In situ preparation of hetero-polymers/clay nanocomposites by CUAAC click chemistry

A series of polymer/clay nanocomposites containing mechanistically two different polymers, poly(ethylene glycol) (PEG) and poly(epsilon caprolactone) (PCL), were prepared by simultaneous copper(I)-catalyzed alkyne-azide cycloaddition click reactions. Both clickable polymers, PEG-Alkyne and PCL-Alkyne, were simultaneously clicked on to azide-functional montmorillonite (MMT-N₃) nanoclay to get corresponding PEG-PCL/MMT nanocomposites. The chemical structures of the resulting nanocomposites were verified by following azide and silicone-oxygen bands using FT-IR and characteristic bands of PEG and PCL segments using ¹H-NMR spectroscopy. The combined XRD and TEM analysis confirmed that all PEG-PCL/MMT nanocomposites had partially exfoliated/intercalated morphologies. In addition, the increase of MMT-N₃ loading not only improved the onset and maximum degradation temperatures of the nanocomposites but also their char yields. Furthermore, the incorporation of MMT-N₃ in the polymer matrix did not significantly influence the crystallization behavior of both PEG and PCL segments.     

Controllable glycosylation of polyphosphazene via radical thiol–yne click chemistry

We describe a versatile approach to synthesize glycosylated polyphosphazenes with controllable density of glycosyl groups. These glycopolymers have been synthesized by the nucleophilic substitution of poly(dichlorophosphazene) with propargylamine and subsequent “thiol–yne” click reaction between poly[di(propargylamine)phosphazene] and 2,3,4,6‐tetra‐O‐acetyl‐1‐thio‐β‐D ‐glucopyranose (SH‐GlcAc₄). The polymers were characterized with FTIR and ¹H NMR. We found that the high steric hindrance of SH‐GlcAc₄ plays a key role in the overall reaction process, and ～55% of the alkyne groups participate in the “thiol–yne” click reaction. About 8% of the alkyne groups convert to alkene groups at the end of click reaction. The substitution of alkyne/alkane mixture was conducted to reduce the alkyne density in the side groups of polyphosphazenes and minimize the influences of this steric effect. Mixed‐substituent polyphosphazene was synthesized with 2:3 ratio of alkyne and alkane. In this case, almost no alkyne group remains after the “thiol–yne” click reaction, and thus the glycosylated polyphosphazene is able to form into micelles through self‐assembly process. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Facile preparation of antibacterial polymer coatings via thiol-yne click photopolymerization

Novel antibacterial polymer coatings were prepared by a facile thiol-yne click photopolymerization of 1-propargyl-3-alkyl-1,3-diazanyl-2,4-cyclopentadiene bromide ([PAIM]Br) and tetra(3-mercapto-propionate) pentaerythritol (PETMP) (2:1 molar ratio) using 2,2-dimethoxy-2-phenylacetophenone (DMPA) as initiator. The antibacterial activity of the coatings was tested against Staphylococcus aureus (ATCC 292130) and Escherichia coli (ATCC 25922) by the dynamic shake method. The evaluation results revealed the antibacterial polymer coatings exhibited excellent inhibitory activity against S. aureus and E. coli, especially for S. aureus.     

Heterofunctional RAFT‐derived PNIPAM via cascade trithiocarbonate removal and thiol‐yne coupling click reaction

An efficient one‐pot process to functionalize the α‐ and ω‐positions of RAFT‐derived poly(N‐isopropylacrylamide) (PNIPAM) by two inherently different mechanistic pathways is reported. The method relies on the RAFT polymerization of NIPAM using a new alkyne‐based RAFT agent, namely 2‐cyano‐5‐oxo‐5‐(prop‐2‐yn‐1‐ylamino)pentan‐2‐yl dodecyltrithiocarbonate (COPYDC) and the combination of thiol‐yne click chemistry and thiocarbonylthio chain‐end removal reactions. COPYDC was prepared in good yield and used as an efficient chain transfer agent during the RAFT polymerization of NIPAM. Well‐defined polymers with controlled molar masses ( = 7500–14,700 g.mol^?1) and narrow dispersities (? = 1.18–1.26) are thus obtained. Cascade thiol‐yne click reaction at the alkyne α‐chain end and trithiocarbonate removal at the ω‐chain end are successfully achieved using benzyl mercaptan and excess AIBN. The reported method provides a facile and mild route to heterofunctional telechelic RAFT polymers with predictable molar masses and low dispersities. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 3597–3606     

Facile synthesis of dendrimers combining aza‐Michael addition with Thiol‐yne click chemistry

We report a highly efficient approach to prepare dendrimers by taking advantage of the orthogonal characteristic of aza‐Michael addition and thiol‐yne reactions. A fifth generation dendrimer was synthesized within five steps without protection/activation procedures. The reactions proceed under benign conditions without byproducts, and the target products can be easily purified via extraction or precipitation without chromatography. The structure of each generation dendrimer was characterized using NMR spectroscopy, size exclusion chromatography, and mass spectrometry. The obtained dendrimers can have peripheral amine or alkyne groups. We demonstrated that these groups can be used for selective and specific conjugation with various functional groups. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Versatile functionalization of aromatic polysulfones via thiol‐ene click chemistry

A facile, efficient approach for preparation of functionalized aromatic polysulfones by postpolymerization modification with thiol‐ene click chemistry is described. The key synthetic strategy is to incorporate a pendant vinyl ether group into polysulfones as a reactive precursor with controlled degrees of functionalization. Synthetic utility of the pendant alkenyl group is demonstrated by generating diverse polymer derivatives using thiol‐ene functionalization including glycosylated polysulfone. The highly reactive alkene platform in the polymer affords convenient, metal‐free, and azide‐free click transformations to create diverse ranges of new functionalized polysulfones that could be applied in various applications. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3237–3243     

Strength enhancement of nanostructured organogels through inclusion of phthalocyanine-containing complementary organogelator structures and in situ cross-linking by click chemistry

Stable photoactive organogels were successfully prepared by a two-step sequence involving: 1) formation of thermoreversible organogels by use of a combination of low-molecular-weight organogelators (LMOGs) and ZnII-phthalocyanine (ZnII-Pc) moieties containing complementary organogelator structures, and 2) strength enhancement of the gels by in situ cross-linking with the aid of CuI-catalysed azide-alkyne [3+2] cycloadditions (CuAACs). The optimum click reaction was carried out between a flexible C6 aliphatic diazide and a suitable dialkyne (molar ratio 1:1) added in a low proportion relative to the organogelator system [LMOG+ZnIIPc]. The dialkyne unit was incorporated into a molecule resembling the LMOGs structure in such a way that it could also participate in the self-assembly of [LMOG+ZnIIPc]. The significant compatibility of the multicomponent photoactive organogels towards this strengthening through CuAACs allowed their sol-to-gel transition temperatures (Tgel) to be enhanced by up to 15 degrees C. The Tgel values estimated by the "inverse flow method" were in good agreement with the values obtained by differential scanning calorimetry (DSC). Rheological measurements confirmed the viscoelastic, rigid, and brittle natures of all Pc-containing gels. Transmission and scanning electron microscopy (TEM, SEM) and atomic force microscopy (AFM) revealed the fibrilar nature of the gels and the morphological changes upon cross-linking by CuAAC. Emission of a red luminescence from the dry nanoscale fibrous structure-due to the self-assembly of the Pc-containing compounds in the organogel fibres-was directly observed by confocal laser scanning microscopy (CLSM). The optical properties were studied by UV/Vis and fluorescence spectroscopy. Fluorescence, Fourier-transform infrared (FTIR) and circular dichroism (CD) measurements were also carried out to complete the physicochemical characterization of selected gels. As a proof of concept, two different organogelators (cholesterol- and diamide-based LMOGs) were successfully used to validate the general strategy.     

Exploring thiol‐yne based monomers as low cytotoxic building blocks for radical photopolymerization

The last decade has seen a remarkable interest in the development of biocompatible monomers for the realization of patient specific medical devices by means of UV‐based additive manufacturing technologies. This contribution deals with the synthesis and investigation of novel thiol‐yne based monomers with a focus on their biocompatibility and also the mechanical properties in their cured state. It could be successfully shown that propargyl and but‐1‐yne‐4‐yl ether derivatives have a significant lower cytotoxicity than the corresponding (meth)acrylates with similar backbones. Together with appropriate thiol monomers, these compounds show reactivities in the range of (meth)acrylates and almost quantitative triple bond conversions. A particular highlight is the investigation of the network properties of photo cured alkynyl ether/thiol resins by means of low field solid state nuclear magnetic resonance spectroscopy. Additionally, dynamic mechanical analysis of those polymers revealed that monomers containing rigid backbones lead to moduli and glass transition temperatures (T_g's), sufficiently high for the fabrication of medical devices by UV based additive manufacturing methods. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3484–3494     

Thiol‐yne Click Adamantane Monolithic Stationary Phase for Capillary Electrochromatography

A porous crosslinked organic polymer based on N‐acryloxysuccinimide (NAS) and ethylene dimethacrylate (EDMA) was prepared inside 75 µm i.d. fused silica capillary as functionalizable monolithic stationary phase for electrochromatographic applications. Succinimide groups on the monolith surface provide reactive sites able to react readily through standard electrophile‐nucleophile chemistry. Propargylamine was used to prepare alkyne functionalized poly(NAS‐co‐EDMA). Onto this thiol‐reactive polymer surface was grafted adamantane units via a photochemically‐driven addition reaction. Chemical characterization was performed in situ after each synthetic step by means of Raman spectroscopy and grafting kinetics was investigated to ensure quantitative grafting of 1‐adamantanethiol. The as‐designed monolithic stationary phase exhibited typical reversed‐phase separation mechanism as evidenced by the linear increase of the logarithm of retention factor of neutral aromatic solutes with the increase of the aqueous buffer content in the mobile phase.     

Silica/poly (N‐vinylimidazolium) nanospheres by combined RAFT polymerization and thiol‐ene click chemistry

We report a facile method that combined sol–gel reaction, reversible addition–fragmentation chain transfer (RAFT)/macromolecular design via interchange of the xanthates process and thiol‐ene click reaction to prepare monodisperse silica core‐poly(N‐vinylimidazole) (PVim) shell microspheres of 200 nm in average diameters. First, silica with C = C double bonds was prepared by the sol–gel reaction of 3‐(trimethoxysilyl)propyl methacrylates (MPS) with tetraethoxysilane in ethanol; SiO₂@PVim were subsequently prepared by grafting PVim chain (Mn = 9800 g/mol, polydispersity index = 1.22) to MPS‐SiO₂ via the thiol‐ene click chemisty. The obtained SiO₂@PVim microspheres show higher catalytic activity toward the hydrolysis of p‐nitrophenyl acetate compared with the PVim homopolymers. The as‐prepared composites have been characterized by scanning electron microscopy, transmission electron microscopy, thermal gravimetric analysis and Fourier transform infrared spectrometry analysis. Copyright © 2014 John Wiley & Sons, Ltd.     

Orthogonal multiple click reactions in synthetic polymer chemistry

This review highlights the concept of multiple click reaction strategy which is utilized for design and synthesis of well‐defined complex macromolecular structures as well as multifunctionalization of well‐defined polymers. This review examines the click combinations mainly from double to quadruple and additionally from the most frequently used to the least. The present review may also be regarded as an update for recent reviews dealing with specifically double and triple click reaction combinations in synthetic polymer chemistry. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3147–3165     

DNA-associated click chemistry

This review highlights the most recent advances in click chemistry associated with DNA.Cu[I]-catalyzed azides-alkynes Huisgen cycloadditions(CuAAC)and a strain-promoted alkyne-azide cycloaddition(SPAAC)are two popular click reactions that have great impact in DNA science.The simplicity,versatility,orthogonality,and high efficiency of click reaction along with a stable triazole product have been instrumental for the successful application of this reaction in the field of nucleic acid chemistry.CuAAC and SPAAC reactions have been widely used for DNA modification,including DNA labeling,metallization,conjugation,cross-linking,and ligation.Modified oligodeoxynucleotides obtained from click reaction have been extensively applied in the fields of drug discovery,nanotechnology,bio-conjugation,and material sciences,among others.The most recent advances in the synthesis and applications of clickable DNAs are discussed in detail in this article.     

Reactive Polymer Coatings: A General Route to Thiol‐ene and Thiol‐yne Click Reactions

Reactive polymer coatings were synthesized via chemical vapor deposition (CVD) polymerization process. These coatings decouple surface design from bulk properties of underlying materials and provide a facile and general route to support thiol‐ene and thiol‐yne reactions on a variety of substrate materials. Through the reported technique, surface functions can be activated through a simple design of thiol‐terminated molecules such as polyethylene glycols (PEGs) or peptides (GRGDYC), and the according biological functions were demonstrated in controlled and low‐fouling protein adsorptions as well as accurately manipulated cell attachments.     

Synthesis of main chain polymeric benzophenone photoinitiator via thiol‐ene click chemistry and Its use in free radical polymerization

Main chain polymeric benzophenone photoinitiator (PBP) was synthesized by using “Thiol‐ene Click Chemistry” and characterized with ¹H NMR, FTIR, UV, and phosphorescence spectroscopies. PBP as a polymeric photoinitiator presented excellent absorption properties (ε₂₉₄ = 28,300 mol^?1L^?1cm^?1) compared to the molecular initiator BP (ε₂₅₂ = 16,600 mol^?1L^?1cm^?1). The triplet energy of PBP was obtained from the phosphorescence measurement in 2‐methyl tetrahydrofurane at 77 K as 298.3 kJ/mol and according to phosphorescence lifetime, the lowest triplet state of PBP has an n‐π* nature. Triplet–triplet absorption spectrum of PBP at 550 nm following laser excitation (355 nm) were recorded and triplet lifetime of PBP was found as 250 ns. The photoinitiation efficiency of PBP was determined for the polymerization of Hexanedioldiacrylate (HDDA) with PBP and BP in the presence of a coinitiator namely, N‐methyldiethanolamine (MDEA) by Photo‐DSC. The initiation efficiency of PBP for polymerization of HDDA is much higher than for the formulation consisting of BP. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

One‐pot preparation of an organic polymer monolith by thiol‐ene click chemistry for capillary electrochromatography

A novel organic monolith was successfully fabricated by a one‐pot thiol‐ene click reaction of triallyl isocyanurate with pentaerythritol tetrakis‐(2‐mercaptoacetate) and mercaptopropionic acid in the presence of porogens. We investigated the effects of the ratio of monomer and cross‐linking agent, the type and ratio of porogen, and click reaction temperature on the permeability and morphology of the prepared poly triallyl isocyanurate‐co‐pentaerythritol tetrakis (2‐mercaptoacetate) monoliths. The monolith was also characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. The results indicated that the monoliths had continuous porous framework, good permeability, and high mechanical stability. A series of analytes with different properties such as alkylbenzenes, polycyclic aromatic hydrocarbons, anilines, and phenols were used to evaluate the electrochromatographic performance of the prepared monoliths in pressurized capillary electrochromatography. The prepared polymer monolith showed typical reversed‐phase electrochromatographic behavior for hydrophobic substances. Moreover, the prepared monolith showed a mix of reversed‐phase and cation exchange interaction modes for basic aniline compounds. The minimum plate height of the monolith was 8.76 μm (132 100 plates/m) for propylbenzene. These results demonstrated that one‐pot thiol‐ene click chemistry can provide a simple and reliable method for the preparation of organic monoliths.