Chameleon-like elastomers with molecularly encoded strain-adaptive stiffening and coloration

Active camouflage is widely recognized as a soft-tissue feature, and yet the ability to integrate adaptive coloration and tissuelike mechanical properties into synthetic materials remains elusive. We provide a solution to this problem by uniting these functions in moldable elastomers through the self-assembly of linear-bottlebrush-linear triblock copolymers. Microphase separation of the architecturally distinct blocks results in physically cross-linked networks that display vibrant color, extreme softness, and intense strain stiffening on par with that of skin tissue. Each of these functional properties is regulated by the structure of one macromolecule, without the need for chemical cross-linking or additives. These materials remain stable under conditions characteristic of internal bodily environments and under ambient conditions, neither swelling in bodily fluids nor drying when exposed to air

Real-time evolution of the lamellar organization of poly(ethylene terephthalate) during crystallization from the melt: High-temperature atomic force microscopy study

High-temperature atomic force microscopy (AFM) was used for in-situ monitoring of melt-crystallization of poly(ethylene terephthalate) (PET) at 233°C. The observed evolution of the lamellar structure allowed identification of the stack thickening process at the secondary crystallization stage. This finding explains the puzzling decrease of the small-angle X-ray scattering (SAXS) long period observed during isothermal annealing of PET. The quantitative analysis of high-temperature AFM images provides statistically meaningful parameters for the semicrystalline structure and an accurate choice of a structural model for the interpretation of SAXS data.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Influence of crystallization conditions on the structure and thermal behavior of syndiotactic polystyrene

The dependence of the crystal structure and morphology of syndiotactic PS on crystallization conditions was studied by the XRD, DSC and atomic-force microscopy techniques. It was found that the final structure in the case of melt crystallization was determined by the melt overheating temperature. Below 280°C, the melt contains triplets, which form the limit ordered α" form upon subsequent crystallization. The crystallization rate is high and the size of crystallites does not vary with time under these conditions. Overheating to 320°C leads to the complete degradation of triplets, and the thermodynamically more stable β modification is formed in substantially slowed crystallization. Low nucleation and growth rates allow crystallites with lateral dimensions up to 850 Å to be obtained. The limiting disordered crystalline a' form is produced by annealing the quenched melt with the triplet structure; as the annealing temperature increases, the degree of crystallinity and the lateral size of crystallites monotonically increase. The kinetics of crystallization determines the super-molecular structure of the samples. It was shown that samples containing the α form are characterized by the sheaflike morphology and the absence of a long spacing. Crystallization in the β form leads to spherulitic morphology and to the appearance of the long spacing.SCOPUS: ar.jinfo:eu-repo/semantics/publishe