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The vision of gluing two bone fragments with biodegradable and biocompatible adhesives remains highly fascinating and attractive to orthopedic surgeons. Possibly shorter operation times, better stabilization, lower infection rates, and unnecessary removal make this approach very appealing. After 30 years of research in this field, the first adhesive systems are now appearing in scientific reports that may fulfill the comprehensive requirements of bioadhesives for bone. For a successful introduction into clinical application, special requirements of the musculoskeletal system, challenges in the production of a bone adhesive, as well as regulatory hurdles still need to be overcome. In this article, we will give an overview of existing synthetic polymers, biomimetic, and bio-based adhesive approaches, review the regulatory hurdles they face, and discuss perspectives of how bone adhesives could be efficiently introduced into clinical application, including legal regulations. [ABSTRACT FROM AUTHOR]

The properties of nanoparticle–polymer composites strongly depend on the network structure of the polymer matrix. By introducing nanoparticles into a monomer (solution) and subsequently polymerizing it, the formation of the polymer phase influences the mechanical and physicochemical properties of the composite. In this study, semi-conducting indium tin oxide (ITO) nanoparticles were prepared to form a rigid nanoparticle scaffold in which 1,6-hexanediol diacrylate (HDDA), together with an initiator for photo-polymerization, was infiltrated and subsequently polymerized by UV light. During this process, the polymerization reaction was characterized using rapid scan Kubelka–Munk FT-IR spectroscopy and compared to bulk HDDA. The conductivity change of the ITO nanoparticles was monitored and correlated with the polymerization process. It was revealed that the reaction rates of the radical initiation and chain propagation are reduced when cured inside the voids of the nanoparticle scaffold. The degree of conversion is lower for HDDA infiltrated into the mesoporous ITO nanoparticle scaffold compared to purely bulk-polymerized HDDA. [ABSTRACT FROM AUTHOR]

Silicone‐based materials often contain vinylsiloxane and hydrosiloxane groups for cross‐linking by a radical or addition reaction. Such functional groups can influence the interactions with fillers or with surfaces of substrates when used as adhesives. This work examined how these functional groups interact with aluminum oxide surfaces. For this purpose, aluminum oxide powders with large surface areas of 150 m2/g and different acid‐base properties were examined. Siloxanes were applied as thin layers to mainly obtain information from the interphase by vibrational spectroscopy. It was observed that vinyl groups show low interactions with aluminum oxide surfaces even at elevated temperatures. In contrast to this, hydrosiloxanes undergo strong interactions and reactions with aluminum oxides already at room temperature. Activated Si─H species were observed as an intermediate state. On the one hand, interactions and reactions might contribute to adhesion, but on the other hand, the cross‐linking reaction can be influenced near the surface, leading to lower mechanical strength. [ABSTRACT FROM AUTHOR]

Abstract This work presents a novel aqueous dispersion prepared from a solvent-borne acrylic copolymer mixture containing carboxylic acid groups for the first copolymer and epoxy groups for the second copolymer. The aim of this work was to test the suitability of the presented dispersion for the preparation of pressure sensitive adhesives (PSA) with post-crosslinking ability. A monomodal particle size distribution was obtained and a successful coemulsification of both copolymers into one particle was proved, although the epoxy containing polymer did not bear carboxylic acid groups. Storage of the dispersion led to intraparticular crosslinking inside the particles, which produced an increase in the shear of the PSA. Post-crosslinking ability was shown for the PSA of the unaged and aged dispersions in the presence of 1-methylimidazole and led to a major increase in shear but did not lead to a considerable decrease in peel. Probe-tack enabled a fast detection of post-crosslinking because of the appearance of a plateau formation in probe-tack curves. The adhesive properties before and after crosslinking demonstrate the potential of the presented dispersion, which yields novel PSA for applications which need high shear but also sufficient peel. Graphical abstract fx1 [ABSTRACT FROM AUTHOR]

Abstract Interactions between polymer matrices and inorganic mineral surfaces are especially relevant in polymer-filler composites and in adhesion science. Knowledge about underlying mechanisms at the interphase is a prerequisite for understanding functionality and aging. Therefore, interactions of poly(dimethylsiloxanes) (PDMS) and octamethylcyclotetrasiloxane (D4) with aluminum oxides comprising different acid-base properties were studied. For this purpose, thin layers of siloxanes were applied on aluminum oxides and analyzed by Raman spectroscopy and thermogravimetric analysis. It was observed that aluminum oxides are able to react with PDMS and D4 by heterolytic bond cleavage of Si O bonds, either by reactions with physisorbed water under catalysis of aluminum oxide or by direct reaction of the surface with siloxanes. Both reaction paths can yield Si O Al bonds and thus chemisorption which lead to strong interactions between siloxanes and aluminum oxides. However, the shown reaction paths concomitantly act as aging mechanisms leading to degradation of polymer. Highlights • Silicones react with surface of aluminum oxides. • Reaction is independent on surface acidity. • Polymer main chain splits and attaches to the surface. • Aluminum oxide surfaces might initiate silicone formation. [ABSTRACT FROM AUTHOR]

Purpose: Cataract surgery can lead to the temporary development or worsening of dry eye symptoms. Contributing factors may include corneal incisions, agents used before, during or after surgery, light from the operating microscope, disruption of ocular surface tissues and inflammatory processes. The purpose of this study was to observe the effect of light exposure on conjunctival fibroblasts in order to determine whether light has an effect on wound healing closure, assuming that operating microscopes might have an effect on the ocular surface.Method: An in vitro scratch assay was performed on porcine conjunctival fibroblasts. Ten minutes of light exposure from a light microscope with a halogen bulb was performed after the scratch assay. Fibroblasts were kept in culture for 48 hours post-exposure and the wound closure rates were visualized by live/dead staining. The fibroblasts which were exposed to light were compared to those without light exposure. Cell viability was also analysed by MTT assay.Results: A Slower wound closure rate was found when fibroblasts were exposed to light compared to the non-light exposed controls. Cell viability reduced by 20% with light exposure compared to controls in p3 cells (p = 0.04; however, the trend was not observed with p4 and p5 cells (p > 0.05).Conclusions: These results suggest that light exposure might be one of the possible contributory factors for dry eye after ophthalmic surgery. Further evaluation of light effects should be carried out with different ocular surface cells. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to the article "Population spherical aberration: associations with ametropia, age, corneal curvature, and image quality," by A. C. Kingston and I. G. Cox in the 2013 issue.

Pressure-sensitive adhesive tapes are used in automotives, railway vehicles and construction, where flame retardancy is of major importance. This is why industrial applicants often buy, and industrial tape manufacturers often produce, flame-retardant adhesive tapes, advertised for their good flammability characteristics. Yet, how flame-retardant tapes influence the fire behavior of bonded materials is a rather open question. To investigate this issue, three different substrates were bonded, using eight double-sided adhesive tapes containing two different carriers and two different flame retardants. The bonded substrates were compared to their monolithic counterparts in terms of flammability, fire behavior and fire stability. The fire behavior of adhesive tape bonded materials differed significantly from the monolithic substrates. The usage of different adhesive tapes let to different burning behavior of the bonded materials mainly due to different carrier systems. In contrast, the implementation of flame retardant into the adhesive had rather minor or no effect on the burning behavior of the bonded substrates despite their positive effect on the flammability of the free-standing tape. The carrier changed the HRR curve in the cone calorimeter and was able to both, reduce and increase fire hazards. Using the carrier with the better fire performance can lower the fire growth rate by 20%, the peak of heat release rate by 27%, and the maximum average rate of heat emission by 30% in cone calorimeter tests. Overall, the fire behavior of bonded materials is a complex interaction between substrate, adhesive, and carrier, and depends on the fire scenario the materials are exposed to. [ABSTRACT FROM AUTHOR]

Pressure-sensitive adhesive tapes are used in a variety of applications such as construction, aircrafts, railway vehicles, and ships, where flame retardancy is essential. Especially in these applications, phosphorus-based flame retardants are often chosen over halogenated ones due to their advantages in terms of toxicity. Although there are pressure-sensitive adhesives with phosphorus flame retardants available on the market, their flame-retardant modes of action and mechanisms are not entirely understood. This research article provides fundamental pyrolysis research of three phosphorus-based flame retardants that exhibit different mechanisms in a pressure-sensitive adhesive matrix. The flame-retardants modes of action and mechanisms of a 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) derivate, an aryl phosphate, and a self-synthesized, covalently bonded DOPO derivate (copolymerized) are investigated. The blended DOPO derivate is volatilized at rather low temperatures while the covalently bonded DOPO derivate decomposes together with the polymer matrix at the same temperature. Both DOPO derivates release PO radicals which are known for their flame inhibition. The aryl phosphate decomposes at higher temperatures, releases small amounts of aryl phosphates into the gas phase, and acts predominantly the condensed phase. The aryl phosphate acts as precursor for phosphoric acid and improves the charring of the pressure sensitive adhesive matrix. All flame retardants enhance the flammability of the adhesives depending on their individual mode of action while the covalently bonded flame retardant additionally improves the mechanical properties at elevated temperatures making it a promising future technology for pressure-sensitive adhesives. • Phosphorus flame retardants in pressure sensitive adhesives. • Decomposition mechanism of phosphorus flame retardants. • DOPO flame retardant mechanism in pressure sensitive adhesives. • Covalently bonded flame retardant for acrylic adhesives. • Pyrolysis GC/MS of phosphorus flame retardants. [ABSTRACT FROM AUTHOR]

Abstract: New type of polyester polyol with alkyl side groups, viz. poly(2,4-diethyl-1,5-pentamethylene adipate) glycol (PDPAD) was synthesized and applied to improve the hydrolytic stability of polyurethane dispersions (PUD), and the results were compared with conventional poly(tetramethylene adipate) glycol (PTAD)-based PUD. It was found that PDPAD-based PUD gave much higher hydrolytic stability in spite of great water swell than the PTAD-based PUD which showed higher hardness, modulus, and tensile strength. Tailor-made properties were possibly obtained by combining the two types of polyol. [Copyright &y& Elsevier]

Cement of the barnacle species, Balanus crenatus, was isolated and separated by SDS-PAGE. Reductive and nonreductive conditions yielded the same result of six major proteins (in the range up to 100 kDa) occurring as two triplets. A third triplet of lower molecular mass was faintly visible. The presence of a reductive agent had only little impact on the solubility of B. crenatus cement. The strong effect of the denaturing conditions (the presence of SDS and the incubation at elevated temperature) on the solubility of the barnacle cement and the absence of disulfide signals in Raman spectra suggest a complex structure of the barnacle cement noncovalently bound. It can be speculated that this protein complex in its quaternary structure is formed by small subunits and is equivalent to the globular cement structures previously detected. [ABSTRACT FROM AUTHOR]

A simple method for partial methylation of the hyperbranched polyglycerol hydroxyl groups was achieved by a combination of phase-transfer catalysis approach with dimethyl sulfate and tetrabutylammonium bromide and the use of a mixed-bed ion exchanger for purification. Various degrees of methylation between 0 and 98% could be adjusted in a controlled manner via the added amount of alkylating agent resulting in modified polymers with moderate polydispersities. NMR spectroscopy was used to determine the methylation progress and the resulting molecular structure. The methylation degree affected associative intra- and intermolecular interactions, such as hydrogen bonds, entailing reduced glass transition temperature and viscosities with increasing hydroxyl group conversion. In addition, the attenuation of hydrogen bonds upon methylation proved to facilitate a straightforward estimation of methylation degree by infrared spectroscopy. [Display omitted] • Hyperbranched polyglycerol with degree of methylation between 0 and 98%. • Two step synthesis for a targeted and adjustable methylation. • Decreasing hydroxyl group content causes decrease in T g and viscosity. • Beneficial combination of alkylating agent and mixed-bed ion exchanger for work-up. [ABSTRACT FROM AUTHOR]

A variety of differently structured PEG-based polymers can form physically cross-linked PEG hydrogels with a-cyclodextrin. The polymer structures strongly influence the properties of the hydrogel and its formation. Four different copolymers of methoxy PEG methacrylate and methacrylic acid are used together with α-cyclodextrin to study hydrogel formation speed and gel strength. The hydrogels are formed within 1-25 min, and the formation process is examined in situ by dynamic light scattering. The gel formation time is pH dependent due to the methacrylic acid present in the polymers. The gel strength examined by texture analyzer also depends on the composition and pH. With prior mechanical destruction, all hydrogels are dissolvable in an excess of water, being a useful feature for an in vivo usage. By analyzing the structures of the hydrogels with confocal light microscopy (laser scanning confocal microscopy) and scanning electron microscope (SEM) after freeze etching, the different hydrogel structures can be observed. [ABSTRACT FROM AUTHOR]

Highlights • A precise and fast measurement for alginate hydrogel formation with CaCl 2 is proposed. • The measurement principle is based on the gel inhomogeneity (core/shell). • The method can supplement high temperature NMR analysis of G/M ratio. Abstract Although alginate-based hydrogels are widely used, determining their mechanical properties and explaining their ability to form a hydrogel in situ remains a challenge. A new method of external gelation using calcium chloride (CaCl 2) is proposed to quantify the formation of alginate hydrogel and its mechanical properties as well as to observe its temporal behaviour. To this end, small inhomogeneous alginate beads were formed, which comprised a shell and a core. The bead's shell consisted of calcium alginate hydrogel, while its core was sodium alginate sol. The beads were mechanically tested with a texture analyser to provide a detailed description of the structure. Different alginate samples could be clearly identified, and the M(mannuron)/G(guluron) acid ratios could be extrapolated quickly and easily from the test results if calibrated by NMR. This enables a fast and cost-effective characterisation of different alginates with regard to their composition and gel formation properties. [ABSTRACT FROM AUTHOR]

Abstract: Bio‐inspired layered ceramic‐polymer composites with high strength and toughness were prepared from sintered aluminum oxide ceramic sheets and cationically curing epoxy resins toughened with poly(ε‐caprolactone) (PCL). The architecture of the composite is inspired by nacre but is arranged on a larger scale. Ceramic sheets with a nominal thickness of 250 μm were assembled into composite plates by adhesive layers with a nominal thickness of 20 μm. Before the manufacturing of the composites, the stress‐strain properties of the polymer component were tailored by the variation in the PCL content between 0 and 39 wt%. For composites with 4 and 15 ceramic layers, the bending strengths achieved 327 MPa and 376 MPa, which are higher than that of pure ceramic sheets. Moreover, composites with 15 ceramic layers show a 16 times higher toughness compared to that of the pure ceramic sheets. The results indicate that the toughness of the layered composites increases significantly with the number of layers. Inspired by the geometrical ratio of the natural sheet composite nacre, we have achieved a similar strength but a 2 times higher toughness than nacre by only adding up to 6 vol% of the polymer. [ABSTRACT FROM AUTHOR]

A synthesis approach for multifunctional crosslinkable hyperbranched prepolymers with tailored degree of methylation and methacrylation with full conversion of all hydroxyl groups was investigated. Prepared by catalyzed esterification various methacrylate substitution degrees could be adjusted using predefined partially methylated polyglycerol-based precursors. The combination of methacrylic anhydride, triethylamine and 4-dimethylaminopyridine was proven to be beneficial for the esterification and full conversion of the remaining primary as well as secondary hydroxyl groups. NMR, IR and Raman spectroscopy were used to prove the insertion of methacrylic crosslinking groups in the polymeric backbone. The obtained prepolymers can be photopolymerized in bulk, while a higher methacrylate content leads to a higher crosslink density after UV curing resulting in higher stiffness and higher glass transition temperature. Atomistic model simulation clarified spatial structure of the crosslinked macromolecules and allowed T g predictions. Viscoelastic to ideal-viscous behaviour dominates in the obtained polymeric products with low network density. [Display omitted] • Methylated hyperbranched prepolymers with tailored degrees of methacrylation in a range of 5 and 26% with full conversion of hydroxyl groups. • Synthesis strategy for a targeted and adjustable methacrylation. • Beneficial combination of anhydride, auxiliary base, catalyst and inhibitor mixture. • Decreasing methacrylation resulted in a decrease in T g as well as mechanical stiffness after UV curing. [ABSTRACT FROM AUTHOR]

Highlights: [•] Direct measures are useful for isotopic signature of seepage. [•] Slow flow dripwater is representative of long residence time percolation. [•] Fast flow dripwater is representative of short residence time percolation. [•] Slow-flow dripwater is a good isotopic marker for seepage. [Copyright &y& Elsevier]

Abstract: The influence of partially crystalline polymeric diols on the morphology and mechanical properties of a cationically polymerized cycloaliphatic epoxy resin is described and significantly enhanced material properties were observed. In particular, poly(ε-caprolactone) (PCL) could be integrated covalently into the epoxy network leading to a toughened material with higher tensile strength and elongation at break combined with less brittleness and enhanced flexibility in the completely transparent thermosetting epoxy polymer. The PCL containing polymers were compared with polycarbonate containing epoxy polymers as rigid polyol phase. Scanning electron microscopy of samples broken below and above the glass transition temperature of PCL as well as above the melting point of PCL showed different fracture behavior of the elastified samples and an ordered morphology of the PCL in the epoxy matrix was observed. A distinct morphology known well from thermoplastic block-copolymers is formed in the prepared thermosetting polymers. [Copyright &y& Elsevier]

Abstract: Novel segmented and covalently crosslinked epoxy/poly(ɛ-caprolactone) (PCL) polymers, showing a shape memory effect are presented and characterized in this work. While a cationically polymerized cycloaliphatic epoxy resin form the required network to store the original shape for the shape recovery process in form of stresses in the deformed shape, we observed the formation of crystalline interactions of the PCL depending on its concentration in the crosslinked polymer. A minimum of PCL concentration is required to act as switchable phase and form crystalline interactions, required for the temporary shape fixation. The material properties of the epoxy/PCL polymers as well as the crystallization of the PCL and the shape memory characteristics are examined in this work. [Copyright &y& Elsevier]

Abstract: Due to optimised processing of epoxy based composite materials containing a low-melting organic–inorganic glass together with an organo clay, the size of the glass particles could be successfully reduced. Thus truly nano-dispersed composites were obtained, with glass particles in the range of 10nm to 200nm. The small particle size allowed efficient interaction of glass particles and organo clay layers. The flame retardancy as well as the thermo-mechanical properties were tested, and the results showed that the low-melting glass led to a remarkable reduction of peak heat release rate by forming an enhanced barrier layer. Nevertheless no further improvement could be achieved by lowering the particle size to the nanometre region. For good flame retardancy a microdispersion of the low-melting glass was already sufficient. [Copyright &y& Elsevier]

Abstract: The afterglow of an atmospheric pressure plasma has been used for the fast oxidative functionalization of multi-walled carbon nanotubes (MWCNTs). Scanning electron microscopy and Raman spectroscopy demonstrate that the MWCNT morphology is mostly preserved when the MWCNTs are dispersed in a solvent and injected as a spray into the plasma. Contact angle measurements show that this approach enhances the wettability of MWCNTs and reduces their sedimentation in an aqueous dispersion. X-ray photoelectron spectroscopy, IR spectroscopy, and electrokinetic measurements show that oxygen plasma incorporates about 6.6at.% of oxygen and creates mainly hydroxyl and carboxyl functional groups on the MWCNT surface. The typical effective treatment time is estimated to be in the range of milliseconds. The approach is ideally suited for combination with the industrial gas phase CVD synthesis of MWCNTs. [Copyright &y& Elsevier]

Abstract: A low-melting organic-inorganic glass with a high molecular weight soluble in solvents was synthesized by hydrolytic polycondensation of phenyltriethoxysilane followed by a subsequent heat treatment. Softening point and thermostability were strongly increased after heat treatment. The composites of glass/epoxy and glass/clay/epoxy were studied with respect to their thermal properties, fire behavior and mechanical properties. Heat release rate as measured by cone calorimetry was remarkably reduced in the presence of glass, relative to neat epoxy resin and polymer/clay composites. The combination of glass and clay is a promising approach. It showed mainly superposition and even synergistic effects in some fire properties for higher filler concentrations due to the formation of an enhanced barrier. The structure of residue was investigated by transmission electron microscopy (TEM). [Copyright &y& Elsevier]

Silicones are commonly used as sealants when high-performance materials are required due to harsh environmental conditions. To ensure a proper sealing function, the buildup of adhesion to the adherends is a prerequisite that is often addressed by the addition of adhesion promoters. However, the investigation of the fundamental adhesion mechanisms of silicones has been widely neglected. This work focuses on adhesive bond properties with aluminum adherends without the usage of adhesion promoters. The influence of high-temperature and high-humidity aging on the adhesive bond and material properties is examined. For this purpose, we formulated an addition curing silicone adhesive with a known composition. Aging took place for up to 56 d at different temperatures ranging from room temperature to 150 °C. In addition, we examined the influence of moisture by applying high-humidity conditions (85 °C/85% relative humidity). Changes in bulk material properties were characterized by stress at break, strain at break, Shore A hardness and swelling degree. Moreover, Fourier-transform infrared (FTIR) spectroscopy provided information about the chemical processes. The adhesive properties were determined using lap-shear joints. At high-temperature aging, the strain at break decreases while the hardness of the bulk material increases. A lower degree of swelling suggests an increasing cross-linking density. At the same time, lap-shear strengths increase and cohesive fracture patterns indicate a substantial buildup of adhesion. The samples aged under high-humidity conditions show a more complicated behavior. The increase in cross-linking density proceeds slower compared to high-temperature conditions (130 °C and 150 °C) but reaches higher values after 56 d. Lap-shear strengths tend to be lower compared to high-temperature storage and are accompanied by a significant amount of adhesive failure. FTIR spectroscopy reveals reactions of the residual hydrosiloxane groups of the cross-linking agent. However, these reactions are insufficient to fully explain the observed behavior. Therefore, reactions of the siloxane backbone are suggested. Although no specific adhesion promoters were used, high-temperature conditions enabled a substantial adhesion buildup of addition curing silicones on aluminum adherends under dry conditions. In contrast, humid conditions disturb adhesion buildup and are rather unfavorable for adhesion. [ABSTRACT FROM AUTHOR]

The development of new bone adhesives is severely restricted due to the lack of a standard test method to examine their bond strength. Therefore, this study presents an in vitro bone-to-bone adhesion test method based on a compression shear test using cortical bone specimens (35 × 15 × 3 mm). The zero-gap lap joint test configuration was used to measure the bonding strengths of two soft tissue adhesives (Histoacryl® and BSA-Glue) and a bone cement (Palacos® LV). For reproducible bonding results, it is crucial to work with specimen having reproducible surface, dimensions and where and how they were taken from a bone. Therefore, this is a focus of the work. The adhesive strengths were determined under dry and physiological conditions to evaluate the reliability of the test procedure. Furthermore, the influence of previous acid etching of the bone surface was also investigated. The adhesives achieved bond strengths of 5.5 MPa (Histoacryl®), 3.2 MPa (BSA-Glue) and 2.8 MPa (Palacos® LV) under dry conditions. Under physiological conditions, the measured adhesive strengths of all three bonding materials decreased by around 90%. The acid etching led to a higher presence of reactive amino groups on the bone surface and improved the adhesion of Histoacryl® and BSA-Glue. The Palacos® LV bone cement suffered a reduction in adhesion as the acid smoothened the bone surface, resulting in less mechanical interlocking. The proposed test method is based on known standards and enables the usability of medical adhesives as a bone adhesive to be evaluated in a reproducible manner. [ABSTRACT FROM AUTHOR]

In spite of many studies, knowledge about the fundamental factors influencing adhesion between addition curing silicones and aluminum substrates is very limited. The aim of this publication is to evaluate the influence of the formulation and the surface state of the adherend on bond strength. For this purpose, the composition of an addition curing silicone was systematically varied and the effects on both material and bond properties were examined. Additionally, the influence of surface aging at different humidities (0% r. h., 34% r. h., 82% r. h.) of acid etch pretreated aluminum substrates was considered. It is shown that the mechanical properties of the silicone material can be easily adjusted over a wide range by changing the formulation. Although high tensile strengths up to 9.2 MPa for the silicone material can be achieved, lap-shear strengths remain moderate at approximately 3.5 MPa. Predominant adhesive failures show the limited adhesive strength of the basic formulation without additives. Basic ingredients of addition curing silicones without additives are able to reach a certain adhesive strength. However, this strength was quite limited and adhesion promoters are required to further improve adhesion. The humidity at which the pretreated substrates are stored has an overall minor influence on bond strength. Surprisingly, bond strength tends to increase with the storage time of aluminum substrates despite lower surface energies in comparison to freshly pretreated substrates. All in all, the storage conditions of aluminum had a rather small influence on adhesion, whereas the composition of the silicone adhesive strongly influences bond strength. [ABSTRACT FROM AUTHOR]