Liangjiu Bai

Triphenylphosphine as Reducing Agent for Copper（II）-catalyzed AGET ATRP

Triphenylphosphine (TPP) was used as reducing agent to continuously generate the Cu(I) activator in copper(II)-catalyzed activators generated by electron transfer atom transfer radical polymerization (AGET ATRP). For example, the polymers prepared with a molar ratio of [MMA]0/[EBiB]0/[CuCl2]0/[PMDETA]0/[TPP]0 = 500/1/0.1/0.5/0.5 had controlled molecular weights and low molecular weight distribution (Mw/Mn) values (∼1.2). TPP as a commercial reducing agent provides a convenient copper-catalyzed AGET ATRP procedure for the preparation of well-defined polymers.

Facile iron(III)-mediated ATRP of MMA with phosphorus-containing ligands in the absence of any additional initiators

A series of phosphorus-containing ligands was employed to establish a novel polymerization system for the iron(III)-mediated polymerization of methyl methacrylate (MMA) just using FeCl3·6H2O or FeBr3 as the catalyst without any additional initiators and reducing agents. The polymerization results showed that this polymerization system involving MMA/FeX3 (X = Cl, Br)/phosphorus-containing ligand was a typical “living”/controlled radical polymerization process: first-order polymerization kinetics with respect to monomer concentration and a linear increase of the molecular weight of the resultant PMMAs with conversion while keeping a narrow molecular weight distribution. Chain end analysis of the obtained PMMA based on 1H NMR, 31P NMR were used to confirm the precise structure of the obtained polymers. The results showed that phosphorus-containing complexes acted as both ligand and thermal radical initiators in this process, which was consistent with a reverse atom transfer radical polymerization (reverse ATRP) mechanism.

Synthesis of Polyvinyltetrazole Resin by Combination of RAFT Polymerization and Click Chemistry for Adsorption of Hg(II)

The combination of reversible addition-fragmentation chain transfer (RAFT) polymerization and Click Chemistry was employed as a new approach to synthesize polyvinyltetrazole resin from acrylonitrile. The chemical composition and structure of the polyvinyltetrazole resin was studied by Fourier-transform infrared spectrometry and UV-Vis spectroscopies. Elemental analysis indicated the higher tetrazole content of the polyvinytetrazole resin. The polyvinyltetrazole resin exhibited excellent adsorption for metal ions and the maximum adsorption capacity for Hg(II) was 5.79 mmol/g. The resin could be reused stably in the adsorption of heavy metal ions.

Synthesis of polyacrylonitrile by reversible-deactivation radical polymerization and its application as electrode materials for electrochemical double layer capacitors

Bis(acetylacetonato) iron(II) (Fe(acac)2) was first selected to mediate the reversible-deactivation radical polymerization (RDRP) of acrylonitrile (AN) with predictable molecular weights, relatively narrow molecular weight distributions and high end-fidelity. The reversible termination (RT) mechanism accounted well for the reaction phenomena. The spinning performance of polyacrylonitrile (PAN) was investigated and the average diameter of the spinning fibers was approximately 300 nm. Activated carbon fibers (ACFs) were prepared via sodium hydroxide (NaOH) direct activation. The maximum specific surface area of the ACF was as high as 1165 m2 g−1. The pore volume of the ACF reached 0.14 cm3 g−1. Most is the contribution of the small mesopores (2–5 nm). The unique microstructures enabled the ACFs to have good compatibility with potassium hydroxide (KOH) as electrolyte. The highest capacitance reached 167 F g−1 at room temperature. The electrode showed well stabilized capacitance after 500 cycles and high energy/power density values due to the formation of small mesopores.

Preparation of corn stalk-based adsorbents and their specific application in metal ions adsorption

Corn stalk-based adsorbents modified from corn stalk were prepared by Cu(0)-mediated reversible-deactivation radical polymerization (Cu(0)-mediated RDRP). They were applied to remove metal ions and they exhibited good adsorption capacity, especially for Hg(II). Adsorption properties of corn stalk can be enhanced by introducing cyano, amino, amidoxime, and carboxyl groups onto its surface, which results in efficient adsorbents for different metal ions. TGA, SEM, EA, and FTIR analyses were employed to characterize the structures of corn stalk-graft-polyacrylonitrile (CS-g-PAN), corn stalk-graft-polyacrylamide (CS-g-PAM), amidoxime corn stalk-graft-polyacrylonitrile (AO CS-g-PAN) and carboxyl corn stalk-graft-poly(methyl acrylate) (CO CS-g-PMA). The maximum adsorption capacity for Hg(II) was 8.06 mmol g−1 of AO CS-g-PAN. Kinetics of the Hg(II) adsorption on AO CS-g-PAN was found to follow the pseudo-second-order model and the adsorption isotherms were well fitted with the Freundlich isotherm model.

Cobalt(III) acetylacetonate initiated RAFT polymerization of acrylonitrile and its application in removal of methyl orange after electrospinning

This study describes reversible addition–fragmentation chain-transfer (RAFT) polymerization initiated by cobalt(III) acetylacetonate (Co(acac)3). With Co(acac)3 as the initiator, RAFT polymerization of acrylonitrile was achieved at 90 °C mediated by 2-cyanoprop-2-yl dithionaphthalenoate. The polymerization exhibited “living”/controlled characteristics with a molar mass distribution as low as 1.25. Homogeneous polyacrylonitrile nanofibers (PAN-nFs) were produced via the electrospinning technique. FTIR, SEM and TGA analyses revealed aminated-PAN-nFs (APAN-nFs) were successfully obtained via ethylenediamine grafting onto the surface of PAN-nFs. The adsorption interaction between methyl orange (MO) dye and APAN-nFs is discussed in detail. The maximum saturation adsorption capacity was 102 mg g−1. The adsorption kinetics followed a pseudo-second-order model. The Langmuir model was better for interpreting the isothermal process for MO and APAN-nFs. The Dubinin–Radushkevich isothermal model indicated that the adsorption proceeded chemically. Intraparticle diffusion was not the only rate-limiting step. The thermodynamics properties indicated the adsorption process was exothermic and spontaneous in nature. The MO dye adsorbed by APAN-nFs could be reversibly desorbed by an aqueous solution of pH = 1. APAN-nFs could be recycled efficiently.

A green Pickering emulsion stabilized by cellulose nanocrystals via RAFT polymerization

As environmental-friendly and renewable materials, cellulose nanocrystals (CNCs), has great potential for replacing the poisonous chemicals. Herein, we investigate a green Pickering emulsion stabilized of CNCs by using reversible addition-fragmentation chain transfer (RAFT) polymerization. The preparation of polymethyl methacrylate (PMMA) with controlled molecular weights and low Mw/Mn values were successfully synthesized by the Pickering emulsion. Moreover, the well-defined PMMA can be obtained in Pickering emulsion with “green” CNCs as a sole emulsifier and the used CNCs are easy to recycle and reuse.

Reversible chain transfer catalyzed polymerization (RTCP) in nitrogen-based solvents without additional catalysts

Nitrogen-based solvents (N,N-dimethylformamide (DMF) or N-methyl-2-pyrrolidone (NMP)) were used for reversible chain transfer catalyzed polymerizations (RTCPs) without additional catalysts. The polymerizations of typical monomers (i.e. methyl methacrylate, styrene, acrylonitrile, glycidyl methacrylate) showed features of RTCP, and well-defined polymers with designable molecular weights and narrow molecular weight distributions were obtained. The frequent activation of Polymer-I as a deactivator leads to narrow molecular weight distributions. Importantly, RTCPs using nitrogen-based solvents as novel catalysts not only could be conducted in the presence of a limited amount of air but also would be applicable as one of the most robust and powerful techniques for polymer synthesis.

Synthesis of novel polymer brushes of poly(acrylonitrile-g-N,Nʹ-dimethylaminoethyl methacrylate) by nitrile modification

Functional polymer brushes of poly(acrylonitrile-g-N,Nʹ-dimethylaminoethyl methacrylate) were efficiently synthesized by a novel approach of combining Cu(0)-mediated controlled/“living” radical polymerization and nitrile click chemistry. The poly(acrylonitrile-g-N,Nʹ-dimethylaminoethyl methacrylate) as a promising material exhibited excellent hydrophile–lipohile balance in the process of self-assembly and could autonomously develop the orderly structure micelle in N,Nʹ-dimethylformamide/water mixture solvent for the potential application of a new drug delivery carrier. In the process of self-assembly, polyacrylonitrile acted as a backbone of the functional polymer brushes due to its hydrophobic feature and poly(N,Nʹ-dimethylaminoethyl methacrylate) as the branch of functional polymer brushes due to its hydrophilic characteristic, which both were prepared by Cu(0)-mediated controlled/“living” radical polymerization with ethyl-bromoisobutyrate as initiator. Poly(N,Nʹ-dimethylaminoethyl methacrylate) containing azide end group was synthesized by substitution reaction of poly(N,Nʹ-dimethylaminoethyl methacrylate) containing bromine end groups with sodium azide in N,Nʹ-dimethylformamide. The click reaction between the nitrile of polyacrylonitrile and the azide group of poly(N,Nʹ-dimethylaminoethyl methacrylate) was carried out under ammonium chloride as catalyst in N,Nʹ-dimethylformamide. The polymer was further confirmed by GPC, FTIR, 1H NMR and TGA. Meanwhile, the micelles with different morphologies were observed by TEM, and the particle diameter distribution of self-assembled micelle from the PAN-g-PDMAEMA brushes was determined by DLS.

PMDETA as an efficient catalyst for bulk reversible complexation mediated polymerization (RCMP) in the absence of additional metal salts and deoxygenation

Reversible-deactivation radical polymerization (RDRP) represents one of the most rapid developments in functional polymer synthesis with a well-defined structure and architecture. In this work, N,N,N′,N′′,N′′-pentamethyldiethylenetriamine (PMDETA) without any metal salts was used as an efficient catalyst for reversible complexation mediated polymerization (RCMP) of methyl methacrylate (MMA) in bulk. The polymerization showed typical features of RDRP. Importantly, well-defined polymers with controllable molecular weights and narrow molecular weight distributions were obtained in the absence of any additional deoxygenation. PMDETA as a catalyst for RCMP not only could simplify the polymerization process and post-treatment but also would be applicable as one of the most robust and powerful techniques for polymer synthesis.