Core-shell nanofibers were prepared by coaxial electrospinning technology, with poly(ethylene oxide) (PEO) as the core while poly(acrylic acid) (PAA) as the shell. PEO and PAA can form polymer complexes based on hydrogen bonding. In order to avoid forming strong hydrogen bonding complexes at nozzle and blocking spinning process, a polar aprotic solvent, N,N-dimethylformamide (DMF), was selected to dissolve PEO and PAA respectively. SEM, TEM and DSC were utilized to characterize the morphology and structure of PEO-PAA core-shell nanofibers. FTIR spectra demonstrated that hydrogen bonding was formed at the core-shell interface. In addition, the PAA shell of the nanofibers can be cross-linked by ethylene glycol (EG) under heat treatment, which increases the stability and extends the potential applications in aqueous environment.

•The ternary composite thin film was fabricated by LbL assembly of CMC@Ln complex nano-particles and cationic cellulose.•CMC@Ln complex nano-particles were prepared by rigorously controlling pH value of the solutions and the molar ratio of the component.•The terneay composite film would show fluorescence under UV-irradiation, and the luminescence color can be adjusted by incorporation different Ln ions.Carboxymethylcellulose (CMC), quaternized cellulose (QC) and lanthanide (Ln) ion ternary complex thin film was fabricated by hierarchical assembly process. CMC is a weak anionic polyelectrolyte while QC is a cationic polyelectrolyte. Strictly controlling pH value and molar ratio, CMC and Ln ion were prepared into polymer-metal complex nano-particles (CMC@Ln) which exhibit negative charge on surface, and then the nano-particles were layer-by-layer (LbL) assembled with positively charged QC to prepare thin films. Three kinds of Ln ion, Ce3+, Eu3+, and Tb3+ were successfully incorporated into films separately, and the corresponding films showed blue, green and red fluorescence color. In addition, we can adjust the luminescence of the film with combination of CMC@Ce, CMC@Eu, and CMC@Tb complex nano-particles.

In this letter, we put forward an approach to prepare hydrogen-bonded complex fibers. First, a spinnable fluid is obtained by restricting hydrogen bonds, and then it is extruded through a spinneret into a coagulation bath where hydrogen bonds are built to induce fiber formation. The hydrogen-bonded poly(acrylic acid)/poly(ethylene oxide) (PAA/PEO) complex was prepared into fibers. PAA/PEO fiber shows excellent elastic behavior and can be drawn to more than 12× its original length without breaking, which is much higher than Spandex fiber or natural rubber fiber. In the fiber, PAA and PEO are miscible in the molecular level. Dynamic hydrogen bonding between PAA and PEO restricts the crystallization of PEO, retains flexibility of polymer chains, and also provides recovery forces when removing stress.

Poly(acrylic acid) (PAA) and lanthanide (Ln) ions, such as Ce3+, Eu3+, and Tb3+, were prepared as dispersed complex colloidal particles through three different protocols with rigorous control of the pH value and mixing ratio. The negatively charged PAA–Ln complex particles were layer-by-layer (LbL) assembled with positively charged poly(diallyldimethyl ammonium) (PDDA) to prepare a thin film. The film thickness growth is much quicker than PDDA/PAA film. Due to the incorporation of Ln3+ ions, the film exhibits fluorescence. During LbL assembly, PDDA–PAA association based on electrostatic force and PAA–Ce association based on coordination are in competition, which leads to the LbL assembly of PDDA and PAA–Ln complex colloidal particles being a complicated dynamic process.

•A nano-composite film with reversible molecular adsorption behavior was fabricated.•With thermal cross-linking, the film can wholly detach from the substrate.•The free-standing film remains stable in a wide pH range for a considerable period of time.•Dynamic hydrogen bonding and electrostatic interaction endowed the free-standing film reversible swelling/shrinking ability.A nano-composite film with reversible small molecules adsorption behavior was fabricated via layer-by-layer (LbL) assembly of boehmite nano-particles and weak polyelectrolyte poly(acrylic acid) (PAA). Both electrostatic force and hydrogen bonding interaction were involved to fabricate the nano-composite thin film. Boehmite/PAA nano-composite thin film was further cross-linked with thermal treatment, which enhanced the stability of the film. When immersed into the basic solution, the thermal cross-linked film wholly detached from the substrate. And the dynamic cross-links such as hydrogen bonding and electrostatic interaction endowed the free-standing film reversible swelling/shrinking ability in response to pH variations at least five times. Furthermore, the free-standing Boehmite/PAA film showed reversible rhodamine B (RB) adsorption behavior, which could be utilized for controlled loading and releasing.

Hydrothermal processing of polyamide 6 (PA6) with the presence of lanthanum chloride (LaCl3) was studied in the temperature region from 160 °C to 250 °C. PA6 will be dissolved in the superheated water when temperature is above 160 °C. And as PA6 is dissolved, hydrolysis will happen, which makes PA6 chains degrade. By adding LaCl3 in the hydrothermal environment, the PA6 hydrolysis will intensify, especially when the hydrothermal temperature is higher than 200 °C. When the hydrothermal system cools down, the hydrolyzed PA6 segments will crystallize from the solution or remain dissolved in the solution depending on molecular weight. In addition, the hydrolyzed compound of LaCl3 would affect the crystallization of PA6 segments with proper size, and γ phase would be presented.

•The RB-doped alumina sol was used to prepare dip-coated film.•In the concentrated sol H-dimers are formed whereas in the corresponding film J-dimers prevail.•As the dip-coated films exposed to high humidity environment and isopropanol vapor, J-dimer to H-dimer transition and J-dimer dissociation are observed respectively.The alumina sol doped with rhodamine B (RB) was concentrated to different degree and then dip-coated to prepare thin film. Dimerization of RB happens in the concentrated sol and the dip-coated thin film. As the sol concentrated, H-dimers are presented whereas in the dip-coated film J-dimers are displayed. When the dip-coated film is exposed to high humidity environment, J-dimer will transfer to H-dimer. Put the film in isopropanol vapor, J-dimer dissociates to monomer.Dimer formation, transformation, and dissociation in dip-coated film.

The asymmetric amphiphilic block copolymer polystyrene962-block-poly(ethylene oxide)227 (PS962-b-PEO227) canforms micelles with N, N-dimethylformamide (DMF) as co-solvent and water as selected solvent, and when the water content of the mixed solvent is higher than 4.5 wt%, the vesicle will be dominated. This work finds that once vesicles are formed in the DMF-water mixed solvent, the vesicle size and membrane thickness can be tuned by further increasing water content. As the water fraction elevated from 4.8 wt% to 13.0 wt%, the vesicle size dercreases from 246 nm to 150 nm, while the membrane thickness increases from 28 nm to 42 nm. In addition, the block copolymer packing and the free energy are analyzed as the vesicle size becomes small and the membrane becomes thick.

The dissolution, crystallization and hydrolysis behaviors of polyamide 6 (PA 6) in superheated water (140 °C ≤ TH ≤ 200 °C) are investigated. The hydrothermal processing of PA 6 can be divided into four regions: (I) TH < 140 °C, (II) 140 °C ≤ TH ≤ 155 °C, (III) 155 °C < TH < 160 °C and (IV) TH ≥ 160 °C. Below 140 °C, the hydrothermal processing does not have obvious impact on PA 6. Between 140 °C and 155 °C, an annealing effect is observed that the hydrothermally treated resin shows increased melting temperature and lamellar thickness compared with the original PA 6. Between 155 °C and 160 °C, the hydrothermal processing induces both annealing and surface swelling. Above 160 °C, PA 6 dissolves fully in the superheated water. As PA 6 dissolves in the superheated water, hydrolysis takes place and becomes more prominent at higher temperatures and longer processing time. The hydrolysis induced molecular weight decrease fits an exponential decay.

Dopamine-modified poly(acrylic acid) (PAA-dopa) and poly(vinylpyrrolidone) (PVPON) was layer-by-layer (LbL) assembled to prepare thin film based on hydrogen bonding. The carboxylic group of acrylic acid and the phenolic hydroxyl group of dopamine can both act as hydrogen bond donors. The critical assembly and the critical disintegration pH values of PVPON/PAA-dopa film are enhanced compared with PVPON/PAA film. The hydrogen-bonded PVPON/PAA-dopa thin film can be cross-linked via catechol chemistry of dopamine. After cross-linking, the film can be exfoliated from the substrate in alkaline solution to get a free-standing film. Moreover, by tuning the pH value, deprotonation and protonation of PAA will make the hydrogen bond in the film break and reconstruct, which induces that the free-standing film has a reversible swelling–shrinking behavior.

The oppositely charged cellulose derivatives, quaternized cellulose (QC) and carboxymethyl cellulose (CMC), were alternately deposited on silicon or quartz substrates by interfacial complexation, i.e. layer-by-layer (LbL) assembly, to prepare thin films. The effects of pH value, ionic strength and temperature on thin-film growth and morphology were investigated. The main chains of QC and CMC, composed of glucose rings, are hydrophilic and rigid, and hence QC and CMC show a different assembly behavior compared with synthetic vinyl polyelectrolytes such as polystyrene sulfonate and poly(diallyldimethyl-ammonium). As the pH value increases, in the region from pH 3 to pH 5, QC and CMC can be LbL-assembled to prepare thin films; in the neutral pH region, it is very difficult to assemble QC and CMC; and when the pH value is higher than 10, QC and CMC can again be deposited to fabricate thin films. The LbL assembly of QC and CMC is sensitive to ionic strength. On adding 0.1 M NaCl into the assembling solution, the thin-film growth decreases enormously. Increasing the temperature accelerates the growth in thickness of the films.

The complexation behavior of PAA and lanthanide (Ln) ions was schematically investigated. As pH increased, the complexation between PAA and Ln ions will greatly strengthen because COO− groups exhibit much stronger interaction with Ln ions than COOH. When the pH values are higher than 2.5, where the ionization of PAA is about 2.0%, the PAA–Ln complex would precipitate out from the solution. The precipitation is a direct indicator for the complexation between PAA and Ln ions. Besides pH values, the complex precipitation is related with the concentration, the molar ratio, and the operation procedure. At the extremely low concentration, there is no polymer–metal complex precipitation but fluorescence spectroscopy reveals that the complexation between PAA and Ln ions still exists when pH value is higher than 2.5. When the molar ratio of PAA and Ln ions exceeds the certain level, it would produce soluble polymer–metal complex, even at the high concentration of Ln ions.

•Rhodamine dyes are loaded into the hydrogen-bonded thin film.•Loading and releasing show strong dependence on pH and temperature of the environment.•Interaction mode between Rhodamine dyes and thin film building polymers is discussed.The hydrogen-bonded poly(vinylpyrrolidone)/poly(acrylic acid) (PVPON/PAA) thin films were prepared by the step-wise interfacial complexation, i.e. layer-by-layer assembly process. Rhodamine B (RB), was utilized as mode compounds to investigate the pH and the temperature effect on the loading and releasing behavior of the hydrogen-bonded thin film. The releasing shows reverse trend compared with the loading. In the pH region from 0.7 to 4.5, as pH value increases the loading content becomes high while the releasing become slow. As temperature increased from 10 to 90, the RB loading slows down while the releasing accelerates.RB loading and releasing show strong dependence on pH and temperature.

Morphology transformation of polystyrene-block-poly(ethylene oxide) (PS-b-PEO) vesicle on solid surface induced by vapor annealing was investigated. The PS-b-PEO diblock copolymer vesicles, prepared by dissolving in a co-solvent and adding a selective solvent, were transferred to silicon wafer surface by spin cast and then incubated in three different vapors, tetrahydrofuran (THF), dioxane (DIOX), and N, N-dimethylformamide (DMF) separately. In THF or DIOX, the vesicular structures quickly fuse together into a droplet which then spreads on the surface. While in DMF vapor, vesicle-cylinder-sphere transformation is present. The vesicle morphology transformation in DMF vapor is very sensitive to water content. A small amount of water in DMF would slow down the transformation rate, and water content would affect the cylinder packing.

The hydrogen bonded polymer complex bulk and thin film was prepared by solution mixing and layer-by-layer assembly, respectively. Poly(vinylpyrrolidone) (PVPON) and poly(ethylene oxide) (PEO) were hydrogen bonding acceptor polymers while poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA) were hydrogen bonding donor polymers. The detachment of hydrogen bond between the chains in polymer complexes was investigated during the dissolution in alkaline solution, ionic liquid and tertiary amine N-oxide. We compared the dissolution process of the polymer complex bulk with the polymer complex thin film, and discussed the polymer chain length, chain entanglement degree and temperature effect on hydrogen bond detachment and dissolution of polymer complexes.

Diblock copolymer polystyrene-block-poly(ethylene oxide) (PS-b-PEO) forms micelles in a mixed solvent of N,N-dimethylformamide (DMF)–water. Poly(acrylic acid) (PAA) and poly(methyl acrylic acid) (PMAA) were introduced to the solution in order to study the effect of hydrogen bonding (H-bonding) complexation on the micellization process. The H-bonding complexation changes the micellization free energy of PS-b-PEO, and more importantly affects the kinetics of the morphological transformation of the micelles with temperature, which provides helpful insights into the time-dependence of the isothermal relaxation process from non-equilibrium to equilibrium.

Hydrogen-bonded films were prepared by layer-by-layer (LBL) assembly of poly(vinylpyrrolidone) (PVPON) and poly(acrylic acid) (PAA). The effect of temperature on the build-up and post hydrothermal process was studied in detail. It was found that the film's cloudiness was sensitive to the fabrication temperature. Below 20 °C the film was cloudy, while above 25 °C it was transparent. The temperature region from 20–25 °C was a mixed zone, transiting from cloudy to transparent. The thickness growth exhibited different temperature dependencies in the cloudy and transparent temperature regions. In the cloudy temperature region it was 5–6 nm °C−1 per cycle while in the transparent temperature region it was as high as 15–16 nm °C−1. At 50 °C, the film thickness increment of a single deposition step reached to ∼600 nm, which was considered as one of the fastest growth rates in LBL assembly. The post hydrothermal processing of the film was performed in acidic water (pH = 2.0) at temperatures higher than the build-up temperature. As the hydrothermal processing temperature elevated to 90 °C, the Fabry-Pérot fringes gradually disappeared and a morphology full of pits formed, like the film that was prepared by layer-by-layer assembly at 50 °C.

Poly(vinylpyrrolidone) (PVPON) and poly(acrylic acid) (PAA) were layer-by-layer (LBL) assembled to prepare the thin films based on hydrogen-bonding complexation. The hydrogen-bonded PVPON/PAA films were incubated in acidic, neutral and basic vapors separately. To study the morphologies after incubation, the films were stained by pH-sensitive fluorescent dyes using chemical and physical ways, and investigated with confocal laser scanning microscope (CLSM). The chemical way (labeling) was covalently linking fluoresceinamine (FAM) to some monomer units of PAA while the physical way was adsorbing rhodamine B (RB) molecules from dilute solution. Atomic force microscope (AFM) was combined with CLSM to find that after incubation in neutral or basic vapor the hydrogen-bonded PVPON/PAA films form porous structure and the pores are through the whole film.Graphical abstractHighlights► Hydrogen-bonded films were stained both by chemical and physical methods. ► The stained films were incubated in different vapor environments. ► The films’ morphologies were studied with confocal laser scan microscopy (CLSM). ► CLSM and AFM were combined together to unveil the film's structure after incubation.