Biobased Aromatic-Aliphatic Polyols from Cardanol by Photochemical Thiol-ene Reaction

Biobased aromatic-aliphatic polyols were previously synthesized from a thermal thiol-ene reaction of propoxylated cardanol with 2-mercaptoethanol(ME)in the presence of azobisisobutyronitrile(AIBN)as a radical initiator.Cardanol used for this purpose was obtained as a dark-brown liquid(Gardner Color Reference^18).The photochemical thiol-ene reaction can also be used to prepare aromatic-aliphatic polyols by employing cardanol.Via the photochemical thiol-ene reaction,2-mercaptoethanol was added successfully to C=C double bond of cardanol,suggesting that phenolic group may not play an inhibitory role in the radical thiol-ene reaction.However,we preferred to alkoxylate the phenolic hydroxyl group of cardanol,which is much more reactive with isocyanates than phenolic hydroxyls,to generate a new aliphatic hydroxyl group.Furthermore,the functionality of polyols was also improved by two methods:1)using 1-thio-glycerol instead of 2-mercaptoethanol and 2)using alkoxylated cardanol with glycidol(Cardanol-GLY)instead of propoxylated cardanol(Cardanol-PO).These polyols were then used in preparation of rigid polyurethane foams that can be useful in various applications such as insulation of freezers,pipes and storage tanks in food and chemical industries.

Biobased Aromatic-Aliphatic Polyols by Thiol-Ene Reactions of Propoxylated Mercaptanized Cardanol

Aromatic-aliphatic polyols were obtained previously from the thiol-ene reactions of propoxylated cardanol with hydroxyalkyl mercaptans;these aromatic-aliphatic polyols were then utilized in the preparation of rigid polyurethane foams with excellent properties.The current work describes a variant of cardanol polyol synthesis by thiol-ene reactions in three steps.The first step is propoxylation of cardanol by reacting cardanol with propylene oxide;the second step is mercaptanization of propoxylated cardanol by reacting double bonds with hydrogen sulfide;and the third step involves the addition of the thiol groups of mercaptanized propoxylated cardanol to the double bonds of allyl alcohol,glycerol-1-allyl ether,and trimethylolpropane allyl ether.Thus,obtained polyols were characterized by standard analytical methods.Rigid polyurethane foams prepared from these polyols show promising physical-mechanical properties.The rigid polyurethane foams can be used for various applications such as thermo-insulation of freezers,storage tanks and pipes for food and chemical industries,wood substitutes and flotation materials.

Eutectic Solution Enables Powerful Click Reaction for In-Situ Construction of Advanced Gel Electrolytes

Thiol-ene click reaction is an intriguing strategy for preparing polymer electrolytes due to its high activity,atom economy and less side reaction.However,the explosive reaction rate and the use of non-electrolytic amine catalyst hamper its application in in-situ batteries.Herein,a nitrogen-containing eutectic solution is designed as both the catalyst of the thiol-ene reaction and the plasticizer to in-situ synthesize the gel polymer electrolytes,realizing a mild in-situ gelation process and the preparation of high-performance gel electrolytes.The obtained gel polymer electrolytes exhibit a high ionic conductivity of 4×10^(−4)S cm^(−1)and lithium-ion transference number(t_(Li)^(+))of 0.51 at 60°C.The as-assembled Li/LiFePO_(4)(LFP)cell delivers a high initial discharge capacity of 155.9 mAh g^(-1),and a favorable cycling stability with the capacity retention of 82%after 800 cycles at 1 C is also obtained.In addition,this eutectic solution significantly improves the rate performance of the LFP cell with high specific capacity of 141.5 and 126.8 mAh g^(-1)at 5 C and 10 C,respectively,and the cell can steadily work at various charge–discharge rate for 200 cycles.This powerful and efficient strategy may provide a novel way for in-situ preparing gel polymer electrolytes with desirable comprehensive performances.

Thiol-ene conjugation of a VEGF peptide to electrospun scaffolds for potential applications in angiogenesis

Vascular endothelial growth factor(VEGF)plays a vital role in promoting attachment and proliferation of endothelial cells,and induces angiogenesis.In recent years,much research has been conducted on the functionalization of tissue engineering scaffolds with VEGF or a VEGF-mimetic peptide to promote angiogenesis.However,most chemical reactions are nonspecific and require organic solvents,which can compromise control over functionalization and alter peptide/protein activity.An attractive alternative is the fabrication of functionalizable electrospun fibers,which can overcome these hurdles.In this study,we used thiol-ene chemistry for the conjugation of a VEGF-mimetic peptide to the surface of poly(ε-caprolactone)(PCL)fibrous scaffolds with varying amounts of a functional PCL-diacrylate(PCL-DA)polymer.30%PCL-DA was selected due to homogeneous fiber morphology.A VEGF-mimetic peptide was then immobilized on PCL-DA fibrous scaffolds by a light-initiated thiol-ene reaction.7-Mercapto-4-methylcoumarin,RGD-FITC peptide and VEGF-TAMRA mimetic peptide were used to validate the thiol-ene reaction on the fibrous scaffolds.Tensile strength and elastic modulus of the 30%PCL-DA fibrous scaffolds were significantly increased after the reaction.Conjugation of the 30%PCL-DA fibrous scaffolds with the VEGF peptide increased the surface water wettability of the scaffolds.Patterned structures could be obtained after using a photomask on the fibrous film.Moreover,in vitro studies indicated that scaffolds functionalized with the VEGF-mimetic peptide were able to induce phosphorylation of the VEGF receptor and enhanced HUVECs survival,proliferation and adhesion.A chick chorioallantoic membrane(CAM)assay further indicated that the VEGF peptide functionalized scaffolds were able to promote angiogenesis in vivo.These results show that scaffold functionalization can be controlled via a simple polymer mixing approach,and that the functionalized VEGF peptide-scaffolds have potential for vascular tissue regeneration.

Employing the thiol-ene click reaction via metal-organic frameworks for integrated sonodynamic-starvation therapy as an oncology treatment

Hypoxia in the tumor microenvironment(TME)greatly limits the tumor-killing therapeutic efficacy of sonodynamic therapy(SDT);this phenomenon is further exacerbated by increased glutathione(GSH)levels in cancer cells.Simultaneously,cancer starvation therapy is increasingly recognized nowadays as a promising clinical translation,but the efficacy of glucose oxidase(GOx)-based starvation therapy is also limited by the lack of oxygen in the tumor.Glyceraldehyde-3-phosphate dehydrogenase(GAPDH)is a key glycolytic enzyme and can therefore be a target for starvation therapy in the absence of oxygen engagement.Here,we proposed thiol-ene click reactions based on a two-dimensional metal-organic framework(MOF)modification for tumor treatments to enable the combination of SDT and starvation therapy.Experimental studies demonstrated that the prepared material could consume GSH and GAPDH free from oxygen in TME,which benefited from the thiol-ene click reactions between the MOFs and thiol substances in cancer cells.Further experiments in vitro and in vivo indicated the prepared MOF materials could kill cancer cells efficiently.This study is expected to create a promising avenue for thiol-ene click reactions in SDT and starvation therapy for cancer.

Functionalized Polyphosphoester via Living Ring-opening Polymerization and Photochemical Thiol-ene Click Reaction

Poly(ethylene phosphonate)was synthesized via the living ring-opening polymerization of cyclic phos-phonate monomer catalyzed by organocatalyst.The pendant vinyl ftmctionalities were employed to perform the pho-tochemical click reactions wi&tMols.We demonstrated that both small thiol molecules and macromolecular thiols could be efficiently coupled into the PPE side chains,enabling the rapid and efficient functionalization of polyphos-phoesters(PPE).

Click-Formed Polymer Gels with Aggregation-Induced Emission and Dual Stimuli-Responsive Behaviors

Stimuli-responsive polymer gels have recently attracted great attention due to their heat/solvent resistance,dimensional stability,and unique sensitivity to external stimuli.In this work,we synthesized thiol-functionalized tetraphenylethylene(TPE)and constructed polymer gels through thiol-ene click reaction.The synthetic process of the polymer gels could be monitored by fluorescence emission of TPE moieties based on aggregation-induced emission mechanism.In addition,due to the dual redox-and acid responsiveness of the polymer gels,in the presence of dithiothreitol and trifluoroacetic acid,fluorescence quenching of the polymer gels can be observed.This stimuli-responsive characteristics endows the polymer gels with potential applications in fluorescent sensing and imaging,cancer diagnosis and selfhealing materials.

Preparation of amphiphilic graft copolymer with polyisoprene backbone by combination of anionic polymerization and "click" reaction

A novel graft copolymer consisting of polyisoprene backbone and hydrophilic side chain with carbamic acid ester functional group was prepared via thiol-ene＂click＂reaction and alcohol-isocyanate reactions.Polyisoprene was synthesized by anionic polymerization using n-butyl lithium as initiator,and the pendant hydroxyl groups were introduced by the thiol-ene reaction of mercaptoethanol with the double bond of 1,2-addition units of PI backbone in the presence of radical initiator azobisisobutyronitrile. Isocyanate end group capped poly（ethylene glycol）（mPEG-NCO） was grafted onto the PI backbone through alcoholisocyanate reaction between the pendant hydroxyl groups and isocyanate group of mPEG-NCO.The structure of the graft copolymer were characterized and confirmed by means of size-exclusion chromatography,~1H NMR and FTIR spectroscopy.

One-pot synthesis of hyperbranched poly(amido amine) clicked with a sugar shell via Michael addition polymerization and thiol click reaction

This paper reports the production of glycopolymers via a simple and flexible method.A novel glycopolymer with a hyperbranched poly(amido amine) core and a sugar shell (HPAA-GLc) was synthesized by using thiol-ene click reaction via facile one-pot method.Hyperbranched poly(amido amine) with vinyl terminals was first synthesized by Michael addition polymerization of N,N'-methylene bisacrylamide (MBA) with 1-(2-aminoethyl) piperazine (AEPZ).Subsequently,thiol-ene click reaction between vinyl units of hyperbranched poly(amido amine) and thio-glucose was performed in situ.Based on the NMR result,all the vinyl groups reacted with thiol-glucose in 120 min.Strong photoluminescence emission was observed from the aqueous solution of HPAA-GLc.

Precision Synthesis of End-Functionalized Star Poly(vinyl alcohol)s by RAFT Polymerization and Post-polymerization Modification

Poly(vinyl alcohol)(PVA)has been widely used in industrial and consumer products.In this study,we aimed to address this challenge by synthesizing well-defined multiarm poly(vinyl acetate)(PVAc)through the use of nonhydrolyzable vinyl ethertype multifunctional RAFT agents.The control over molecular weights was achieved by the RAFT process to afford polymers with dominant head-to-head linkages at the terminal.Especially,quantitative end-functionalization of the synthesized PVAc was performed using Michael thiol−ene or disulfide exchange reactions.Consequently,saponification of the PVAc enabled the synthesis of end-functionalized multiarm PVA in an efficient manner.This straightforward approach afforded well-defined functional PVAs,which enable further chemical modification,thus widening the utility of PVA in a range of applications,such as precisely controlled network synthesis and bioconjugation.

Postsynthetic Modification of Metal-Organic Frameworks through Click Chemistry

The postsynthetic modification （PSM） of metal-organic frameworks （MOFs） has emerged as a powerful tool to chemically tailor the interior of MOFs. In this review, we summarize the research progress of PSM of MOFs through click chemistry, including azide-alkyne click reaction and thiol-ene reaction.

Cube-octameric silsesquioxane (POSS)-capped magnetic iron oxide nanoparticles for the efficient removal of methylene blue

Octavinyl polyhedral oligomeric silsesquioxane (POSS) was polymerized on the surface of Fe3O4 nanoparticles (NPs) and then the NPs were functionalized with carboxylic acid groups using thiol-ene click reactions with thioglycolic acid.The as-prepared Fe3O4@POSS-COOH magnetic hybrid NPs had mesoporous structures with an average particle diameter of 15 nm and a relatively high specific surface area of 447 m^2· g^-1.Experimental results showed that 4 mg of Fe3O4@POSS-COOH NPs efficiently adsorbed and removed methylene blue from water at 5 min.This is due to the presence of both carboxylic acid and pendant vinyl groups on the Fe3O4@POSS-COOH NPs.These NPs could be easily withdrawn from water within a few seconds under moderate magnetic field and showed high stability in acid and alkaline aqueous mediums.

Robust and Self-healable Antibiofilm Multilayer Coatings

The infection induced by implantation of biomedical materials may result from the biofilm formation after bacteria attachment.Hence,the antibiofilm surface coating represents a novel technique to improve the antibacterial activity of biomedical materials.The traditional antibiofilm surface coatings exhibited some disadvantages and provided a limited service life.In this work,we used polyethyleneimine grafted 3-maleimidopropionic acid(PEIM)and poly(acrylic acid)grafted 2-furfurylamine(PAAF)to achieve robust and self-healable crosslinked multilayer coatings,employing Layer-by-Layer(LbL)self-assembly technique and Diels-Alder reaction.Then,thiol-terminated poly((3-acrylamidopropyl)trimethylammonium chloride)(PAMPTMA-SH)was grafted onto the crosslinked multilayer coating by thiol-ene click reaction to form a novel multilayer coating(PEIM/PAAF)_(10)-PAMPTMA.We found that this coating showed robust and self-healable activity,and significantly inhibited the bacterial growth and biofilm formation after infection with Escherichia coli(E.coli)and Staphylococcus aureus(S.aureus)by in vitro and in vivo assays for 120 h.In addition,the multilayer coating did not induce significant hemolysis or affect the cell viability of red blood cells.In vivo studies also showed that(PEIM/PAAF)_(10)-PAMPTMA coating efficiently blocked the infiltration of inflammatory cells and gene expression in the mouse skin challenged with E coli or S.aureus.Taken together,these results showed that the prepared multilayer coating exhibited strong antibiofilm activity and provided a new strategy for the application of highly efficient antibiofilm surface coating of biomedical materials.

Preparation of click-driven cross-linked anion exchange membranes with low water uptake

Significant advancement in anion exchange membrane(AEM)fuel cell(AEMFC)technology is important in the field of renewable energy.AEMs with comb-shaped architectures have attracted considerable research interest because of some unique features,including high anion conductivity,low swelling,and high alkaline stability.Here,we report preparation,characterization,and performance evaluation of a novel comb-shaped cross-linked AEM synthesized by the thiol-ene click and Menshutkin reactions.The prepared ionomer decreases the trade-off between the water uptake and the conductivity.The thiol-ene click reaction was used to synthesize the 1,14-di(1H-imidazol-1-yl)-6,9-dioxa-3,12-dithiatetradecane(IDDT)cross-linker.IDDT was then introduced into the brominated poly(2,6-dimethyl-1,4-phenylene oxide)backbone by the Menshutkin reaction.The prepared ionomers show high thermomechanical stability,which is needed in AEMFC technology.The CLINK-15-100 membrane(ion exchange capacity 1.23 mmol/g)shows relatively good conductivities of 19.66 and 34.91 mS/cm at 30 and 60℃,respectively.Interestingly,the membrane shows water uptake of only 14.22%at room temperature,which is considerably lower than many previously reported membranes.After 16 days of alkaline treatment in 1 M NaOH solution at 60℃,the CLINK-15-100 membrane retains 77%of its initial conductivity,which is much better than the traditional quaternized poly(2,6-dimethyl-1,4-phenylene oxide)membrane.

Togni-ⅡReagent Mediated Selective Hydrotrifluoromethylation and Hydrothiolation of Alkenes

Based on the redox reactions of Togni-Ⅱreagent and thiols,a thiol-tuned selective functionalization of unactivated olefins was disclosed.In combination with aryl thiols,stoichiometric amount of Togni-Ⅱreagent prompted a hydrotrifluoromethylation of alkenes,in which,aryl thiols played as reductant and hydrogen source;while by utilization of alkyl thiols,catalytic amount of Togni-Ⅱreagent initiated thiol-ene and thiol-yne reactions.The reported applications are characterized by their operational simplicity and wide functional group tolerance.

Hydroxyl-terminated Polyethylenes Bearing Functional Side Groups:Facile Synthesis and Their Properties

A series of hydroxyl-terminated polyethylenes(HTPE)bearing various functional side groups(e.g.carboxyl,ester and butane groups)were synthesized by the combination of ring opening metathesis polymerization(ROMP)and visible light photocatalytic thiol-ene reaction.The products are named as a,w-dihydroxyl-polyllpropionyloxythio)methinetrimethylene](HTPECarboxy),a,w dihydroxy-poly(methylpropionatethio)methinetrimethylene](HTPEeser)and a,wdihydroxyl-poly[(butylthio)methinetrimethylene](HTPEbutane)respectively.The investigation of ROMP indicated that the molecular weight of resultant hydroxy-terminated polybutadiene(HTPB)can be tailored by varying the feed ratios of monomer to chain transfer agent(CTA).The exploration of the photocatalytic thiol-ene reaction between HTPB precursor and methyl-3-mercaptopropionate revealed that blue light as well as oxygen accelerated the reaction.1H-NMR and 13C-NMR results verified all the double bonds in HTPB can be modified,and the main chain of resultant polymer can be considered as polyethylene.Subsequently,relationship between the structure of side groups and the thermal properties of functional PEs was studied.And the results suggested that the Tg was in the order of HTPEbuane<HTPEester<HTPEarboxy+.Greater interaction between side groups resulted in higher Tg.Moreover,all the functional PE samples exhibited poor thermostability as compared to HTPB.Finally,the promising applications for functional PEs were explored.HTPEcarboxy1 can be utilized as a smart material with pH-responsive properties due to its pH-dependent ionization of carboxyl side groups.HTPEbutane can be employed as a macro-initiator for building the triblock copolymer due to the presence of active hydroxyl end groups.HTPEester can serve as a plasticizer for PVC which can enhance the ductilityt of PVC without obviously sacrificing strength.