Preparation and Applications of Polydimethylsiloxane-Based Fluorescent Materials.

In the past few years, fluorescent materials have received significant attention due to their fascinating luminescent properties and wide-ranging applications. Polydimethylsiloxane (PDMS) has also attracted the interest of many researchers due to its remarkable performances. The combination of fluorescence and PDMS will undoubtedly produce abundant advanced multifunctional materials. Although numerous achievements have been made in this field, there is still no review to summarize the relevant research. This review summarizes the state-of-the-art achievements made in PDMS-based fluorescent materials (PFMs). First, the preparation of PFM is overviewed following a classification according to the fluorescent sources, including organic fluorescent molecules, perovskite, photoluminescent nanomaterials, and metal complexes. Their applications in sensors, fluorescent probes, multifunctional coatings, and anticounterfeiting are then introduced. Finally, the challenges and development trends in the field of PFMs are presented.

Synthesis and Characterization of a New Copolymer Consisting of Polyamide 1210 and Reactive Phosphorus-Nitrogen Flame-Retardant.

The thermal stability and reactivity of organophosphorus flame-retardants play a critical role in synthesizing copolymerized flame-retardant polyamides. Herein, this work successfully synthesizes a flame-retardant CEPPA-DDA salt (CDS) with both good thermal stability and high reactivity by reacting 2-carboxyethyl phenyl phosphonic acid (CEPPA) with 1,12-dodecanediamine (DDA). Flame-retardant polyamide 1210 (FRPA) is further prepared by copolymerizing the CDS, DDA, and sebacic acid (SEA). The test results show that the introduction of CDS can significantly improve the flame-retardant properties of FRPA. Specifically, the flame-retardant polyamide 1210 (FRPA-7) with 7 wt% CDS addition can reach V-0 grade according to UL-94 standard, accompanying limiting oxygen index value of 30.2% and tensile strength of 38.62 MPa. Compared with pure polyamide 1210, the peak heat release rate and total heat release rate of FRPA-7 reduce by 24.11% and 9.40%, respectively. This study provides a simple strategy to prepare flame-retardant polyamides with high flame retardancy and good mechanical properties, which are expected to show great potentials in future industrial applications.

Helix-Sense-Selective Polymerization of Achiral Monomers for the Preparation of Chiral Helical Polyacetylenes Showing Intense CPL in Solid Film State.

Polymer-based circularly polarized luminescent (CPL) materials have attracted ever-increasing interest. However, to construct CPL materials from achiral monomers is still a big challenge. Here, a series of chiral helical substituted polyacetylenes are prepared by helix-sense-selective polymerization (HSSP) of achiral acetylenic monomers (achiral monomer + fluorescent monomer). HSSPs are accomplished in a bi-solvent mixture consisting of chloroform and chiral α-pinene (chiral component). Chirality transfers from the chiral component to the helical copolymers during polymerization, thereby endowing the copolymers with helical chirality. The resulting copolymers are then fabricated into blend films which exhibit intense optical activity and CPL. The monomer ratio and the physical state of the copolymers have significant impacts on their chiroptical and CPL properties. The maximum luminescence dissymmetry factor of the blend films can be up to 1.3 × 10-2 . The universality of the established strategy for exploring polymer-based CPL materials is demonstrated by using different achiral fluorescent monomers. The present work opens a novel alternative for developing CPL-active polymeric materials starting from achiral monomers.

Optically active porous hybrid particles constructed by alkynylated cellulose nanocrystals, helical substituted polyacetylene, and inorganic silica for enantio-differentiating towards naproxen.

This article reports on a novel type of ternary chiral porous hybrid particles (TCPHPs) constructed by alkynylated cellulose nanocrystals (A-CNCs), helical substituted polyacetylene, and inorganic silica. The resulting TCPHPs combine the respective advantages of the three components. A-CNCs serve as stabilizer, co-monomer, and chiral source simultaneously and transfer their chirality to the resulting helical substituted polyacetylenes in the course of copolymerization with achiral acetylenic monomer following "sergeants and soldiers rule". Helical substituted polyacetylenes form chiral helical structures and thus endow TCPHPs with the anticipated optical activity. Inorganic silica constitutes the rigid framework and is covalently bonded with the organic components through hydrolysis of Si-O-Et groups. Phase separation between the organic and inorganic components renders TCPHPs with abundant pores. Scanning electron microscope (SEM) images confirm the formation of spherical particles with porous structures. Circular dichroism spectra demonstrate the optical activity of the chiral hybrid particles. The as-prepared TCPHPs exhibit capacity for enantio-differentiating performance towards chiral naproxen.

Preparation and Chiral Applications of Optically Active Polyamides.

Chirality is omnipresent in nature and plays vital roles in living organism, and has become a hot research topic across multidisciplinary fields including chemistry, biology, physics, and material science. Meanwhile, polyamides constitute an important class of polymers and have received significant attention owing to their outstanding properties and wide-ranging applications in many areas. Judiciously introducing chirality into polyamides will undoubtedly obtain attractive chiral polymers, namely, optically active polyamides. This review describes the preparation methods of chiral polyamides, including solution polycondensation, interfacial polycondensation, ring-open polymerization, and others; the newly emerging categories of chiral polyamides, i.e., helical polyamides, chiral polyamide-imides, are also presented. The applications of optically active polyamides in chiral research fields including asymmetric catalysis, membrane separation, and enantioselective crystallization are also summarized. In addition, current challenges in chiral polyamides are further presented and future perspectives in the field are proposed.

A One-Pot Polymerization for Concurrently Inducing Predominant Helicity in Optically Inactive Helical Polymer and Constructing Graphene-Based Chiral Hybrid Foams.

Synthetic chiral helical polymers have achieved impressive progress in past few decades. Unfortunately, how to construct chiral helical polymer-derived functional materials still remains highly challenging. The present contribution reports an unprecedented, one-step strategy for judiciously combining chiral helical polymer with graphene to construct chiral hybrid foams. Graphene oxide (GO), ascorbic acid (L-AA), Rh catalyst, and an achiral acetylenic monomer bearing phenylboronic acid group are mixed in an aqueous dispersion. Under mild conditions, the monomer underwent polymerization; meanwhile GO transforms into reduced graphene oxide (RGO) which in situ self-assembles to construct a 3D porous structure. Herein, L-AA simultaneously plays double roles: 1) working as a chiral source for the monomer to undergo helix-sense-selective polymerization or transferring its chirality to the polymer chains via forming borate structure; and 2) working as a reducing agent for reducing GO. The preparation strategy combines four processes into one single step: monomer polymerization, chirality transfer, reduction of GO, and RGO's self-assembly. The eventually obtained chiral hybrid foams demonstrate advantages of porous structure, chirality, and reversible borate functional groups. The established preparation strategy promises a potent platform for conveniently constructing advanced chiral polymeric materials and even chiral hybrids starting from achiral monomers.

Seed-Surface Grafting Precipitation Polymerization for Preparing Microsized Optically Active Helical Polymer Core/Shell Particles and Their Application in Enantioselective Crystallization.

Core/shell particles constructed by polymer shell and silica core have constituted a significant category of advanced functional materials. However, constructing microsized optically active helical polymer core/shell particles still remains as a big academic challenge due to the lack of effective and universal preparation methods. In this study, a seed-surface grafting precipitation polymerization (SSGPP) strategy is developed for preparing microsized core/shell particles with SiO2 as core on which helically substituted polyacetylene is covalently bonded as shell. The resulting core/shell particles exhibit fascinating optical activity and efficiently induce enantioselective crystallization of racemic threonine. Taking advantage of the preparation strategy, novel achiral polymeric and hybrid core/shell particles are also expected.

Emulsification-Induced Homohelicity in Racemic Helical Polymer for Preparing Optically Active Helical Polymer Nanoparticles.

Optically active nano- and microparticles have constituted a significant category of advanced functional materials. However, constructing optically active particles derived from synthetic helical polymers still remains as a big challenge. In the present study, it is attempted to induce a racemic helical polymer (containing right- and left-handed helices in equal amount) to prefer one predominant helicity in aqueous media by using emulsifier in the presence of chiral additive (emulsification process). Excitingly, the emulsification process promotes the racemic helical polymer to unify the helicity and directly provides optically active nanoparticles constructed by chirally helical polymer. A possible mechanism is proposed to explain the emulsification-induced homohelicity effect. The present study establishes a novel strategy for preparing chirally helical polymer-derived optically active nanoparticles based on racemic helical polymers.

A facile method for preparing porous, optically active, magnetic Fe3 O4 @poly(N-acryloyl-leucine) inverse core/shell composite microspheres.

The first synthesis of porous, optically active, magnetic Fe3 O4 @poly(N-acryloyl-leucine) inverse core/shell composite microspheres is reported, in which the core is constructed of chiral polymer and the shell is constructed of Fe3 O4 NPs. The microspheres integrate three significant concepts, "porosity", "chirality", and "magneticity", in one single microspheric entity. The microspheres consist of Fe3 O4 nanoparticles and porous optically active microspheres, and thus combine the advantages of both magnetic nanoparticles and porous optically active microspheres. The pore size and specific surface area of the microspheres are characterized by N2 adsorption, from which it is found that the composite microspheres possess a desirable porous structure. Circular dichroism and UV-vis absorption spectroscopy measurements demonstrate that the microspheres exhibit the expected optical activity. The microspheres also have high saturation magnetization of 14.7 emu g(-1) and rapid magnetic responsivity. After further optimization, these novel microspheres may potentially find applications in areas such as asymmetric catalysis, chiral adsorption, etc.

Employing the plasmonic effect of the Ag-graphene composite for enhancing light harvesting and photoluminescence quenching efficiency of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene-vinylene].

In this work, we report that the Ag-graphene composite (AGC) can effectively enhance the light harvesting and photoluminescence (PL) quenching efficiency of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene-vinylene] (MEH-PPV). Loading the AGC on MEH-PPV leads to improved light absorption ability and PL quenching efficiency, which is due to the strong interaction between localized surface plasmon resonance (LSPR)-activated Ag nanoparticles and the MEH-PPV molecule. Control experiment reveals that the combination of graphene and Ag nanoparticles achieves superior light absorptivity and PL quenching ability compared with individual graphene and Ag NPs. The exponential shape of the Stern-Volmer plot implies that both Ag and graphene in the AGC can offer the quenching pathway for the PL quenching process. We also found that the AGC with a broader LSPR absorption range is competitive in enhancing the light absorption ability and PL quenching efficiency of the MEH-PPV-AGC composite, because it can expand LSPR-induced light harvesting and PL quenching response to a wider absorption range.

Au@poly(N-propargylamide) nanoparticles: preparation and chiral recognition.

This communication reports the first gold nanoparticles (NPs) chirally functionalized with optically active helical substituted polyacetylene (the resulting hybrid particles are defined as Au@PPA NPs). The novel nanoparticles consist of gold as core and optically active helical poly(N-propargylamide) as shell and show considerable optical activity derived from helical poly(N-propargylamide) chains with predominantly one-handed screw sense. The Au@PPA NPs are prepared by a three-step approach: i) a thiol-containing N-propargylamide monomer [Mth , HC≡CCH2 NHCO(CH2 )10 SH] is synthesized and characterized with FTIR and(1) HNMR spectroscopy and elemental analysis; ii) a copolymer (poly(Mth -co-Mch )) was prepared by starting from monomer Mth and another chiral N-propargylamide monomer (Mch ); poly(Mth -co-Mch ) formed helical conformations and showed optical activities; and, iii) Au@PPA NPs are prepared from hydrogen tetrachloroaurate (III) and poly(Mth -co-Mch ) through a one-spot procedure by using LiBH4 as reducing agent. The as-obtained hybrid nanoparticles are characterized by FTIR spectroscopy, TEM, UV-vis absorption and circular dichroism (CD) techniques. UV-vis and CD measurements demonstrated the remarkable optical activity of the Au@PPA NPs. More interestingly, the Au@PPA NPs show much stronger UV-vis and CD sigals when compared to the corresponding orginal helical copolymer, poly(Mth -co-Mch ). The chiral hybrid nanoparticles demonstrate different absorption toward (R)-(+)- and (S)-(-)-1-phenylethylamines, preferentially adsorbing the (S)-isomer.

Optically active particles of chiral polymers.

Particles constructed by chiral polymers (defined as PCPs) have emerged as a rapidly expanding research field in recent years because of their potentially wide-ranging applications in asymmetric catalysis, enantioselective crystallization, enantioselective release, amongst many others. The particles show considerable optical activity, due to the chirality of the corresponding polymers from which the particles are derived. This review article presents an overview on PCPs with emphasis on our group's recent achievements in the preparation of PCPs derived from optically active helical polymers and their applications. PCPs can be prepared via emulsion polymerization, precipitation polymerization, and suspension polymerization by starting from monomers. Emulsification of preformed chiral polymers and self-assembly approaches also can lead to PCPs. Chiral polymer-based core/shell particles, hollow particles, and magnetic particles are also covered because of their remarkable properties and significant potential applications.

Helical polymer as mimetic enzyme catalyzing asymmetric aldol reaction.

This Communication reports optically active helical substituted polyacetylenes which solely catalyzed asymmetric Aldol reaction between cyclohexanone and p-nitrobenzaldehyde; more importantly the helical structures are found to play crucial roles in the asymmetric catalysis, with a remarkable yield and ee (both up to 80%). A synergic effect is observed between the helical structures in the polymer main chains and the pendent prolinamide moieties for successfully catalyzing the asymmetric reaction. The role of the helical polymer backbones is further verified by tuning the relative helical structure content.

Using cellulose, starch and ß-cyclodextrin poly/oligosaccharides as chiral inducers for preparing chiral particles.

Poly/oligosaccharides are renewable natural resources with abundant chirality. Herein, we develop a general route to prepare optically active particles by using poly/oligosaccharides as both chiral inducers and growth templates. By complexing with Cu(NH3)42+ ions, OH groups on C2 and C3 in poly/oligosaccharides can transfer the chirality to Cu(II) and retain it in CuO. At the same time, poly/oligosaccharides direct growth of CuO by in situ transformation of Cu(NH3)42+ ions. Cellulose nanocrystal (CNC) and starch (ST) are used as representative polysaccharides, and ß-cyclodextrin (ß-CD) as a representative oligosaccharide, thus dandelion, duchesnea, and chrysanthemum-like composite particles with chiroptical activity are obtained. Besides, chiral CuO/poly(oligo)saccharide particles (CSP) demonstrate enantioselective ability by differentiating coordination with tryptophan (Trp) enantiomers and form Cu-Trp metal organic framework architectures with different morphologies. The study provides an easily accessible approach to prepare novel functional materials by poly/oligosaccharide-based chiral induction and hold great promise in chiral applications.

Fabrication of shape-controllable polyaniline micro/nanostructures on organic polymer surfaces: obtaining spherical particles, wires, and ribbons.

A novel strategy was developed in order to prepare various micro/nanostructured polyanilines (PANI) on polymer substrates. The strategy involved two main steps, i.e., a grafting polymerization of acrylate acid (AA) onto the surface of a polypropylene (PP) film and subsequently an oxidative polymerization of aniline on the grafted surface. By tuning the conformation of the surface-grafted poly acrylate acid (PAA) brushes, as well as the ratio of AA to aniline, the shape of the PANIs fixated onto the surfaces of the polymer substrate could be controlled to go from spherical particles to nanowires and eventually to nanoribbons. In these structures, the PAA brushes not only acted as templates but also as dopants of PANI, and thereby, the nanostructured PANIs could be strongly bonded with the substrate. In addition, the surface of the PP films grafted with polyaniline nanowires and nanoribbons displayed superhydrophobicity with contact angles for water of approxiamtely 145 and 151 degrees , respectively.

Biomass Vanillin-Derived Polymeric Microspheres Containing Functional Aldehyde Groups: Preparation, Characterization, and Application as Adsorbent.

The contribution reports the first polymeric microspheres derived from a biomass, vanillin. It reacted with methacryloyl chloride, providing monomer vanillin methacrylate (VMA), which underwent suspension polymerization in aqueous media and yielded microspheres in high yield (>90 wt %). By controlling the N2 bubbling mode and by optimizing the cosolvent for dissolving the solid monomer, the microspheres were endowed with surface pores, demonstrated by SEM images and mercury intrusion porosimetry measurement. Taking advantage of the reactive aldehyde groups, the microspheres further reacted with glycine, thereby leading to a novel type of Schiff-base chelating material. The functionalized microspheres demonstrated remarkable adsorption toward Cu(2+) (maximum, 135 mg/g) which was taken as representative for metal ions. The present study provides an unprecedented class of biobased polymeric microspheres showing large potentials as adsorbents in wastewater treatment. Also importantly, the reactive aldehyde groups may enable the microspheres to be used as novel materials for immobilizing biomacromolecules, e.g. enzymes.

Thermosensitive magnetic liposomes with doxorubicin cell-penetrating peptides conjugate for enhanced and targeted cancer therapy.

To specifically deliver cytotoxic drug to tumor cells and enhance cellular uptake is the key for effective cancer therapy. In this paper, we described a novel drug targeting system, which is designed to combine features of biological (cell-penetrating peptides, CPPs) and physical (magnetic) drug targeting for use in the magnetic hyperthermia-triggered release. A doxorubicin-CPPs conjugate (DOX-CPPs) was loaded into thermosensitive magnetic liposomes (TSMLs) (DOX-CPPs/TSMLs), and in vitro DOX-CPPs thermosensitive release activity, anti-proliferation effect, in vivo targeted delivery as well as in vivo antitumor activity were determined. The results demonstrated that the DOX-CPPs/TSMLs showed good physicochemical properties, effective anti-proliferation effect in MCF-7 cells in vitro. Additionally, in vivo study, DOX-CPPs/TSMLs under AC magnetic field displayed superior in vivo targeted delivery efficacy, antitumor efficacy in an MCF-7 xenograft murine model. In conclusion, the application of DOX-CPPs/TSMLs under AC magnetic field may provide a strategy for the selective and efficient delivery of drug.

Embolization of dural arteriovenous fistula of the anterior cranial fossa through the middle meningeal artery with Onyx.

OBJECTIVE: Dural arteriovenous fistula (DAVF) of the anterior cranial fossa is usually treated by surgical disconnection or endovascular embolization via the ophthalmic artery. The middle meningeal artery is a rarely used approach. This study investigated the safety and efficacy of embolization of DAVF of the anterior cranial fossa with Onyx through the middle meningeal artery. METHODS: A retrospective review of a prospective cerebral vascular disease database was performed. Patients with DAVF of the anterior cranial fossa managed with embolization through the middle meningeal artery with Onyx were selected. Information on demography, symptoms and signs, angiographic examinations, interventional treatments, angiographic and clinical results, and follow-up was collected and analyzed. RESULTS: Five patients were included in this study, four of whom had hemorrhage. All fistulas were fed by the bilateral ethmoidal arteries arising from the ophthalmic artery and by the anterior branch of the middle meningeal artery. The abnormal shunt unilaterally drained into the superior sagittal sinus with interposition of the cortical veins all five patients. All endovascular treatments were successful with evidence of an angiographic cure. No complications occurred, and all patients recovered uneventfully without neurologic deficits. There were nearly no symptoms among the patients during follow-up. CONCLUSION: Embolization of DAVF of the anterior cranial fossa via the middle meningeal artery with Onyx is safe, effective, and a good choice for management of DAVF. More cases are needed to verify these findings.

Preparation and application of abietic acid-derived optically active helical polymers and their chiral hydrogels.

A novel chiral monomer N-propargyl abietamide, M1, was synthesized from abietic acid and catalytically polymerized with (nbd)Rh+B-(C6H5)4 (nbd=norbornadiene), providing polymer [poly(1)] with a molecular weight of 13,000-36,000 at a yield of 59-84%. Poly(1) did not form stable helices in tetrahydrofuran at room temperature whereas copolymerization of M1 and the achiral N-propargylamide monomer, M2, led to the formation of helical optically active copolymers as indicated by circular dichroism studies, UV-vis spectroscopy, and specific optical rotation measurements. Hydrogels were prepared based on an optically active helical copolymer, poly(M1(0.32)-co-M2(0.68)) that exhibited enantioselective recognition toward l-alanine. The novel chiral polymers derived from abietic acid are expected to find applications in such areas as chiral recognition, chiral resolution, and chiral catalysis.

Treatment of dural arteriovenous fistula by balloon-assisted transarterial embolization with Onyx.

OBJECTIVE: This study evaluated the feasibility, safety, and efficacy of embolization of dural arteriovenous fistula via a very small, short feeding artery with the assistance of a balloon placed proximal to the tip of the microcatheter, such that the balloon serves as a plug. METHODS: Eight patients who underwent treatment of DAVF by balloon-assisted transarterial embolization with Onyx were retrospectively reviewed. Gender, age, angiography findings, procedure details, clinical and angiographic outcomes, complications, and follow-up were recorded and analyzed. RESULTS: Nine embolization procedures were performed in eight male patients via extracranial arteries. Balloon-assisted embolization was successful in all eight patients. A Hyperglide balloon was used in five patients, and a Hyperform balloon was used in three patients. Angiographic resolution of the fistula was achieved in all patients without complications. All patients recovered uneventfully. During the follow-up period of 7-19 months, all patients were asymptomatic except for one patient who experienced mild headaches. CONCLUSIONS: Treatment of DAVF by balloon-assisted embolization with Onyx achieved promising results, even in patients with very small and short feeding arteries. This technique allowed the treatment of DAVF cases where other techniques have failed.