An efficient strategy for engineering nanostructured surfaces by coupling soft polymeric nanoarchitectures to functionalized surfaces is presented. Self‐assembly of polymeric nanoarchitectures from amphiphilic triblock copolymers can yield both filled and hollow spherical nanoarchitectures, depending on the properties of the polymer chosen. These nanoarchitectures are immobilized on solid substrates via a biocompatible thiol–ene reaction, and conditions are optimized to maintain structural integrity of polymeric assemblies. Two routes of surface modification are also implemented to allow inclusion of a polymeric spacer that can mediate between soft polymeric assemblies and solid substrates. Nanostructured surfaces with both filled and hollow nanoarchitectures attached to the surface directly or with a spacer are successfully generated with this protocol. This concept of generating nanostructured surfaces using preassembled polymeric architectures is an important step toward active surfaces, because entrapment of active molecules in the nanoarchitectures prior to their immobilization opens the door to easy generation of surfaces with predetermined activities.
The assembly of natural and synthetic polymers into fibrous nanomaterials has applications ranging from textiles, tissue engineering, photonics, and catalysis. However, rapid manufacturing of these materials is challenging, as the state of the art in nanofiber assembly remains limited by factors such as solution polarity, production rate, applied electric fields, or temperature. Here, the design and development of a rapid nanofiber manufacturing system termed pull spinning is described. Pull spinning is compact and portable, consisting of a high‐speed rotating bristle that dips into a polymer or protein reservoir and pulls a droplet from solution into a nanofiber. When multiple layers of nanofibers are collected, they form a nonwoven network whose composition, orientation, and function can be adapted to multiple applications. The capability of pull spinning to function as a rapid, point‐of‐use fiber manufacturing platform is demonstrated for both muscle tissue engineering and textile design.
Conductive textiles with exceptional electrical properties have been prepared by coating the conjugated polymer, poly(3,4‐ethylenedioxyphiophene)‐polystyrenesulfonate(PEDOT‐PSS), on polyethylene terephthalate (PET) nonwoven fabrics. Phase segregation from covalent bond formation to surface silica particles generates PEDOT‐PSS coated textiles that hold potential for wearable electronics due to the breathability of the fabric, low toxicity, easy processing and lightweight with high current carrying capacity. The conductive textiles were demonstrated for applications such as electrical connections and resistive heating.
The N‐containing conjugated microporous polymers (CMPs) are synthesized by 2,5‐dibromopyrazine or its isomeric pyridazine monomer and 1,3,5‐triethynylbenzene via the Pd(0)/Cu(I)‐catalyzed Sonogashira–Hagihara cross‐coupling polycondensation. The resulting CMPs exhibit diverse porosity and morphology, which reveals macroscopically porous 3D networks for BQCMP‐1, agglomerated and amorphous structure for DQCMP‐1, arising from the variation of isomeric monomer. In addition, metal ions adsorption capacity of Zn(II), Cr(VI), Ni(II) have been investigated due to the good porosity of CMPs. Compared with Zn(II) and Cr(VI), the adsorption capacity of Ni(II) for BQCMP‐1 and DQCMP‐1 is maximal, which is 272 mg g?1 and 559 mg g?1. Our study may provide a useful guidance to manipulate CMPs by varying the constitution of isomeric monomer.
The polycondensation of sebacic acid with glycerol leads to the obtaining of poly(glycerol sebacate), a tough biocompatible polymer, which exhibits shape memory properties. Due to its low glass transition and melting temperatures, the temporary shape has to be kept below room temperature. In this study, the goal is to control the melting of the polyester by adding various amount of stearic acid into the synthesis in order to store the deformed material at room temperature. The reaction is carried out with microwave heating at 180 °C until a gel is obtained. The molar ratio of sebacic acid/glycerol is fixed to 1, while the molar ratio of stearic acid/glycerol varies between 0 and 0.5. The use of a molar ratio of 0.5 leads to the obtaining of materials having a melting temperature of 29 °C able to keep their temporary shape substantially at room temperature and to recover their initial shape in water bath at 37 °C by 85%.
Polymerization shrinkage of dental composites remains a major concern. Free‐radically polymerizable cyclic monomers can be a conceivable alternative to methacrylates for the development of low‐shrinkage composites. In this study, the one‐step synthesis of the novel low viscosity difunctional vinylcyclopropanes 1 – 4 is described. Photopolymerization kinetics of these monomers are investigated by photo‐differential scanning calorimeter, using bis(4‐methoxybenzoyl)diethylgermane as photoinitiator. Real‐time near‐infrared photorheology measurements are performed to evaluate rheological behavior (i.e., time of gelation, polymerization‐induced shrinkage force) and chemical conversion (i.e., double bond conversion at the gel point, final double bond conversion) of the vinylcyclopropanes in situ. The potential of these monomers as reactive diluents in dental restorative materials is evaluated. Composites based on vinycyclopropanes 1 – 4 show good mechanical properties and exhibit significantly lower volumetric shrinkage and shrinkage stress than corresponding dimethacrylate‐based materials. The results indicate that such monomers are promising candidates for the replacement of commonly used low viscosity dimethacrylates such as triethylene glycol dimethacrylate in dental composites.
Visible light curing of photopolymers has gained increasing interest in recent years. Dental materials are one of the important areas of application, where the bimolecular camphorquinone/amine initiator system is currently state of the art initiator. In this study, the authors describe the synthesis and photochemistry of tetrakis(2,4,6‐trimethylbenzoyl)silane, as cleavable Type I visible light photoinitiator. Besides excellent photobleaching behavior, this photoinitiator can well compete with up to now used long wavelength initiators.
The rise in resistant bacteria strains worldwide is proving to be a challenge to the healthcare industry. These “superbugs” are emerging faster than the rate of new antibiotic discovery. This has a heavy impact on medical devices as they are susceptible to biofilm production. Antimicrobial resistance (AMR) causes infections to be difficult to treat, especially postimplantation of a medical device. To prevent bacterial adhesion on devices, various types are coatings are introduced. By binding antibiotics to polymers, an effective adhesive coating on the surface can be created. However, with AMR on the rise, these polymers are losing their efficacy in the application. Another class of antimicrobial polymers with a different mode of mechanism will be explored in this project. Biocidal polymers are effective antimicrobial agents as they rely on the electrostatic interactions between the polymeric charged groups and the charged microbial membrane. Polyethylenimine (PEI) can be modified to achieve a macromolecule containing various charged cationic groups. Quaternizing low‐molecular‐weight PEI with different alkyl groups of short, long, and aromatic groups will give rise to various structural differences. The structure of the quaternized PEI is characterized, and its antimicrobial activity and compatibility are shown to be remarkably improved.
Preparation of novel nanocomposite hydrogels opens up new avenues to next generation of biocompatible materials to be used in bioengineering and drug delivery. Toward this goal, chitosan nanocomposite hydrogels using click chemistry inspired cross‐linking are prepared. To enable this, Diels–Alder reaction of furan‐containing chitosan and maleimide‐coated gold nanoparticles is employed. The viscoelastic properties of the obtained nanocomposites as well as the effect of the nanoparticles as cross‐linkers are studied, indicating that they play significant role in hydrogel formation and stability. Nanoparticle‐enriched hydrogels are also found to demonstrate pH‐sensitivity therefore showing their potential for future biosensing applications.
This study deals with the investigation of photocurable thiol‐yne resins covering several important aspects for the production of medical devices by UV‐based manufacturing processes. In this context, the performance of different low‐toxic photoinitiators (PIs) and stabilizers are evaluated in thiol‐yne formulations based on di(but‐1‐yn‐4‐yl) carbonate and various multifunctional thiol monomers. Photodifferential scanning calorimetry measurements reveal that the conversion of all resin formulations is mostly independent on the type and concentration of the applied photoinitiator; however, significant differences in their curing speed are observed. It turns out that the migration of an alkyne derivatized photoinitiator is significantly reduced while providing almost similar photoactivity as its nonfunctionalized reference. Moreover, it is found that lauryl gallate and butylated hydroxytoluene lead to significant stabilization without affecting the overall photoreactivity. Notably, the thermomechanical properties of the investigated photopolymers are only slightly affected by water absorption. Using ester free thiols, water absorption can be reduced and hydrolytically stable polymers are realized. These results highlight the versatility of the present thiol‐yne system for the production of medical materials by photopolymerization.
Hybrid organic–inorganic membranes based on sulfonated poly(ether ether ketone) (sPEEK), zirconium oxide, and the protic ionic liquid (PIL) diethylmethylamine triflate ([dema][TfOH]) have been synthesized. Their structure has been investigated by X‐ray diffraction and small‐angle X‐ray scattering and correlated to their electrical and thermomechanical properties. The membranes present good mechanical and chemical stabilities, as well as thermal stability over 300 °C. Zirconia contents up to 5 wt% (10 wt% PIL) lead to the formation of isolated zirconia‐rich aggregates dispersed in the polymer matrix, constituted of spatially correlated zirconia nanoparticles. This segregation of zirconia species in nanodomains, interacting with sulfonic groups of sPEEK, inhibits conductivity. Differently, zirconia content of 6 wt% (10 wt% PIL) induces a conductivity much higher than pristine sPEEK, due to the formation of an extended fractal structure in the whole sample, constituted of connected zirconia‐rich aggregates. Interaction of PIL molecules with the zirconia aggregates along this extended structure shall form new conducting channels for ion transport, favoring conductivity.
Photo‐reversible polyurethane (PU) coatings based on coumarin diol (CD) are obtained. Initially, pre‐polymers based on different amounts of coumarin (5, 15, and 25 mol%) and 1,6‐hexamethylene diisocyanate are prepared to obtain PUs with a large incorporation of CD and high molecular weight. The pre‐polymer is posterior reacted with poly(ε‐caprolactone) diol (PCL‐diol), either with molecular weight = 530 or 2000 g mol–1. The thermal stabilities of the PUs are studied using thermogravimetric analysis. Polymers with a higher content of CD present higher stability. The thermal transitions and the mechanical response are analyzed using differential scanning calorimetry and strain‐stress tests, respectively. Moreover, the photo‐reversibility of CD‐based PUs is followed by UV absorption. In general, photo‐dimerization induces better mechanical properties of the final PUs. Materials obtained with short PCL‐diol ( = 530 g mol–1) and the highest amount of CD present higher reversibility processes. Therefore, these polymers are promising for application as coating systems.
A series of drawn melt‐crystallized linear polyethylenes (LPEs) with different molecular weight distributions (MWD = M w/M n) ranging from 2 to 25 are investigated with respect to the visible‐light transparency. The results indicate that the MWD of the LPEs significantly influences the visible‐light transparency of drawn melt‐crystallized LPEs. At a high MWD, drawn melt‐crystallized LPEs films are transparent and glass‐like, this in contrast to the LPEs with a low MWD. A mechanism behind the observed results is proposed based on differential scanning calorimetry (DSC) analysis, small‐angle X‐ray scattering, wide‐angle X‐ray scattering, and small‐angle light scattering experiments. A correlation between the molecular characteristics, especially the MWD, and the visible‐light transparency of the drawn melt‐crystallized LPEs is proposed.
To endow nanofibers with the desirable antibacterial and mechanical properties, a facile strategy using Pickering emulsion (PE) electrospinning is proposed to prepare functional nanofibers with core/shell structure for the first time. The water‐in‐oil (W/O) Pickering emulsion stabilized by oleic acid (OA)‐coated magnetite iron oxide nanoparticles (OA‐MIONs) is comprised of aqueous vancomycin hydrochloride (Van) solution and poly(lactic acid) (PLA) solution. The core/shell structure of the electrospun Van/OA‐MIONs‐PLA nanofibers is confirmed by scanning electron microscopy and transmission electron microscopy observation. Sustained release of Van from the PE electrospun nanofiber membrane is achieved within the time of 600 h. Compared with the neat PLA electrospun nanofiber membrane, 57% increase of tensile strength and 36% elevation of elongation at break are achieved on PE electrospun nanofiber membrane. In addition, the PE electrospun nanofiber membrane demonstrates excellent antibacterial property stemming from the combinational antibacterial activities of OA‐MIONs and Van. The Van‐loaded PE electrospinning nanofibers with sustained antibacterial performance possess potential applications in tissue engineering and drug delivery.
The ability to fabricate high‐quality colloidal photonic crystal (CPC) films in large areas is critical in many applications, ranging from flexible displays, security devices to optical enhancement. Herein, a large‐scaled CPC film with crack‐free structure and uniform optical performance is prepared via a hydrogen‐bond‐assisted method. The crack‐free CPC film is ascribed to the intermolecular hydrogen bonds between carboxyl ( COOH) moieties of poly(styrene‐methyl methacrylate acrylic acid) microspheres and isocyanate ( NCO ) moieties of polyurethane. Furthermore, the as‐prepared CPC film is applied as a Bragg reflection mirror for fluorescence enhancement. It is demonstrated that a fourfold enhancement of fluorescence signal is achieved when the stopband of CPCs overlaps with the emission wavelength of quantum dots. This simple method of preparing large‐area and crack‐free CPC film is promising for developing efficient optical devices.
For major advances in microfabricated drug delivery systems (DDS), fabrication methods with high throughput using biocompatible polymers are required. Once these DDS are fabricated, loading of drug poses a significant challenge. Here, hot punching is presented as an innovative method for drug loading in microfabricated DDS. The microfabricated DDS are microcontainers fabricated in photoresist SU‐8 and biopolymer poly‐l ‐lactic‐acid (PLLA). Furosemide (F) drug is embedded in poly‐ε‐caprolactone (PCL) polymer matrix. This F‐PCL drug polymer matrix is loaded in SU‐8 and PLLA microcontainers using hot punching with >99% yield. Thus, it is illustrated that hot punching allows high‐throughput, parallel loading of 3D polymer microcontainers with drug‐polymer matrices in a single process step.
Development of artificial soft materials that have good mechanical performances and autonomous healing ability is a longstanding pursuit but remains challenging. This work reports a kind of highly flexible, tough, and self‐healable poly(acrylic acid)/Fe(III) (PAA/Fe(III)) hydrogels. The hydrogels are dually cross‐linked by triblock copolymer micelles and ionic interaction between Fe(III) and carboxyl groups. Due to the coexistence of these two cross‐linking points, the resulting PAA/Fe(III) hydrogels are tough and can be flexibly stretched, bent, knotted, and twisted. The hydrogels can withstand a deformation of 600% and an ultimate stress as high as 250 kPa. Moreover, the dynamic ionic interaction also endows the hydrogels self‐healing properties. By varying the ratio of Fe(III)/AA, a compromised healing efficiency of 73% and an ultimate stress of 200 kPa are obtained.
Green synthesis is one of the hot topics in the chemistry of hybrid organic–inorganic materials. A alcohol‐free sol–gel process has been developed to prepare optically transparent hybrid films from an epoxy bearing alkoxide, [2‐(3,4‐epoxy‐cyclohexyl)‐ethyl]‐trimethoxysilane (ECTMS). The synthesis is simple and effective because only two components, ECTMS and an aqueous solution of NaOH, are employed. Infrared spectroscopy has been used to monitor the reactivity of the precursor sol as a function of the aging time. Organic–inorganic hybrid films have been then prepared with the different sols via spin‐coating. The presence of the cyclohexyl ring slows down dramatically both the epoxide opening and the capability of the resulting diols in forming a tricyclic dioxane derivative. The highly basic conditions employed in the synthesis favor the formation of the cyclohexyl rings and cage‐ and ladder‐like silica structures. The hybrid films have shown a high transmittance in the visible range and a thermal stability up to 200 °C.
Although graphene‐based materials have been used as fillers in polymer nanocomposites, a deleterious trade‐off in mechanical strength and ductility is typically observed with increasing graphene loading, resulting in strong but brittle polymer nanocomposite materials. To provide outstanding compatibility with a standard high strength polymer, thermoplastic polyurethane (TPU), the use of a simple and mild sol‐gel reaction to chemically attached silica nanoparticles to graphene oxide (GO) basal plane is reported. The silica modification imparts a highly porous GO surface structure, providing noncovalent attachment sites that improve physical entanglement between the GO and TPU. Furthermore, the silica modification enhances surface polarity, which imparts chemical affinity between the silica/GO nanocomposite and TPU. As a result, the prepared polymer nanocomposites exhibit significantly improved Young's modulus and tensile strength with only a small reduction of elongation at break over the neat polymer.
In this study, the development and characterization of an intrinsically self‐healable material have been reported based on bromobutyl rubber (BIIR) modified with imidazole (Im) and loaded with carbon nanotubes (CNTs) as reinforcing and electrically conducting agent. The ionic imidazolium groups facilitate an ionic network, which imparts the composites a pronounced self‐healing behavior. The cation‐π bondings between modified BIIR and CNT surface improve the rubber‐filler interaction leading to a better mechanical performance and a higher electrical conductivity of the composites. It has been demonstrated that the healing process can be accelerated by applying an electrical current across a damaged surface of a test specimen owing to the Joule heating effect. The recovery of the mechanical and electrical properties of the composites is investigated under different test conditions and specifically discussed in terms of the rubber‐filler interactions and the filler dispersion. The applied scientific approach with the exploration of the unique nature of the imidazolium modified and CNT loaded BIIR may promote developments for a new class of rubber materials for different smart and technological applications.
下载免费PDF全文