Polymeric Precursor Research Articles

The effect of using two stabilization temperatures and fixation process on preparation of carbon nanofibers

Carbon nanofibers (CNFs) are prepared from electrospun polyacrylonitrile (PAN) because of their high carbon content. Heat treatment (oxidative stabilization and carbonization) is necessary to convert PAN nanofibers into CNFs. The fixation of fibrous structure of polymer precursor during heat treatment is always considered as a problem. The aim of this work is to study the effects of two different stabilization temperatures and fixation on CNFs prepared from electrospun PAN nanofibers. In this study, we use two different stabilization temperatures (275 and 300 °C) to investigate the effect of temperature on the oxidation, cyclization, crosslinking, aromatization, and dehydrogenation processes that occur during the stabilization heat treatment. Further, we study the effect of electrospun sheet fixation during heat treatment on the fibrous structure of electrospun fibers and methods to prevent shrinkage and folding of the electrospun sheet. Fourier transform infrared spectroscopy revealed the effectiveness of stabilization at 300 °C when transforming PAN elctrospun nanofibers to CNFs. Raman spectroscopy showed that carbonization at 800 °C after stabilization at 300 °C lowers the R-value (ID/IG ratio) comparing with that stabilized at 275 °C which indicates increasing the amount of structurally ordered graphite crystallites relative to the disordered structure. Scanning electron microscopy (SEM) revealed that fixation process maintained a uniform fibrous structure for the stabilized sheets without shrinkage, whereas carbonization at 800 °C without fixation resulted in deformed and folded carbonized PAN with loss in the fibrous structure.

Tailoring the stress-free two-way shape memory effect in sol–gel crosslinked poly(ϵ-caprolactone)-based semicrystalline networks

Two-way shape memory polymers are stimulus-responsive materials capable of changing their shape between two configurations based on an on/off thermal stimulus. While the traditional effect has been studied under the application of an external mechanical load, it was demonstrated also in the absence of an external load. Such a response only relies on a carefully tailored macromolecular architecture of the polymer combined with a specific thermo-mechanical protocol. In particular, semicrystalline networks, either consisting of a multi-phase copolymer network or a homopolymer based network with broad phase transitions, have been proposed to this aim under ad hoc thermo-mechanical histories. In this work, the two-way shape memory behavior is studied on a poly(ϵ-caprolactone)-based network, crosslinked by means of a sol–gel approach and tailored on the selection of the molecular weight of the precursor polymer. Changing the prepolymer precursor allowed to tune the melting/crystallization regions of the networks, thus the thermal region of the reversible shape memory effect. The application of properly designed thermo-mechanical cycles allowed to study the two-way shape memory effect without the application of an external load under tensile conditions. Given a specific network, the stress-free actuation of the reversible elongation-contraction cycle under tensile conditions was induced across its specific melting/crystallization region. The extent of the effect was found to depend on the crystalline fraction remaining for the given actuation temperature and on the tensile stretched state imposed on the materials during the training step. The results were compared with the response achieved under the traditional two-way shape memory protocol under stress. The stress-free two-way shape memory effect was also successfully demonstrated and emphasized, under flexural conditions, which suggests the potential of these materials as intrinsically reversible actuators, promising for applications in the biomedical field and/or for soft robotics.

Controllable construction of mesoporous hollow carbon spheres rich in micropores from waterborne benzoxazine and their application in supercapacitors

Mesoporous hollow carbon spheres (MHCSs) with mesoporous channels and nanocages structure have unique advantages in energy storage. However, this structure alone does not significantly enhance the electrochemical double layer capacitance (EDLC). Additionally, the current hydrophobic nature of polymer precursors with high char yield impedes effective binding with templates due to polarity differences. Moreover, the use of toxic organic solvents presents obstacles to further development. So, it remains a challenge to prepare MHCSs rich in micropores using polar polymers with high char yield in green solvent. In this work, we prepared MHCSs rich in micropores (MMHCSs) using waterborne benzoxazine as a carbon sources and dendritic/fibrous nano-silica as a sacrificial hard template using water as the solvent and combined with freeze-drying, curing, carbonization and an activation step. The optimal MMHCSs (MMHCSs306–1–7000.5h) has a large specific surface area (1057 m2 g−1), and has a maximum specific capacitance value near 221.45 F g−1 at 0.5 A g−1 in a three-electrode system, the specific capacitance still reaches 156.66 F g−1 at a high current density (20 A g−1) due to the full utilization of micropores in the presence of mesoporous-shell and hollow-core. When assembled into a symmetrical supercapacitor, the energy density reaches 5.91 Wh kg−1 when the power density is 137.5 W kg−1. The study provides an eco-friendly method for preparing MMHCSs, and the unique structure has potential application in supercapacitors.

Why Single-Chain Nanoparticles from Weak Polyelectrolytes Can Be Synthesized at Large Scale in Concentrated Solution?

Here, the unresolved question of why single-chain nanoparticles (SCNPs) prepared from a weak polyelectrolyte (PE) precursor can be synthesized on a large is addresses, unlike SCNPs obtained from an equivalent neutral (nonamphiphilic) polymer precursor. The combination of the standard elastic single-chain nanoparticles (ESN) model -developed for neutral chains- with the classical scaling theory of PE solutions provides the key. Essentially, the long-range repulsion between electrostatic blobs in a weak PE precursor restricts the cross-linking process during SCNPs formation to the interior of each blob. Consequently, the maximum concentration at which PE-SCNPs can be prepared without interchain cross-linking is not determined by the full size of the PE precursor but, instead, by the smaller size of its electrostatic blobs. Therefore, PE-SCNPs can be synthesized up to a critical concentration where electrostatic blobs from different chains touch each other. This concentration can be 30 times higher than that for non-PE polymer precursors. Upon progressive dilution, the size of PE-SCNPs synthesized in concentrated solution increases until it reaches the bigger size of PE-SCNPs prepared under highly diluted conditions. PE-SCNPs do not adopt a globular conformation either in concentrated or in diluted solution. It shows that the main model predictions agree with experimental results.

Thermal degradation of nanoporous Si-containing hybrid terpolymer

AbstractIn this work development of structural and chemical properties of four nanoporous hybrid carbons has been presented. The carbons were synthesized by direct carbonization at 450, 600, 750 and 900 °C of the terpolymeric hybrid precursor composed of methacrylamide, divinylbenzene and trimethoxyvinylsilane and impregnated with sulfanilic acid (SA) as the surface modifier. The conditions of the carbonization process were set on the basis of the thermogravimetric analysis combined with FTIR analysis of the evolved gases (TGA-EGA). The use of SA contributed to the reduction of the carbonization temperature by about 100 °C and resulted in carbons with very uniform and bimodal porosity with the width range of about 1 and 14–28 nm. Spectral (ATR, Raman, XPS) and X-ray diffraction methods used to characterize the resulting carbon products allowed to define the gradual changes taking place in the morphological and chemical structure of the prepared materials. Cyclic and symmetrical structures of silicates species were gradually replaced by amorphous arrangements. At the same time, the increase in the sp2/sp3 carbon ratio from 1 to 65% proved progressive ordering and aromatization of the carbonized polymeric hybrid precursor. Some functional groups (e.g., N-containing) were built into carbon clusters forming pyridinic, pyrrolic and N-graphitic like structures, while others (e.g., carbonyls) were removed from the surface.

Initiator‐Free Synthesis of Semi‐Interpenetrating Polymer Networks via Bergman Cyclization

AbstractSemi‐interpenetrating polymer networks (semi‐IPNs), composed of two or more polymers, forming intertwined network‐architectures, represent a significant type of polymer combination in modern industry, especially in automotive and medical devices. Diverse synthesis techniques and plentiful raw materials highlight semi‐IPNs in providing facile modifications of properties to meet specific needs. An initiator‐free synthesis of semi‐interpenetrating polymer networks via Bergman cyclization (BC) is reported here, acting as a trigger to embed a second polymer via its reactive enediyne (EDY) moiety, then embedded into the first network. (Z)‐oct‐4‐ene‐2,6‐diyne‐1,8‐diol (diol‐EDY) is targeted as the precursor of the second polymer, swollen into the first polyurethane network (PU), followed by a radical polymerization induced by the radicals formed by the BC. The formation of the semi‐IPN is monitored via electron paramagnetic resonance (EPR) spectroscopy, infrared‐spectroscopy (FT‐IR), and thermal methods (DSC), proving the activation of the EDY‐moiety and its subsequent polymerization to form the second polymer. Stress−strain characterization and cyclic stress−strain investigations, together with TGA and DTG analysis, illustrate improved mechanical properties and thermal stability of the formed semi‐IPN compared to the initial PU‐network. The method presented here is a novel and broadly applicable approach to generate semi‐IPNs, triggered by the EDY‐activation via Bergman cyclization.

Synthesis of Metallic and Metal Oxide Nanoparticles Using Homopolymers as Solid Templates: Luminescent Properties of the Eu+3 Nanoparticle Products

Starting from poly(4-vinylpyridine) ((P4VP)n), poly(2-vinylpyridine) ((P2VP)n), and [N=P(O2CH2CF3)]m-b-P2VP20 block copolymers, a series of metal-containing homopolymers, (P4VP)n⊕MXm, (P2VP)n⊕MXm, and [N=P(O2CH2CF3)]m-b-P2VP20]⊕MXm MXm = PtCl2, ZnCl2, and Eu(NO3)3, have been successfully prepared by using a direct and simple solution methodology. Solid-state pyrolysis of the prepared metal-containing polymeric precursors led to the formation of a variety of different metallic and metal oxide nanoparticles (Pt, ZnO, Eu2O3, and EuPO4) depending on the composition and nature of the polymeric template precursor. Thus, whereas Eu2O3 nanostructures were obtained from europium-containing homopolymers ((P4VP)n⊕MXm and (P2VP)n⊕MXm), EuPO4 nanostructures were achieved using phosphorus-containing block copolymer precursors, [N=P(O2CH2CF3)]m-b-P2VP20]⊕MXm with MXm = Eu(NO3)3. Importantly, and although both Eu2O3 and EuPO4 nanostructures exhibited a strong luminescence emission, these were strongly influenced by the nature and composition of the macromolecular metal-containing polymer template. Thus, for P2VP europium-containing homopolymers ((P4VP)n⊕MXm and (P2VP)n⊕MXm), the highest emission intensity corresponded to the lowest-molecular-weight homopolymer template, [P4VP(Eu(NO3)3]6000, whereas the opposite behavior was observed when block copolymer precursors, [N=P(O2CH2CF3)]m-b-P2VP20]⊕MXm MXm= Eu(NO3)3, were used (highest emission intensity corresponded to [N=P(O2CH2CF3)]100-b-[P2VP(Eu(NO3)3)x]20). The intensity ratio of the emission transitions: 5D0 → 7F2/5D0 → 7F1, suggested a different symmetry around the Eu3+ ions depending on the nature of the polymeric precursor, which also influenced the sizes of the prepared Pt°, ZnO, Eu2O3, and EuPO4 nanostructures.

Tuning the Emission of Bis-ethylenedioxythiophene-thiophenes upon Aggregation.

The ability of small lipophilic molecules to penetrate the blood-brain barrier through transmembrane diffusion has enabled researchers to explore new diagnostics and therapies for brain disorders. Until now, therapies targeting the brain have mainly relied on biochemical mechanisms, while electrical treatments such as deep brain stimulation often require invasive procedures. An alternative to implanting deep brain stimulation probes could involve administering small molecule precursors intravenously, capable of crossing the blood-brain barrier, and initiating the formation of conductive polymer networks in the brain through in vivo polymerization. This study examines the aggregation behavior of five water-soluble conducting polymer precursors sharing the same conjugate core but differing in side chains, using spectroscopy and various computational chemistry tools. Our findings highlight the significant impact of side chain composition on both aggregation and spectroscopic response.

Influence of cobalt doping on structural, optical, and electrical properties of zinc oxide nanoparticles prepared by polymeric precursor method

Cobalt-doped ZnO nanoparticles at different compositions have been obtained by the polymeric precursor method. The nanoparticles were obtained at the working pH from 8.3 to 8.5 and synthesized at 550 °C. The properties were studied using X-ray diffraction (XRD), vibrational spectroscopy (FTIR/Raman), diffuse reflectance absorbance spectroscopy (DR UV–Vis), photoluminescence spectroscopy (PL), scanning electron microscopy (SEM/EDS), and impedance spectroscopy. The lattice parameters were determined at room temperature by Rietveld refinement, confirming single-phase composition with a hexagonal wurtzite structure. FTIR and Raman analyzes identified the characteristic vibrations of the synthesized system and the typical deformations of the wurtzite-type hexagonal structure, corroborating the results obtained from XRD. A redshift in the optical energy band gap (Egopt) was observed with increasing cobalt content compared to the ZnO sample. Considering the doping percentage, Egopt value varied between 3.13 eV and 3.04 eV for pure ZnO and Co-doped ZnO with 5 at. %., indicating that the optical properties of the nanoparticles were affected by dopant concentration. PL and SEM/EDS characterization were used to determine the associated defects for each sample and the morphology and composition of the nanoparticles. PL results showed a strong blue emission at around 439 nm (2.83 eV), which is redshift with cobalt content (ΔE between 0.05 eV and 0.01 eV), attributed to the surface defects present in the doped samples. Conductivity analysis to temperature revealed a semiconductor behavior for all samples, and their respective activation energies determined. The results provide an easy method to obtain Co-doped ZnO nanoparticles with interesting properties for optoelectronics devices.

Synthesis of silicon carbide thin film as a source for white light emission

Synthesis of doped silicon carbide (SiC) thin film on silicon (111) wafer was carried out employing chemical vapour deposition (CVD) technique using boron-doped liquid polycarbosilane (LPCS) as polymer precursor under inert atmosphere of argon and nitrogen gas. The present study investigated the physical and optical properties of fabricated SiC thin films by varying doping concentrations. Subsequent analysis of bonds and phases by Fourier transform infrared (FTIR) spectroscopy, micro-Raman spectroscopy and X-ray diffraction (XRD) affirm the formation of Si–C, Si–N and unique silicon carbonitride (SiC–N). Stable photoluminescence has been observed across the entire visible spectra with enhanced quantum efficiency and lifetime, which ensures its application in opto-electronic devices such as LED.

Synthesis and Characterization of Nanocellulose/Polyacrylonitrile‐based Carbon Nanofibers: An Approach toward Low Cost and Sustainable Agro Waste based Carbon Nanomaterials

AbstractThe cost of polymer precursors and high energy need in carbonization for the preparation of carbon materials are two limiting factors in the commercialization of carbon‐based materials. In this study, carbon nanofiber films were prepared by adding a very small concentration of polymer polyacrylonitrile in nanocellulose (extracted from agro waste i.e., rice straws) with an overall aim of producing carbon nanomaterials with cost effective, renewable and sustainable carbon source. Polyacrylonitrile (PAN) added nanocellulose solution was drop‐casted to prepare Nanocellulose/Polyacrylonitrile‐based nanofibers film (NC/PAN). It was further stabilized in air atmosphere at 280 °C followed by carbonized in nitrogen atmosphere at 700 °C. It was found that addition of NC/PAN have 18 % lower activation energies than PAN. Results of tunneling electron microscopy showed that polyacrylonitrile/nanocellulose films carbonized at 700 °C temperature exhibited amorphous carbon nanofibers structure similar to bare polyacrylonitrile based carbon film carbonized at higher temperature of 1000 °C‐1200 °C. Furthermore, polyacrylonitrile/nanocellulose based carbon nanofibers have showed high degree of carbonization ((ID)/(IG)=0.87) as compared to bare polyacrylonitrile based carbon nanofibers film ((ID)/(IG)=1.02). This may be attributed to chiral nature of nanocellulose which served as a template to orientation of graphene planes and showed efficient carbonization.

Bio‐based semi‐aromatic waterborne PIEK‐C sizing agent to construct a robust interface for CF/PEEK composites

AbstractDespite the impressing advances on sizing agents for CF/PEEK composites, the aromatic backbone of the polymer precursors utilized in the vast majority of reports compromises the dispersity and ductility of the slurry, subsequently resulting in inferior overall performance of the composites. Meanwhile, most resins employed for sizing agents in existing reports are based on petroleum resources. Herein, a bio‐based waterborne sizing agent utilizing semi‐aromatic poly ether ketones (PIEK‐C) derived from isosorbide and phenolphthalein has been disclosed, featured by its salutary dispersity, exceptional thermal stability, higher glass transition temperatures, and broader applicability. Due to the structural similarity between the sizing and resin matrix, the protocol endowed CF/PEEK composites with ameliorated overall performance, addressing issues related to inadequate adhesion of CF with PEEK resin, as well as environmental pollution commonly associated with existing commercial epoxy and solvent‐based sizing agents. The Tg and T5% of PIEK‐C‐5050 were 205.08 and 427.16°C, respectively. The particle size range of the PIEK‐C sizing agents spanned from 66.32 to 84.63 nm. The flexural strength and interlaminar shear strength of the composites experienced a respective 993.92 MPa (30.73%) and 83.32 MPa (36.97%) increase compared to untreated CF/PEEK composites following sizing treatment with PIEK‐C‐5050, underscoring expedient intermolecular interactions based on comparable solubility and π‐π stacking effects between the PEEK and PIEK‐C components. This study introduced an efficient and eco‐friendly approach to enhance the interfacial properties of CF/PEEK composites.Highlights PIEK‐C resin is employed for the first time to prepare carbon fiber sizing agents. The PIEK‐C sizing agent significantly fortified the surface energy and wettability of carbon fibers. The CF/PEEK composites after treatment with PIEK‐C sizing agent showed excellent heat resistance. The ILSS and bending strength of the composites were significantly increased by 36.97% and 30.73%, respectively.

Efficient and sustainable design of pyridyl-bis-thiourea pincer ligand-immobilised Merrifield polymer precursor for arsenic ions adsorption

ABSTRACT An improved yield of a composite named Merrifield-pyridoyl-bis-thiourea derivative (MR-PyBTU) was effectively synthesised from the Merrifield Polymer Precursor (MR) and utilised for the adsorption of arsenic trioxide (As3+) ions from wastewater samples containing 1.5 mg/L of As3+ ions. The structure of the (PVAm-MMB) composite was confirmed using various analytical techniques, ensuring successful functionalization. Key experimental conditions namely pH, equilibrium time, starting concentration of As3+ ions, composite dosage, temperature, and choice of eluting agents were systematically optimised. At an ambient temperature, a pH value of 4.5, with 20 minutes of agitation, and an initial concentration of 250 mg/L As3+ ions, the composite demonstrated its highest sorption efficiency at a capacity of 50 mg/g. Equilibrium isotherm analyses indicated that the experimental data aligned more closely with the Langmuir model compared to the Freundlich model. Remarkably, the Langmuir model’s predicted uptake capability of 51.282 mg/g closely matched the actual observed values. Kinetic analyses supported by the pseudo-first-order model accurately described the sorption process, yielding a theoretical sorption capability of 49.113 mg/g. Thermodynamic assessments suggested that the sorption process is exothermic, spontaneous, and more favourable at lower temperatures. Efficient desorption of As3+ ions from the saturated composite was attained with 0.025 M NaOH, reaching approximately 98% efficiency. This composite’s ability to remove As3+ ions from wastewater aligns with Food and Agriculture Organization (WHO) and World Health Organization (FAO) guidelines, ensuring its safe discharge into marine environments after a single treatment cycle. Additionally, the compound 4-amino-N2, N6-bis((3-chloro-1,4-dioxo-1,4-dihydronaphthalen-2-yl) carbamothioyl) pyridine-2,6-dicarboxamide (PyBTU) exhibited potent antioxidant and antibacterial properties against Gram-negative bacteria, Gram-positive bacteria, Escherichia coli, and Bacillus subtilis.

Insights into molecular and bulk mechanical properties of glassy carbon through molecular dynamics simulations and mechanical tensile testing

With increasing interest in the use of glassy carbon (GC) for a broad range of application areas, the need for developing a fundamental understanding of its mechanical properties has come to the forefront. Furthermore, recent theoretical and modeling works that highlight the synthesis of GC via the pyrolysis of polymer precursors has explored the possibilities of a revisit to the investigation of their mechanical properties at a fundamental level. Although there are isolated reports on the experimental determination of its elastic modulus, insights into the stress-strain behavior of a GC material under tension and compression obtained through simulations, either at the molecular level or for the bulk materials, are missing. This study fills the gap at the molecular level and investigates the mechanical properties of GC using molecular dynamics (MD) simulations, which model the atomistic-level formation and breaking of bonds using bond-order-based reactive force field formulations. The molecular model considered in this simulation has a characteristic 3D cage-like structure of five-, six-, and seven-membered carbon rings and graphitic domains of a flat graphene-like structure. The GC molecular model was subjected to loading under varying strain rates (0.4, 0.6, 1.25, and 2.5 ns−1) and temperatures (300 K–800 K) in each of the three axes: x, y, and z. The simulations show that the GC nanostructure has distinct stress-strain curves under tension and compression. In tension, MD modeling predicted a mean elastic modulus of 5.71GPa for a single GC nanostructure with some dependency on the strain rate and temperature, whereas, in compression, the elastic modulus was also found to depend on the strain rate and temperature and was predicted to have a mean value of 35 GPa. To validate the simulation results and develop experimental insights into the bulk behavior, mechanical tests were conducted on dog-bone-shaped testing coupons that were subjected to uniaxial tension and loaded until failure. The GC test coupons demonstrated a bulk modulus of 17 ±2.69 GPa in tension, which compares well with those reported in the literature. However, comparing MD simulation outcomes to those of uniaxial mechanical testing reveals that the bulk modulus of GC in tension found experimentally is higher than the modulus of single GC nanostructures predicted by MD modeling, which inherently underestimates the bulk modulus. With regard to failure modes, the MD simulations predicted failure in tension accompanied by the breaking of carbon rings within the molecular structure. In contrast, the mechanical testing demonstrated that failure modes are dominated by brittle failure planes largely due to the amorphous structure of GC.

Vat photopolymerization of poly(styrene-b-isoprene-b-styrene) triblock copolymers

Vat photopolymerization (VPP) additive manufacturing (AM) produces complex geometries with micron-scale resolution and smooth surface finish from a wide range of photocrosslinkable polymeric precursors. However, mass transport limitations typically constrain VPP amenable precursors to viscosities less than 10 Pa·s. Reactive oligomers and monomers comprise the majority of VPP polymeric precursors, which result in highly crosslinked and brittle 3D objects upon printing. This work describes colloidal high molecular weight ABA triblock copolymers, or latex, as a feedstock for aqueous photoreactive compositions to enable AM of thermoplastic elastomers (TPE). Photorheological analysis determined 15 wt% aqueous reactive monomers and oligomers generated a structural scaffold that achieved sufficiently high modulus to maintain feature fidelity for iterative layer formation. Subsequent thermal post-processing removed water and promoted polymeric particle coalescence throughout the scaffold resulting in an interpenetrating network (IPN) that exhibited an isotropic dimensional shrinkage of 25 %. Small-angle X-ray scattering (SAXS) confirmed microphase-separated morphologies typical of triblock copolymers, revealing a characteristic length scale of 30 nm. Using commercially available VPP printers, ABA triblock copolymer poly(styrene-b-isoprene-b-styrene) latex yielded printed elastomers with precise feature fidelity and tensile extensibility exceeding 800 %.

Synthesis of a symmetrically meta-substituted poly(diphenylacetylene) bearing chiral amide groups and its application as a chiral stationary phase for high-performance liquid chromatography

Abstract A symmetrically meta-substituted poly(diphenylacetylene) bearing chiral amide groups was synthesized by reacting (R)-1-phenylethylamine with a carboxy-group-containing precursor polymer, which was obtained by polymerizing the corresponding ester-containing diphenylacetylene using a modified Mo(V)-based catalytic system followed by hydrolysis. The polymer formed a one-handed helical conformation when thermally annealed in a solvent. The chiral recognition ability of the polymer before and after thermal annealing was investigated when used as a chiral stationary phase for high-performance liquid chromatography.

In Situ Preparation of Chlorine-Regenerable Antimicrobial Polymer Molecular Sieve Membranes.

Microbial contamination has profoundly impacted human health, and the effective eradication of widespread microbial issues is essential for addressing serious hygiene concerns. Taking polystyrene (PS) membrane as an example, we herein developed report a robust strategy for the in situ preparation of chlorine-regenerable antimicrobial polymer molecular sieve membranes through combining post-crosslinking and nucleophilic substitution reaction. The cross-linking PS membranes underwent a reaction with 5,5-dimethylhydantoin (DMH), leading to the formation of polymeric N-halamine precursors (PS-DMH). These hydantoinyl groups within PS-DMH were then efficiently converted into biocidal N-halamine structures (PS-DMH-Cl) via a simple chlorination process. ATR-FTIR and XPS spectra were recorded to confirm the chemical composition of the as-prepared PS-DMH-Cl membranes. SEM analyses revealed that the chlorinated PS-DMH-Cl membranes displayed a rough surface with a multitude of humps. The effect of chlorination temperature and time on the oxidative chlorine content in the PS-DMH-Cl membranes was systematically studied. The antimicrobial assays demonstrated that the PS-DMH-Cl membranes could achieve a 6-log inactivation of E. coli and S. aureus within just 4 min of contact time. Additionally, the resulting PS-DMH-Cl membranes exhibited excellent stability and regenerability of the oxidative chlorine content.

Inverse Vulcanization of Activated Norbornenyl Esters – A Versatile Platform for Functional Sulfur Polymers

Elemental sulfur has shown to be a promising alternative feedstock for development of novel polymeric materials with high sulfur content. However, the utilization of inverse vulcanized polymers is restricted by the limitation of functional comonomers suitable for an inverse vulcanization. Control over properties and structure of inverse vulcanized polymers still poses a challenge to current research due to the dynamic nature of sulfur‐sulfur bonds and high temperature of inverse vulcanization reactions. In here, we report for the first time the inverse vulcanization of norbornenyl pentafluorophenyl ester (NB‐PFPE), allowing for post‐modification of inverse vulcanized polymers via amidation of reactive PFP esters to yield high sulfur content polymers under mild conditions. Amidation of the precursor material with three functional primary amines (α‐amino‐ω‐methoxy polyethylene glycol, aminopropyl trimethoxy silane, allylamine) was investigated. The resulting materials were applicable as sulfur containing poly(ethylene glycol) nanoparticles in aqueous environment. Cross‐linked mercury adsorbents, sulfur surface coatings, and high‐sulfur content networks with predictable thermal properties were achievable using aminopropyl trimethoxy silane and allylamine for post‐polymerization modification, respectively. With the broad range of different amines available and applicable for post‐polymerization modification, the versatility of poly(sulfur‐random‐NB‐PFPE) as a platform precursor polymer for novel specialized sulfur containing materials was showcased.

Inverse Vulcanization of Activated Norbornenyl Esters-A Versatile Platform for Functional Sulfur Polymers.

Elemental sulfur has shown to be a promising alternative feedstock for development of novel polymeric materials with high sulfur content. However, the utilization of inverse vulcanized polymers is restricted by the limitation of functional comonomers suitable for an inverse vulcanization. Control over properties and structure of inverse vulcanized polymers still poses a challenge to current research due to the dynamic nature of sulfur-sulfur bonds and high temperature of inverse vulcanization reactions. In here, we report for the first time the inverse vulcanization of norbornenyl pentafluorophenyl ester (NB-PFPE), allowing for post-modification of inverse vulcanized polymers via amidation of reactive PFP esters to yield high sulfur content polymers under mild conditions. Amidation of the precursor material with three functional primary amines (α-amino-ω-methoxy polyethylene glycol, aminopropyl trimethoxy silane, allylamine) was investigated. The resulting materials were applicable as sulfur containing poly(ethylene glycol) nanoparticles in aqueous environment. Cross-linked mercury adsorbents, sulfur surface coatings, and high-sulfur content networks with predictable thermal properties were achievable using aminopropyl trimethoxy silane and allylamine for post-polymerization modification, respectively. With the broad range of different amines available and applicable for post-polymerization modification, the versatility of poly(sulfur-random-NB-PFPE) as a platform precursor polymer for novel specialized sulfur containing materials was showcased.

Preparation of Autoclavable and Injectable Silk Fibroin Cryogels for Tissue Engineering Applications.

A cryogel is a supermacroporous gel network that is generated at subzero temperatures by polymerizing monomers or gelating polymeric precursors. Since cryogels possess inherent characteristics such asinterconnectedmacroporous structures, excellent mechanical properties,and high resistanceto autoclave sterilization,they are highly desirable for tissue engineering and regenerative medicine. Silk fibroin, a natural protein obtainedfrom Bombyx morisilkworms, is an excellent raw material for cryogel preparation. The aim of this study is toestablish acontrolled method for preparing silk fibroincryogels with suitable properties for application as tissue engineering scaffolds. Using a dual crosslinking strategy consisting of low-temperature radical polymerization coupled with methanol-induced conformational transformation, porous cryogels are prepared. The cryogelsdisplay many unique characteristics, such as an interconnected macroporous structure, a high water absorption capacity, water-triggered shape memory, syringe injectability, and strong resilience to autoclave sterilization. Furthermore, the cryogels demonstrate excellent biocompatibility and cell affinity, facilitating cell adhesion, migration, andproliferation. The interconnected supermacroporous architecture resembling the nativeextracellular matrix, together with their unique physical properties and autoclaving stability, suggests that cryogels are promising candidate scaffolds for tissue engineering and cell therapy.