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.
Spider major ampullate silk is often schematically represented as a two-phase material composed of crystalline nanodomains in an amorphous matrix. Here we are interested in revealing its more complex nanoscale organization by probing Argiope bruennichi dragline-type fibers using scanning X-ray nanodiffraction. This allows resolving transversal structural features such as an about 1 μm skin layer composed of around 100 nm diameter nanofibrils serving presumably as an elastic sheath. The core consists of a composite of several nm size crystalline nanodomains with poly(l-alanine) microstructure, embedded in a polypeptide network with short-range order. Stacks of nanodomains separated by less ordered nanosegments form nanofibrils with a periodic axial density modulation which is particularly sensitive to radiation damage. The precipitation of larger β-type nanocrystallites in the outer core-shell is attributed to MaSp1 protein molecules.
The microstructure of banded spherulites of a typical semirigid-chain polymer, poly(trimethylene terephthalate), PTT, has been explored with microbeam X-ray diffraction. It is shown that during microbeam scans along the spherulite radius, different diffraction peaks exhibit oscillations with the same periodicity, which means that the lamellar twist is strictly uniform and regular. The twisted PTT crystals formed from the melt at 170°C reveal a one-to-one correlation between the handedness and growth axis polarity. Thus, the lamellae are right-handed for the growth along the negative growth direction (−a) while they are left-handed for the positive growth direction (+a). This is in line with predictions of the KP-model, although the original model cannot explain why, for example left-handed crystals have to grow along (−a). The direction of the chain tilt in the lamellar crystal correlates with the lamellar handedness as postulated by the KP-model. However, the measured chain tilt in the crystal (4°) is too faint to be the primary source of the surface stresses required for twisted lamellar growth.
A novel wedge-shaped amphiphilic molecule bearing a sulfonate group at the tip displays humidity-induced phase transitions from a hexagonal columnar structure to a bicontinuous cubic phase. The mesophases can be frozen by photopolymerization of acrylic end-groups resulting in free-standing membranes with different topology of ionic nanochannels. The obtained membranes with a well-ordered ionic channel structure hold promise for applications in separation and catalysis.
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