There has been a significant effort to create spiral sensors by changing either the periodic d-spacing of the structure or the dielectric constants of the materials by combining the multi-faceted environmental responsiveness of polymer hydrogels with dielectrical structures.1 Reversible spiral switches with dimensional functionalities that respond to chemical environment were constructed. When the spiral photonic actuator was swollen in hydrophilic acetic acid, right-handed spiral structures are formed, while the spiral photonic actuator was swollen in hydrophobic hexane, left-handed spiral structures are formed. All actuators returned back to the transparent planar state after deswelling processes. These reversible spiral photonic actuators can be applied in the application of mechanical actuators, electrical devices, and optical components.

The degradation behavior of biodegradable multiblock copolymers (PDC) containing poly(p-dioxanone) hard segments (PPDO) and crystallizable poly(epsilon-caprolactone) switching segments (PCL) synthesized via co-condensation of two oligomeric macrodiols with an aliphatic diisocyanate as junction unit was explored in in vivo and in vitro experiments. The in vitro experiments for enzymatic degradation resulted that the poly(epsilon-caprolactone) segments are degraded faster, than the poly(p-dioxanone) segments. During degradation the outer layer of the test specimen becomes porous. Finally non-soluble degradation products in form of particles were found at the surface. This observation is in good agreement with the in vivo studies, where the non-soluble degradation products in the periimplantary tissues showed a diameter of 1 – 3 micron.

Thermo-sensitive multiphase polymer networks with triple-shape capability have been recently introduced as a new class of active polymers that can change on demand from a first shape A to a second shape B and from there to a permanent shape C. Such multiphase polymer networks consist of covalent cross-links that determine shape C and at least two phase-segregated domains with distinct thermal transitions Ttrans,A and Ttrans,B , that are associated to shape A and B. In general the application of a two step programming or a one step programming procedure is required for creation of triple-shape functionality. In this study we report about a series of CLEGC nanocomposites consisting of silica coated nanoparticles (SNP) incorporated in a multiphase graft polymer network matrix from crystallisable poly(ε-caprolactone) diisocyanatoethyl methacrylate (PCLDIMA) and poly(ethylene glycol) monomethyl ether monomethacrylate (PEGMA) forming crystallisable side chains. These CLEGC nanocomposites were designed to enabling non contact activation of triple-shape effect in alternating magnetic field. Composites with variable PCLDIMA content ranging from 30 wt-% and 70 wt-% and different SNP amounts (0 wt-%, 2.5 wt-%, 5 wt-% and 10 wt-%) were realized by thermally induced polymerization. The thermal and mechanical properties of the CLEG nanocomposites were explored by means of DSC, DMTA and tensile tests. The triple-shape properties were quantified in cyclic, thermomechanical experiments, which consisted of a two step programming procedure and a recovery module under stress-free conditions for recovery of shapes B and C. While the thermal properties and the Young’s modulus of the investigated polymer networks were found to be independent from the incorporated amount of SNP, the elongation at break (εB) decreases with increasing nanoparticle content. All investigated composites exhibit excellent triple-shape properties showing a well separated two step shape recovery process.

Polymer networks synthesized by UV-curing of Oligo[(ε-caprolactone)-co-glycolide]dimethacrylates are hydolytically degradable. Their architecture with covalent netpoints and crystallizable domains is the molecular basis for the potential shape-memory capability. The molecular weight and glycolide content of the oligomeric precursors can be varied over a broad range of compositions to tailor the thermomechanical properties of the polymer network while having only a minor influence on the shape-memory effect. Recently, drug incorporation adding controlled drug release as further functionality to the polymer network was demonstrated [4]. Here, enoxacin and ethacridine lactate as test drugs were incorporated into the networks by soaking. Alternatively, defined amounts of ethacridine lactate were mixed with the precursors, which were subsequently crosslinked to the drug containing networks. The composition of the oligomeric precursors in molecular weight between 3800 and 12800 g�mol-1 and in glycolide content ϝG between 0 and 30 mol-% to explore the influence of the drug incorporation on networks with varying compositions while retaining properties and functionalities. Polymer networks prepared from precursors with ϝG ? 14 mol-% and Mn ? 6900 g�mol-1 have a Tsw of 35-52 �C and sufficient crystallinity to ensure a high shape fixity in the programming step. These limits have to be kept to ensure the desired multifunctionality, otherwise drug incorporation can have an undesired influence on thermal, mechanical, and shape-memory properties.

Molecular photoswitches like spiropyrans derivatives offer exciting possibilities for the development of analytical platforms incorporating photo-responsive materials for functions such as light-activated guest uptake and release and optical reporting on status (passive form, free active form, guest bound to active form). In particular, these switchable materials hold tremendous promise for microflow-systems, in view of the fact that their behaviour can be controlled and interrogated remotely using light from LEDs, without the need for direct physical contact. We demonstrate the immobilisation of these materials on microbeads which can be incorporated into a microflow system to facilitate photoswitchable guest uptake and release. We also introduce novel hybrid materials based on spiropyrans derivatives grafted onto a polymer backbone which, in the presence of an ionic liquid, produces a gel-like material capable of significant photoactuation behaviour. We demonstrate how this material can be incorporated into microfluidic platforms to produce valve-like structures capable of controlling liquid movement using light.

Although epoxy-based polymers remain infrequently used as shape memory polymers (SMP’s), they are a promising base material for highly demanding applications due to their intrinsic physical properties and ease of processing. A series of epoxy SMP’s was synthesized with varying mechanical properties and with glass transition temperatures ranging from 31 to 93 °C, tunable via the variations of the molecular structures. The influence of chemical structures and physical properties of these epoxy SMP’s on their shape memory (SM) behavior is examined in detail along with the impact of the shape memory cycling conditions. While the results show that lower crosslink densities and/or higher molecular flexibility/mobility leads decreased SM performance, at low crosslink density the effect of molecular flexibility/mobility becomes dominant in influencing the SM response.

The conjugated polymeric backbone of polydiacetylenes (PDAs), comprising of alternating ene-yne groups, undergo intriguing stress-, chemical- or temperature-induced chromatic phase transitions associated with the disruption of the backbone structure and shortening of the conjugation length. PDAs, such as polymerized 10, 12 pentacosadiynoic acids (PCDA), when incorporated with inorganic oxides form nanocomposites and uniform blends with polymers. Blends of poly-PCDA with polymers, such as polyvinyl alcohol, polyvinylidene fluoride and cellulose increase the blue to red transition temperature without affecting the irreversibility of the red phase. However, the addition of zinc oxide to pure poly-PCDA makes the red phase highly reversible and substantially increases the blue to red transition temperature. The addition of TiO2 to poly-PCDA on the other hand does not affect the irreversibility of the red phase and the chromatic transition temperature. In order to understand the atomic scale interactions associated with these changes in the chromatic transitions, we have investigated both the nanocomposites and polymer blends using Raman and Fourier-transform infrared spectroscopy, and extended X-ray absorption fine structure (EXAFS) measurements

This paper presents a thermoviscoelastic model for shape memory polymers (SMPs). The model has been developed base on the hypothesis that structural and stress relaxation are the primary shape memory mechanisms of crosslinked, glassy SMP, and that consideration of these mechanisms is essential for predicting the time-dependence of the shape memory response. Comparisons with experiments show that the model can reproduce the rate-dependent strain-temperature and stress-strain response of a crossslinked, glassy SMP. The model also captures many important features of the temperature and time dependence of the free strain recovery and constrained stress recovery response.

To develop efficient organic and/or hybrid organic-inorganic solar energy devices, it is necessary to use, among other components, an active donor–acceptor layer with highly ordered nanoscale morphology. In an idealized morphology, the effectiveness of internal processes is optimized leading to an efficient conversion of photons to electricity. Using a poly(3-hexylthiophene)-block-poly(L-lactide) rod-coil block copolymer as a structure-directing agent, we have rationally designed and developed an ordered nanoscale morphology consisting of self-assembled poly(3-hexylthiophene) donor domains of molecular dimension, each of them separated by fullerene C60 hydroxide acceptor domains. Using this morphological control, one can begin to probe structure-property relationships with unprecedented detail with the ultimate goal of maximizing the performance of future organic/hybrid photovoltaic devices.

Tumor resection done by minimally invasive procedure owns the challenge of a fast and reliable differentiation between healthy and tumorous tissue. We aim at investigating and developing a method for an intraoperative visualization of tumor cells with functionalized nanoparticles. The goal is to use this technique for the intraoperative use. Our so-called biohybrid systems consist of nanoparticles that are produced by Stöber synthesis and coupled with bio active proteins. Such biomimetic nanostructures are capable of imitating the effects of membrane-bound cytokines, which bind to tumor cells for labeling them. A flexible and modular test environment has been developed to evaluate the spraying properties of the particles and to study tissue probes. It enables a fast investigation of different particle configurations and spraying parameters like pressure, spray volume, nozzle geometry, etc.