion chromatography (SEC) is the IUPAC-recommended method for measuring propagation rate coefficients, *k*_{p}, of radical polymerization. Pulse repetition rate, *v*_{rep}, and photoinitiator concentration need to be adjusted to the termination rate of the monomer, preferably via the quantity *β*, the fraction of radicals terminating prior to applying the successive laser pulse. By PREDICI simulation, the prerequisites for successful PLP-SEC work are demonstrated. Slow termination, as with fully ionized monomers, is specifically addressed. Both very high and very low *v*_{rep} are not suitable for accurate *k*_{p} measurements.

**The PLP-SEC method runs into difficulties with radical termination being** too fast or too slow and in case of significant chain transfer and SEC broadening. The suitable selection of pulse repetition rate and photoinitiator concentration is emphasized for slow termination as with ionized monomers.

Five models are discussed giving the equilibrium constant for the catenation of two ring oligomers as a function of their Effective Molarity (EM), the physico-chemical parameter expressing the ease of cyclization of a chain. The first three models (A–C) are derived from the revision of previous theories of catenation, that neglect excluded volume effects. A fourth model (D) is obtained from the results of Monte Carlo simulations by Deguchi and co, that can also account for excluded volume effects. Finally, a fifth model (E) is introduced which has the same functional form of models A, B, D, but is parameterized using the available experimental catenation constant.

**On the basis of theories and simulations, the authors propose five models** giving the equilibrium constant *K _{ij}* for the catenation of two ring oligomers, C

The orientation of a three-layered silicate particle in uncompatibilized and compatibilized polymer melts is studied under shear flows utilizing dissipative particle dynamics (DPD). Based on trajectories, pair distribution functions are calculated in orthogonal planes. Regardless of the applied flow direction, it is shown that the layers rearrange themselves so that their surfaces would be normal to the velocity gradient direction. The maximum shear stress values fall in numerical uncertainties in uncompatibilized systems while they show a characteristic overshoot in compatibilized counterparts. This overshoot is shown to be a result of (i) the large interfaces between the silicate layers and the matrix due to the exfoliation, and (ii) the increased energy dissipation due to friction at the interface.

**The orientation of a three-layered silicate particle in uncompatibilized** and compatibilized polymer melts is studied under shear flows utilizing dissipative particle dynamics. It is shown that the layers rearrange themselves so that their surfaces would be normal to the velocity gradient direction. The orientation process is found to be more stable in compatibilized systems even at low shear-rates.

This study focuses on the estimation and validation of some interaction parameters of the Consistent Valence Force-Field (CVFF), which are required for the calculation of thermodynamic and transport properties of oxaliplatin (a colorectal anticancer drug) in poly(lactic-co-glycolic) acids (PLGAs) matrices. Our methodology to validate the parameters for PLGAs consisted on calculation of glass transition temperature and correlations between structural properties as: fractional free volume, polymer density, and cohesive energy density using Molecular dynamic simulations. For the oxaliplatin, metal-dependent and independent interaction parameters were included into CVFF and validated with an ab-initio method (RHF/LanL2DZ). The results achieved in the present work showed that the CVFF has been wellparameterized.

**Drug delivery systems (DDS) based on poly(lactic- co-glycolic acid) nanoparticles including platinum** complexes as oxaliplatin have been recommended for the enhancement of the efficiency in colorectal cancer treatment. The influence of different factors affecting the delivering rates of oxaliplatin in this type of DDS can be analyzed through Molecular Dynamic Simulations with the adaptation of existent force-fields for organic molecules.

Using self-consistent field (SCF) theory, we studied the self-assembly characteristics of polyurethane pre-polymer dispersions in aqueous solutions. With a molecularly detailed model implementing the Scheutjens–Fleer discretization scheme, it is shown how the stability, equilibrium size, and internal structure of the (swollen) micelles in polyurethane (PU) dispersions depend on the chemical structure and the molecular composition of the charged pre-polymer mixtures. The stability region of these micelles is found to increase when acid groups become deprotonated and when the ionic strength is lowered. Insight into the physical–chemical behavior of PU pre-polymer dispersions is important for the subsequent process of film formation from the PU dispersions for the final coating properties.

**Using self-consistent field (SCF) theory with a molecularly detailed model,** the authors study the self-assembly of polyurethane pre-polymer dispersions in aqueous solutions. Insight into the physical–chemical behavior of PU pre-polymer dispersions is obtained. Details like radial volume fraction distribution of six representative PU pre-polymers and water on a single swollen micelle are shown in this paper.

Technology for designing functional polymers needs to incorporate biomimetic structures for a new functionality. A simulation method, referred to as “molecular-cluster-assembly,” is used to design aggregate structures comprised of oligomers in a bottom-up manner and predict the capability of molecular capture. Acrylic acid oligomer forms an arched and syndiotactic structure with minimum energy. In accordance with the degree of aggregation, arched oligomers form a constricted structure with a unique channel width. The aggregate structures capture ethylene carbonates (ECs) inside the constricted channel and produce attractive energy between the ECs in host-guest complexes. The optimum numbers of ECs stably captured are determined when the binding energy at which the guests are captured at the outside wall of the channel exceeds the attractive energy between the guests in the constricted channel.

**Aggregate structures of acrylic acid oligomers** and the capability of capturing ethylene carbonates (ECs) are analyzed by molecular-cluster-assembly method. A hexamer comprised of arched oligomers captures two ECs in series inside the middle of a constricted channel. Methylene and carbonyl groups of the two ECs form hydrogen bondings and attractive interaction between them.

A dynamic Monte Carlo simulation is performed to investigate the dynamical heterogeneity during cooling toward the glass transition temperature (*T*_{g}). By tracking the evolution of the probability of segment movement (PSM), it is found that the ring polymer exhibits higher *T*_{g} than that of the linear polymer. The distributions of the mean square displacements (MSDs) of segments for the two kinds of polymers indicate the presence of heterogeneous dynamics upon approaching *T*_{g}. Compared with the linear chains, the ring chains exhibit weaker dynamical heterogeneity. The relatively weak dynamical heterogeneity in the ring chains is mainly caused by the mobility difference between the gauche- and trans-conformations. The observation on the local domains of blocked segments (LDBS) demonstrates that end segments with high mobility hinder the growth of LDBS, and thus enhance the dynamical heterogeneity.

**Ring polymer has larger local domains of blocked segments,** and thus narrower distributions of segmental mobility or weaker dynamical heterogeneity. Linear polymer has end segments with high mobility, which hindered the growth of local domains of blocked segments, and therefore wider distributions of segmental mobility, namely, stronger dynamical heterogeneity.

A mathematical model for describing the bulk free-radical polymerization of methyl-methacrylate was developed. This model includes a novel methodology for describing the diffusive step of the kinetic rate coefficients, which is based on geometric considerations and application of the Einstein diffusion Equation. The effect of polymer content and temperature on the *R*_{p} behavior is discussed in terms of the evolution of the interdependent parameters defining the *R*_{p}. The applicability of Smoluchowski equation and the importance of the translational diffusion of short radicals in the rate of termination reaction are questioned in this context. Similitudes and differences between the model results and experimental data are discussed including minima in the *R*_{p} curves at low conversions.

**The proposed model includes a novel methodology** for describing the diffusive step of the kinetic rate coefficients, which is based on geometric considerations and application of the Einstein diffusion equation instead of the Smoluchowski equation whose applicability is questioned in this context. An explanation for the rate of polymerization behavior and the onset of auto-acceleration effect is proposed.

The structure and thermodynamic aspects of symmetric poly(styrene-*block*-acrylicacid)(PS-*b*-PAA) copolymer micelle in salt-free aqueous solution as a function of ionization (*f*) of PAA was probed by molecular dynamics simulations. Quantitative comparison of micelle radius shows that the GROMOS parameter set gives the best agreement with experiment. As *f* increases, Micelle size increases, attains spherical shape, PS surface area increases, and PAA water hydrogen-bonds increases. Pair correlation functions and solvation enthalpy show that PS interactions are insensitive to *f*. Density profiles and solvation enthalpy of PAA–Na^{+}, water–Na^{+} pairs confirm the micelle being in the “osmotic regime” experiments.

**The polystyrene- block-polyacrylic acid (PS-b-PAA) micelle** in aqueous solution shows the linear increase in micelle radius and constant PS core size as a function of ionization of PAA (

Modification of inorganic particles with organic polymer layers leads to well defined hybrid nanoparticles with tunable properties. Studies of such systems rely on the investigation of polymers near to or attached at a surface. In the present investigation, size, shape, and orientation are investigated as functions of the distance of the center of gravity of linear and star-branched polymers from the surface by use of Monte Carlo methods for neutral and attractive surfaces in good and moderate solvents. To quantify the strength of interaction, a parameter “excluded distance” is introduced. It vanishes if repulsive interaction due to the excluded volume effect and attractive ones compensate, which is roughly the case for surface–polymer interactions similar to polymer–polymer interactions in theta solvents.

**The paper deals with the interaction of unconstraint** as well as anchored single chains and stars with energetically neutral and attractive walls representing surfaces of nanoparticles. Although simulations are based on lattice models, lattice independent results of general validity are obtained by extrapolation to infinite chain-length, at least for neutral surfaces. A new method to determine some sort of critical adsorption point is introduced.

Reactivity ratio estimation was carried out in various nonlinear models using Markov Chain Monte Carlo (MCMC) technique and an error-in-variables (EVM) regression model. The implementation steps for three different polymerization case studies are discussed in detail and the results from this work are compared to previously used approximation methods. Approximation techniques that rely on linear regression theory are shown to produce inaccurate joint confidence regions (JCRs). Therefore, in this paper, we explore MCMC techniques that can be used to produce JCRs with correct shape and probability content. In addition, the paper illustrates how an EVM model can be used in tackling any type of regression problem, including multi-response problems.

**Markov Chain Monte Carlo methods are applied in the estimation of reactivity** ratios in various nonlinear models. An error-in-variables approach is used and the analysis shows that application of MCMC and EVM methods produce the most reliable results in nonlinear regression.

Three dimensional self-consistent field theoretic simulations have been performed to determine the equilibrium morphologies formed by linear ABC triblock polymer melts confined between two parallel plates that favor the middle block. Our primary goal is to elucidate the conditions under which the perpendicular lamella is stabilized, since this morphology plays a central role in many nanotechnology applications. Key factors, namely, the chain architecture, surface energy and the mismatch between the film thickness d and the bulk lamella period, L_{0}, determine the final morphologies, e.g., perpendicular and parallel lamella, perforated lamella and wet substrate with parallel cylinders in the core, have been identified. Overall, our findings are fully consistent with the results of limited experimental studies focused on morphology development in thin films of triblock polymer melts. Finally, we have clearly demonstrated that ABC triblocks hold technological advantages over diblocks for nano-lithographic fabrications.

**Morphological transition of symmetric linear ABC triblock terpolymer** melt as a function of surface interaction and film thickness, d. In the presence of strong surface interaction, a wetting layer adjacent to the walls exists and in the center of the film, stable and metastable morphologies including C_{||}, L⊥ and PL are observed.

**Front Cover:** Providing equilibrated starting states for computer simulations of dense, long-chain polymer melts marks a huge challenge. The cover image shows a snapshot of a melt of M = 1000 chains of length N = 2000, highlighting one chain of characteristic shape, generated by an improved feedback methodology, which directly constructs the chains and does not require long-time equilibrations runs. Further details can be found in the article by L. A. Moreira, G. Zhang, F. Mueller, T. Stuehn, and K. Kremer* on page 419.

**Back Cover:** Extended molecular dynamics simulations for G = 4 neutral and protonated PAMAM-EDA in water and its subsequent coarse-graining permit an accurate analysis of conformational properties. The trajectories are used to compute binary interactions between bead-like dendrimers. These interactions are shown to obey the theoretically predicted Gaussian behavior. Further details can be found in the article by J. J. Freire,* A. M. Rubio, and C. McBride on page 432.

Conditions for azeotropic copolymerization derived for irreversible systems are not satisfactory for reversible copolymerizations. The presented theoretical treatment leads to formulation of conditions for a terminal (dyad) model equilibrium copolymerization to form copolymer azeotropes. Numerical simulations of kinetics of copolymer formation confirm validity of the derived relationships between rate and equilibrium constants and comonomer concentrations.

**Reversible copolymerization can behave azeotropically** only when certain relationships, given in the paper, between the equilibrium and rate constants of homo- and cross-propagations are held. The main conditions for azeotropicity of the reversible copolymerization ensure that the compositions and microstructures of initially formed copolymer and of that at the system equilibrium are identical.

Topological constraints due to chain connectivity and uncrossability greatly impact the long time dynamics and rheology of high molecular weight polymer melts. Computer simulations to study properties of such melts are very advantageous, since perfect control of molecular conformation and melt morphology is available. We present a methodology to prepare well-equilibrated polymer melts which only requires local relaxation. The approach efficiently leads to equilibrated ensembles of bead-spring polymer melts of 1 000 chains of up to 2 000 beads, which correspond to 24 (fully flexible) and 45 entanglement lengths (semi-flexible chains). Entanglements are identified by a primitive path analysis and a master curve of the entanglement lengths for different chain and persistence lengths is presented.

**Excluded volume and topological constraints (entanglements)** lead to difficulties for polymer melt equilibration in computer simulations. To avoid long equilibration runs, an improved feedback loop methodology is introduced, which only needs relaxation on short length scales. The analysis shows that a homogeneous density and perfect internal distances along the chain backbone can be reached for melts of chains of up to about 45 entanglement lengths.

Extensive fully-atomistic molecular dynamics simulations have been performed for the *G* = 4 generation of the dendrimer PAMAM-EDA in water, with fully protonated and non-protonated amine groups. Some parameters from these results have been incorporated into a coarse-grained model suitable for Monte Carlo simulations. Satisfactory agreement is found between the dendrimer density profiles obtained from the Monte Carlo and the molecular dynamics simulations, both for the protonated and neutral molecules. The Monte Carlo and molecular dynamics trajectories have also been employed to calculate binary interactions between pairs of dendrimers. The interactions between *G* = 4 PAMAM-EDA dendrimers can be satisfactorily described by a theoretically proposed Gaussian potential.

**Extended molecular dynamics simulations for protonated and neutral** *G* = 4 PAMAM-EDA in water permit an accurate analysis of conformational properties. The trajectories are used to compute binary interactions between dendrimer molecules. These interactions are shown to obey the theoretically predicted Gaussian behavior.

The penultimate model of copolymerization taking into account the dependence of the reactivity of a macroradical on the type of the unit preceding the ultimate one is well-known in polymer chemistry. All types of chemical structure of multiblock copolymers capable to form during copolymerization processes described by such a model are revealed in the present work. Phase diagrams of copolymers of all these types specifying the regions of thermodynamic stability of spatially periodic mesophases differing in morphology are constructed in the framework of the weak segregation theory. Besides, the periods and amplitudes of the variation of different type densities of units in mesophases as well as volume fractions of these latter within the regions of their coexistence are calculated.

**Finding of the dependence of the phase behavior of heteropolymer liquids on the chemical structure of their macromolecules is of utmost importance**. Theoretical consideration of such a behavior of multiblock copolymers whose architectures are describable by the extended Markov chain has been undertaken in this paper. Our analysis reveals the possibility of the existence in their melts of phase diagrams of nontraditional appearance.

In this paper, we employ a molecular theory to study HCl gas-adsorption/desorption properties of PNIPAM brushes. Here, PNIPAM–HCl hydrogen bonds and theirs explicit coupling to the PNIPAM conformations are considered. We find that hydrogen bonding becomes a key element in determining HCl gas-adsorption/desorption behaviors of PNIPAM brushes. Our results indicate that, when at moderate grafting densities, the association of PNIPAM–HCl hydrogen bonds can result in a dependence of PNIPAM brush-height on HCl concentration, and the morphology of PNIPAM brushes may have a significant effect on the HCl gas-adsorption/desorption properties.

**HCl gas adsorption capacity of poly( N-isopropylacrylamide) (PNIPAM)** brushes is described by PNIPAM–HCl hydrogen bonds. Hydrogen bonding becomes a key element in determining HCl adsorption/desorption behaviors of PNIPAM brushes. The morphology of PNIPAM brushes may have a significant effect on the HCl adsorption/desorption properties.

Hierarchical lamellae self-assembled from linear multiblock copolymers in thin films are investigated by self-consistent field theory. The thin films are confined between two parallel substrates. The confinement strategy allows generating hierarchical microstructures with various numbers and different orientations of small-length-scale lamellae. Effects of film thickness and surface affinity on the structures are studied. It is found that not only the period of the large- and small-length-scale lamellae but also the orientation of small-length-scale lamellae relative to large-length-scale lamellae can be tuned by varying the film thickness. Moreover, the structures of the hierarchical lamellae can be tailored by changing the surface affinity. Through analyzing free energies of various lamellae, phase diagrams are mapped out. The present work could provide guidance for fabricating hierarchical microstructures in a controllable way.

**In thin films of linear multiblock copolymers**, not only the period of large- and small-length-scale lamellae but also the orientation of small-length-scale lamellae can be tuned by varying film thickness. Moreover, a reentrant phase transition of perpendicular lamellae-in-lamellae with increasing the film thickness is revealed.

A dynamic Monte Carlo method was employed to study regular as well as irregular dendrimers with up to *G* = 8 generations with functionality *F* = 3 under athermal conditions. The size of dendrimers showed the same scaling law with respect to chain-length *n* as linear chains, keeping *G* at a constant value. If *n* was varied via *G* at fixed spacer-length *m* its scaling behavior was similar to that of collapsed globules, at least for large values of *G*. Asphericity strongly decreased with an increase of *G*. The composition of irregular dendrimers remained unchanged with respect to *F* and *G* but the spacer-lengths were distributed according to several models. Quite generally, distributions became broader, size larger and shape less symmetric compared to the regular case. These effects increased with an increase of dispersity of the branches.

**Regular and irregular dendritic polymers, the latter realized for several types of branch-length distributions**, are simulated and their properties are compared. In addition, for the regular case emphasis is given to parameters in the limit of infinite branch length (spacer length) in order to obtain model independent results.

The equilibrium partition coefficients () are calculated for self-avoiding, semiflexible chains with the same finite contour length () and a variety of persistence length () values, partitioning between a macroscopic dilute solution phase and confined solution phases in cylindrical voids in the steric exclusion limit. It is found that, for the range of -values most relevant to polymer separation in size exclusion chromatograph (), the geometric mean of the radius of gyration () and the mean span () performs better than or alone in collapsing the partition curves of the various linear semiflexible chains onto a single curve. The dependence of the confinement free energy () on the persistence length is also examined. For those chains having the same , the pore diameter is found to be the necessary and sufficient condition for to decrease with the increase of .

**Two questions are answered:** (i) which size parameter correlates best with the equilibrium partition coefficients of linear semiflexible chains in the range relevant to polymer separation in GPC? (ii) For two chains with the same contour length but different persistence length in equilibrium with a cylindrical pore, which chain spends less free energy to get in.

This work reconsiders a refined Flory model designed to approximately describe molar-mass distributions obtained from irreversible step-growth polymerizations of *α*,*ω*-heterodifunctional molecules with competing cyclization. By comparing to both quantitative analytical and accurate numerical solutions, we show that the refined Flory model is a reasonable approximation that allows for an intuitive understanding of the chemical system discussed. Building upon this insight, we present a recursive transformation of the refined Flory model by probabilistic means resulting in Szymanski's quantitative description of molar-mass distributions.

**A refined Flory model for describing approximate molar-mass distributions** obtained from irreversible step-growth polymerizations is reconsidered. It is shown that this model is a good approximation if either step growth or cyclization is predominant. Based on this insight, a probabilistic transformation of the refined model to a quantitative description is presented.

An important high-temperature polyimide, namely HFPE-30, has been coarse grained to three different levels of detail. It has been shown that while it is possible to successfully calibrate bonded and non-bonded forcefields and attain realistic densities with all levels of coarse graining, reproducing chain structures and dynamic properties requires an adequate level of atomistic detail to be retained. A model that coarse grains the HFPE-30 molecule into eight beads, approximates both chain structure and dynamic properties well. Alternately, the unrealistically fast dynamics in coarse-grained models can be slowed down by increasing the thermal coupling constant by a scaling factor that is estimated by comparing mean square displacements in detailed atomistic and coarse-grained simulations. In general, stress-strain responses of coarse-grained systems do not match those of the detailed atomic systems except when the coarse graining involves eight beads. In cases where lesser number of beads are used, slowing the dynamics down by the estimated scaling factor takes the stress-strain response of the coarse-grained system close to that of the detailed atomistic one.

**The figure shows three mapping schemes of molecular fragments in the backbone of the commercial polyimide HFPE-30**. A coarse-grained representation with large number of beads is necessary to predict static and configurational properties. However, with smaller number of beads and an appropriate amount of friction on the beads, we are able to predict glass transition temperature and stress–strain response.

Polymers can be used in diverse applications in daily life because of their various microstructures. Molecular weight distribution and chemical composition distribution are the two most important microstructural indices for many copolymers. Monte Carlo simulation is an efficient method to obtain those specific distributions that cannot be easily determined via traditional equation-based methods. However, this method requires long computation time. In this project, a parallel method is proposed for Monte Carlo simulation on a graphics processing unit platform. Both steady state and dynamic state cases are presented to show the accuracy and efficiency of the proposed method. The computation time of the proposed method is greatly decreased by at least 30-fold compared with the time required by CPU platform.

**Monte Carlo method is suitable to simulate the microstructural distributions**, but it normally requires a long time for the computation. By decomposing the conventional Monte Carlo simulation of all chains into millions of threads, the calculation is parallelized on a GPU platform and more than 30-fold speedup ratio is obtained.