Unreacted Groups Research Articles

Systematic evaluation of cyanate ester/ epoxidized cresol novolac copolymer resin system for high temperature power electronic packaging applications

The power electronics industry has been actively seeking high temperature stable epoxy molding compound (EMC) materials that can meet the requirements for encapsulating future SiC chips operating at a temperature (250 °C) that exceeds the capability of current epoxy chemistry. This work provides a detailed evaluation of a high heat resistant cyanate ester (CE)/epoxidized cresol novolac (ECN) copolymer system with varied compositions regarding their high temperature performances. Owing to the novolac nature of ECN which provides a high crosslink density, it is found that the copolymers with a low CE concentration (25–33 mol%) are able to produce a comparable glass transition temperature (>230 °C) and decomposition temperature (T10%>400 °C) to those of the high CE formulations. Moreover, long-term high temperature (250 °C) storage test of reveals a less severe weight loss and blistering in the lower CE formulations. A distinguished degradation mechanism involving hydrolysis of unreacted cyanate groups in the high CE compositions was determined through various thermal and chemical analyses. It was concluded that the CE/ECN copolymers with low CE concentrations are promising candidates for the high temperature EMC formulation.

Elimination of Unreacted Acrylate Double Bonds in the Polymer Networks of Microparticles Synthesized via Flow Lithography.

Flow lithography (FL), a versatile technique used to synthesize anisotropic multifunctional microparticles, has attracted substantial interest, given that the resulting particles with complex geometries and multilayered biochemical functionalities can be used in a wide variety of applications. However, after this process, there are double bonds remaining from the cross-linkable groups of monomers. The unreacted cross-linkable groups can affect the particles' biochemical properties. Here, we verify that the microparticles produced by FL contain a significant number of unreacted acrylate double bonds (UADBs), which could cause irreversible biochemical changes in the particle and pernicious effects to biological systems. We also confirm that the particles contain a considerable number of UADBs, regardless of the various synthetic (lithographic) conditions that can be used in a typical FL process. We present an effective way to eliminate a substantial amount of UADBs after synthesis by linking biochemically inert poly(ethylene glycol) based on click chemistry. We verify that eliminating UADBs by using this click chemistry approach can efficiently resolve problems, such as the occurrence of random reactions and the cytotoxicity of UADBs.

Conversion of an Injectable MMP-Degradable Hydrogel into Core-Cross-Linked Micelles.

In this study, a new type of injectable hydrogel called “HyMic” that can convert into core cross-linked (CCL) micelles upon exposure to matrix metalloproteinases (MMP’s), was designed and developed for drug delivery applications. HyMic is composed of CCL micelles connected via an enzyme cleavable linker. To this end, two complementary ABA block copolymers with polyethylene glycol (PEG) as B block were synthesized using atom transfer radical polymerization (ATRP). The A blocks were composed of a random copolymer of N-isopropylacrylamide (NIPAM) and either N-(2-hydroxypropyl)methacrylamide-cysteine (HPMA-Cys) or N-(2-hydroxypropyl) methacrylamide-ethylthioglycolate succinic acid (HPMA-ETSA). Mixing the aqueous solutions of the obtained polymers and rising the temperature above the cloud point of the PNIPAM block resulted in the self-assembly of these polymers into flower-like micelles composed of a hydrophilic PEG shell and hydrophobic core. The micellar core was cross-linked by native chemical ligation between the cysteine (in HPMA-Cys) and thioester (in HPMA-ETSA) functionalities. A slight excess of thioester to cysteine groups (molar ratio 3:2) was used to allow further chemical reactions exploiting the unreacted thioester groups. The obtained micelles displayed a Z-average diameter of 80 ± 1 nm (PDI 0.1), and ζ-potential of −4.2 ± 0.4 mV and were linked using two types of pentablock copolymers of P(NIPAM-co-HPMA-Cys)-PEG-peptide-PEG-P(NIPAM-co-HPMA-Cys) (Pep-NC) to yield hydrogels. The pentablock copolymers were synthesized using a PEG-peptide-PEG ATRP macroinitiator and the peptide midblock (lysine-glycine-proline-glutamine-isoleucine-phenylalanine-glycine-glutamine-lysine (Lys-Gly-Pro-Gln-Gly-Ile-Phe-Gly-Gln-Lys)) consisted of either l- or d-amino acids (l-Pep-NC or d-Pep-NC), of which the l-amino acid sequence is a substrate for matrix metalloproteases 2 and 9 (MMPs 2 and 9). Upon mixing of the CCL micelles and the linker (l/d-Pep-NC), the cysteine functionalities of the l/d-Pep-NC reacted with remaining thioester moieties in the micellar core via native chemical ligation yielding a hydrogel within 160 min as demonstrated by rheological measurements. As anticipated, the gel cross-linked with l-Pep-NC was degraded in 7–45 days upon exposure to metalloproteases in a concentration-dependent manner, while the gel cross-linked with the d-Pep-NC remained intact even after 2 months. Dynamic light scattering analysis of the release medium revealed the presence of nanoparticles with a Z-average diameter of ∼120 nm (PDI < 0.3) and ζ-potential of ∼−3 mV, indicating release of core cross-linked micelles upon HyMic exposure to metalloproteases. An in vitro study demonstrated that the released CCL micelles were taken up by HeLa cells. Therefore, HyMic as an injectable and enzyme degradable hydrogel displaying controlled and on-demand release of CCL micelles has potential for intracellular drug delivery in tissues with upregulation of MMPs, for example, in cancer tissues.

Precise Synthesis of a Homogeneous Thermoresponsive Polymer Network Composed of Four-Branched Star Polymers with a Narrow Molecular Weight Distribution

In this study, the synthesis of a star-shaped polymer with a narrow molecular weight distribution and subsequent formation of a homogeneous polymer network composed of the star-shaped polymer were realized by combining single-electron transfer living radical polymerization, click reaction, and amide bond formation with a condensing agent, which are toolized reactions. First, a 4-armed star polymer consisting of N-isopropylacrylamide was synthesized by living radical polymerization using N,N′-ethylenebis (2,2-dichloroacetamide) as a 4-branched initiator. By this polymerization method, a terminal Cl 4-branched star poly(N-isopropylacrylamide) (PNIPA) with a narrow molecular weight distribution could be obtained, but it was found that the reaction activity of the polymer terminal was lost in the process of purification and isolation. Therefore, after obtaining the terminal Cl 4-branched star PNIPA by living radical polymerization, an azide reaction was carried out in one pot without purification and isolation of the star-shaped polymer. As a result, the azide group was successfully introduced to all ends of the star-shaped polymer. By introducing a carboxyl group or an amino group into the 4-branched star polymer with azide groups using a click reaction, two types of 4-branched star polymers with different end groups were obtained. Equal amounts of both 4-branched star polymers were mixed at a polymer concentration equal to or higher than the overlapping concentration, and as a result of forming an amide bond with a condensing agent, a polymer gel was obtained. The swelling behaviors of the polymer gel indicate that almost no unreacted carboxyl group or amino group was present in the obtained polymer gel. That is, it was found that both 4-branched star polymers reacted efficiently to form a polymer network. In addition, structural observation of the polymer network by the small-angle X-ray scattering method showed that a polymer gel consisting of a network of uniform size was obtained. As mentioned above, we succeeded in constructing a polymer gel consisting of a homogeneous network structure using a temperature-responsive 4-branched star polymer as the building block. The living radical polymerization method, the click reaction, and the amide formation by condensation reaction used in this study can be applied not only to the NIPA used here but also to various other monomers. If the construction of a precise network structure is realized by many polymers and the relation with the functional expression derived from the structure is clarified, it will be possible to design the network structure in accordance with the usage of the polymer gel.

Microporous Bio-orthogonally Annealed Particle Hydrogels for Tissue Engineering and Regenerative Medicine.

Microporous annealed particle (MAP) hydrogels are an emerging class of biomaterials with the potential to improve outcomes in tissue repair and regeneration. Here, a new MAP hydrogel platform comprising poly(ethylene) glycol (PEG) hydrogel microparticles that are annealed in situ using bio-orthogonal tetrazine click chemistry is reported (i.e., TzMAP hydrogels). Briefly, clickable PEG-peptide hydrogel microparticles with extracellular matrix mimetic peptides to permit cell adhesion and enzymatic degradation were fabricated via submerged electrospraying and stoichiometrically controlled thiol-norbornene click chemistry. Subsequently, unreacted norbornene groups in the microparticles were leveraged for functionalization with bioactive proteins as well as annealing into TzMAP hydrogels via the tetrazine-norbornene click reaction, which is highly selective and proceeds spontaneously without requiring an initiator or catalyst. The results demonstrate that the clickable particles can be easily applied to a tissue-like defect and then annealed into an inherently microporous structure in situ. In addition, the ability to produce TzMAP hydrogels with heterogeneous properties by incorporating multiple types of hydrogel microspheres is demonstrated, first with fluorophore-functionalized hydrogel microparticles and then with protein-functionalized hydrogel microparticles. For the latter, tetrazine-modified alkaline phosphatase was conjugated to PEG hydrogel microparticles, which were mixed with nonfunctionalized microparticles and used to produce TzMAP hydrogels. A biomimetic mineralized/nonmineralized interface was then produced upon incubation in calcium glycerophosphate. Finally, platelet-derived growth factor-BB (PDGF-BB) and human periodontal ligament stem cells (PDLSC) were incorporated into the TzMAP hydrogels during the annealing step to demonstrate their potential for delivering regenerative therapeutics, specifically for periodontal tissue regeneration. In vitro characterization revealed excellent PDGF-BB retention as well as PDLSC growth and spreading. Moreover, PDGF-BB loading increased PDLSC proliferation within hydrogels by 90% and more than doubled the average volume per cell. Overall, these results demonstrate that TzMAP hydrogels are a versatile new platform for the delivery of stem cells and regenerative factors.

Enantioselective Copper-Catalyzed Borylative Cyclization with Cyclic Imides.

An enantioselective borylative cyclization cascade utilizing cyclic imides has been developed. We employ a highly enantioselective borylcupration process that includes a 1,2-addition to a cyclic imide. The products contain a valuable hemiaminal and boronate handle for further elaborations within a congested framework. This work demonstrates the utility of cyclic imides as simple precursors to unlock access to sought-after polycyclic indolines. Futhermore, this report highlights the capability to harness reactive catalytic intermediates to exploit otherwise unreactive functional groups.

A thermo-kinetic study on acrylic copolymer nanocomposite particles containing GMA-modified nanosilica prepared via miniemulsion polymerization

Silica/polyacrylic nanocomposite particles are the most attractive hybrid materials due to their outstanding physical and chemical properties. This paper deals with the chemical incorporation of glycidyl methacrylate-modified silica nanoparticles (GMA-modified SNPs) into acrylic copolymer through miniemulsion polymerization with a well dispersion. Fractional conversions and rate of polymerizations were investigated to study the role of GMA-modified SNPs on the polymerization kinetics by probable radical engagement. DSC analyses revealed some enhancement in Tg for the obtained polyacrylic nanocomposite particles because of the occurrence of limited chain flexibility. However, appearance of an exothermic peak above 90 °C in these thermograms was attributed to the possible radical generation by unreacted and trapped methacrylate groups of GMA on the surface of SNPs and their subsequent involvement in the progress of exothermic grafting reactions. Besides, the effect of GMA-modified SNPs on thermal degradation and thermo-oxidative stability of the prepared nanocomposites were evaluated by TGA. Storage modulus in the glassy and rubbery regions before and after thermal treatment were studied by DMTA and the results confirmed the above observations too.

On the Dielectric Behavior of Amine and Anhydride Cured Epoxy Resins Modified Using Multi-Terminal Epoxy Functional Network Modifier.

A range of modified amine- and anhydride-cured epoxy systems based upon diglycidyl ether of bisphenol A was produced, through the systematic incorporation of moieties termed functional network modifiers (FNMs) that serve to change the network structure in controlled ways. Here, the chosen FNM was trimethylolpropane triglycidyl ether (TTE). The resulting materials were characterized by Fourier transform infrared spectroscopy, thermal analysis, dielectric spectroscopy and measurements of direct current conduction. A progressive reduction in the glass transition temperature of the modified samples was seen with increasing TTE, which is interpreted in terms of changes in the network architecture of the resin. The molecular origins of the dielectric γ and β relaxation processes are proposed. The observed increase in conduction seen exclusively with increasing TTE content in the amine-cured systems is considered in terms of the chemistry of the FNMs, variations in free volume, changes in molecular dynamics and residual unreacted groups retained from the curing reaction. Specifically, we relate the observed increase in conduction to the presence of unreacted amine groups.

Thermal degradation of highly crosslinked rigid PU-PIR foams based on high functionality tall oil polyol

This study presents the development and analysis of rigid polyurethane-polyisocyanurate (PU-PIR) foam synthesized from high functionality tall oil (TO) based polyols. Three PU-PIR formulations with varied high functionality TO based polyol content (45, 75 and 95 pbw) and a different tier of isocyanate (NCO) indexes (110, 150, 200, 300 and 400) for each formulation were compared to a formulation developed using conventional raw materials, mainly obtained from petrochemicals. Using the Fourier transform infrared spectral analysis (FTIR), the chemical structure of the foams was evaluated with emphasis on the characteristic PU-PIR signal ratio and isocyanurate signal peaks. The thermal properties of the PU-PIR polymer matrix were characterized using the thermogravimetric analysis (TGA) method by comparing the thermal degradation temperatures at 5%, 25% and 50% and residual masses. Technological parameters and thermal degradation results indicate that TO is a suitable renewable resource for polyol in a rigid PU-PIR foam formulation, but the results from FTIR analysis suggest that a small optimization in the foam developing process is necessary due to an increasing amount of unreacted NCO groups in samples with the NCO index above 200.

Influence of boric acid on radial structure of oxidized polyacrylonitrile fibers

AbstractThe surface modification of polyacrylonitrile (PAN) fibers with boric acid was utilized to modulate the homogeneity of the radial structure of the PAN fibers during thermal stabilization. Exothermic peaks of the fibers were put off by boric acid, and unreacted nitrile groups of the oxidized PAN fibers increased with the boron content, indicating that boric acid on the fiber surface had an retardant effect on the thermal stabilization of PAN fibers. The relative skin thicknesses of the oxidized PAN fibers were quantitatively measured by sulfuric acid etching and SEM observation. The value increased obviously with the boron content, which could be further elevated by increasing stabilization time or decreasing stabilization temperature. Oxidized PAN fibers with more homogeneous radial structure can thus be obtained with the modification of boric acid, which might be beneficial for the preparation of high performance carbon fibers.

Functional Hyper-Crosslinked Polypyrene for Reductive Decolorization of Industrial Dyes and Effective Mercury Removal from Aqueous Media.

A rigid and valuable hyper-crosslinked polymer (HCP) has been synthesized from the polycyclic aromatic hydrocarbon pyrene: hyper-crosslinked polypyrene (HCPPy). HCPPy was prepared through a simple one-step Friedel-Crafts alkylation reaction that involves ZnBr2 -catalyzed crosslinking in the presence of an external crosslinker, bromomethyl methyl ether (BME). Interestingly, the unreacted bromomethyl groups (-CH2 Br) on the surface of HCPPy could be quantified, which later aided in modification as per our requirement. We aimed at modifying with disulfide-containing cystamine dihydrochloride (Cys-HCPPy). Cys-HCPPy exhibited an extended π-conjugated system with uniform (∼1 μm diameter) morphology and high porosity (specific surface area: 445 m2 g-1 ). As a fundamental application, the Cys-HCPPy composite was used as a sorbent to remove Hg2+ ions from aqueous media. Thus, at pH 6, the adsorption capacity for mercury ions reached 1124.82 mg g-1 after 24 h. Furthermore, the immobilization of Ag nanoparticles on the surface of Cys-HCPPy (Ag@Cys-HCPPy) enhanced the catalytic properties, which allowed for the reductive decolorization of industrial dyes such as methylene blue, methyl orange, and Congo Red in the presence of NaBH4 as a reducing agent.

Visible light induced one-pot synthesis of amphiphilic hyperbranched copolymers

Dimanganese decacarbonyl (Mn2(CO)10) and alkyl halide combination has unique visible light radical generating property which is useful in the fabrication of many complex macromolecular structures. Herein, we present a generic simple and rapid synthetic approach for the preparation amphiphilic hyperbranched macromolecular structures with controlled branching density and hydrophilicity. The method is based on the visible light induced self-condensing vinyl copolymerization of methyl methacrylate (MMA), 2-(2-bromoisobutryloxy)ethyl methacrylate (BIBEM) and poly(ethylene glycol) methyl ether methacrylate as monomer, inimer and hydrophilic comonomer, respectively, in the presence of Mn2(CO)10. The resulting polymers possess both hydrophobic and hydrophilic sequences offering many potential bio applications such as controlled drug delivery and release. Moreover, the resulting polymers contain also unreacted bromide groups in the final structure which allow postfunctionalization through copper(I)-catalyzed alkyne-azide cycloaddition “click” reactions.

Regulation of polar microenvironment on the surface of tertiary amines functionalized polyacrylonitrile fiber and its effect on catalytic activity in Knoevenagel condensation

Two fiber supported tertiary amine catalysts were prepared by immobilization of 3-dimethylamino-1-propylamine (PANDF) and 3-dimethylamino-N-methylpropylamine (PANTF) on polyacrylonitrile fiber. Both fiber catalysts contain polar microenvironments constructed by amide groups, tertiary amine groups and unreacted cyano groups. The difference between the two catalysts lies in that the PANDF contains hydrogen bond network while the PANTF does not. Employing Knoevenagel condensation as a model reaction, the cooperative action of immobilized tertiary amines with hydrogen bonds was evaluated in detail. At the same time, the aggregation of reactants in the polar microenvironment under different solvents was also investigated. The results showed that hydrogen bonds and the supporting basic groups can promote the reaction by the synergistic catalytic effect in most solvents. The catalysts displayed different catalytic behaviors in solvents with different polarities. The catalysts can achieve highly efficient catalytic activity in the more polar solvents which were well compatible with the catalysts. Moreover, the reaction can also occur in less polar solvents due to their incompatible property with the fiber catalysts, which can compel the polar reactants to accumulate on the fiber surface with strong polar microenvironment.

Hyper-Cross-Linked Polyacetylene-Type Microporous Networks Decorated with Terminal Ethynyl Groups as Heterogeneous Acid Catalysts for Acetalization and Esterification Reactions.

Heterogeneous catalysts based on materials with permanent porosity are of great interest owing to their high specific surface area, easy separation, recovery, and recycling ability. Additionally, porous polymer catalysts (PPCs) allow us to tune catalytic activity by introducing various functional centres. This study reports the preparation of PPCs with a permanent micro/mesoporous texture and a specific surface area SBET of up to 1000 m2 g-1 active in acid-catalyzed reactions, namely aldehyde and ketone acetalization and carboxylic acid esterification. These PPC-type conjugated hyper-cross-linked polyarylacetylene networks were prepared by chain-growth homopolymerization of 1,4-diethynylbenzene, 1,3,5-triethynylbenzene and tetrakis(4-ethynylphenyl)methane. However, only some ethynyl groups of the monomers (from 58 to 80 %) were polymerized into the polyacetylene network segments while the other ethynyl groups remained unreacted. Depending on the number of ethynyl groups per monomer molecule and the covalent structure of the monomer, PPCs were decorated with unreacted ethynyl groups from 3.2 to 6.7 mmol g-1 . The hydrogen atoms of the unreacted ethynyl groups served as acid catalytic centres of the aforementioned organic reactions. To the best of our knowledge, this is first study describing the high activity of hydrogen atoms of ethynyl groups in acid-catalyzed reactions.

Competing Reactions of Vinyl and Hydroxyl Groups of Vinyl Alcohol on Ge(100): Effects of Vinyl Substituent on Dissociative Adsorption

We investigated the adsorption of vinyl alcohol onto Ge(100) surface by performing density functional theory calculations. The C–O dissociative adsorption of vinyl alcohol produces two fragments, a hydroxyl group and a vinyl group, each of which bonds with a different germanium atom. The dissociated vinyl and hydroxyl groups passivate the dangling bonds of surface germanium atoms to form the most stable configurations containing HO–Ge–Ge–CH═CH2 linkages. The reactions of the C═C bond of the vinyl group can generate enantiomer products with characteristic stereochemistry. The cycloaddition of the vinyl group is not favored thermodynamically, although paired adsorption at an adjacent site can stabilize cycloaddition structures. Our kinetic study reveals that the C–O dissociative adsorption has a larger activation barrier than O–H dissociative adsorption, although the transition state energy is close to that of the reactants. According to our analysis of the kinetics and thermodynamics of this system, the C–O dissociative adsorption, which produces an unreacted vinyl group perpendicular to the germanium surface, is a major reaction at room temperature. Our simulated images of the stable adsorption structures show the characteristic electronic density features of the functional groups.

Critical transition of epoxy resin from brittleness to toughness by incorporating CO2-sourced cyclic carbonate

A five-membered cyclic carbonate as CO2-sourced monomer was prepared from ethylene glycol diglycidyl ether (EGDE) with CO2 by cycloaddition reaction, abbreviated as 5CC-EGDE, at 130 ℃ under 10 bar CO2 pressure in the presence of quaternary ammonium salt modified amberlyst (D296) for 20 h. The complete conversion and 98.6% selectivity were obtained, respectively. The incorporation of 5CC-EGDE into epoxy resin could reduce the viscosity during preparation process and improve the toughness effectively. It was ascribed to the ring-opening reaction of 5CC-EGDE with curing agent, and hydrogen bonding, formed between urethane groups and other polar groups. Besides, the low crosslinking density and unreacted carbonate groups remaining in epoxy network were beneficial to the movement of molecular chains and dissipation of energy during deformation process. In addition, effects of hydrogen-bonding interactions and crosslinking density on mechanical performances were also investigated by varying EGDE conversion and amount of added curing agent, respectively. The results indicated that mechanical performances of epoxy resin were promoted by combined effects of urethane linkage, hydrogen bonding, low crosslinking density and unreacted carbonate groups.

Consequences of chitosan decomposition by nitrous acid: Approach to non-branched oligochitosan oxime

It is well known that chitosan degradation by nitrous acid leads to oligochitosan (oligoCHIt–ahm) bearing reactive 2,5-anhydromannose (3,4-dihydroxy-5-hydroxymethyl-tetrahydrofuran-2-aldehyde) units at the new reducing ends of macromolecules. Standard protocol requires reduction of oligoCHIt–ahm with NaBH4 to corresponding oligoCHIt–hml bearing unreactive hydroxymethyl group instead of reactive aldehyde group. For the first time, HP SEC as well as UV and CD spectroscopy methods have revealed that the reduction leads to an indefinite side modification and the formation of a branched oligoCHIt-hml with increased molecular weight. Here, it is shown that the branching and modification can be prevented by means of the simple and reproducible reaction of oligoCHIt–ahm with hydroxylamine that allows preparation of a stable linear oligochitosan oxime, oligoCHIt–oxm. Cytotoxicity tests show that oligoCHIt–ahm, oligoCHIt–hml and oligoCHIt–oxm are non-toxic at concentration below 2.5 mg/ml, and the cytotoxicity is concentration dependent and decreases in the order oligoCHIt–ahm > oligoCHIt–hml > oligoCHIt–oxm at higher concentrations both before and after long shelf-storage. The elaborated approach and cytotoxicity data give an opportunity to use the non-branched oligoCHIt–oxm for biomedical applications.

An immunosensor for parasite lactate dehydrogenase detection as a malaria biomarker – Comparison with commercial test kit

This paper describes the development of an affinity sensor for the detection of Plasmodium falciparum parasite lactate dehydrogenase (pLDH) as one of the biomarkers used for malaria detection. The gold sensor was functionalised with anti-pLDH after cleaning the electrode surface to remove impurities (120 °C, 1 h). The sensor was then treated to block unreacted groups on the surface and minimise matrix interference, before applying it in a sandwich assay to detect pLDH in buffer samples using a dose concentration assay. The sensor was optimised to achieve the best detection sensitivity before using it for pLDH detection in serum samples. The developed sensor achieved a limit of detection (LOD) of 1.80 ng mL−1 and 0.70 ng mL−1 for the detection of pLDH in buffer and in serum samples respectively. The sensor sensitivity was enhanced further with the use of AuNP conjugated to the detection anti-pLDH-enzyme, achieving an LOD of 19 pg mL−1 in buffer and 23 pg mL−1 in serum samples. The performance of the sensor was compared to commercially available Plasmodium immunochromatographic (ICT) malaria kits. The developed sensor was able to detect pLDH in the Dd2luc culture medium supernatant at 0.002% parasitaemia without the use of AuNP signal enhancement when compared to the OptiMAL-IT ICT kit (detect pLDH) and the BinaxNOW ICT kit (detection of both pLDH and PfHRP 2) samples. Therefore, the sensor developed in this work is highly sensitive and can be used for pLDH detection for on-site diagnosis of malaria. A cheap and simple device as developed in this work is required to tackle malaria detection.

Novel hydrogels based on a high‐molar‐mass water‐soluble dimethacrylate monomer

AbstractThis report describes the preparation and swelling behaviour of novel hydrogels based on a water‐soluble dimethacrylate monomer (EBisEMA), which is characterized by a relatively high molar mass (Mn ∼ 1700 g mol−1) and contains a high proportion of aliphatic ether bonds in its structure. This feature results in moderately crosslinked and flexible polymer networks. Significant differences were observed in degree of swelling, depending on the synthesis method employed to obtain the hydrogels. The equilibrium water sorption of EBisEMA photopolymerized in bulk was 68 wt% while that of EBisEMA photopolymerized in aqueous solution (0.5 g mL−1) was 104 wt%. Thiol–methacrylate hydrogels were prepared by visible light photopolymerization of EBisEMA with a tetrafunctional thiol (PETMP) at various EBisEMA‐to‐PETMP molar ratios. These hydrogels contained unreacted thiol groups because of a faster homopolymerization reaction of EBisEMA. Hydrogels were also prepared in bulk by propylamine‐catalysed Michael addition reaction. No significant differences in swelling were observed between EBisEMA homopolymer and photocured EBisEMA–PETMP copolymer. Conversely, a marked increase in water uptake (110 wt%) was observed in the EBisEMA–PETMP hydrogels prepared by the Michael addition reaction catalysed by propylamine. These trends are explained in terms of a balance between the mass fraction of hydrophilic groups and the crosslinking density of the network. EBisEMA–PETMP hydrogels formulated with thiol in excess showed a noticeable tendency to adhere to diverse substrates, including paper, metals, glass and skin. This feature makes them especially attractive in applications for which adhesion is particularly critical such as dermatological patches. © 2018 Society of Chemical Industry

Sequential alkyne-azide cycloadditions for functionalized gelatin hydrogel formation

While click chemistry reactions for biopolymer network formation are attractive as the defined reactions may allow good control of the network formation and enable subsequent functionalization, tailoring of gelatin network properties over a wide range of mechanical properties has yet to be shown. Here, it is demonstrated that copper-catalyzed alkyne-azide cycloaddition of alkyne functionalized gelatin with diazides gave hydrogel networks with properties tailorable by the ratio of diazide to gelatin and diazide rigidity. 4,4′-diazido-2,2′-stilbenedisulfonic acid, which has been used as rigid crosslinker, yielded hydrogels with Young’s moduli E of 50–390 kPa and swelling degrees Q of 150–250 vol.%, while the more flexible 1,8-diazidooctane resulted in hydrogels with E = 125–280 kPa and Q = 225–470 vol.%. Storage moduli could be varied by two orders of magnitude (G′ = 100–20,000 Pa). An indirect cytotoxicity test did not show cytotoxic properties. Even when employing 1:1 ratios of alkyne and azide moieties, the hydrogels were shown to contain both, unreacted alkyne groups on the gelatin backbone as well as dangling chains carrying azide groups as shown by reaction with functionalized fluorescein. The free groups, which can be tailored by the employed ratio of the reactants, are accessible for covalent attachment of drugs, as was demonstrated by functionalization with dexamethasone. The sequential network formation and functionalization with click chemistry allows access to multifunctional materials relevant for medical applications.