Photo‐Thermo‐Mechanical Behaviour Under Quasi‐Static Tensile Conditions of a PMMA‐Core Optical Fibre

As the optical power transmitted by an optical fibre under tensile stress varies with strain, it can be used as a sensor for strain monitoring in structural elements. In the present work, quasi‐static tensile tests of step index polymer optical fibres (POF) with simultaneous measurement of surface temperature and optical power are described. Young's modulus, yield stress and tensile strength are derived from experimental tests. Morphological characterization of the POF fibres using scanning electron microscope images and differential calorimetry technique is performed. The contributions of both elastic and plastic strain components to the variation of temperature and optical power loss are also estimated. The evolution of the POF mechanical properties as well as that of temperature and optical power loss is explained in terms of the progressive relative movement and alignment of the molecular chains in the direction of the applied load. Strain, temperature and optical power loss are then correlated.     

Thermo‐Switchable Materials Prepared Using the OEGMA‐Platform

We describe here the advantages of oligo(ethylene glycol)‐based (co)polymers for preparing thermoresponsive materials as diverse as polymer‐enzyme bio‐hybrids, injectable hydrogels, capsules for drug‐release, modified magnetic particles for in vivo utilization, cell‐culture substrates, antibacterial surfaces, or stationary phases for bioseparation. Oligo(ethylene glycol) methacrylates (OEGMAs) can be (co)polymerized using versatile and widely‐applicable methods of polymerization such as atom transfer radical polymerization (ATRP) of reversible addition‐fragmentation chain‐transfer (RAFT) polymerization. Thus, the molecular structure and therefore the stimuli‐responsive properties of these polymers can be precisely controlled. Moreover, these stimuli‐responsive macromolecules can be easily attached to–or directly grown from–organic, inorganic or biological materials. As a consequence, the OEGMA synthetic platform is today a popular option for materials design. The present research news summaries the progress of the last two years.     

Multifunctional POSS‐Based Nano‐Photo‐Initiator for Overcoming the Oxygen Inhibition of Photo‐Polymerization and for Creating Self‐Wrinkled Patterns

Oxygen inhibition remains a challenge in photo‐curing technology despite the expenditure of considerable effort in developing a convenient, efficient, and low‐cost prevention method. Here, a novel strategy to prevent oxygen inhibition is presented; it is based on the self‐assembly of multifunctional nano‐photo‐initiators (F₂‐POSS‐(SH)₄‐TX/EDB) at the interface of air and the liquid monomer. These nano‐photo‐initiators consist of a thiol‐containing polyhedral oligomeric silsesquioxane (POSS) skeleton onto which fluorocarbon chains and thioxanthone and dimethylaminobenzoate (TX/EDB) photo‐initiator moieties are grafted. Real‐time Fourier‐transform infrared spectroscopy (FT‐IR) is used to investigate the photo‐polymerization of various acrylate monomers that are initiated by F₂‐POSS‐(SH)₄‐TX/EDB and its model analogues in air and in N₂. FT‐IR results show that F₂‐POSS‐(SH)₄‐TX/EDB decreases the effects of oxygen inhibition. X‐ray photo‐electron spectroscopy and atomic force microscopy reveal that the self‐assembly of F₂‐POSS‐(SH)₄‐TX/EDB at the air/(liquid monomer) interface forms a cross‐linked top layer via thiol–ene polymerization; this layer acts as a physical barrier against the diffusion of oxygen from the surface into the bulk layer. A mismatch in the shrinkage between the top and bulk layers arise as a result of the different types of photo‐cross‐linking reactions. Subsequently, the surface develops a wrinkled pattern with a low surface energy. This strategy exhibits considerable potential for preventing oxygen inhibition, and the wrinkled pattern may prove very useful in photo‐curing technology.     

Cyanine‐Anchored Silica Nanochannels for Light‐Driven Synergistic Thermo‐Chemotherapy

Smart nanoparticles are increasingly important in a variety of applications such as cancer therapy. However, it is still a major challenge to develop light‐responsive nanoparticles that can maximize the potency of synergistic thermo‐chemotherapy under light irradiation. Here, spatially confined cyanine‐anchored silica nanochannels loaded with chemotherapeutic doxorubicin (CS‐DOX‐NCs) for light‐driven synergistic cancer therapy are introduced. CS‐DOX‐NCs possess a J‐type aggregation conformation of cyanine dye within the nanochannels and encapsulate doxorubicin through the π–π interaction with cyanine dye. Under near‐infrared light irradiation, CS‐DOX‐NCs produce the enhanced photothermal conversion efficiency through the maximized nonradiative transition of J‐type Cypate aggregates, trigger the light‐driven drug release through the destabilization of temperature‐sensitive π–π interaction, and generate the effective intracellular translocation of doxorubicin from the lysosomes to cytoplasma through reactive oxygen species‐mediated lysosomal disruption, thereby causing the potent in vivo hyperthermia and intracellular trafficking of drug into cytoplasma at tumors. Moreover, CS‐DOX‐NCs possess good resistance to photobleaching and preferable tumor accumulation, facilitating severe photoinduced cell damage, and subsequent synergy between photothermal and chemotherapeutic therapy with tumor ablation. These findings provide new insights of light‐driven nanoparticles for synergistic cancer therapy.     

Photosystem I (PSI)/Photosystem II (PSII)‐Based Photo‐Bioelectrochemical Cells Revealing Directional Generation of Photocurrents

Layered assemblies of photosystem I, PSI, and/or photosystem II, PSII, on ITO electrodes are constructed using a layer‐by‐layer deposition process, where poly N,N′‐dibenzyl‐4,4′‐bipyridinium (poly‐benzyl viologen, PBV²⁺) is used as an inter‐protein “glue”. While the layered assembly of PSI generates an anodic photocurrent only in the presence of a sacrificial electron donor system, such as dichlorophenol indophenol (DCPIP)/ascorbate, the PSII‐modified electrode leads, upon irradiation, to the formation of an anodic photocurrent (while evolving oxygen), in the absence of any sacrificial component. The photocurrent is generated by transferring the electrons from the PSII units to the PBV²⁺ redox polymer. The charge‐separated species allow, then, the injection of the electrons to the electrode, with the concomitant evolution of O₂. A layered assembly, consisting of a PSI layer attached to a layer of PSII by the redox polymer PBV²⁺, leads to an anodic photocurrent that is 2‐fold higher, as compared to the anodic photocurrent generated by a PSII‐modified electrode. This observation is attributed to an enhanced charge separation in the two‐photosystem assembly. By the further nano‐engineering of the two photosystems on the electrode using two different redox polymers, vectorial electron transfer to the electrode is demonstrated, resulting in a ca. 6‐fold enhancement in the photocurrent. The reversed bi‐layer assembly, consisting of a PSII layer linked to a layer of PSI by the PBV²⁺ redox polymer, yields, upon irradiation, an inefficient cathodic current. This observation is attributed to a mixture of photoinduced electron transfer reactions of opposing effects on the photocurrent directions in the two‐photosystem assembly.     

Photo‐Induced Polymerization and Reconfigurable Assembly of Multifunctional Ferrocene‐Tyrosine

The photo‐induced reconfigurable assembly of nanostructures via the simultaneous noncovalent and covalent polymerization of a functional ferrocene‐tyrosine (Fc‐Y) molecule is reported. The Fc‐Y monomers can directly self‐assemble into nanospheres with a smooth surface driven by noncovalent interactions. By covalent photo‐crosslinking of the Fc‐Y monomers, the nanospheres transform spontaneously into hollow vesicles composed of hierarchically ordered lamellar structures. It is worth noting that the formed nanostructures exhibit both reducing property for in situ mineralization of gold nanoparticles with tunable biocatalytic behavior, and the redox activity for superior energy storage capacity. The measured energy storage capacity is 31 mAh g⁻¹ for the nanospheres, which is the highest value reported so far for peptide assemblages as supercapacitor. The results offer insights into the dynamic self‐assembly of highly ordered multifunctional materials with promising applications in catalysis, sensing, energy and biomedical fields.     

Thermo‐hydro‐mechanical modeling of fluid geological storage by Godunov‐mixed methods

The efficient solution to the coupled system of PDEs governing the mass and the energy balance in deformable porous media requires advanced numerical algorithms. A combination of mixed/Galerkin finite elements and finite volumes along with a staggered method are employed. Fluid flow and heat transfer are addressed iteratively by a fully coupled approach and the medium deformation by an explicitly coupled scheme, at each time step. Such formulation allows for stable numerical solutions, element‐wise conservative velocity fields and accurate prediction of sharp temperature convective fronts. The proposed model is experimented with in realistic applications of a deep aquifer fluid injection. Copyright © 2012 John Wiley & Sons, Ltd.