Macromolecular Materials and Engineering

Front Cover: Actively moving polymers can convert molecular level stimuli-responsiveness into movement on the macroscopic level, and are highly desirable as components of smart systems. As illustrated in the cover image, this Special Issue highlights recent advances in the area of actively moving polymers and showcases a wide range of applications. Further details can be found in the essay by Adam L. Sisson and Andreas Lendlein* on page 1135.

Back Cover: The cover illustrates the wide range of applications of spiropyran-polymeric systems. The center puzzle piece represents the spiropyran-modified polymers, which connects all the pieces together. The puzzle itself shows the great versatility of spiropyran-polymeric systems to generate multifunctional photo-responsive materials. Further details can be found in the article by L. Florea, D. Diamond, F. Benito-Lopez* on page 1148.

This work focuses on carbon nanopaper-enabled SMP composites from electrical actuation to multifunctionalization. Studies exploring nanopaper-enabled SMP composites in various design principles are included, especially for those induced by electricity and rendered multifunctional, providing a comprehensive account of the systemic progress in SMP composites incorporated with carbon nanopaper.

The development of new synthetic routes to produce photo-responsive spiropyran polymeric structures has received much attention over the past decade. Smart engineering of spiropyran polymeric materials allows photo-modulation of their physical, chemical and electrical properties, ranging from their photochromic behaviour to the wettability and permeability of surfaces to ‘on-demand’ sensing behaviour.

The shape-memory behavior of amorphous networks can be strongly influenced by altering the conditions at which they are programmed, stored, or recovered. This article highlights how recovery is affected at each step of the shape-memory cycle, specifically focusing on programming temperature, long-term storage, partially constrained recovery, and mechanically driven recovery.

In azo-CP2-xx polyimides, polarization-controlled forward/backward bending motions strongly depend on azobenzene/crosslinker concentration as well as the cantilever's thickness and reciprocal aspect ratio. Cantilever geometry can affect the symmetry in bending motion, and lead to twisting motion. Such a change in motional symmetry is discernable only in azo-CP2-30 cantilevers.

The synthesis of new pH-responsive hyperbranched copolymers via one-pot RAFT copolymerization of PAA and a branching co-monomer PEGDA ( = 258 Da) is described. These hyperbranched copolymers demonstrate composition- and size-dependent membrane disruptive properties by red blood cell hemolysis assay.

Novel dual-shape hydrogels based on N-vinyl-2-pyrrolidone (NVP) as backbone and grafted oligo(ω-pentadecalactone) (OPDL) side chains as switching segments are presented. The swelling behavior in water as well as the thermal, mechanical, and shape-memory properties are a function of the OPDL content, which enables tailoring of the material properties of these new thermally sensitive hydrogels, to specific application derived requirements.

Shape memory polymer substrates are utilized to create 3D softening substrates for neural interfaces. This substrate system softens in vivo from more than 600 to 6 MPa. A nerve cuff electrode that coils around a 1 mm diameter vagus nerve in a rat and is still capable of driving neural activity is demonstrated.

In nematic, main-chain LCEs based on mesogens featuring a low degree of orientation, the liquid crystalline alignment can be significantly enhanced by copolymerization with small amounts of mesogens showing a high degree of orientation. In this way the phase transition temperature and the actuator performance of the LCE can be controlled.

Degradable shape-memory SP/PU polymer blends are synthesized using an environmentally-friendly aqueous dispersion technique. The stress recovery of the blend reached a maximum value at w_SP = 0.1. A porous structure is generated using scCO₂. The degradable blend with shape-memory capability is suggested as a candidate material for biomedical applications.

The key prerequisites for distinct appearance of multiple shape-memory and in particular of triple-shape behavior of covalent networks on the basis of binary and ternary blends of semi-crystalline polymers are first a sufficient decoupling of the blend phases due to the formation of island-matrix phase morphology and second the existence of a continuous phase of blends having the lowest melting temperature.