The well-defined block copolymer of poly(ethylene oxide)-b-poly(N-isopropylacrylamide) (PEOb-PNIPAm) was synthesized by the reversible addition fragmentation transfer (RAFT) polymerization, and its thermo-induced aggregation process in dilute aqueous solution was studied by laser light scattering. At temperatures below the cloud point of PNIPAm, the PEO-b-PNIPAm chains were associated together to form large and loose structures, which were in a fast equilibrium with the single chains. The association was weakened with increasing concentration, which was against the common ideas about aggregation. Because of such "abnormal" behavior, PEO-b-PNIPAm underwent three stages of transformation during the heating process at 0.1 mg/mL: the disassociation of loose associates at temperatures below 28 °C, the micellization above 42 °C, and the aggregation in between. At each stage, the size and M w,app exhibited distinct features. On the basis of these observations, possible mechanisms of the association and aggregation were also proposed.

As-synthesized single-walled carbon nanotubes (SWNTs) are bundled mixtures of different species. The current challenge in the field of carbon nanotube research lies in the processing and separation of SWNTs, which first require efficient dispersion of individual SWNTs in solvents. We report DNA-mimicking polysoap surfactants that disperse SWNTs in aqueous solutions more effectively than DNA. The polysoaps are synthesized by functionalizing the side chain of poly(styrene-alt-maleic acid) with aminopyrene. The synthetic nature of the polysoap opens a new approach to further optimization of not only SWNT dispersion efficiency but also multi-functional SWNT dispersing surfactant.

The polymerization-induced micellization of poly(ethylene oxide)-b-poly(styrene-alt-maleic anhydride) (PEO-b-P(S-alt-MAn)) in CHCl3 was monitored in situ by laser light scattering. Reversible addition−fragmentation chain transfer (RAFT) polymerization was used to grow the P(S-alt-MAn) block onto the PEO macromolecular chain transfer agents (macro-CTAs) at 55 °C. The whole process underwent three stages over time: the induction period, the formation of loose aggregates, and the formation of micelles. The polymerization process and the micellization process were affected mutually: the increase in the degree of polymerization induced the micellization of PEO-b-P(S-alt-MAn); meanwhile, the formation of core−shell micelles retarded the polymerization rate. At higher polymer concentrations, the mutual effect was even stronger, where smaller size micelles with higher density were obtained.

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An electron-transport layer with appropriate energy alignment and enhanced charge transfer is critical for perovskite solar cells (PSCs). In addition, interface stress and lattice distortion are inevitable during the crystallization process of perovskite. Herein, IT-4F is introduced into PSCs at the buried SnO2 and perovskite interface, which assists in releasing the residual stress in the perovskite layer. Meanwhile, the work function of SnO2/IT-4F is lower than that of SnO2, which facilitates charge transfer from perovskite to ETL and consequently leads to a significant improvement in the power conversion efficiency (PCE) to 23.73%. The V OC obtained is as high as 1.17 V, corresponding to a low voltage deficit of 0.38 V for a 1.55 eV bandgap. Consequently, the device based on IT-4F maintains 94% of the initial PCE over 2700 h when stored in N2 and retains 87% of the initial PCE after operation for 1000 h.

chromophore-immobilized nylon membranes have been applied to detect toxic chemical compounds at ultratrace level by fluorescence measurements. [13,14] K + -selective film sensors were fabricated by introducing electrically charged solvatochromic dyes into nylon films. The fluorescence response to K + possesses the features of excellent selectivity and fast rate. [15] However, the postmodifications often suffer from incomplete functionalization, poor miscibility, or weak stability.Herein, we prepared fluorescent nylon-6 by using tetraphenylethylene (TPE), a typical aggregation-induced emission luminogen, [16,17] carrying two amino functionalities as coinitiator. The synthetic procedure is fully adapted to the traditional nylon-6 polymerization. The resulting polymer, named TPE-labeled nylon-6, exhibits unique fluorescence property. Its fluorescence color can be tuned by controlling the intramolecular rotation of the TPE's phenyl rings. Nylon-6 is a semicrystalline polymer. During its melting transition at high temperature, the movement of the nylon chain will interfere the intramolecular motion of TPE to induce fluorescence change of the chromophoric unit. [18][19][20] TPE-labeled nylon-6 was synthesized by ring-opening polymerization of caprolactam in the presence of 1,2-bis(4aminophenyl)-1,2-diphenyl ethylene (1) as coinitiator (Scheme 1). Since the amount of compound 1 used is tiny, the polymerization efficiency will not be affected. The synthetic procedure is suitable for industrial production. The 1 H NMR spectrum of the obtained polymer shows characteristic Nylon is the first synthetic fiber material and is widely used throughout the world. However, traditional nylons show limited optical applications as they emit no or weak fluorescence. Herein, a fluorescent nylon-6 is synthesized by utilizing tetraphenylethylene (TPE) carrying two amino groups as coinitiator. The resulting TPE-labeled nylon-6 exhibits reversible thermal-induced fluorescence color change. This unique property arises from the synergistic effect of its chemical structure and conformation. The thermal expansion of the polymer at high temperature induces the phenyl rings of TPE to rotate in a greater extent, which decreases the conjugation of TPE to lead to a blueshift in its fluorescence. The novel fluorescence property of TPE-labeled nylon-6 enables it to find applications in fields like chemosensor and security label. Fluorescent Nylon-6

The reversible addition‐fragmentation chain transfer (RAFT) polymerization of N‐vinylcarbazole (NVK) mediated by macromolecular xanthates was used to prepare three types of block copolymers containing poly(N‐vinylcarbazole) (PVK). Using a poly(ethylene glycol) monomethyl ether based xanthate (PEG‐X), the RAFT polymerization of NVK proceeded in a controlled way to afford a series of PEG‐b‐PVK with different PVK chain lengths. Successive RAFT polymerization of NVK and vinyl acetate (VAc) with a small molecule xanthate (X1) as the chain transfer agent was tested to prepare PVK‐b‐PVAc. Though both monomers can be homopolymerized in a controlled manner with this xanthate, only by polymerizing NVK first could give well‐defined block copolymers. The xanthate groups in the end of PVK could be removed by radical‐induced reduction using tributylstannane, and PVK‐b‐PVA was obtained by further hydrolysis of PVK‐b‐PVAc under basic conditions. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010

As a classic flexible material, hydrogels show great potential in wearable electronic devices. The application of strain sensors prepared using them in human health monitoring and humanoid robotics is developing rapidly. However, it is still a challenge to fabricate a high-toughness, large-tensile-deformation, strain-sensitive. and human-skin-fit hydrogel with the integration of excellent mechanical properties and high electrical conductivity. In this study, a flexible sensor using a highly strain-sensitive skin-like hydrogel with acrylamide and sodium alginate was designed using liquid metallic gallium as a “reactive” conductive filler. The sensor had a low elastic modulus (30 kPa) similar to that of skin, a high-toughness (2.25 MJ m–3), self-stiffness, a large tensile deformation (1400%), recoverability, and excellent fatigue resistance. Moreover, the addition of gallium might enhance the electrical conductivity (1.9 S m–1) of the hydrogel while maintaining high transparency, and the flexible sensor device constructed from it showed high sensitivity to strain (gauge factor = 4.08) and pressure (gauge factor = 0.455 kPa–1). As a result, the hydrogel sensor could monitor various human motions, including large-scale joint bending and tiny facial expression, breathing, voice recognition, and handwriting. Furthermore, it might even be used for human–computer communication.