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Chiral Helical Polymer Nanomaterials with Tunable Morphology: Prepared with Chiral Solvent To Induce Helix-Sense-Selective Precipitation Polymerization
摘要： We report an unprecedented strategy for using achiral monomer to construct chiral helical polymer nanomaterials with tunable morphology—helix-sense-selective precipitation polymerization induced by a chiral solvent (HSSPP-CS). CHCl3, chiral α-pinene, and an alkanol were employed to constitute a solvent mixture for performing HSSPP-CS. (R)- or (S)-α-pinene worked as chiral source and transferred its chirality to the resulting helical polyacetylenes derived from achiral monomer in the course of polymerization, thereby forming chiral helical polymers and endowing the nanomaterials thereof with optical activity. Simply changing solvent composition provided chiral polymer products varying in morphology from fibrous to rod-like and finally to spherical morphology. This is the first report dealing with chirality transfer from chiral solvent to induce helix-sense-selective precipitation polymerizations. The study establishes a straightforward and effective alternative for making use of achiral monomers to construct chiral helical polymer nanomaterials with diverse morphology.
关键词： tunable morphology,chiral solvent,achiral monomer,chiral helical polymer nanomaterials,helix-sense-selective precipitation polymerization
更新于2025-09-23 15:21:01
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Effect of light absence or attenuation on biaxial flexural strength of dual-polymerized resin cements after short- and long-term storage
摘要： Objective: To evaluate whether biaxial flexural strength (BFS) of dual resin cements is affected by light absence or attenuation, storage time, or cements' chemical nature. Materials and methods: One hundred and twenty disk-shaped specimens were made from each cement (non-self-adhesive cement and self-adhesive cement) using Teflon molds on a controlled temperature surface (35°C). Specimens were polymerized as follows (N = 30): self-cured, directly light-cured, light-cured at a distance of 6 mm between the light tip and the specimen, and through a 6-mm thick composite resin barrier (indirectly light-cured). Each group was divided (N = 10) for storage purposes (15 minutes, 24 hours, and 6 months). Specimens were placed into a biaxial-flexure jig and a vertical load was applied until failure. The BFS values were subjected to generalized linear models statistical analysis and Weibull distributions (α = 0.05). Results: After 15 minutes aging, neither material achieved enough polymerization to perform the BFS test when polymerized using the self-curing mode. The self-adhesive product demonstrated much lower variation in strength with storage time than did the non-self-curing cement. Conclusions: Attenuated/light-curing reduced BFS values only for 15-minutes storage period for both materials. Flexural strength of the self-adhesive cement was less affected by light absence/attenuation and storage time.
关键词： resin cements,Weibull analysis,biaxial flexural strength,physical properties,polymerization
更新于2025-09-23 15:21:01
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Fabrication of highly durable polysiloxane-Zinc Oxide (ZnO) coated Polyethylene Terephthalate (PET) fabric with improved ultraviolet resistance, hydrophobicity, and thermal resistance
摘要： Developing a universal strategy to improve the properties of PET fibers, such as UV resistance, hydrophobicity, and thermal resistance, is highly desirable in expanding the application of PET fibers. Herein, a highly durable and robust ZnO layer was deposited onto polyethylene terephthalate (PET) fabric via radiation-induced graft polymerization (RIGP) of γ-methacryloxypropyl trimethoxysilane (MAPS) and the subsequent sol-gel in situ mineralization with zinc acetate to produce wurtzite nanocrystalline ZnO. The as-obtained material, denoted as PET-g-PMAPS/ZnO. The interfacial layer consisted of Zn-O-Si and Si-O-Si covalent bonds not only leads to an improvement in adhesion between ZnO nanoparticles and its support, but it also overcomes the poor film-forming ability of inorganic particles. Most importantly, photocatalytic self-degradation of its organic support caused by the high photocatalytic activity of ZnO can be eliminated because of high bond energy of the organic-inorganic hybrid structure. PET-g-PMAPS/ZnO exhibited excellent thermal resistance, UV resistance and durability. Superhydrophobicity was achieved by simply annealing the PET-g-PMAPS/ZnO fabric at 200 °C in ambient air, and the coated fabric still retains its superhydrophobicity after 40 laundering cycles test and even stored for a few weeks. This study presents an effective method to overcome the bottle-necks in growing inorganic nanocrystals on polymeric supports surface.
关键词： ZnO,UV resistance,self-degradation,polyethylene terephthalate fabric,radiation-induced graft polymerization
更新于2025-09-23 15:21:01
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Effect of oxidants on morphology of interfacial polymerized polyaniline nanofibers and their electrorheological response
摘要： Polyaniline (PANI) nano?bers were fabricated via an interfacial polymerization method at 0 °C by using 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPSA) and ammonium peroxysulfate as a dopant and an oxidant, respectively. The molar ratio of the oxidant to aniline monomer in?uenced the morphology (shape and size) of the resulting PANI/AMPSA nano?ber and was investigated using a scanning electron microscope and transmission electron microscope images. The conductivity of synthesized PANI/AMPSA nano?ber changed when its synthetic conditions were varied. Electrorheological (ER) performance with and without an electric ?eld was tested for ER ?uids composed of either PANI nano?bers or normal PANI. Both conventional Bingham and Cho-Choi-Jhon models were utilized to describe shear stress behavior as a function of shear rate, especially under a low shear rate range. Finally, the ?bril morphology of PANI nano?bers showed a pronounced e?ect on the dispersion stability of the ER ?uid by measuring the transmittance as a function of sedimentation time via an optical analyzer of Turbiscan.
关键词： Interfacial polymerization,Electrorheological,Nano?ber,Polyaniline
更新于2025-09-23 15:21:01
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Microencapsulation of energy conversion photochromic materials with epoxy resin shell by interfacial polymerization
摘要： In this study, a novel type of photochromic spirooxazine microcapsule was prepared by interfacial polymerization between epoxy resin and polyamine compound. The effects of different process parameters on the formation, microstructure and performance of microcapsules, such as curing reaction temperature, emulsification shear rate and the addition of silica nanoparticles were studied in this paper. The morphology, microstructure, diameter and distribution, as well as the thermal stability of microencapsulated photochromic spirooxazine were also investigated by field emission scanning electron microscope, laser particle size analyzer and thermogravimetric analysis systematically. In addition, the photochromic performance of microcapsule was studied as well.
关键词： microencapsulation,photochromic,epoxy resin,spirooxazine,interfacial polymerization
更新于2025-09-23 15:21:01
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High-performance electrochromic device based on novel polyaniline nanofibers wrapped antimony-doped tin oxide/TiO2 nanorods
摘要： We report a novel electrochromic device (ECD) using polyaniline nanofibers wrapped antimony-doped tin oxide/TiO2 (ATO/TiO2@PANI) nanorods as electrochromic electrode material. The nanocomposites with core-shell structure were prepared by in situ chemical oxidative polymerization where aniline was polymerized in ATO/TiO2 nanorods aqueous dispersion. PEDOT:PSS film which was a complementary coloring material was used as counter electrode. A gel electrolyte (GE) was used in ECD. The architectural design of ECD based on ATO/TiO2@PANI film was ITO/ATO-TiO2@PANI/GE/PEDOT:PSS/ITO (ECD-TPN). Compared with the ECD based on pure PANI film (ECD-PANI), higher optical contrast (38.5% at 660nm), higher coloration efficiency 202.2 cm2/C, faster response speed (tc=1.2 s, tb=1.0 s) and better cycling stability (sustaining 99.5% of its initial optical modulation after subjecting 5000 s) are archived by the ECD-TPN. The enhanced electrochromic properties are mainly attributed to the formation of the donor-acceptor system between the PANI nanofiber shell layer and the ATO/TiO2 nanorod, and the porous space among the ATO/TiO2@PANI nanocompsites and the PANI nanofibers, which can improve the efficiency of redox reaction, make the ion diffusion easier and provide larger surface area for charge-transfer reactions, respectively.
关键词： Chemical oxidative polymerization,ATO/TiO2,Electrochromism,Core-shell nanostructures,Polyaniline
更新于2025-09-23 15:21:01
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Preparation and photochromic behavior of spiropyran-containing fluorinated polyacrylate hydrophobic coatings
摘要： In this study, spiropyran (SP)-containing fluorinated polyacrylate (F-PA-SP) latex was prepared by emulsion polymerization using fluorinated and SP-based acrylic monomers as raw materials. FT-IR and 1H-NMR demonstrate that the F-PA-SP copolymer has been successfully synthesized, and DLS and TEM analyses indicate that the synthesized latex has presented a uniform particle size of approximately 200 nm. XPS, AFM and water contact angle (WCA) analysis were used to investigate the surface properties of the F-PA-SP coating and demonstrate that its hydrophobicity is enhanced by addition of a fluorinated acrylic monomer. The photochromic properties of the coating were investigated by UV-Vis spectroscopy, and the results reveal that the F-PA-SP coating possesses better photo-responsiveness, fatigue resistance, and photo-reversibility under UV/Vis irradiation than the coating prepared using fluorinated polyacrylate/SP blended latex. Moreover, the WCA of the F-PA-SP coating subjected to UV/Vis irradiation shows minimal changes and retains its excellent hydrophobicity. Finally, the F-PA-SP latex was applied to cellulosic paper, and the resulting photochromic paper exhibits outstanding reversible color changes and hydrophobicity.
关键词： emulsion polymerization,hydrophobicity,fluorinated polyacrylate,spiropyran,photochromic
更新于2025-09-23 15:21:01
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Photopolymerization of acrylates by enzymatically synthesized PCL based macrophotoinitiator
摘要： Polycaprolactone based macrophotoinitiator was synthesized via enzymatic ring-opening polymerization by using commercially available Irgacure-2959 as the nucleophilic initiator and Novozyme-435 as the immobilized lipase catalyst. The macrophotoinitiator was further utilized to photopolymerize benzyl acrylate (BzA), tetrahydrofurfurly acrylate (THFA), 2-hydroxyethyl acrylate (HEA) and poly (ethylene glycol) methyl ether acrylate (Mn ~ 480 g/mole) (PEGMEA-480) under Ar atmosphere. The obtained polymers were characterized by 1H Nuclear Magnetic Resonance, Fourier Transform Infrared Spectroscopy, Differential Scanning Calorimetry and Size Exclusion Chromatography. The highest dry polymer conversions were achieved with BzA and THFA. However, due to the gel formation during the photopolymerization reactions of HEA and PEGMEA-480, the dry polymer conversions were comparably lower. The photopolymerization product of BzA demonstrated a single glass transition temperature at –6.5 °C. The enzymatically synthesized macrophotoinitiator was shown to be an efficient catalyst for light-induced polymerization of the abovementioned monomers.
关键词： polycaprolactone,photopolymerization,biocomposites,enzymatic polymerization,macrophotoinitiator,biopolymers
更新于2025-09-23 15:21:01
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Synthesis and Characterization ofBaTiO3/Polypyrrole Composites with Exceptional Dielectric Behaviour
摘要： Higher concentrations of ceramic fillers induce brittleness in the ceramic/polymer hybrids which restrict their applications to limited fields especially when such hybrids are prepared for their use as dielectrics. We have synthesized and characterized different BaTiO3-polypyrrole (PPy) composites by changing the concentration of BaTiO3 from 1% by weight of PPy taken to 5 wt % to explore its effect on the dielectric parameters of the final product and found that the BaTiO3-polypyrrole composite with weight ratio of 0.05:1 exhibited highest dielectric constant, lowest dielectric loss and thermally most stable. All the composites were prepared using in-situ polymerization of pyrrole in an aqueous dispersion of low content of BaTiO3 in the presence of small amount of Hydrochloric acid. These composites were characterized for their microstructure and crystallinity by X-ray diffractometer (XRD), Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM) while thermal stability by thermo gravimetric (TGA) analysis. An impedance analyser (LCR meter) was utilized to investigate the dielectric parameters. FT-IR data confirmed the presence of the two phases and their interaction, inferred from the shifting of normal PPy peaks. The data obtained from XRD confirmed the presence of crystallites of 2.8 to 5 nm with dominant crystallinity of the filler, TGA analysis (25 to 600 ?C) confirmed the higher thermal stability induced on successive addition of the filler into the prepared composites as compared to that of pure PPy in a wide temperature range which is unusual for such a low % age addition of the filler. The SEM analysis together with XRD results reveal that the successive introduction of BaTiO3 particles produced crystallites of 2 to 5 nm size which bonded together and changed the hemispherical shaped larger grains of the matrix to regular shaped smaller grains. The dielectric constant of the composites was enhanced with filler contents from 178 to 522 at 1 MHz for 1 wt % and 5 wt % BaTiO3 respectively. It was concluded that the introduction of BaTiO3 into the polymer matrix with this new procedure has greatly affected the polymerization process, thermal stability, morphology and dielectric properties of the host matrix and has resulted in a novel series of the composites which may have broad applications.
关键词： barium titanate,polymerization,dielectric behaviour,polypyrrole
更新于2025-09-23 15:21:01
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Photoactive Functional Soft Materials (Preparation, Properties, and Applications) || Photoresponsive Supramolecular Polymers
摘要： According to the definition by Meijer and coworkers in their seminal review [1], supramolecular polymers are polymeric assemblies of small molecular units that are brought together through reversible and directional noncovalent interactions, leading to polymeric properties in solution and bulk states [1–5]. Owing to the reversible nature of their main‐chain formation, supramolecular polymers have attracted considerable attention as highly stimuli‐responsive polymeric materials compared to conventional polymer counterparts. Needless to say, supramolecular polymers have high responsiveness in terms of “degree of polymerization” to temperature change mainly due to entropic reasons, and to solvent media mainly due to enthalpic reasons. Such high responsiveness to external environment has enabled not only the exploration of temperature‐ and solvent‐dependent supramolecular polymer systems, but also the analyses of the supramolecular polymerization process regulated by these parameters [6]. From a technical viewpoint, furthermore, supramolecular polymers have another advantage over conventional polymers, i.e. quite ambient polymerization conditions without using any chemical reagents. This allows more flexible monomer design and enables introduction of a wide variety of functional molecules into supramolecular monomers.
关键词： stimuli-responsive,photoresponsive,supramolecular polymers,polymerization,noncovalent interactions
更新于2025-09-23 15:21:01