Ganwei Zhang

Simple approach towards fabrication of highly durable and robust superhydrophobic cotton fabric from functional diblock copolymer

We report here a simple and reproducible strategy for fabricating highly durable and robust superhydrophobic cotton fabrics (SCFs) from a series of functional diblock copolymers. These diblock copolymers consisted of both poly(glycidyl methacrylate) (PGMA) and poly(2,2,2-trifluoroethyl methacrylate) (PTFEMA) blocks that were synthesized via sequential atom transfer radical polymerization (ATRP). While the PTFEMA block provides the low surface free energy, the PGMA block serves as an anchor and forms covalent bonds with the surfaces of cotton fibers. These covalent bonds are formed via the epoxy ring-opening reaction between the epoxy groups of the PGMA block and the hydroxyl groups on the surface of the cotton fiber, and self-crosslinking of epoxy groups from PGMA chains. Structures exhibiting nano- and microscale roughness were created in one-step by combining copolymer-based nanobumps onto surfaces of micro-sized fibers of the cotton fabric, as confirmed by SEM and AFM analysis. The modified cotton fabrics show excellent water repellency with water contact angles (WCAs) of ∼163° and water sliding angles (WSAs) of ∼3° under optimized conditions. Since the low-fluorinated PTFEMA chains are chemically bound to the cotton fibers, the SCFs possess long-term stability, ultra-high durability and robustness. In particular, these SCFs withstood mechanical abrasion by sandpaper, strong laundering conditions, ultrasonication treatment in tetrahydrofuran (THF) or trifluorotoluene (TFT), soaking in a wide range of organic solvents, as well as acidic and basic aqueous solutions, exposure to UV-irradiation and even refluxing in TFT or THF.

Bi-functional random copolymers for one-pot fabrication of superamphiphobic particulate coatings

Random bi-functional copolymers bearing fluorinated units and sol–gel forming units were prepared and used together with silica particles in a one-pot process for preparing superamphiphobic coatings. The copolymers P(FOEA-r-IPSMA) were prepared by atom transfer radical polymerization (ATRP) of 2-(perfluorooctyl)ethyl acrylate (FOEA) and 3-(triisopropyloxy)silylpropyl methacrylate (IPSMA). The uniform silica particles were prepared using a modified Stober process. Stirring P(FOEA-r-IPSMA), silica, water, and HCl together with substrates triggered the sol–gel reactions of the IPSMA units. These involved first the hydrolysis of IPSMA to yield silanol groups and then the condensation of the IPSMA silanol groups among themselves, and with silanol groups on silica or glass surfaces or with hydroxyl groups on cotton or filter paper. At optimized mass ratios of P(FOEA-r-IPSMA) to silica, the resultant coatings consisted of lightly covered silica particles that were embedded in a crosslinked P(FOEA-r-IPSMA) film. By optimizing the molar ratio between FOEA and IPSMA in P(FOEA-r-IPSMA), the rough particulate coatings on cotton, filter paper, and glass plates exhibited superamphiphobicity. More importantly, the particulate coatings were resistant to solvent extraction and NaOH etching.

Amylose-directed synthesis of CuS composite nanowires and microspheres

Reported are the synthesis and characterization of CuS composite nanowires and microspheres in the presence of amylose. The preparation involved first the complexation of amylose with Cu(2+) of CuCl(2) at 70°C. Cu(2+) complexation was confirmed by a conductivity reduction of CuCl(2) after amylose addition. Also, the aggregation state of the amylose changed after Cu(2+) as revealed by transmission electron microscopy (TEM) and dynamic light scattering (DLS). At the Cu(2+) to α-D-glucopyranosyl unit molar ratio r of 0.70 and 1.41, the amylose aggregated into microspheres that were approximately 150 and 250 nm in diameter. Adding sodium thiosulfate resulted in the production of an amorphous precipitate consisting presumably of CuS(2)O(3). At r=0.70 and 1.41, CuS(2)O(3) precipitated inside the template of Cu(2+)/amylose microspheres as nanoparticles, while a twisted nanowire-like structure was produced at r=0.92. CuS(2)O(3) decomposed under heating at 100 °C to yield crystalline CuS nanoparticles.

Superhydrophobic Hierarchically Assembled Films of Diblock Copolymer Hollow Nanospheres and Nanotubes

Reported are the formation of rough particulate films from cross-linked diblock copolymer vesicles and nanotubes and the wetting properties of the resultant films. The diblock copolymers used were F66M200 and F95A135, where the subscripts denote the repeat unit numbers, whereas M, A, and F denote poly(2-cinnamoyloxyethyl methacrylate), poly(2-cinnamoyloxyethyl acrylate), and poly(2,2,2-trifluoroethyl methacrylate), respectively. The precursory polymers to F66M200 and F95A135 were prepared by atom transfer radical polymerization. In 2,2,2-trifluoroethyl methacrylate (FEMA), a selective solvent for F, vesicles and tubular micelles were prepared from F66M200 and F95A135, respectively. Photo-cross-linking the M and A blocks of these aggregates yielded hollow nanospheres and nanotubes bearing F coronal chains. These particles were dispersed into CH2Cl2/methanol, where CH2Cl2 was a good solvent for both blocks and methanol was a poor solvent for F. Casting CH2Cl2/methanol dispersions of these particles yielded films consisting of hierarchically assembled diblock copolymer nanoparticles. For example, the hollow nanospheres fused into microspheres bearing nanobumps after being cast from CH2Cl2/methanol at methanol volume fractions of 30 and 50%. The roughness of these films increased as the methanol volume fraction increased. The films that were cast at high methanol contents were superhydrophobic, possessing water contact angles of ∼160° and water sliding angles of ∼3°.

Hydrophilization of polysulfone membranes using a binary graft copolymer

An amphiphilic binary graft copolymer polysulfone-graft-[poly(methyl methacrylate)-random-poly(acrylic acid)], PSf-g-(PMMA-r-PAA), was synthesized via a combination of atom transfer radical polymerization (ATRP) and click chemistry. This copolymer and polysulfone (PSf) were used to prepare porous membranes through the phase inversion method, which involved dissolving the polymers in a common solvent N-methyl pyrrolidone (NMP), casting the solution onto a glass plate to obtain a film, and subsequently immersing this film into a coagulant (a mixture of dimethylformamide and water at a given pH). The surfaces of the membrane and its pore walls were covered by the copolymer, and these surfaces were enriched with PAA domains due to the immiscibility of PAA and PSf and the miscibility of PMMA and PSf. More specifically, while the hydrophobic PMMA component served as an anchor to fix the graft copolymer onto the PSf bulk substrate, the hydrophilic PAA component assembled and became exposed at the surfaces of the membrane and the pore walls. Factors influencing this surface AA concentration or carboxyl group content (CGC) enrichment and the surface and pore morphologies of the membranes include the ratio between the amount of the copolymer and PSf in the mixture, the solvent quality of the coagulant for PSf, and the temperature as well as the pH of the coagulant. These factors have been systematically adjusted to optimize the hydrophilization of the PSf membrane and the resultant membranes have been characterized by water contact angle (WCA) measurements, scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). Optimization of the phase inversion process yielded membranes with nearly complete surface coverage by PAA, even when the graft copolymer represented only 8 wt% of the membranes composition. The hydrophilized membranes exhibited increased water flux and even pH-responsive water flow without adversely affecting their mechanical properties. In addition, these hydrophilic membranes exhibited long-term stability. Therefore, this novel binary amphiphilic graft copolymer-based approach for membrane modification may be of commercial value.

Poly(3-imidazolyl-2-hydroxypropyl methacrylate) – a new polymer with a tunable upper critical solution temperature in water

Opening the epoxide rings of poly(glycidyl methacrylate) (PGMA) with imidazole produces poly(3-imidazolyl-2-hydroxypropyl methacrylate) (PiGMA). PiGMA is soluble in room-temperature water due to protonation of the unsubstituted imidazole nitrogen atom at pH values below 5.9 but becomes insoluble at pH values above 6.5 due to deprotonation. At pH values between 6.2 and 6.5, partially protonated PiGMA is insoluble in water at low temperatures but becomes soluble upon heating. The transmittance variation of aqueous PiGMA solutions at 500 nm has been measured and used to monitor the dissolution or aggregation of PiGMA samples. The cloud temperature Tc determined from these transmittance curves increases at pH = 6.30 from 23.2 ± 0.3 to 93.2 ± 0.3 °C as the repeat unit number of PiGMA increases from 15 to 140. Increasing the solution pH from 6.2 to 6.5 for a PiGMA sample with 50 repeat units increases its Tc from 20.4 ± 0.6 to 89.7 ± 0.5 °C. Since PGMA can be readily synthesized and the reaction between imidazole and PGMA occurs under mild conditions, this paper offers a ready recipe for a family of pH- and thermo-responsive polymers.

Synthesis of poly(2-hydroxyethyl methacrylate) end-capped with asymmetric functional groups via atom transfer radical polymerization

Poly(2-hydroxyethyl methacrylate) (PHEMA) end-capped with living chloride and alkyne groups was synthesized via ATRP of HEMA using CuCl/CuCl2/2,2′-bipyridine as a catalyst in a solvent mixture of methanol and 2-butanone. The effects of parameters including the initiator, solvent, temperature and initial monomer to initiator ratios on polymerization were studied in terms of polymerization kinetics, the degree of polymerization (DP) and molar mass dispersity (Đ) of the resulting PHEMA polymer. ATRP of HEMA using propargyl 2-bromoisobutyrate (PBiB) as an initiator was poorly controlled, but those using 3-(trimethylsilyl)propargyl 2-bromoisobutyrate (TMSPBiB) and 3-(triisopropysilyl)propargyl 2-bromoisobutyrate (TiPSPBiB) as initiators were well-controlled. Moreover, the apparent propagation rate constant for ATRP of HEMA using the TMSPBiB initiator was higher than that using the TiPSPBiB initiator. The solvent mixture of methanol–2-butanone at different compositions greatly affected the polymerization controllability. A high molecular weight PHEMA sample with a DP of 1000 and a Đ of 1.34 was obtained under appropriate conditions. The poly(2-hydroxyethyl methacrylate)-block-poly(butyl acrylate) (PHEMA-b-PBA) diblock copolymer was prepared through ATRP of BA using (CH3)3Si–CC–PHEMA–Cl as a macroinitiator. The methoxyl polyethylene glycol-block-poly(2-hydroxyethyl methacrylate) (MPEG-b-PHEMA) diblock copolymer was prepared by click reaction between MPEG-N3 and HCC–PHEMA–Cl. These two reactions demonstrated the reactivity of the asymmetric functional groups end-capping the PHEMA, and further provided modular examples for the synthesis of a novel well-defined (co)polymer with complex architectures.

SYNTHESIS AND SELF-ASSEMBLY BEHAVIORS OF BLOCK COPOLYMER A- b -(B- r -C) BEARING RANDOM COMPONENTS: SYNTHESIS AND SELF-ASSEMBLY BEHAVIORS OF BLOCK COPOLYMER A- b -(B- r -C) BEARING RANDOM COMPONENTS

通过原子转移自由基（ATRP）方法合成了其中一个嵌段是由2种单体无规共聚的两嵌段聚合物——聚丙烯酸肉桂酸乙酯-b-（聚苯乙烯-r-聚丙烯酸叔丁酯）,（记为PCEA-b-（PtBA-r-PS））.讨论了聚合过程中影响分子量分布以及分子量控制的各种因素.通过氢核磁（1H-NMR）确定各嵌段的重复单元数分别为50,111,138.通过透射电镜（TEM）观察,研究了该嵌段聚合物在选择性溶剂1-氯癸烷以及环戊烷中的自组装行为,发现该嵌段聚合物在环己烷中直接分散可以形成有聚集倾向的短棒状或球形胶束,而在1-氯癸烷中直接分散得到的胶束,在膜表面随着1-氯癸烷溶剂的缓慢挥发可以组装得到具有规则微纳结构的相互连接的柱状胶束.