Suobo Zhang

Chitin and chitosan dissolved in ionic liquids as reversible sorbents of CO2

A novel dissolving process for chitin and chitosan has been developed by using the ionic liquid 1-butyl-3-methyl-imidazolium chloride ([Bmim]Cl) as a solvent, and a novel application of chitin and chitosan as substitutes for amino-functionalized synthetic polymers for capturing and releasing CO2 has also been exploited based on this processing strategy.

Fabrication of Superhydrophobic Cellulose-Based Materials through a Solution-Immersion Process

An industrial waterproof reagent [(potassium methyl siliconate) (PMS)] was used for fabricating a superhydrophobic surface on a cellulose-based material (cotton fabric or paper) through a solution-immersion method. This method involves a hydrogen bond assembly and a polycondensation process. The silanol, which was formed by a reaction of PMS aqueous solution with CO 2, was assembled on the cellulose molecule surface via hydrogen bond interactions. The polymethylsilsesquioxane coatings were prepared by a polycondensation reaction of the hydroxyl between cellulose and silanol. The superhydrophobic cellulose materials were characterized by FTIR spectroscopy, thermogravimetry, and surface analysis (XPS, FESEM, AFM, and contact angle measurements). Analytical characterization revealed that nanoscale roughness protuberances uniformly covered the surface, thus transforming the cellulose from superhydrophilic to superhydrophobic with a water contact angle of 157 degrees . The superhydrophobic coatings were satisfactory with regard to both chemical and mechanical durability, and because of the transparency of the coatings the native cotton fabric displayed no changes with regard to either morphology or color. The easy availability of the materials and simplicity of this method render it convenient for mass production.

A novel guanidinium grafted poly(aryl ether sulfone) for high-performance hydroxide exchange membranes

A novel poly(aryl ether sulfone) ionomer containing hexaalkylguanidinium groups was synthesized, and membranes formed from this polymer displayed large ionic clusters, high hydroxide conductivity, and excellent solubility in low boiling point water-soluble solvents such as ethanol and methanol.

Facile transformation of hydrophilic cellulose into superhydrophobic cellulose

Superhydrophobic cellulose-based materials coupled with transparent, stable and nanoscale polymethylsiloxane coating have been successfully achieved by a simple process via chemical vapor deposition, followed by hydrolyzation and polymerization.

Functional microporous polyimides based on sulfonated binaphthalene dianhydride for uptake and separation of carbon dioxide and vapors

A series of novel microporous polyimides (SMPIs) were synthesized from 4,4′-binaphthyl-1,1′,8,8′-tetracarboxylic dianhydride (BTDA), 6,6′-disulfonic-4,4′-binaphthyl-1,1′,8,8′-tetracarboxylic dianhydride (SBTDA) and tetrakis(4-aminophenyl)methane (TAPM). The non-sulfonated SMPI-0 (SMPI-x, where “x” is the molar percent of SBTDA) exhibited a BET surface area of 574 m2 g−1 and a CO2 uptake of 2.53 mmol g−1, while sulfonated samples, i.e. SMPI-10, SMPI-50 and SMPI-100, possessed relatively low BET surface areas (from 23 to 112 m2 g−1) but high CO2 capture capacities (from 2.82 to 3.15 mmol g−1) and CO2/N2 selectivities (from 32 to 57). With the increase of sulfonation degree, the polymers were graded from hydrophobic to hydrophilic. Hydrophobic SMPI-0 and SMPI-10 adsorbed a large amount of non-polar benzene (134.7 wt% for SMPI-0 and 104.7 wt% for SMPI-10) and cyclohexane (42.5 wt% for SMPI-0 and 42.8 wt% for SMPI-10) vapor, whereas hydrophilic SMPI-50 and SMPI-100 adsorbed more polar methanol (68.5 wt% for SMPI-50 and 72.2 wt% for SMPI-100).

Novel functionalized microporous organic networks based on triphenylphosphine.

This article describes the synthesis and functions of phosphine or phosphine oxide functionalized networks (PP-P or PP-PO; PP = porous polymer). These materials were predominantly microporous and exhibited high surface areas (S(BET): 1284 and 1353 m(2)  g(-1) for PP-P and PP-PO, respectively), with high CO2 (2.46 and 3.83 mmol g(-1) for PP-P and PP-PO, respectively) uptake capacities. Pd nanoparticles can be simply incorporated into the functionalized networks (PP-P-Pd or PP-PO-Pd) through a facile one-step impregnation. A yield of 98 % was obtained in the Suzuki reaction between 1-chlorobenzene and p-tolylboronic acid with the PP-P-Pd system, which was higher than that obtained when PP-PO-Pd (53.2 %) or [Pd(PPh3)4] (38.2 %) was used as the catalyst. The superior catalytic ability of PP-P-Pd can be attributed to the structural features that incorporate triarylphosphine within a microporous structure.

Ionic-Liquid-Grafted Rigid Poly (p-Phenylene) Microspheres: Efficient Heterogeneous Media for Metal Scavenging and Catalysis

Novel guanidinium ionic liquid-grafted rigid poly(p-phenylene) (PPPIL) microspheres have been developed for metal scavenging and catalysis. The noble-metal nanoparticles supported on the microspheres surface can be used as efficient heterogeneous catalysts. The combination of nanoparticles and ionic liquid fragments on the microsphere surfaces enhance the activity and durability of the catalyst. The PPPILPd(0) catalyst has been tested in the Suzuki cross-coupling reaction, and exhibits much higher catalytic activity than Pd catalysts supported on porous polymer matrices. The PPPILPd(0) catalyst can be recycled at least for nine runs without any significant loss of activity. The present approach may, therefore, have potential applications in transition-metal-nanocatalyzed reactions.

Double-responsive polyampholyte as a nanoparticle stabilizer: application to reversible dispersion of gold nanoparticles

Water-soluble and durable Au nanoclusters, smaller than 4 nm with a narrow size distribution, were supported on a pH- and solvent-responsive water-soluble polyampholyte (SPES). Such synthesized Au@SPES hybrids possessed clear pH- and solvent-sensitive properties, and exhibited precipitation behaviors in response to pH and solvent changes in aqueous solution. Furthermore, the recycled catalyst could be redissolved in water for reuse via simple procedures based on the pH-sensitivity of the polyampholyte. By employing such catalysts, aerobic oxidation of alcohols should be able to be carried out in a homogeneous manner and may thus give rise to similar catalytic activities and selectivities as the homogeneous parent system. The phase separation and sensitivity of the SPES-stabilizing Au nanoclusters permitted a facile separation of the clusters from the reaction mixture without any negative aggregation.

Synthesis and characterization of a novel poly(arylene ether sulfone) containing pendent imidazole groups for high temperature proton exchange membranes

A series of poly(arylene ether sulfone) containing pendent imidazole groups (PSf-Im-x) have been successfully synthesized based on a novel monomer 2,2′-bis-(2-methyl-imidazol-1-yl-methyl)-biphenyl-4,4′-diol (MIPO). The pendent imidazole groups along the polymer chain were expected to provide functional sites for the acid–base interaction with the doping phosphoric acid (PA) when they are used as polymer electrolyte membranes for high temperature fuel cell applications. The PA content of the linear PSf-Im-x membranes is about 172.3–235.8% in 85 wt% H3PO4 at room temperature. The volume swelling of these membranes is 114.4–194.0%, lower than that of polybenzimidazole (PBI) with similar PA content. The proton conductivities of the membranes are 0.021–0.053 S cm−1 at 140 °C under absolutely dehydrated state. The low volume swelling and good proton conductivity may be attributed to the “side-chain-type” structures of pendent imidazole groups, which facilitate ion transport. To obtain higher acid doping while maintaining mechanical properties, cross-linked membranes were prepared by the reaction of the imidazole group of the polymer and p-xylene dichloride. The PA content of the membranes with 20% cross-linking is 313.2% in 85 wt% H3PO4 at 80 °C. The stress at breaking and the proton conductivity of the membrane is 3.2 MPa at room temperature and 0.063 S cm−1 at 140 °C in an absolutely dehydrated state.

Ultrathin films of organic networks as nanofiltration membranes via solution-based molecular layer deposition.

Ultrathin films of organic networks on various substrates were fabricated through the solution-based molecular layer deposition (MLD) technique. The rigid tetrahedral geometries of polyfunctional amine and acyl chloride involved in the reaction ensure the continuity of the polymerization process. A linear increase in film thickness with respect to cycle number was observed by UV-vis adsorption, ellipsometry, and quartz crystal microbalance. The growth rate per MLD cycle is 1.6 nm, which can be controlled at the single molecular level. For the first time, we develop the MLD method on the top of hydrolyzed PAN substrate, resulting in nanofiltration (NF) membranes. The stepwise growth was monitored via attenuated total reflectance infrared studies. The separation performance of the obtained membrane for various solutes was sensitive to the terminated layers and number of cycles. The rejection of NH(2)-terminated membranes follows the order of CaCl(2) > Na(2)SO(4) > NaCl, while the order for COOH-capped surface is Na(2)SO(4) > CaCl(2) > NaCl. The absolute value of zeta potential for the MLD membranes decreases with the addition of deposition layers. The moderate water flux for the resulting membrane is due to the reduced porosity of the support as well as the low roughness and hydrophilicity of the membrane surface. This bottom-up process provides a promising approach for construction of long-term steady NF membranes with nanoscale dimensions.