Self‐Healing Micellar Ion Gels Based on Multiple Hydrogen Bonding

Ion gels, composed of macromolecular networks filled by ionic liquids (ILs), are promising candidate soft solid electrolytes for use in wearable/flexible electronic devices. In this context, the introduction of a self‐healing function would significantly improve the long‐term durability of ion gels subject to mechanical loading. Nevertheless, compared to hydrogels and organogels, the self‐healing of ion gels has barely investigated been because of there being insufficient understanding of the interactions between polymers and ILs. Herein, a new class of supramolecular micellar ion gel composed of a diblock copolymer and a hydrophobic IL, which exhibits self‐healing at room temperature, is presented. The diblock copolymer has an IL‐phobic block and a hydrogen‐bonding block with hydrogen‐bond‐accepting and donating units. By combining the IL and the diblock copolymer, micellar ion gels are prepared in which the IL phobic blocks form a jammed micelle core, whereas coronal chains interact with each other via multiple hydrogen bonds. These hydrogen bonds between the coronal chains in the IL endow the ion gel with a high level of mechanical strength as well as rapid self‐healing at room temperature without the need for any external stimuli such as light or elevated temperatures.     

Controlled Fabrication of Micropatterned Supramolecular Gels by Directed Self‐Assembly of Small Molecular Gelators

Herein, the micropatterning of supramolecular gels with oriented growth direction and controllable spatial dimensions by directing the self‐assembly of small molecular gelators is reported. This process is associated with an acid‐catalyzed formation of gelators from two soluble precursor molecules. To control the localized formation and self‐assembly of gelators, micropatterned poly(acrylic acid) (PAA) brushes are employed to create a local and controllable acidic environment. The results show that the gel formation can be well confined in the catalytic surface plane with dimensions ranging from micro‐ to centimeter. Furthermore, the gels show a preferential growth along the normal direction of the catalytic surface, and the thickness of the resultant gel patterns can be easily controlled by tuning the grafting density of PAA brushes. This work shows an effective “bottom‐up” strategy toward control over the spatial organization of materials and is expected to find promising applications in, e.g., microelectronics, tissue engineering, and biomedicine.     

Mechanochromic Photonic Gels

Polymer gels are remarkable materials with physical structures that can adapt significantly and quite rapidly with changes in the local environment, such as temperature, light intensity, electrochemistry, and mechanical force. An interesting phenomenon observed in certain polymer gel systems is mechanochromism – a change in color due to a mechanical deformation. Mechanochromic photonic gels are periodically structured gels engineered with a photonic stopband that can be tuned by mechanical forces to reflect specific colors. These materials have potential as mechanochromic sensors because both the mechanical and optical properties are highly tailorable via incorporation of diluents, solvents, nanoparticles, or polymers, or the application of stimuli such as temperature, pH, or electric or strain fields. Recent advances in photonic gels that display strain‐dependent optical properties are discussed. In particular, this discussion focuses primarily on polymer‐based photonic gels that are directly or indirectly fabricated via self‐assembly, as these materials are promising soft material platforms for scalable mechanochromic sensors.     

Methods for Controlling Structure and Photophysical Properties in Polyfluorene Solutions and Gels

Knowledge of the phase behavior of polyfluorene solutions and gels has expanded tremendously in recent years. The relationship between the structure formation and photophysics is known at the quantitative level. The factors which we understand control these relationships include virtually all important materials parameters such as solvent quality, side chain branching, side chain length, molecular weight, thermal history and myriad functionalizations. This review describes advances in controlling structure and photophysical properties in polyfluorene solutions and gels. It discusses the demarcation lines between solutions, gels, and macrophase separation in conjugated polymers and reviews essential solid state properties needed for understanding of solutions. It gives an insight into polyfluorene and polyfluorene beta phase in solutions and gels and describes all the structural levels in solvent matrices, ranging from intramolecular structures to the diverse aggregate classes and network structures and agglomerates of these units. It goes on to describe the kinetics and thermodynamics of these structures. It details the manifold molecular parameters used in their control and continues with the molecular confinement and touches on permanently cross‐linked networks. Particular focus is placed on the experimental results of archetypical polyfluorenes and solvent matrices and connection between structure and photonics. A connection is also made to the mean field type theories of hairy‐rod like polymers. This altogether allows generalizations and provides a guideline for materials scientists, synthetic chemists and device engineers as well, for this important class of semiconductor, luminescent polymers.     

Gelatine Gels and Polyoxyethylene-Polyoxypropylene Gels: Comparative Study of Their Properties

ABSTRACT

Gelatine gels and polyoxyethylene-polyoxypropylene (Pluroni^R) F-108 and F-127 gels were prepared at concentrations ranging between 5 and 25% (W/V), the former by dispersion at 37°C, the later by dispersion at 4°C. The viscosity, the gel-sol transition temperature and the “in vitro” release kinetics of these gels were compared as a first step for the elaboration of parented controlled release formulations. Phenolsulphonftaleine (PR) was used as a tracer.

In all cases the viscosity increased with the rise in the concentration of gelatin (20 to 264 cps for 5 to 20%) or pluronic (260 and 1,520 cps for 20 and 25% F-108). The gel-sol transition temperature for gelatine gels was directly related to the concentration. On the contrary, for pluronic gels an inverse relation was observed, being the gel-sol transition temperature higher in copolymers with a large percentage of polyoxyethylene groups (30±0.2 °C for 25 % F-108). In both types of gels, a rise in pH and ionic strength decreased the gel-sol transition temperature, whereas PR increase this temperature. The release of the tracer, from the gels to the aqueous medium, showed a zero-order kinetics and the release rates were inversely proportional to the concentration of gelling agent.     

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.     

Self‐Healing Hydrogels

Over the past few years, there has been a great deal of interest in the development of hydrogel materials with tunable structural, mechanical, and rheological properties, which exhibit rapid and autonomous self‐healing and self‐recovery for utilization in a broad range of applications, from soft robotics to tissue engineering. However, self‐healing hydrogels generally either possess mechanically robust or rapid self‐healing properties but not both. Hence, the development of a mechanically robust hydrogel material with autonomous self‐healing on the time scale of seconds is yet to be fully realized. Here, the current advances in the development of autonomous self‐healing hydrogels are reviewed. Specifically, methods to test self‐healing efficiencies and recoveries, mechanisms of autonomous self‐healing, and mechanically robust hydrogels are presented. The trends indicate that hydrogels that self‐heal better also achieve self‐healing faster, as compared to gels that only partially self‐heal. Recommendations to guide future development of self‐healing hydrogels are offered and the potential relevance of self‐healing hydrogels to the exciting research areas of 3D/4D printing, soft robotics, and assisted health technologies is highlighted.     

Patient perceptions of remote monitoring for nocturnal home hemodialysis

Adoption of nocturnal home hemodialysis (NHHD) has been slow, due in part to patient-perceived barriers, such as anxiety and lack of self-efficacy. This study investigates patient perception of remote monitoring in addressing these barriers. Perceptions of remote patient monitoring (RPM) were studied through a quantitative survey and qualitative interviews. The NHHD and conventional hemodialysis (CHD) were included in the survey (209 in total). Twenty semistructured interviews were conducted as well as a focus group that included NHHD patients and family caregivers. The CHD patients had greater interest in adopting NHHD with RPM than without (1.90±1.37 vs. 1.71±1.28, P<0.002), with the negative intensity ratio declining from 10.50 to 5.56. Interest in RPM was correlated with interest in NHHD (r=0.768, P<0.001). Other significant factors correlated with interest in NHHD include the belief that remote monitoring will ease the performing of NHHD (r=0.452, P=0.001) and the belief that RPM should be mandatory (r=0.541, P=0.000). Qualitative findings supported three themes: (1) There is an expectation for the use of RPM, (2) RPM should be used at a minimum transitionally, and (3) RPM acts as a surrogate support of family-caregivers. The RPM may lower perceived barriers to the adoption of NHHD, in part through its surrogate support of family caregivers. However, RPM alone is likely insufficient to alter patients' attitudes to undergo NHHD. RPM is a common expectation of CHD patients considering the therapy, at a minimum during the transitional phase.