Hyperbranched polymers formed through step polymerization of AB_{2}-type monomer with equal reactivity for both B groups in a continuous flow stirred-tank reactor (CSTR) are investigated theoretically. The weight fraction distribution at high molecular weight tail follows a power law, *W*(*P*) ∝ *P*
^{−1/ξ} for ξ ≤ 0.5 with , where is the mean residence time. The degree of branching (DB) at the large degree of polymerization (*P*) limit is DB_{
P∞} = 0.6 irrespective of the ξ-value, which is larger than the case for the corresponding batch polymerization that gives DB_{
P∞} = 0.5. The relationship between the radius of gyration 〈*s*
^{2}〉_{0} and *P* shows that the hyperbranched polymers formed in a CSTR are very compact, and the 〈*s*
^{2}〉_{0}-values for large polymers are even smaller than the smallest possible case for a batch reactor with DB_{
P∞} = 1. For large polymers, the power law 〈*s*
^{2}〉_{0}∝*P*
^{ 1/3} holds, which is 〈*s*
^{2}〉_{0}∝*P*
^{ 1/2} for batch polymerization.

**Irreversible step polymerization of AB _{2} monomer in a continuous flow stirred-tank reactor** leads to produce hyperbranched polymers with larger degree of branching (DB) for large polymers, compared with batch polymerization. The 3D structure of large polymer is much more compact than the polymers synthesized in batch polymerization, even more compact than those with DB = 1 produced in batch polymerization.

The effect of graphene (G) and graphene oxide (GO), used as the nanofiller in polymer nanocomposites (NC), on the structural and dynamic properties of polymer chains, has been studied by means of molecular dynamics (MD) simulations. Two polymers, i.e., poly(propylene) and poly(vinyl alcohol), are employed as matrices to cover a wider range of polymer–filler interactions. The local structural properties, e.g., density profile, average *R*_{g}, and end-to-end distance as well as dynamic properties, e.g., estimated translational and orientational relaxation times, of polymer chains are studied. In addition, the interaction energies are estimated between polymers and nanofillers for different hybrid systems using MD pullout simulations. Strong heterogeneities in polymer structural and dynamic properties have been observed such that chains are more oriented and exhibit slower dynamics in the vicinity of the nanofillers (G and GO) as compared to bulk. It is also found that the orientation of polymer chains at the interface is more influenced by the nanofiller in such a way that the more oriented polymer chains are observed in G-based NC for both polymers. However, the immobilization of polymer chains at the interface proves to be very much dependent on the polymer–filler interactions.

**The effect of graphene and graphene oxide on the structural** and dynamic properties of poly(propylene) and poly(vinyl alcohol), are studied by means of molecular dynamics simulations. Strong heterogeneities in polymer properties are found such that chains are more oriented and exhibit slower dynamics close to nano-fillers. Energetic analysis proves different roots for heterogeneity in structural and dynamic properties.

A statistical–mechanical theory of thermoreversible gelation which is formed by monodisperse telechelic associating polymers with junction multiplicity of three is developed. In the present theory, the effect of loop formation is considered. Using the theory, the properties of the system are obtained, such as the state of association of polymers, the sol–gel transition line, and the number concentration of elastically effective chains. In addition, a Monte Carlo simulation of a bead-spring model of monodisperse telechelic associating polymers is performed. The simulation results are in good agreement with the present theoretical results. Furthermore, the shear modulus is calculated by an application of phantom network theory and compared with the experimental data. The theoretical results agree well with the experimental results. It is shown that the loop formation occurs especially in dilute regime and causes the decrease of the modulus in the regime.

**A statistical–mechanical theory of thermoreversible gelation** which is formed by monodisperse telechelic associating polymers with junction multiplicity of three is developed. In the present theory, the effect of loop formation is considered. Using a Monte Carlo simulation, the theoretical results are confirmed. Furthermore, the theoretical results agree well with the experimentally obtained shear modulus.

The mechanism of the lower critical solution temperature (LCST) in thermoresponsive polymer solutions has been studied by means of a coarse-grained single polymer chain simulation and a theoretical approach. The simulation model includes solvent explicitly and thus accounts for solvent interactions and entropy directly. The theoretical model consists of a single chain polymer in an implicit solvent where the effect of solvent is included through the intrapolymer solvophobic potential proposed by Kolomeisky and Widom. The results of this study indicate that the LCST behavior is determined by the competition between the mean energy difference between the bulk and bound solvent, and the entropy loss due to the bound solvent. At low temperatures, solvent molecules are bound to the polymer and the solvophobicity of the polymer is screened, resulting in a coiled state. At high temperatures the entropy loss due to bound solvent offsets the energy gain due to binding which causes the solvent molecules to unbind, leading to the collapse of the polymer chain to a globular state. Furthermore, the coarse-grained nature of these models indicates that mean interaction energies are sufficient to explain LCST in comparison to specific solvent structural arrangements.

**The mechanism of lower critical solution temperature (LCST)** in thermoresponsive polymers is a major issue in polymer physics. Using coarse-grained simulation and theory, in which we use spherically symmetric solvent and monomeric beads, we show that the LCST can arise purely as a result of the interplay between mean energetics of bound and bulk solvent, and the entropy of solvent. The results of this study show that a thermodynamic description of the solvent is sufficient to exhibit LCST and a description of the solvent structure is not required. The model can also be utilized to study the effect of cosolvents and additives on the LCST.

This paper proposes a new and systematic approach for optimum design of thermosetting resin systems based on molecular-dynamics simulations. Specifically, the results of simulations for chemical reaction (cross-linking) and mechanical properties of epoxy resin are clustered with a self-organizing map (SOM) that enables to comprehensibly visualize the characteristics of complex structured polymers. Moreover, the scatter-plot matrix (SPM) is introduced to analyze the specific data. Thus, SOM is used to find common features in a molecular structure, and SPM helps to clarify molecular-scale mechanism in the clusterization. Through the analysis, the authors find that base resins with multireactive functional groups contribute to superior mechanical properties, and these properties stem from the hydrogen-bond network distributed throughout the system. The approach, which is thought to be one of chemical informatics, has broad ranges of applications that are not limited to epoxy resin but can be applied to any kind of thermosetting resins.

**Multidisciplinary optimization of cross-linked polymer systems** is studied by integrating molecular dynamics simulation and self-organizing map. This integration achieves high efficiency in measuring material characteristics and clarifies the molecular scale mechanism governing those characteristics. Base resins with multifunctional group are expected to be candidate for transport due to their superior mechanical properties.

**Front Cover**: General analytic formulas for the number- and weightaverage molecular weights of the core cross-linked star polymers are proposed. The method to extract important structural information from the experimentally measurable quantities is discussed. The full MWD profiles could be estimated by using the Monte Carlo simulation method. This is reported by Hidetaka Tobita in article number 1600037.

The importance of the development of kinetic modeling tools to mechanistically understand and design bulk and solution reversible addition fragmentation chain transfer (RAFT) polymerization is highlighted. Both deterministic and stochastic kinetic modeling methods are covered, considering a detailed reaction scheme and accounting for the impact of diffusional limitations on the reaction rates. A novel strategy is introduced to fundamentally calculate the diffusional contributions for the apparent RAFT addition and fragmentation rate coefficients. Next to literature examples, case studies are included to demonstrate that detailed theoretical studies are indispensable to completely map the effect of the polymerization conditions and RAFT agent reactivity on the control over microstructural properties and the overall polymerization time. Guidelines for future kinetic modeling activities are formulated to enhance joined theoretical and experimental research.

**Detailed kinetic modeling to map the impact of the reversible addition fragmentation chain transfer (RAFT) agent** and reaction conditions on the RAFT polymerization rate and microstructural control is applied. The interplay between chemical and diffusional phenomena needs to be accurately accounted for to equip the experimentalist with a powerful tool to minimize time consuming experimental screening.

The effects of blockiness and compositional/sequential polydispersity on the order–disorder transition of random block copolymers are studied using a segment model of random block copolymers. Specifically, the copolymers are randomly assembled from a collection of equal-length “segments,” while the characteristics of the segments are chosen according to the nature of the polydispersity. The phase behavior of the model system is examined using the random phase approximation. The critical points of the system are calculated over a range of blockiness and polydispersity for a variety of segment models. It is observed that the critical value of the Flory–Huggins parameter χ, above which the homogeneous phase becomes unstable, is inversely proportional to the blockiness. Furthermore, it is found that sequential and compositional dispersity decreases the critical value of χ, but that the effect of sequential dispersity is much weaker. At sufficiently large compositional dispersity, the random block copolymers can undergo macrophase separation. In this region of phase space, the critical point is entirely determined by the compositional polydispersity.

**A generic model of random block copolymers is developed**, in which each chain is modeled as a series of segments, the sequences of which are drawn from a distribution. The model is used to study the effects of blockiness and compositional dispersity on the phase behavior.

Long chain branches improve the viscoelastic properties of polyolefins and make them easier to process. The frequency of long chain branching in polyethylenes made with coordination catalysts can be substantially increased by copolymerizing ethylene with small amounts of nonconjugated dienes using an adequate catalyst. In this work, the kinetics of copolymerization of ethylene and 1,9-decadiene is investigated using a constrained geometry catalyst in a solution polymerization semi-batch reactor, and a novel mathematical model is proposed to describe the resulting molecular weight distributions. A hybrid approach, combining particle swarm optimization, parameter identifiability procedures, and the Gauss–Newton method is applied to estimate the model parameters. The proposed mechanism includes macromonomer reincorporation through pendant double bonds that result from diene incorporation. The predicted long chain branching frequencies are validated by Monte Carlo simulation. Experimental average molecular weights and ethylene feed flow rates are successfully predicted by both methods.

**This article studies the solution copolymerization of ethylene and 1,9-decadiene** with a constrained geometry catalyst using a mathematical model that includes macromonomer reincorporation by pendant double bonds. Experimental data and Monte Carlo simulation validate long-chain branches frequencies and build the polymer distributions of molecular weight.

Semiflexible polymers under good solvent conditions confined by two planar parallel repulsive walls are investigated for a wide range of monomer concentrations and distances between the walls, for a case where persistence length and contour length of the macromolecules are almost equal. Chain conformations and local nematic ordering near the walls are studied by both molecular dynamics methods and density functional theory, putting it in perspective with the recent work where the isotropic phase of semiflexible polymer solutions in the vicinity of a single repulsive wall in semi-infinite geometry is considered. Profiles of the total density of monomers as well as densities of end- and middle-monomers and also the local orientational order parameter across the slit are computed. For small distances between the walls, the increase of monomer density causes a gradual onset of nematic order without a sharp transition while for large distances between the walls a first-order “capillary nematization” transition is found at a monomer concentration somewhat smaller than needed for the onset of nematic order in the bulk. A brief comparison with related treatments for other models is made.

**Repulsive walls cause an ordering** of semiflexible macromolecules parallel to the walls and can thus enhance liquid crystalline order in solutions of stiff polymers. The resulting “capillary nematization” is explored by both molecular dynamics and density functional theory.

The analytic formulas for the number- and weight-average molecular weights (MWs) of the core cross-linked star polymers (CCSPs) are proposed. In the arm-first method, the number- and weight-average MWs of the arms ( and ) and CCSPs ( and ) can be determined experimentally. From , , and weight fraction of the arms *w*_{A} (or the core, *w*_{C} = 1−*w*_{A}), the number-average number of the arms () and the number-average core MW () can be determined. Because of the correlation between the core MW and the number of the arms, the general solution of for CCSPs presented requires attention to the nature of correlation. When the average and variance of the arm-number distribution are linear function of core MW, the weight-average number of the arms () and the weight-average core MW () can be determined. The approximate estimation method for is also discussed.

**General analytic formulas for the number- and weight-average molecular weights** of the core cross-linked star polymers, applicable to any type of arm and core polymer distributions, are proposed. The method to extract important structural information from the experimentally measurable quantities is discussed for the arm-first method. The full molecular weight distribution profile can be estimated by using the Monte Carlo simulation method.

Kinetic simulations of polymer chain propagation in an aqueous medium in an initial stage of emulsifier-free, emulsion organotellurium-mediated living radical polymerization (emulsion TERP) of styrene with sodium poly(methacrylic acid)-methyltellanyl (PMAA-TeMe) as a control agent and 4,4′-azobis(4-cyanovaleric acid) as a water-soluble azo-initiator at various polymerization temperatures, which is carried out experimentally at pH > 9 in a previous article, is performed using PREDICI software from CiTGmbH. The approach based on *α*-chain end-separated kinetic simulation leads us to get important aspects of individual polymer chain growths from both *α*-end groups, i.e., initiator and PMAA end groups. The larger number percentage of polystyrene (PS) chain having PMAA end group relative to all PS chains is generated at lower polymerization temperature. In addition, the PS chain growth is also pronounced at lower temperature. In other words, the self-assembly nucleation, in which the control agents are contained, predominantly occurs at the lower polymerization temperature than the homogeneous nucleation, in which they are not contained. This indicates that the emulsion TERP effectively proceeds at lower temperature, which is well accorded with the experimental result in the previous article.

**Kinetic simulations of polymer chain propagation in an aqueous medium in an initial stage** of emulsifier-free, emulsion organotellurium-mediated living radical polymerization of styrene with sodium poly(methacrylic acid)-methyltellanyl as a control agent and 4,4′-azobis(4-cyanovaleric acid) as a water-soluble azo-initiator at various polymerization temperatures, which is carried out experimentally at pH > 9 in a previous article, is performed using PREDICI software.

A mathematical model is developed for the arborescent polyisobutylene system in a batch reactor, using multidimensional method of moments, to predict the concentrations of monomer and inimer as well as number and weight average molecular weight. This model is significantly efficient in computation, making parameter estimation practical. Simulation results agree with results obtained by Monte Carlo simulations. Parameter estimation results show that using the weight average molecular weight data provide better overall fit than leaving them out in the previous model.

**Multidimensional method of moments** is used to track molecular weight development and end groups in an arborescent polyisobutylene system. Simulation results agree with Monte Carlo simulations. The method enables parameter estimation using extra data to obtain improved model fit to data.

The accuracy of a model prediction relies heavily on the quality of the parameters used. Some of the available methods to estimate the activation and deactivation rate constants in atom transfer radical polymerization (ATRP) are done in the absence of monomer, hence they may not be representative of the polymerization conditions. Others offer great accuracy but requires data that are not commonly measured in experiments. In this study, a simple method is proposed to estimate activation and deactivation rate constants through correlating the recently reported theoretical equations with experimental data of monomer conversion and polymer molecular weight dispersity. The kinetics and dispersity equations used are straightforward and explicit, thus can be easily calculated. Only two parameters (activation and deactivation rate constant) are involved in the correlation of two data sets without any other adjustable parameters. In addition, the experimental data required are some of the most often measured quantities in polymerization, thus no additional experiments or measurements are required. Since the conversion and dispersity are obtained from actual polymerization, the reaction rate constants estimated are representative of the real reaction conditions. The applicability of this method is demonstrated by estimating parameters using reported experimental data of ATRP of methyl methacrylate conducted at various conditions.

**A straightforward approach to estimate the activation and deactivation rate constants for ATRP** is proposed by utilizing some of the most commonly measured data in polymerization studies, namely kinetics and dispersity data. These widely available data are used in correlation with two explicit equations to estimate the two reaction rate parameters. Several published experiment data are used to demonstrate the simple estimation approach.

For the first time a new analytical procedure to analyze small oligomers produced in a butyl acrylate-methyl methacrylate emulsion copolymerization is applied. With this method, low molecular weight co-oligomers are studied using MALDI-ToF-MS. Both the oligomers in the aqueous phase and the oligomers in the particle phase can be seen. Varying the initiator system, it is observed that the initiation step has an influence on the composition of these oligomers and hence on the absorption on to latex particles. Chain length dependent average compositions in the aqueous phase are observed. The chain length dependent oligomer composition can be described in terms of kinetic effects and preferential/selective adsorption of co-oligomers on the particle surface. The kinetic effects and the extent of adsorption on the particle phase are both dependent on the various end groups. The preferential/selective adsorption of co-oligomers on the particle phase is explained on the basis of solubility and interactions with the surface. The chain length dependent absolute oligomer amount decreases exponentially with chain length as confirmed by Monte Carlo simulations.

This information is important to further understand the events of the aqueous phase of an emulsion copolymerization as well as the entry of radicals into the particles.

**Experimental determination of co-oligomer composition** in the aqueous phase of an emulsion copolymerization as determined with MALDI-ToF MS. The diagram shows an experimentally determined chemical composition distribution with superimposed model description on how the selective adsorption of co-oligomers relates to solubility and surface activity.

Results are presented for the density, free volume, self-diffusion, structure, and conformation of short linear and cyclic *n*-alkanes in their own melt and in blends at equal carbon number from detailed atomistic molecular dynamics (MD) simulations in the isothermal-isobaric (NPT) statistical ensemble using the explicit-atom optimized potentials for liquid simulations (OPLS-AA) force-field. In agreement with experimental data reported in an earlier study by von Meerwall et al. (2003), cyclic alkanes are characterized by higher densities and diffuse more slowly than their equivalent linear alkanes. Their configurations are also dominated by certain conformers whose exact shape depends on the molecular length *n* of the cyclic alkane. The smaller the value of *n* the more symmetric the shape of these conformers. The MD results support the findings of von Meerwall et al. (2003) that the overall (single average) diffusion coefficient of linear and cyclic alkanes in their blend is equal to the weight-average of the diffusion coefficients of the neat species at the same temperature. Simulation results are also presented for the average size, individual diffusivities, and intermolecular CC pair distribution function of the two components (linear and cyclic) as a function of molecular weight and blend concentration in cyclic molecules.

**All-atom molecular dynamics simulations of linear and cyclic n-alkanes in melt** and blends at equal carbon number demonstrate that cyclic alkane conformations are populated by highly rigid and geometrically symmetric structures which strongly influence their density, local packing, and self-diffusive behavior.

The presence of nanoparticles in a diblock copolymer leads to changes in the morphology and properties of the matrix and can produce highly organized hybrid materials. The resulting material properties depend not only on the polymer composition but also on the size, shape, and surface properties of the colloids. The dynamics of this kind of systems using a hybrid mesoscopic approach has been studied in this work. A continuum description for the polymer is used, while colloids are individually resolved. The method allows for a variable preference of the colloids, which can have different sizes, to the different components the block copolymer is made of. The impact that the nanoparticle preference for either, both, or none of the blocks has on the collective properties of nanoparticle–block copolymer composites can be analyzed. Several experimental results are reproduced covering colloid-induced phase transition, particles' placement within the matrix, and the role of incompatibilities between colloids and monomers.

**Cell Dynamic Simulation combined with Brownian Motion** are used to describe a mixture of block copolymer and nanoparticles, respectively. The changes in the morphology of the matrix are studied when including colloids, as well as its assembly depending on their size and affinity with one of the blocks. Several experiments are reproduced.

Recent years have seen a surge of interest in nanopores because such structures show a strong potential for characterizing macromolecules, e.g., DNA. Here, the authors theoretically investigate the translocation of a spherical nanoparticle through a conical nanocapillary, by numerically solving the coupled system of electrokinetic continuum equations. Based on their findings, the authors formulate simple guidelines for obtaining the maximum current signal during the translocation event, which should be transferable to other nanopore geometries. In addition, the dependence of the signal strength on particle properties, such as surface charge and size, is evaluated. Finally, the authors identify conditions under which the translocation is prevented by the formation of a strong electroosmotic barrier and show that the particle may even become trapped at the pore orifice, without imposing an external hydrostatic pressure difference.

**Nanoparticle translocation through conical nanocapillaries** using a simulation model based on the electrokinetic equations are theoretically investigated. The authors identify parameters for the maximum current modulation during translocation, investigate the dependence of the signal strength on the particle charge and size, and identify conditions preventing translocation or even trapping particles.

Two single-site-type metallocene catalysts can be combined to produce polymers with well-controlled and broad molecular weight distributions (MWD). As polyolefins with unimodal and bimodal MWDs have different mechanical and rheological properties, a criterion to determine whether a system of two single-site-type catalysts produces polymers with unimodal or bimodal distributions is useful for product development and property optimization. In this work, a generalized MWD bimodality criterion is developed and represented as a comprehensive 3D map. The proposed criterion is validated with both simulated and previously reported experimental data. The effect of number average chain length and mass fraction on MWD bimodality criteria are also examined. The results show that unimodal MWDs are more likely to be observed when the mass fraction of one of the copolymers is much higher than the other and when both copolymers have similar average chain lengths.

**A generalized molecular weight distribution (MWD) bimodality criterion to determine** whether a system of two single-site-type catalysts produces polymers with unimodal or bimodal distributions is developed and represented as a comprehensive 3D map. The effect of number average chain length and mass fraction on MWD bimodality criteria are examined.