Crosslinking-Dependent Drug Kinetics in Hydrogels for Ophthalmic Delivery

Drug-diffusion kinetics in 2-hydroxyethyl methacrylate hydrogels were studied as a function of the crosslinking density and porosity. By varying the concentration of the crosslinker, tetraethylene glycol dimethacrylate, we demonstrated how the release of Timolol maleate could be optimized to allow for efficient drug delivery. FTIR and spectrophotometry supplied optical inferences into the functional groups present. By studying the swelling and degradation of hydrogels, supplemented with drug-release kinetics studies, the relationship between these two tenets could be formulated.

Enhancing the physico-mechanical properties of ethylene propylene diene monomer rubber via ץ-radiation in the presence of bi-functional and tri-functional monomers

This study, uses two polyfunctional monomers (PFMs) namely ethylene glycol dimethacrylate (EGDMA) as a bifunctional monomer and trimethylolpropane triacrylate (TMPTA) as a trifunctional monomer were used as co-agents in irradiation crosslinking of Ethylene Propylene Diene Monomer Rubber (EPDM). The effect of concentration of each PFM and irradiation dose on the crosslinking density, gel content, swelling behavior in motor and brake oils, in addition to the mechanical and thermal stability properties of EPDM was investigated in detailed. The results showed a remarkable increase in the gel content, crosslinking density and mechanical properties as the concentration of PFMs increased from 1 to 5 phr (parts per hundred parts of rubber). The various blends of EPDM with the trifunctional monomer express the highest gel content and crosslinking density than those with the bifunctional monomer. The addition of 5 phr of TMPTA to EPDM causes a dramatic improvement in tensile strength (TS) of the prepared blend reached to 188% compared to neat EPDM at 50 kGy. At the same time, the maximum TS of the blend containing 5 phr of EGDMA achieved only 41% compared to neat EPDM at an irradiation dose of 100 kGy. The swelling of irradiated samples in brake oil revealed a stronger oil resistance than motor oil. For all irradiated samples, the oil uptake decreased with the irradiation dose up to 100 kGy. The EPDM samples containing 5 phr of TMPTA recorded the highest oil resistance at 100 kGy. The results also showed that the addition of PFMs and irradiation treatment of the various prepared blends improved the thermal stability of EPDM. Finally, neat EPDM and the blends containing 1 and 3 phr of EGDMA can be used as radiation dosimeters in the very high dose range (50–200 kGy).

Synthesis and characterization of new biodegradable gels based on 2,2 '-(ethylenedioxy) diethanethiol and pentaerythritol triacrylate

The work is devoted to the synthesis and characterization of gels based on the monomers pentaerythritol triaacrylate (PETriA) and 2,2 '-(ethylenedioxy)diethanethiol (EDODET) by thiol-ene "click" polymerization. The properties of the obtained gels were investigated by IR, Raman spectroscopy, mechanical analysis. Sol-gel analysis of obtained networks was carried out and the degradability was investigated. The results of IR spectroscopy confirmed the presence of -C = O and -C-O-C- groups in the composition of the obtained gels. The presence of unreacted C = C bonds conjugated with C = O, as well as thiol groups, varies depending on the composition of the initial monomer mixture (IMM). Raman spectroscopy results correlate well with IR data. Raman spectra also show C-S, S-S and SH characteristic bands that are difficult to identify by IR spectroscopy. It was found that the composition of MM affects the physicochemical properties of the synthesized gels. The highest yield of the gel fraction of obtained polymers was found in samples with an equimolar composition of IMM. The analysis of mechanical properties showed that gels with an excess of PETriA exhibit more elastic properties, and an excess of EDODET leads to the formation of networks with a higher crosslinking density. The study of the ability of obtained PETria-EDODET gels to degrade in a 3% solution of hydrogen peroxide showed that the polymer network degrades by 12% within 60 days. This property of the obtained gels can find application in the creation of targeted drug delivery systems with their prolonged release.

Study on tri-imidazole derivatives modified with triazine-trione structure as latent curing agents for epoxy resin

In this paper, four novel kinds of triazine-trione based tri-imidazole derivatives (IM-TT, 2MI-TT, 2EI-TT and EMI-TT) were synthesized through the addition reaction between triglycidyl isocyanurate (TGIC) and imidazole (IM), 2-methylimidazole (2MI), 2-ethylimidazole (2EI) and 2-ethyl-4-methylimidazole (EMI), respectively. The triazine-trione based tri-imidazole derivatives were blended with epoxy resin and the reactivity, thermal latency and thermal property were investigated. The results on curing behaviors indicated that the curing exothermic peaks of the blends with triazine-trione based tri-imidazole derivatives shifted to higher temperatures compared with those with commercial imidazoles. The curing exothermic peak temperatures (Tps) of the synthesized tri-imidazole derivatives were increased by 23–32 ℃ compared with the unmodified imidazoles. In addition, Rheological behavior results indicated that the EP blends with tri-imidazole derivatives also exhibited excellent storage stability which was as long as 38 days under room temperature. Last but not the least, the EP blends with triazine-trione based tri-imidazole derivatives also exhibited high glass transition temperatures due to introducing of triazine-trione structures with high crosslinking density. The glass transition temperatures (Tgs) of the prepared thermosets ranged from 128 to 152 ℃. The triazine-trione based tri-imidazole derivatives provide a way to prepare latency epoxy resin with high high glass transition temperature and long storage stability. Article Highlights Four novel kinds of triazine-trione based tri-imidazole derivatives were synthesized. The EP cured with the tri-imidazole derivatives displayed great thermostability. The EP cured with the tri-imidazole derivatives exhibited long storage stability.

Synthesis of Biobased and Hybrid Polyurethane Xerogels from Bacterial Polyester for Potential Biomedical Applications

Organic–inorganic xerogel networks were synthesized from bacterial poly (3-hydroxybutyrate) (PHB) for potential biomedical applications. Since silane-based networks usually demonstrate increased biocompatibility and mechanical properties, siloxane groups have been added onto polyurethane (PU) architectures. In this work, a diol oligomer (oligoPHB-diol) was first prepared from bacterial poly(3-hydroxybutyrate) (PHB) with an environmentally friendly method. Then, hexamethylene diisocyanate or biobased dimeryl diisocyanate was used as diisocyanate to react with the short oligoPHB-diol for the synthesis of different NCO-terminated PU systems in a bulk process and without catalyst. Various PU systems containing increasing NCO/OH molar ratios were prepared. Siloxane precursors were then obtained after reaction of the NCO-terminated PUs with (3-aminopropyl)triethoxysilane, resulting in silane-terminated polymers. These structures were confirmed by different analytical techniques. Finally, four series of xerogels were prepared via a sol–gel process from the siloxane precursors, and their properties were evaluated depending on varying parameters such as the inorganic network crosslinking density. The final xerogels exhibited adequate properties in connection with biomedical applications such as a high in vitro degradation up to 15 wt% after 12 weeks.

Designing polymer coatings for lithium metal protection

Protection of lithium metal has been one of the great challenges to realize a long-life, high-energy-density battery. Polymer coatings on lithium metal surface have been proven to be an effective protection method in terms of improved morphology, higher coulombic efficiency, and a longer cycle life. However, there is a variety of design principles of polymer coatings proposed by the research community, and the influence of polymer swelling in liquid electrolytes remains poorly understood. Herein we use crosslinking density and solvent–polymer interaction to quantitatively explain the mechanical property and the ion-transport property of polymer coatings when swollen in liquid electrolytes. Low crosslinking density is beneficial for reducing the rigidity and enhancing the viscosity of the polymer. Ion conductivity increases with the swelling ratio, and activation energy of lithium-ion transport increases in a polar polymer with strong ion–polymer coupling. We propose that polymer coatings must be combined with the emerging electrolytes with unconventional solvent compositions to realize a practical high-performance lithium metal battery. This study can provide design guidelines for polymer coatings through the optimized interactions with upcoming high-performance electrolytes.

Polybutadiene Vitrimers with Tunable Epoxy Ratios: Preparation and Properties

Traditional crosslinked diene rubber has excellent thermal–mechanical properties and solvent resistance, yet it is incapable of being recycled via universal molding or injecting. Vitrimers, a new class of covalently crosslinked polymer networks, can be topologically rearranged with the associative exchange mechanism, endowing them with thermoplasticity. Introducing the concept of vitrimers into crosslinked networks for the recycling of rubbers is currently an attractive research topic. However, designing tailored rubber vitrimers still remains a challenge. Herein, polybutadiene (PB) vitrimers with different structures were prepared via partial epoxidation of double bonds and ring-opening esterification reactions. Their mechanical and relaxation properties were investigated. It was found that the increasing crosslinking density can increase tensile strength and activation energy for altering the network topology. The influence of side-group effects on their relaxation properties shows that an increase in the number of epoxy groups on the polybutadiene chain can increase the chance of an effective exchange of disulfide units. This work provides a simple network design which can tune vitrimer properties via altering the crosslinking density and side-group effects.

Internal Polymerization of Epoxy Group of Epoxidized Natural Rubber by Ferric Chloride and Formation of Strong Network Structure

In this work, studies are carried out to understand the crosslinking reaction of epoxidized natural rubber (50 mol% epoxy, ENR-50) by metal ion namely ferric ion (Fe3+, FeCl3, ferric chloride). It is found that a small amount of FeCl3 can cure ENR to a considerable extent. A direct interaction of the ferric ion with the epoxy group as well as internal polymerization enable the ENR to be cured in an efficient manner. It was also found that with the increased concentration of FeCl3, the crosslinking density of the matrix increased and therefore, the ENR offers higher mechanical properties (i.e., modulus and tensile strength). In addition, the glass transition temperature (tg) of ENR vulcanizate is increased with increasing concentration of FeCl3. Moreover, the thermal degradation temperature (Td) of the ENR-FeCl3 compound was shifted toward higher temperature as increasing concentration FeCl3.

Tandem Osmotic Engine Based on Hydrogel Particles with Antipolyelectrolyte and Polyelectrolyte Effect Fuelled by Both Salinity Gradient Modes

In this study, we propose a new approach to attain energy by salinity gradient engines with pistons based on hydrogels possessing polyelectrolyte and antipolyelectrolyte effects in a tandem arrangement, providing energy in each salinity gradient mode in a repeatable manner. The swelling of hydrogel with a polyelectrolyte effect and shrinking of hydrogel particles possessing an antipolyelectrolyte effect in desalinated water, and subsequent shrinking of hydrogel with polyelectrolyte and swelling of hydrogel antipolyelectrolyte effect in saline water, generate power in both increasing and decreasing salinity modes. To investigate the energy recovery, we scrutinized osmotic engine assemblies by a setup arrangement of pistons with hydrogel particles, with polyelectrolyte and antipolyelectrolyte effects, in tandem. The energy recovery from the tandem engine setup (calculated based on dry form for each polyelectrolyte polyacrylate-based hydrogel-SPA) and antipolyelectrolyte–sulfobetaine-based gel with methacrylate polymeric backbone-SBE) up to 581 J kg−1 and a mean power of 0.16 W kg−1 was obtained by the tandem setup of SPA and SBE hydrogel containing 3% crosslinking density and particle size of 500 microns with an external load of 3.0 kPa. Exchange of sulfobetaine with methacrylamide (SBAm), the main polymer backbone, revealed a positive increase in energy recovery of 670 J kg−1 with a mean power of 0.19 W kg−1 for the tandem system operating under the same parameters (SPA@SBAm). The energy recovery can be controlled, modulated and tuned by selecting both hydrogels with antipolyelectrolyte and polyelectrolyte effects and their performing parameters. This proof of concept provides blue energy harvesting by contributing both polyelectrolyte and antipolyelectrolyte effects in a single tandem setup; together with easy accessibility (diaper-based materials (SPA)) and known antibiofouling, these properties offer a robust alternative for energy harvesting.

Molecular dynamics simulations of mechanical properties of epoxy-amine: cross-linker type and conversion degree effects

In this work, molecular dynamics (MD) simulations are conducted to study the thermo-mechanical properties of a family of thermosetting epoxy-amine. The crosslinked epoxy resin EPON862 with a series of cross-linkers are built and simulated under the polymer consistent force-field (PCFF). Three types of curing-agents (rigidity1,3-phenylenediamine (1,3-P), 4,4-diaminodiphenylmethane (DDM), and phenol-formaldehyde-ethylenediamine (PFE)) with different number of active sites are selected in the simulations. We focus on the effects of the cross-linkers on thermo-mechanical properties such as density, glass transition temperature (T g), elastic constants, and strength. Our simulations show a significant increase in T g, Young’s modulus and yield stress with the increase of conversion degree. The simulation results revealed that the mechanical properties of thermosetting polymers are strongly dependent on the molecular structures of cross-linker and network topological properties, such as end-to-end distance, crosslinking density and conversion degree.