Fabrication of attapulgite-based dual responsive composite hydrogel and its efficient adsorption for methyl violet

In this work, attapulgite (ATP)-based dual sensitive poly (N-isopropylacrylamide-co-acrylic acid) composite hydrogel, P(NIPAM-co-AA)/ATP, was prepared by free radical polymerization. The prepared composite hydrogel was characterized via methods of scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), zeta potential analysis and Brunauer, Emmett, and Teller (BET) etc. The composite hydrogel showed pH and temperature sensitive behaviour, with lower critical solution temperature (LCST) of 35°C and highest swelling occurred at pH 8.0. The adsorption of methyl violet (MV) can be controlled by the hydrogel responsiveness, and 95.78% of MV can be removed at pH 8.0 and 35°C. The addition of a small amount of ATP (3 Wt%) can improve the swelling ratio and adsorption capacity. Kinetic analysis demonstrated that the experimental data were best fitted to the pseudo-second order model. Isotherm analysis showed that the equilibrium data followed Langmuir model with the adsorption capacity of 168.35 mg g^-1. In addition, the composite hydrogel has high adsorption selectivity for cationic dyes, and MV-loaded hydrogel is easy to regenerate, which can be used for successive adsorption cycles. These results demonstrate that the composite hydrogel has potential application in dye wastewater treatment.

Polyrotaxanes created by end-capping polypseudorotaxanes self-assembled from β-CDs with distal azide terminated PHEMA using propargylamine monosubstituted β-CDs

When a distal azide terminated PHEMA was allowed to self-assemble with varying amounts of β-CDs in water, followed by in situ reaction with PA-β-CDs via the CuAAC, linear polyrotaxanes (PRs) and a mixture of linear and hyperbranched PRs were obtained.

Azo group(s) in selected macrocyclic compounds

Azobenzene derivatives due to their photo- and electroactive properties are an important group of compounds finding applications in diverse fields. Due to the possibility of controlling the trans-cis isomerization, azo-bearing structures are ideal building blocks for development of e.g. nanomaterials, smart polymers, molecular containers, photoswitches, and sensors. Important role play also macrocyclic compounds well known for their interesting binding properties. In this article selected macrocyclic compounds bearing azo group(s) are comprehensively described. Here, the relationship between compounds' structure and their properties (as e.g. ability to guest complexation, supramolecular structure formation, switching and motion) is reviewed.

Establishment of a molecular design to obtain visible-light-activated azoxy polymer actuators

Visible-light-activated main-chain and hyperbranched azoxy polymers were prepared directly from bis-/trinitro-functionalized monomers via photochemical reduction.

Photoactive and Physical Properties of an Azobenzene-Containing Coordination Framework

A new three-dimensional coordination framework, [Zn4(tbazip)3(bpe)2(OH)2]·bpe·{solvent} (where bpe = 1,2-di(4-pyridyl)ethene) containing the novel photoactive ligand tbazip (tbazip = 5-((4-tert-butyl)phenylazo)isophthalic acid) has been synthesised and crystallographically characterised. The photoactivity of discrete tbazip was investigated and compared with its photoactivity while incorporated within the framework. The effect of isomerisation of the incorporated azobenzene on the chemical and physical properties of the framework were investigated using UV-vis and Raman spectroscopies. The framework is porous only to hydrogen gas at 77 K, but displayed an appreciable uptake for CO2 at 195 K.

A new thermoresponsive polymer of poly(N-acryloylsarcosine methyl ester) with a tunable LCST

A thermoresponsive polymer of the tertiary amide-based polyacrylamide, PNASME, was synthesized and its tunable thermoresponse was investigated.

Preparation of Well-Defined Propargyl-Terminated Tetra-Arm Poly(N-isopropylacrylamide)s and Their Click Hydrogels Crosslinked with β-cyclodextrin

As an important class of reversible deactivation radical polymerization (RDRP), reversible addition fragmentation chain transfer (RAFT) polymerization has attracted great attention attributed to its facile and flexible features to prepare well-defined polymers with different complex structures. In addition, the combination of RAFT with click chemistry provides more effective strategies to fabricate advanced functional materials. In this work, a series of temperature responsive tetra-arm telechelic poly(N-isopropylacrylamide)s (PNIPAs) with propargyl end groups were prepared for the first time through RAFT and subsequent aminolysis/Michael addition modification. The temperature sensitivities of their aqueous solutions were researched via turbidity measurement. It was found that the phase transition temperature of obtained PNIPAs increased with their molecular weights ascribed to their distinctions in the hydrophobic/hydrophilic balance. Subsequently, β-cyclodextrin (β-CD) functionalized with azide moieties was used to crosslink the prepared propargyl-terminated tetra-arm PNIPAs through click chemistry, fabricating corresponding hydrogels with thermoresponse. Similar to their precursors, the hydrogels demonstrated the same dependence of volume phase transition temperature (VPTT) on their molecular weights. In addition, the incorporation of β-CD and the residual groups besides crosslinking may provide a platform for imparting additional functions such as inclusion and adsorption as well as further functionalization.

Star-shaped and star-block polymers with a porphyrin core: from LCST–UCST thermoresponsive transition to tunable self-assembly behaviour and fluorescence performance

The micelles self-assembled from star-shaped and star-block copolymers present a transition of LCST–UCST thermoresponsive properties through a facile quaternization reaction.

A straightforward approach for the one-pot synthesis of cyclic polymers from RAFT polymers via thiol–Michael addition

A straightforward approach for the synthesis of cyclic polymers in a one-pot reaction.

Biomacrocyclic side-chain liquid crystalline polymers bearing cholesterol mesogens: facile synthesis and topological effect study

Biomacrocyclic side-chain liquid crystalline polymers bearing cholesterol mesogens with three different length methylene spacers were prepared. Meanwhile, the liquid crystalline phase behaviors were investigated systematically.

Regulation of the self-assembly morphology of azobenzene-bearing double hydrophobic block copolymers in aqueous solution by shifting the dynamic host–guest complexation

The complexation equilibrium between azo and β-CD can be shifted by various methods, thus the micellar morphology of azo-bearing block copolymers is altered.

Poly(N-isopropylacrylamide) hydrogels fabricated via click chemistry: well-defined α,ω-bis propargyl linear poly(N-isopropylacrylamide)s as crosslinkers

This work provides a facile method to regulate swelling properties and/or to impart special functions for click poly(N-isopropylacrylamide) (PNIPA) hydrogels, by adjusting the chain length of crosslinkers or by introducing other functional groups.