Synthesis and reactions of cysteine‐based telechelic polymers

The radical polyaddition of N‐4‐vinylbenzoyl‐L ‐cysteine methyl ester (VCM) was carried out in the presence of 2,2′‐azobisisobutyronitrile (AIBN, 3 mol %) as an initiator in dimethyl formamide (DMF) with monomer concentrations of 0.5 and 1.0 M at 60 °C for 20 h under nitrogen atmosphere to afford the corresponding polymers [poly(VCM), PVCM] with number‐average molecular weights (M_n)'s of 5300 and 18,000 in 92 and 95% yields, respectively. The obtained polymers had a heterotelechelic structure with thiol and olefin end moieties. The radical polymerization of methyl methacrylate and trityl methacrylate was carried out in the presence of PVCM with AIBN (3 mol %) as an initiator in DMF at 60 °C for 20 h to afford the block copolymers with M_n values in the range of 13,000–26,800 in good yields. PVCM [M_n = 18,000; polydispersity (M_w/M_n) = 1.56] was treated with 4 equiv of NaOH aq. (1.0 M) to afford the polymer having carboxyl groups in the side chain with a M_n of 17,300 and M_w/M_n of 1.88 in 95% yield and was also oxidized to polysulfoxide and polysulfone with 4 equiv of H₂O₂ per sulfide unit in CH₂Cl₂ (1.0 M) for 20 h. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 23–31, 2001     

介孔分子筛表面功能膜的制备及对水体中铅汞镉的去除作用

表面改性;功能膜材料;重金属;吸附;介孔分子筛表面功能膜的制备及对水体中铅汞镉的去除作用     

Synthesis of a New Phosphonate Methacrylate Monomer

In this work, a new methacrylate phosphonate monomer synthesis was described according to a two-step reaction. First the monoaddition of thioglycolic acid onto dimethylvinyl phosphonate monomer led to dimethyl–5-carboxymethyl-2-thiaethylphosphonate, a new phosphonate acid compound. This reaction also led to the thioester homologue of dimethyl–5-carboxymethyl-2-thiaethylphosphonate with a 15% yield by reaction of a thioglycolic acid thioester with dimethylvinyl phosphonate. Second, dimethyl carboxy-4-thia-butyl phosphonate reacted with glycidyl methacrylate. This epoxy-acid addition reaction was catalyzed by chromium salt at 70°C and led to the new methacrylate phosphonate monomer. We showed that only the secondary alcohol was obtained via a β addition. The two-step reaction final yield was calculated to be about 85%.     

Photo‐initiated thiol–ene “click” hydrogels from RAFT‐synthesized poly(N‐isopropylacrylamide)

Despite the efficiency and robustness of the widely used copper‐catalyzed 1,3‐dipolar cycloaddition reaction, the use of copper as a catalyst is often not attractive, particularly for materials intended for biological systems. The use of photo‐initiated thiol‐ene as an alternative “click” reaction to synthesize “model networks” is investigated here. Poly(N‐isopropylacrylamide) precursors were synthesized by reversible addition fragmentation chain transfer (RAFT) polymerization and were designed to have trithiocarbonate moieties as end groups. This structure design provides opportunity for subsequent end‐group modifications in preparation for thiol‐ene “click.” Two reaction routes have been proposed and studied to yield thiol and ene moieties. The advantages and disadvantages of each reaction path were investigated to propose a simple but efficient route to prepare copper‐free “click” hydrogels. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4626–4636     

Thiol–ene polymerizations using imide‐based monomers

New diene and dithiol monomers, based on aromatic imides such as benzophenone‐3,3′,4,4′‐tetracarboxylic diimide were synthesized and used in thiol‐ene polymerizations which yield poly(imide‐co‐thioether)s. These linear polymers exhibit limited solubility in various organic solvents. The molecular weights of the polymers were found to decrease with increasing imide content. The glass transition temperature (T_g) of these polymers is dependent on imide content, with T_g values ranging from ?55 °C (with no imide) up to 13 °C (with 70% imide). These thermal property improvements are due to the H‐bonding and rigidity of the aromatic imide moieties. Thermal degradation, as studied by thermogravimetric analysis, was not significantly different to the nonimide containing thiol‐ene polymers made using trimethyloylpropane diallyl ether and 3,5‐dioxa‐1,8‐dithiooctane. It is expected that such monomers may lead to increased glass transition temperatures in other thiol‐ene polymer systems as these normally exhibit low glass transition temperatures. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4637–4642     

Synthesis of well‐defined poly(dimethylsiloxane) telechelics having nitrobenzoxadiazole fluorescent chain‐ends via thiol‐ene coupling

Well‐defined PDMS telechelics having nitrobenzoxadiazole (NBD) fluorescent probes covalently attached at both chain‐ends were prepared in two steps and a series of fractionation procedures starting from commercially available divinyl‐terminated PDMS having a broad molar mass dispersity. First, thiol‐ene coupling between 6‐mercapto‐1‐hexanol and vinyl chain‐ends allowed the formation of dihydroxy‐terminated PDMS telechelics through the formation of a thioether linkage. The resulting material was then sequentially fractionated using dichloromethane/methanol mixtures to afford several well‐defined dihydroxy‐terminated PDMS fractions having sharp distributions of molar masses (M_n = 99.5–158 kDa and ? < 1.2). The NBD fluorescent probes were then attached at both chain‐ends by N,N′‐dicyclohexylcarbodiimide/4‐(dimethylamino)pyridine esterification coupling between the hydroxyl groups and 6‐(7‐nitrobenzofurazan‐4‐ylamino)hexanoic acid. The resulting fluorescent PDMS telechelics were characterized by SEC, ¹H NMR, UV–visible, and fluorescence spectroscopies. These materials are suitable probes to investigate the dynamics of polymer chains in bulk or at interfaces by the fringe pattern fluorescent recovery after photobleaching technique. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Functional aliphatic polyesters and nanoparticles prepared by organocatalysis and orthogonal grafting chemistry

We describe the use of organic catalysis for the ring‐opening polymerization of functionalized lactones and conversion of the resulting aliphatic polyesters into crosslinked nanoparticles that carry additional functional groups amenable to further modification. Specifically, highly functional aliphatic polyester homopolymers, as well as random and block copolymers, were prepared by 1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene catalysis, giving polyesters with pendent alkene and alkyne groups. Azide‐alkyne click and thiol‐ene chemistries were used for postpolymerization modification of diblock copolymers possessing alkene groups on one block and alkyne groups on the other block. The polyesters were crosslinked using azide/alkyne cycloaddition, by reaction of α,ω‐diazides with the pendent alkynes on the polyester backbone. This gave polyester nanoparticles possessing alkene functionality, which were subjected to further modification using thiol‐ene reactions to introduce additional functionality. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Thiol‐functionalized 1,3‐benzoxazine: Preparation and its use as a precursor for highly polymerizable benzoxazine monomers bearing sulfide moiety

We describe a new strategy for preparation of benzoxazine monomers based on in situ preparation of a thiol‐functionalized benzoxazine and successive chemical modification of the thiol moiety. The thiol‐functionalized benzoxazine can be prepared from its precursor bearing two benzoxazine moieties linked by disulfide bond. Reductive cleavage of the disulfide bond of the precursor with using triphenylphosphine as a reducing agent allows successful preparation of the thiol‐functionalized benzoxazine. By performing this reduction process in the presence of epoxides and acrylates, the formation of the thiol moiety and its successive reaction with those electrophiles proceed efficiently to give the corresponding benzoxazines with sulfide moieties. The benzoxazine monomers thus prepared exhibit much higher polymerization ability than those without sulfide moiety. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1448–1457