Compatibilization of poly(vinyl chloride) and polyolefin elastomer blends with multiblock/blocky chlorinated polyethylenes

Super-tough PVC/CPE composites: an efficient CPE network by an MGA copolymer prepared through a vibro-milling process

Vibro-milling, a solid-phase mechanochemistry method, was used to prepare an amphiphilic composite particle, which is referred to as MGA. The Molau test, Fourier-transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC) results indicated that the core-shell structure of the acrylic impact modifier, acrylate core-shell rubber (ACR), was destroyed after vibro-milling. The ACR core was exposed and reacted with polyvinyl chloride (PVC) chains. Using 1.75 parts per hundred rubber (phr) MGA instead of 1.25 phr MC and 0.5 phr ACR, a significant enhancement effect was achieved. The notched impact strength of the PVC composites increased from 4.24 kJ m^-2 for neat PVC and 23.79 kJ m^-2 for C7A0.5MC1.25 to 65.5 kJ m^-2 for C7M1.75. Additionally, the tensile strength and elongation at break of the PVC composites were enhanced. Studies using a variety of characterization techniques show that the addition of MGA can promote the formation of an intermingled and riveted structure, and thus increase interfacial interactions and the effects of stress transfer, releasing the planar strain. The introduction of MGA can also induce the chlorinated polyethylene (CPE) phase to form a network structure at a lower CPE content, which contributes to networking and crazing and is the main toughening mechanism.

Surface-Initiated Controlled Radical Polymerization: State-of-the-Art, Opportunities, and Challenges in Surface and Interface Engineering with Polymer Brushes

The generation of polymer brushes by surface-initiated controlled radical polymerization (SI-CRP) techniques has become a powerful approach to tailor the chemical and physical properties of interfaces and has given rise to great advances in surface and interface engineering. Polymer brushes are defined as thin polymer films in which the individual polymer chains are tethered by one chain end to a solid interface. Significant advances have been made over the past years in the field of polymer brushes. This includes novel developments in SI-CRP, as well as the emergence of novel applications such as catalysis, electronics, nanomaterial synthesis and biosensing. Additionally, polymer brushes prepared via SI-CRP have been utilized to modify the surface of novel substrates such as natural fibers, polymer nanofibers, mesoporous materials, graphene, viruses and protein nanoparticles. The last years have also seen exciting advances in the chemical and physical characterization of polymer brushes, as well as an ever increasing set of computational and simulation tools that allow understanding and predictions of these surface-grafted polymer architectures. The aim of this contribution is to provide a comprehensive review that critically assesses recent advances in the field and highlights the opportunities and challenges for future work.

Polymer loop formation on a functionalized hard surface: quantitative insight by comparison of experimental and Monte Carlo simulation results

Polystyrene terminated with carboxylic acid end groups (telechelic polymer) was grafted from the melt onto a silicon wafer that contained a monolayer of epoxy groups. Ellipsometry and fluorimetry were employed to monitor the kinetics of the grafting and loop formation, respectively. These results are quantitatively correlated with bond fluctuation Monte Carlo (BFMC) simulations that model the grafting and loop formation process. The quantitative correlation found between experiment and simulation provides unique insight into the process of polymer loop formation. Specifically, this correlation provides a calibration of the fluorescence intensity to the amount of singly bound chains present on the surface, revealing that about 80% of the bound chains form loops on the surface at the longest reaction time studied, and provides the time evolution of singly and doubly bound chains during the reaction. Moreover, this correlation is broadly applicable and can be used to readily monitor the impact of a broad range of reaction conditions (e.g., temperature, telechelic concentration, surface density of functional groups) on the loop formation process. This correlation, therefore, provides a method to access fundamental information that is not accessible by experiment alone and yet is required to tailor surface properties through adjusting the coverage and fraction of loops in the grafted layer and to correlate surface-sensitive properties to specific grafted layer structure.

Monte Carlo simulation study of the kinetics of brush formation by irreversible adsorption of telechelic polymers onto a solid substrate

The irreversible adsorption of telechelic polymer chains from solution and melts onto solid substrates has been studied using the bond fluctuation Monte Carlo model. Complex brush formation kinetics dominated by diffusion of chains to the substrate at short times (diffusion-limited regime or DLR) and by penetration of chains through the maturing brush at longer times (penetration-limited regime or PLR) were observed. During the entire adsorption process, the rate of chain adsorption decreases monotonically with time. In the DLR, characterized by a maximum in the concentration of singly bound chains and a rapidly increasing fraction of doubly bound chains (loops), this decrease is due primarily to the depletion of free chains near the substrate and the formation of concentration gradients of free (nonadsorbed) chains in the bulk solution. The DLR and PLR are separated by an intermediate regime during which the brush becomes dominated by doubly bound chains and both penetration of the maturing brush and diffusion of chains to the brush surface play a role in determining the kinetics of brush growth. The PLR is characterized by steep gradients of free chains within the growing brush and the disappearance of concentration gradients for free chains in the bulk solution. In the PLR, the concentration of singly bound chains is low and decreases slowly while surface coverage and the fraction of doubly bound chains increase slowly. The rates of adsorption of new chains and the formation of loops in the PLR slow dramatically with increasing surface coverage and increasing chain length and less dramatically with decreasing bulk concentration.