Synthesis and Characterization of High-Performance Polymers Based on Perfluoropolyalkyl Ethers Using an Environmentally Friendly Solvent.

In comparison with polymers containing long perfluoroalkyl chains (CnF2n+1, n ≥ 8), perfluoropolyalkyl ethers (PFPEs) have been demonstrated to be environmentally friendly polymeric materials. Thus, PFPEs are expected to be alternatives to long perfluoroalkyl chain polymers. However, due to the poor solubility in common organic solvents they are generally prepared and used in fluorinated solvents, which can also cause harmful impacts on the environment. Therefore, it is urgent to explore a strategy for the preparation of high-performance PFPE polymers using environmentally friendly solvents. In this study, three kinds of novel methacrylate macromers bearing PFPE chains with low molar mass were designed and synthesized. The PFPE polymer coatings on polycarbonate plates were obtained by a combinational strategy of spin-coating and in situ photopolymerization of the macromers under UV irradiation. The results indicated that the polymer coatings could be prepared in nonfluorinated solvents, such as 2-propanol. Then the surface properties of the polymer coatings were investigated. It was found that the surface properties of the polymer coatings were related to the structures of the polymers. When CONH-C6H4 as a spacer was incorporated between the backbone and the PFPE chain, the hydrophobicity and oleophobicity of the polymer coatings were significantly enhanced, which is attributed to hydrogen bonds and π-π interaction between the PFPE chains. It is obvious that the synergetic effect of hydrogen bonds and π-π interaction can facilitate the PFPE chains to form a more stable fluorine-rich surface of the polymer coatings. Therefore, synthesis of a high-performance PFPE polymer has been successfully achieved based on PFPEs using an environmentally friendly solvent.

A New Strategy for the Synthesis of Fluorinated Polyurethane.

An alternating fluorinated copolymer based on chlorotrifluoroethylene (CTFE) and butyl vinyl ether (BVE) was synthesized by RAFT/MADIX living/controlled polymerization in the presence of S-benzyl O-ethyl dithiocarbonate (BEDTC). Then, using the obtained poly(CTFE-alt-BVE) as a macro chain transfer agent (macro-CTA), a block copolymer was prepared by chain extension polymerization of vinyl acetate (VAc). After a basic methanolysis process, the poly(vinyl acetate) (PVAc) block was transferred into poly(vinyl alcohol) (PVA). Finally, a novel fluorinated polyurethane with good surface properties due to the mobility of the flexible fluorinated polymer chains linked to the network was obtained via reaction of the copolymer bearing the blocks of PVA with isophorone diisocyanate (IPDI) as a cross-linking agent.

Cobalt-Mediated Radical Copolymerization of Chlorotrifluoroethylene and Vinyl Acetate.

Controlled radical copolymerization of chlorotrifluoroethylene (CTFE) and vinyl acetate (VAc) was successfully achieved in the presence of bis(acetylacetonato)cobalt(II) (Co(acac)2) as a mediated agent and 2,2'-azo-bis-isobutyronitrile (AIBN) as initiator. Both the molar mass and the fluorinated unit content of the copolymer could be controlled, and the chain extension polymerization of the obtained fluorinated copolymer was also achieved.

Photoinduced Reversible Morphological Transformation of Azobenzene-Containing Pseudo-2D Polymers.

2D polymer sheets containing azobenzene are successfully prepared by a facile strategy of "2D self-assembly polymerization (2DSP)" via free radical polymerization in solution. A bola amphiphile containing azobenzene as a novel monomer is designed and synthesized. The results indicate that single-layer covalent pseudo-2D polymers on a micrometer scale are obtained after polymerization with vinyl monomers. Moreover, the 2D polymer sheets are highly sensitive to UV light due to incorporation of azobenzene groups into the polymer. Upon alternative irradiation with UV and visible light, the morphological transformation between sheets and rolled-up nanotubes can be achieved based on the reversible trans-to-cis photoisomerization of azobenzene units in the 2D polymer sheets.

Self-exfoliation of 2D covalent organic frameworks: morphology transformation induced by solvent polarity.

Recently, covalent organic nanosheets (CONs) have emerged as functional two-dimensional (2D) materials for versatile applications. Strong interaction among layers and the instability of borate ester in moisture are the major hurdles to obtain few layered boron-containing CONs by exfoliation of their bulk counterparts. In this paper, we report a facile approach for preparation of few layered borate ester-containing CONs based on electrostatic repulsion of ions. We incorporated organic ionic groups into porous covalent organic frameworks (COFs) and it has been proved that the COFs with quaternary ammonium group could self-exfoliate into few layered ionic covalent organic nanosheets (iCONs) in polar organic solvents. Interestingly, the morphology of the iCOFs-A could be changed from a multilayered aggregation to nanocapsules, or 2D sheets when solvents with different polarity were used. In contrast, non-ionic covalent organic frameworks COFs-B could not self-exfoliate in various solvents. In addition, the self-exfoliated nanosheets could be used to fabricate uniform thin films on SiO2 wafer and the film exhibited explicit optical and electrical properties.

From 1D Polymers to 2D Polymers: Preparation of Free-Standing Single-Monomer-Thick Two-Dimensional Conjugated Polymers in Water.

Recently, investigation on two-dimensional (2D) organic polymers has made great progress, and conjugated 2D polymers already play a dynamic role in both academic and practical applications. However, a convenient, noninterfacial approach to obtain single-layer 2D polymers in solution, especially in aqueous media, remains challenging. Herein, we present a facile, highly efficient, and versatile "1D to 2D" strategy for preparation of free-standing single-monomer-thick conjugated 2D polymers in water without any aid. The 2D structure was achieved by taking advantage of the side-by-side self-assembly of a rigid amphiphilic 1D polymer and following topochemical photopolymerization in water. The spontaneous formation of single-layer polymer sheets was driven by synergetic association of the hydrophobic interactions, π-π stacking interactions, and electrostatic repulsion. Both the supramolecular sheets and the covalent sheets were confirmed by spectroscopic analyses and electron microscope techniques. Moreover, in comparison of the supramolecular 2D polymer, the covalent 2D polymer sheets exhibited not only higher mechanical strength but also higher conductivity, which can be ascribed to the conjugated network within the covalent 2D polymer sheets.

Preparation of Hydrophilic Encapsulated Carbon Nanotubes with Polymer Brushes and Its Application in Composite Hydrogels.

Carbon nanotubes can be used as promising reinforcement materials to improve the mechanical properties of hydrogels, but their poor dispersibility in aqueous solution severely limits their application in preparation of composite hydrogels. Therefore, to develop method for modification of carbon nanotubes is still highly desired. In this paper, a facile approach for preparation of the hydrophilic carbon nanotube was reported. The encapsulated multiwalled carbon nanotubes (E-CNT-PAA) with cross-linked shell structure were obatined through the self-assembly of the amphipathic azide diblock copolymers poly(acrylic acid)-b-poly(4-vinylbenzyl azide-co-styrene) (PAA-b-(PVBA-co-PS)), and the cross-linking of inside azide groups under UV irradiation. The encapsulated MWCNT was characterized by FT-IR, Raman and TEM. It was demonstrated that the dispersibility of the hydrophilic encapsulated MWCNTs was related to the length of the poly(acrylic acid) brushes. Subsequently, thermal-responsive composite hydrogels (PNIPAM/E-CNT-PAA) were prepared by in situ polymerization of N-isopropylacrylamide (NIPAM) in the solution of dispersed E-CNT-PAA. The results showed that the composite hydrogels possessed high mechanical properties compared to the pure PNIPAM hydrogel. The tensile strength and elongation of the composite hydrogels were highly dependent on the content of the modified MWCNTs. The composite hydrogels with 0.46 wt % MWCNTs exhibited tensile strength of 97.7 kPa and elongation of 465%, which were at least 3.5× higher than those of the PNIPAM hydrogel. Moreover, the composite hydrogels displayed significant and reversible stimuli-responsiveness.

A Diheteroatom Fluoroalkylation Reagent for Preparation of S- and N-Containing Fluoroalkyl Compounds and Sulfonic Acid Polymer.

The first stable diheteroatom fluoroalkylation reagent, 2-((2-azido-1-chloro-1,2,2-trifluoroethyl)thio)pyrimidine (ACTP), has been prepared by a novel method. By using this reagent, various fluorinated thioethers and sulfones have been successfully prepared. The dearylation and dearylation-oxidation of fluoroalkyl 2-pyrimidyl sulfone in one-pot reaction were investigated systematically, and the results demonstrated that both fluoroalkyl sulfinates and sulfonates could be obtained in high yields. In addition, ACTP proved to be useful for the preparation of a fluorinated sulfonic acid proton-exchange membrane.

Novel Reversible Mechanochromic Elastomer with High Sensitivity: Bond Scission and Bending-Induced Multicolor Switching.

Although the rational designed mechanochromic polymer (MCP) materials have evoked major interest and experienced significant progress recently, it is still a great challenge to develop a facile and effective strategy for preparation of reversible broad-spectrum MCPs with a combination of wide-range color switch ability and high sensitivity, which thus make it possible to mimic gorgeous color change as in nature. Herein, we designed and synthesized a novel rhodamine-based mechanochromic elastomer. Our results demonstrated that the elastomer exhibited very promising and unique properties. Three primary fluorescence colors were presented during continuous uniaxial extension and relaxing process, and reversible broad-spectrum fluorescence color change could be achieved consequently. The fluorescence quantum yield of the opened zwitterion of this new mechanophore was as high as 0.67. In addition, the elastomer showed very high sensitivity to stress with a detectable activation strain of ∼0.24, which was much smaller than those reported in the previous literature reports. Meantime, the easy-to-obtain material, facile preparation, and good mechanical property also made it suitable for potential practical applications.

Pyrene boronic acid cyclic ester: a new fast self-recovering mechanoluminescent material at room temperature.

Two pyrene boronic acid cyclic esters, PPB and NPB, were prepared and their solid state fluorescence properties were investigated. Interestingly, the results showed that PPB with a 5-membered ring possessed reversible mechanoluminescence and vapochromic behaviour with a fast self-recovering ability at room temperature, whereas NPB with a 6-membered ring did not. It was demonstrated that the mechanically responsive fluorescence properties of PPB and NPB were highly related to the molecular packing mode and the solid state plasticity.

A highly stable and versatile heterobifunctional fluoroalkylation reagent for preparation of fluorinated organic compounds.

A highly stable heterobifunctional fluoroalkylation reagent, 1-azido-2-chloro-1,1,2-trifluoro-2-iodoethane (ACTI) has been prepared in high yield for the first time by a new method. Moreover, the reactivity of both the azido group and the iodine atom of the reagent was systematically investigated and the results demonstrate that this compound is a very versatile and useful new fluoroalkylation reagent for preparation of fluorinated organic compounds.

Synthesis of Photodegradable Polystyrene with Trithiocarbonate as Linkages.

Multiblock polystyrenes (PS) with trithiocarbonate groups as linkages are prepared via reversible addition-fragmentation chain-transfer polymerization using polytrithiocarbonate as a chain transfer agent. The photodegradability of the multiblock PS in the solid state is investigated under UV irradiation at room temperature in an air atmosphere. The experimental results demonstrate that the trithiocarbonate linkages in the multiblock PS can be broken under UV light irradiation at room temperature and the multiblock PS is degraded into separate PS blocks. Gel permeation chromatography measurement reveals that the molecular weight of multiblock PS is reduced from 27 900 to 7900 g mol(-1) after UV light irradiation for 745 h. Moreover, the thermal stability of the multiblock PS is examined and the results indicate that the incorporation of trithiocarbonate shows little influence on the thermal stability of multiblock PS.

Flavone-based ESIPT ratiometric chemodosimeter for detection of cysteine in living cells.

We have designed and synthesized a novel ratiometric fluorescent chemodosimeter MHF-based ESIPT process for specific detection of cysteine among the biological thiols. The probe MHF shows very weak blue fluorescence under UV excitation. Upon addition of cysteine (Cys), the reaction of Cys with MHF induces acrylate hydrolysis, thereby enabling the ESIPT process to shift the weak blue emission to a strong green emission with about 20-fold enhancement. We utilized (1)H NMR spectra to elucidate the fluorescence sensing mechanism. Moreover, the cellular imaging experiment indicated the MHF possessed excellent selectivity, low cytotoxicity, and desirable cell permeability for biological applications.

A facile one pot strategy for the synthesis of well-defined polyacrylates from acrylic acid via RAFT polymerization.

A facile one pot strategy for the preparation of linear and hyperbranched polyacrylates has been successfully developed by the combination of in situ esterification of acrylic acid with halogenated compounds promoted by 1,1,3,3-tetramethylguanidine (TMG) and RAFT polymerization.

A novel poly(2,6-dimethyl-1,4-phenylene oxide) with trifunctional ammonium moieties for alkaline anion exchange membranes.

2,4,6-Tri(dimethylaminomethyl)-phenol was synthesized as a trifunctional moiety and incorporated onto poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) to obtain a novel quaternary ammonium functionalized PPO (PPO-TQA). Membranes of the polymer were fabricated and exhibited high conductivity, a low swelling ratio and water uptake.

Facile and Highly Efficient Strategy for Synthesis of Functional Polyesters via Tetramethyl Guanidine Promoted Polyesterification at Room Temperature.

A facile and highly efficient strategy for the synthesis of functional polyesters from 10-undecenoic acid, which is abundantly available and derived from ricin oil, has been successfully achieved using 1,1,3,3-tetramethyl guanidine (TMG) as a promoter at room temperature. The experimental results indicate that high molecular weight polyesters have been obtained and a variety of functional groups, such as alkenyl, alkynyl, nitro, epoxy, hydroxyl, and bromoisobutyrate, can be incorporated as pendant groups. The structures of the obtained polymers were demonstrated by 1H and 13C NMR spectroscopy and their thermal properties were studied by DSC and TGA.

POSS-containing red fluorescent nanoparticles for rapid detection of aqueous fluoride ions.

Polyhedral oligomeric silsesquioxane (POSS)-containing red fluorescent nanoparticles were designed and prepared for rapid detection of aqueous fluoride ions by virtue of the fluoride-triggered self-quenching of perylene bisimide dyes in nanoparticle cores.

Utilizing modified flavonoids to construct a chemodosimeter array for discrimination of different palladium species by using principal component analysis.

A simple chemodosimeter array has been successfully achieved for the detection and discrimination of different palladium species by using principal component analysis.

Use of alcohols as reducing agents for synthesis of well-defined polymers by AGET-ATRP.

Alcohols have been demonstrated to be efficient reducing agents for AGET-ATRP for the first time. Well-controlled polymerizations have been successfully achieved with the typical characteristics of "living"/controlled radical polymerization.

A new ratiometric ESIPT sensor for detection of palladium species in aqueous solution.

An aqueous ratiometric ESIPT sensor with a 87 nM (15.4 ppb) detection limit was successfully synthesized and applied for detection of all oxidation states of palladium species.