最新刊期
卷 ， 期 6 ， 2017
- 摘要：Janus is named after the Roman god who is depicted to have two opposite faces looking at the past and the future. In 1991, de Gennes introduced the Janus particles in his Nobel lecture. Janus materials have triggered extensive research interests in academia and industry. Janus composites possess two different chemical regions and functions that are distinctly compartmentalized onto the same object. While the organic polymer components provide tunable wettability and responsive performances, the inorganic (or metallic) components offer desired functionalities such as magnetic manipulation and light thermal effect. We have developed methods to precisely tune shape, size, microstructure and chemistry of Janus composites and therefore their performance. In analogy to molecular surfactants or copolymers, the amphiphilic Janus composites can stabilize interfaces more effectively. Similarly, the Janus composites can serve as emulsifiers in emulsion polymerization and as compatibilizers for polymer alloys. Moreover, the interfaces stabilized with the Janus composites can be easily manipulated by using external stimuli, and functionalized by delivering desired species thereby. By grafting responsive polymer chains, the emulsions can be de-stabilized by simple changing pH, temperature, light irradiation or exchanging of ions. When Janus composites contain paramagnetic species, the emulsion droplets can be withdrawn with a magnet. The droplets are further coalesced, leading to de-emulsification under a stronger magnetic field. This performance is important to remedy polluted water or soil with organic species in the presence of surfactants. By conjugation of heterogeneous catalysts onto the Janus composites, the catalytic efficiency of the catalysts is greatly enhanced. Functional species such as Fe3O4 or Au nanoparticles (NPs) can be delivered toward an oil/water interface when these NPs are grafted with hydrophobic and thermally responsive chains such as PNIPAM at the opposite sides. The de-emulsification can be easily achieved under NIR irradiationeven when the continuous phase temperature is below the LCST of PNIPAM(~32 ℃). The performance is enhanced from an interactive interplay between the hyperthermia effect of nanoparticles and a thermal energy transfer to fast locally heat PNIPAM.This performance is promising in heterogeneous catalysis and recycling of expensive catalysts. Wettability of Janus composites can be significantly magnified by nanoscale roughness. Robust superhydrophobic coatings are easily fabricated by forming a self-assembled monolayer of coarsening Janus microparticles and catalytic crosslinking the intermediate epoxy resin adhesive. In this Review, recent progress in manipulation of interfaces by Janus composites is summarized, including in emulsions and polymer alloys, interfacial heterogeneous catalysis, functional coatings, cell diagnosis and therapy.关键词：Janus;Composites;Amphiphilic;Functional;Interface
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发布时间：2021-03-19
Feature Articles
- 摘要：Stereocomplex crystallization is a generalbehaviour in polymer crystallizationand it is also a special cocrystallization process between different polymers. The polymers with complementary configurations and chiralities can form stereocomplex crystallites in their blends and stereoblock copolymers. Stereocomplex crystallization includes homo and hetero types; the former and latter represent the stereocomplex formation between the enantiomeric polymers having the identical and different structures, respectively. Stereocomplex crystallites of the polymers usually have denser chainpacking in the crystalline lattice than that in the common homocrystallites, because of the presence of additional intermolecular interactions (e.g., hydrogen bonding interactions). Due to their unique structural feature, the stereocomplexed polymers generally have distinct physical performances from the corresponding homocrystalline polymers. Stereocomplex crystallization can change melting temperature of the original polymers, and improve their thermal resistance, crystallizability, degree of crystallinity, processability, mechanical properties, and solvent-resistance. Some polymers, that are non-crystallizable or difficult to crystallize, can become crystallizable through stereocomplex crystallization; this can significantly change the physical performances of the resulted materials.Stereocomplex crystallization offers therefore a feasible andefficient avenue to manipulate and optimize the physical properties of the involved polymers. Stereocomplexed polymers havea variety of potential applications as biomedical materials and thermal-resistant engineeringplastics. A large number of polymer systems have been reported to fit for stereocomplex crystallization, including aliphatic polyesters, aliphatic polycarbonates, polymethacrylate, polyimide, polyketone,etc. Among them, the aliphatic polyesters and polycarbonates are two majorclasses of the stereocomplexable polymers; these polymers are biodegradable and can be partially derived from the biomass. Stereocomplex crystallization of enantiomeric polymers is affected by a variety of factors such as the chemical structure of the polymer components, blending ratio, crystallization and processing conditions. This paper gives a review on the stereocomplex formation conditions, structural characteristics, and physicalproperties for all reported stereocomplexable polymer systems according to the chemical structures of the polymers. We hope that this review can provide a theoretical guideline for the development of the stereocomplexable polymers.关键词：Stereocomplex crystallization;Polyester;Polycarbonate;Crystalline structure;Thermal property
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发布时间：2021-03-19 - 摘要：Rechargeable lithium ion batteries become an very important technology in the contemporary society. They are expanding their application in electric vehicles and power grids. However, current lithium ion batteries with liquid electrolyte have been suffering from potential safety crisis mainly due to their highly flammable organic liquid carbonate organic electrolyteand explosion hazards. These potential risks (combustion and explosion) would retard the commercialization of electric vehicles or hybrid electric vehicles. Thus, the safety issue of lithium ion battery merits further study. Solid electrolytes have attracted ever-increasinginterest owing to their enhanced safety issue and higher energy density of lithium battery. Solid electrolyte materials mainly include inorganic solid electrolytes (ISEs) and solid polymer electrolytes (SPEs). The ISEs are classified into oxide-based, sulfide-based andetc. However, in spite of the presence of highly ion conductive ISEs, there are still many undergoing issues that limit the practical application at the present stage, like the large interface impedance between electrode and ISEs and the difficulty of processing. More attention has been paid to solid polymer electrolytes due to their superior flexibility and processability, which are also subjected to thermal expansion at elevated temperature. Poly(ethylene oxide) (PEO) solid polymer electrolyte has undergone a sort of renaissance in the past few decades. However, the quintessential frailty of PEO solid polymer electrolyte is low ionic conductivity (in the order of 10-7 S cm-1) at room temperature with a relatively narrow electrochemical window. Hence, it is essential to develop new solid polymer electrolytes with comprehensive performance in terms of high ionic conductivity, wide electrochemical window, superior mechanical strength, excellent thermal stability as well as good interfacial compatibility. In this review, a series of polycarbonate-based solid polymer electrolytes (such as PEC, PPC, PTMC and PVC et al.) are summarized. In addition, we also present a brief review on preparation, electrochemical property, modification, ionic transportation mechanism and future development direction for each of these solid polymer electrolytes.关键词：Polycarbonate;Solid-state polymer electrolyte;Lithium battery;Classification and performance;Ionic transportation mechanism
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发布时间：2021-03-19
Reviews
- 摘要：Polymer solar cells (PSCs) based on the conjugated polymers as donor material have attracted considerable attention because of their various advantages such as lightweight, solution processability, flexibility and low-cost. Ullazine is an interesting multiring compound with conjugated plane and effective intramolecular charge transfer (ICT). In this study, the bipolymer PB and terpolymer PT were designed and synthesized by introducing an ullazine unit into the main chain or side chain of the conjugated polymer, by copolymerizing with diketopyrrolopyrrole (DPP) or 2, 5-bi(trimetyltin) thiophene. The molecular weight was measured by gel permeation chromatography (GPC) and the thermal property was investigated with thermogravimetric analysis (TGA). The number-average molecular weight (Mn) and polydispersity index (PDI)were 2.8×104 and 1.7 for PB, 7.6×104 and 2.1 for PT. The polymers PB and PT showed high decomposition temperatures (Td, 5% weight loss) of 431 and 432 ℃, respectively. The photophysical, electrochemical, and photovoltaic properties of the two polymers were studied systematically. In diluted CHCl3 solution, the bipolymer PB exhibited two absorption bands at 300-450 nm and 500-800 nm, and compared with PB, the terpolymer PT showed wider absorption bands and a red-shifted one to 900 nm. The HOMO and LUMO energy levels of the polymers PB and PT were determined to be-5.22 eV/-3.73 eV and-4.99 eV/-3.61 eV, respectively. The bulk heterojunction PSCs were fabricated with a device structure of ITO/PEDOT:PSS(~40 nm)/polymer:PC61BM(~100 nm)/LiF(0.5 nm)/Al(~80 nm) and measured under100 mW cm-2 AM 1.5G illumination. As a result, polymer solar cells based on bipolymer PB: PC61BM blends (3% DIO additive) exhibited a low PCE of 0.88% (Jsc =3.37 mA cm-2, Voc=0.79 V, FF =0.33), and the PSC based on terpolymer PT exhibited a double PCE of 1.54% (Jsc =6.63 mA cm-2, Voc=0.61 V, FF =0.38), due to its wider absorption spectra and higher hole mobility in comparison with thebipolymer PB.关键词：Ullazine;Conjugated polymer;Synthesis;Polymer solar cells;Photoelectric performance
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发布时间：2021-03-19 - 摘要：Controlled/living radical polymerization (CLRP) is one of themost rapidly developingareas in polymer science. Amongthe various existing techniques, nitroxide-mediated polymerization (NMP) was the first to be proposed. Up to now, most of the nitroxides studied in NMP are dialkyl or alkyl-arylnitroxides, while the use of diarylnitroxides as control radicals has not been extensively studied. In this paper, 4, 4'-dimethoxydiphenyl nitroxide (DMDPN) and its corresponding alkoxyamine initiator were easily synthesized and used to mediate the polymerization of methyl methacrylate (MMA). DMDPN was highly stable at high temperature and the single electron delocalisation on the aromatic rings prevented the undesired hydrogen abstraction between the nitroxide and the propagating radical chain. The polymerization kinetics was monitored by gravimetric method while the molecular weight and the distribution of poly(methyl methacrylate) (PMMA) synthesized were determined by gel permeation chromatography (GPC).The dissociation rate constants (kd) of the DMDPN-based alkoxyamine initiator wasdetermined by electron spin resonance (ESR) experiments performed at temperatures ranging from 100℃ to 120 ℃, yielded thefollowing Arrhenius parameters: Ea=135.2 kJ·mol-1 and A=3×1014. The kd value of macromolecular species was also determined at 110 ℃. As the low steric hindrance around the aminoxyl group in DMDPN, the penultimate unit effect, which was significant in a MMA/SG1(N-tert-butyl-N-(1-diethyl-phosphono-2, 2-di-methylpropyl) nitroxide) system, had only a weak influence on kd in the MMA/DMDPN system. A 6-fold increase of kd between the DMDPN-based alkoxyamine initiator and PMMA-DMDPN macro-alkoxyamine was observed. A bulkpolymerization of MMA was performed at 110 ℃ using 1 mol% of DMDPN-based alkoxyamine in the presence of 0.5 mol% of the corresponding free nitroxide to determine the equilibrium constant K. The recombination rate constant (kc) was then derived from the constant K. A Fischer's diagram for the polymerization of MMA at 110℃ was made and the values of kd and kc lied in the living and controlled area, proving the livingness of this polymerization system.关键词：Nitroxide-mediated polymerization;Methyl methacrylate;4, 4'-Dimethoxydiphenyl nitroxide;Kinetic constant;Fischer's diagram
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发布时间：2021-03-19 - 摘要：Cationic polymers have been widely explored as non-viral gene delivery vectors. The high density of cationic charges and high molecular weight of cationic polymers enable them efficiently condense DNA into nanosized polyplexes, which protect DNA from degradation and facilitate DNA cellular internalization. However, these characters also make the polyplexes hardly dissociate to release DNA, hindering its access to the DNA transcription process for gene expression. In this study, we synthesized two kinds of linear quaternized ammonium-based cationic polymers from 2, 6-dibromomethylphenolic esters using Menschutkin Reaction. The esterases in cytosol could hydrolyze the phenolic ester and trigger a self-immolative chain fragmentation, leading to the quick release of the packed DNA for efficient transcription. The DLS measurements of the size and zeta potential of the resulting polyplexes showed that these cationic polymers could pack DNA molecules efficiently into positively-charged nanoparticles. Agarose-gel electrophoresis experiment revealed that anionic DNA molecules were condensed stably and compactly with cationic polymers. Furthermore, self-immolative elimination was successfully monitored by high performance liquid chromatography (HPLC), which confirmed the esterase-responsiveness and compatibility of this well-designed cationic polymers. Gel retardation assay showed that the packed DNA could be quickly released after incubation with esterase solution, indicating that the polyplexes would become incompact and disassemble once in the cytosol. Meanwhile, compared with commercially available PEI, the polycation had a lower cytotoxicity in cancer cells, which might contribute to the fragmentation and the removal of the quaternary amine cationic charges. In A549 and Hela cancer cells, these two kinds of polyplexes achieved excellent gene transfection efficiency. But complex1 was better than complex 2 at high N/P ratios, thanks to the activation of self-immolative elimination by intracellular esterases.关键词：Gene delivery;Cationic polymers;Self-immolative;Menschutkin Reaction;Esterase-responsive
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发布时间：2021-03-19 - 摘要：A new diamine monomer, 3, 3'-diisopropyl-4, 4'-diaminodiphenyl-4"-trifluoromethyltoluene (PATFT) was designed and synthesized, and its structure was confirmed by FTIR, NMR and mass spectrometry. A series of fluorinated aromatic polyamides were obtained by Yamazaki phosphorylating condensation method with aromatic dicarboxylic acids, such as terephthalic acid, isophthalic acid, and 4-(4-carboxyphenoxy)benzoic acid. All the obtained polyamides were studied with FTIR, NMR, GPC, TGA, DSC and WAXD.The chemical structure of the polymers was in good agreement with the proposed structures. The weight-average molecular weight of the polyamides were in the range of3.8 ×104 -9.6 ×104, with the molecular weight distributionvaried from 3.2 to 3.7. These results indicate that the polymerswere of high molecularweight with low polydispersity index, and theymust be suitable toprepare flexible and tough films. The solubility of the polyamides was also tested, and the results showedthat theypossessed good solubilityat room temperature inhigh-boiling organic solvents, such as N, N-dimethylacetamide(DMAc), N, N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), and dimethyl sulfoxide(DMSO). Moreover, they could be dissolved in low-boiling solventsunder heating, such astetrahydrofuran (THF), chloroform, methylene chloride and acetone. They also have outstanding thermal and thermo-oxidative stability with the glass transition temperature (Tg) in the range of 213-220 ℃ in nitrogen atmosphere, as well as T5% weight loss temperature range of 453-458℃ andthat for T10% from 470℃ to 482 ℃ in nitrogen atmosphere. Furthermore, char yields ofthe polyamides at 800 ℃ was in the range from 55% to 66%. Obviously, these polymers exhibited excellent optical properties with the cutoff wavelength in the range of 322-350 nm, and 80% transmittance with the wavelengths of 403 nmor longer. The polyamide films showed outstanding mechanical property with tensile strength of 68-397 MPa, elongation at break of 14.8%-316.7%, and Young's modulus of 1.9-32.9 GPa. The results of WAXD indicated that all the polymers were amorphous.关键词：Polyamides;Solubility;Thermal stability;Yamazaki phosphorylation;Transparency
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发布时间：2021-03-19 - 摘要：As animportant member of supramolecular hydrogel, pseudopolyrotaxane (PPR) hydrogel has attracted tremendous attention in recent years due to its good biocompatibility. Compared with conventional approaches reported, a new method was developed for PPR hydrogel preparation in this study, which can increase the strength of the hydrogel more efficiently. First, monoaccharide group-functionalized methoxypolyethylene glycols (MPEG)(MPEG-Glc, MPEG-Man and MPEG-Gal) were synthesizedby click chemistry. After that, a series of PPR hydrogels (Glc-PPR, Man-PPR and Gal-PPR) with high stability and strengthwere successfully prepared via the "host-guest" interactions betweenα-CD and monoaccharide group-functionalized MPEG(MPEG-Glc, MPEG-Man and MPEG-Gal, respectively). However, similar hydrogel cannot be obtained usingα-CD and MPEG without monoaccharide modification. The properties of Glc-PPR, Man-PPR and Gal-PPR were characterizedby rheometer test, X-ray diffraction (XRD) and scan electron microscopy (SEM).Surprisingly, rheometer test results indicated that the elasticity modulus of Glc-PPR, Man-PPR and Gal-PPR could be up to 1.0 × 105 Pa, which was much higher than that of the clay-enhanced hydrogel in the previous reports. As for this phenomenon, we propose that new sugar cross-linking agents from "carbohydrate-carbohydate interaction" have constructed among monoaccharide terminals of MPEG, so that the strength of Glc-PPR, Man-PPR and Gal-PPR could be improved efficiently. Furthermore, in order to demonstrate the mechanism of the strength enhancement of PPR hydrogel, phenylboronic acid cyclic monoester (PNIPAM-co-PBOB) and concanavalin A (Con A) were added into Glc-PPR, Man-PPR and Gal-PPR, respectively to eliminate the sugar cross-linking agents, which led to a significant decrease in the strengthof Glc-PPR, Man-PPR and Gal-PPR. SEM and XRD results showed that the microstructures of Glc-PPR, Man-PPR and Gal-PPR were basically identical withPPR hydrogel reported in the references, which further confirmed that the PPR hydrogel was prepared successfully. Given its many merits of high intensity, non-toxicity and excellent biocompatibility of the obtained PPR hydrogel, it is expected that the PPR as prepared here will play an important role in drug delivery and biomedical engineering.关键词：α-Cyclodextrins;Host-guest inclusion complexation;PPR hydrogel;Carbohydrate-carbohydate interaction
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发布时间：2021-03-19 - 摘要：We investigate the phase behaviors of nanoparticles/AB diblock copolymer/C homopolymer system confined in a sphere. The nanoparticles are attracted to the B block, and are neutral toward the A block, monomers A, B, and C are incompatible with each other. All of them are confined in a hard sphere, and the sphere surface is neutral. First, we investigate the phase behaviors of the diblock copolymer/homopolymer confined in a hard sphere.Various ordered morphologies can be formed in the mixture by adjusting the composition ratio and the confining environment. The C component always forms a shell-shaped structure in the outer sphere which encloses the AB diblock copolymer. The AB diblock copolymer shows a variety of morphologies within the sphere, such as the double helix structure (SⅠ), the single helix structure (SⅡ), the lamellae structure (SⅢ), and the onion ring structure (SⅣ). In this study, we add nanoparticles (NPs) of different nature at various concentrations to the above four types of the structures to investigate their effect on the polymer system. For the SI structure, when the particle concentration (cp) is 0.05 ≤ cp ≤ 0.15, and the strength of wetting (g) is 0.005 ≤ g < 0.03, an ordered transformation from the double helix structure to the lamellar structure occurs.For the SⅡ structure, when the particle concentration is 0.05≤ cp ≤ 0.1, and the strength of wetting is 0.01≤ g < 0.015, an ordered transformation from the single helix structure to the double helix structure occurs.For the SⅢ structure, when the particles concentration is 0.05 ≤ cp ≤ 0.15, and the strength of wetting is 0.005 ≤ g < 0.04, an ordered transformation from the lamellar structure to the single helix structure occurs. For the SⅣ structure, the addition of NPs has little effect on thephase morphology of the system. The results provide a method of controlling polymer self-assembly for experimental studies.关键词：Diblock copolymer/homopolymer;Nanoparticles;Sphere confinement;Self-assembly
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发布时间：2021-03-19 - 摘要：The aggregation and assembly behavior of the amphiphilic block copolymer, polystyrene-b-poly(4-vinyl pyridine) (PS-b-P4VP), on water-air interface was investigated. With chloroform as the solvent, the dilute solution of PS-b-P4VP was spread on water surface. After chloroform evaporation, surface pressure-area isotherms of PS-b-P4VP at the air/water interface were drawn. Langmuir-Blodgett (LB) technique was applied to prepare films by transferring PS-b-P4VP monolayer from the air-water interface to a solid substrate. Atomic force microscopy (AFM) was used to characterize the morphologies of the films. Effect of the segment ratio of the block copolymer, surface pressure, and small molecule addition on the morphologies of the PS-b-P4VP film was studied. Three morphologies were obtained depending on the block ratio, termed planner, nanostrands and nanodots regimes. As size of the hydrophilic block (P4VP) increased, the film morphologies changed from nanoplate to nanostrands, and then to nanodots. With increasing P4VP block content, LB film thickness decreased and Langmuir isotherms moved to higher molecular areas. Understanding and controlling the compression processes of the monolayers at air-water interface is a key issue for producing determined patterns and dimensions with well-defined order. Surface pressure is another controlling factor. Based on investigations of LB films of PS-b-P4VP, morphology involved a change in packing order. Under different surface pressures, diverse morphologies of LB films were discovered by AFM. With an increase of the surface pressure, pattern density increased.Meanwhile, molecular arrangement became closer and the film thickness became much thicker. At high pressure, monolayer may collapse at the water-air interface, forming bilayer or multilayer structures, so film thickness is increased. Pyrenebutyric acid (PBA) is a fluorescent probe molecule. PBA molecules form hydrogen-bonding with P4VP between its carboxylic acid group and the pyridine ring of P4VP. After adding PBA, it is equivalent to an increase in the ratio of the hydrophilic segment P4VP, and the morphology transition of the film shows the trends like increasing the volume fraction of the hydrophilic segment.关键词：Block copolymer;LB film;Hydrogen bonding
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发布时间：2021-03-19 - 摘要：Two series of poly(aryl ether sulfone)s with different rigidity are synthesized by the polymerization of bis(4-fluorophenyl) sulfone (DFDPS) with 9, 9'-bis(4-hydroxyphenyl) fluorine (BHPF) or 2, 2'-bis(4-hydroxy phenyl) propane (BPA)/2, 2-bis(4-hydroxyphenyl) hexafluoropropane (6FBPA). Two novel types of blend anion exchange membranes (AEMs) are prepared through solution casting by co-dissolving the synthesized poly(aryl ether sulfone) and its chloromethylated products with various weight ratios, while the phase-separation is avoided successfully during membrane formation. The rigidity of the polymer main chains is adjusted by introducing the monomers of BHPF (BQPAES series) and BPA (BQPES series), respectively, and their influence on membrane properties is studied in details. The ion exchange capacity (IEC), water absorbing and swelling properties, as well as ion conductivity of the obtained blend AEMs are characterized, and the hydrolytic and alkaline stability are investigated. The precursory and corresponding chloromethylated polymers show fine compatibility and their resultant blend AEMs are uniform, ductile and transparent, with moderate water uptakes and dimensional changes.Both the water uptakes and the dimensional change increase along with temperature and decrease with poly(aryl ether sulfone) content. The ion conductivity of the blend AEMs reaches the maximum of 89 mS/cm at 90℃. After aging in hot water for 24 h, they still retain high mechanical strength with mass loss less than 5%; they also maintain 65% ~ 80% of the original ion conductivity after treated with 2 mol/LNaOH solutions for 168~240 h at 30℃. Because of the higher rigidity of BHPF moieties, the BQPAES series blend membranes show better dimensional stability and chemical stability than those of the BQPES series at similar IEC level, while maintaining high ionic conductivity. The results imply that the blend treatment and appropriate enhancement in rigidity in the polymer main chain are helpful to improve the overall properties of the membrane.关键词：Fuel cell;Anion exchange membrane;Quaternized poly(aryl ether sulfone);Blend materials;Hydrolysis
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发布时间：2021-03-19 - 摘要：Multilayer flame-retardant coatings, consisting of opposite-charged polyelectrolyte polyethyleneimine (PEI), ammonium polyphosphate (APP) and polyacrylic acid (PAA), were constructed on the surface of soft and porous ramie fabrics by layer-by-layer (LBL) assembly technique. Attenuated total reflectionFourier transform infrared spectroscopy (ATR-FTIR) and field-emission scanningelectron microscopy with an energy-dispersive X-ray (SEM-EDX)analysis confirmedthat PAA was successfully introduced into the bi-component PEI/APP multilayer flame-retardant coatings.The P/C (phosphorus/carbon) ratio was clearly increased on the surface of the ramie fabric with the increase of the number of layers. The effect of PAA as a supplementary acid source on the flame retardancy of the treated ramie fabrics was studied by thermogravimetic analysis (TGA), microscale combustion calorimetry (MCC) and vertical flame testing (VFT).The results of the thermal propertiesshowed thatthe char residue of the coated fabrics at high temperature during thermogravimetric analysis was significantly enhanced as compared with the untreated sample. Furthermore, the microscale combustion calorimetry revealed a reduction for both peak heat release rate (PHRR) and total heat release (THR). The surface morphologies of all the untreated and treatedramie fabrics after VFTdemonstrated that the PEI/APP/PAA coated specimenpreserved the integrity of the original texture of the ramie fabrics, and a dense and continuous expansion carbon layer was formedon the surface of the ramie fabric. The carbon layer effectively prevented oxygen and heat from penetrating into the substrate, thereby giving the ramie fabric excellent self-extinguishing properties.EDX spectra also revealed that the ratio of P/O (phosphorus/oxygen) and P/C of the char of the treated ramie fabric became high after combustion test. Compared to the bi-component (PEI/APP) n sample, the introduction of the third component PAA seemed to work at low assembly cycles by increasing the charge density of PEI, thus to improve the add-on of the FR coating on the fabric, but the concentration of PAA had little influence on the assembly process. However, the same charges may repel each other from the confusion of APP and PAA with high layers, causing the FR effect not that favorable.关键词：Flame retardancy;Thermal property;Ramie fabrics;Layer-by-layer assembly;Multi-component
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发布时间：2021-03-19 - 摘要：Aseries of multi-block copolymers(PDMS-b-PEG)m were synthesized byhydrosilylation starting from polyethylene glycol diallyl ether (PEG) and hydride terminated polydimethylsioxane (PDMS)with different molecular weights.Trimethoxysilane terminated PEG precursors were synthesized based on the multi-block copolymers(PDMS-b-PEG)m and trimethoxysilane.Furthermore, PEG precursors were mixed with fluorine-containing precursors (FMS-9922) and silicone resin to prepare PEG-containing fluorosilicone elastomeric antifouling coatings by condensation reaction. This coating only needs to be cured at room temperature. Thechemical composition of the PEG precursor was characterized by 1H-NMR and FTIR. The length effect of the hydrophobic segments in the PEG-containing precursors and the content of fluorine precursors on the surface reconstructionwere investigated by SEM-EDS, water uptake and contact angle measurements.The results showed that the coating was more stable in water when the hydrophobic segments in PEG precursor were longer. The reason was that the surface containing longer hydrophobic segments was not easy to suffer reconstruction. The longer the PEG precursor chain segmentwas, the easier to form a stable hydration layer on the surface of the coating. However, the presence of fluorine-containing precursors facilitated the emigration of PEG chains to the coating/water interface.This was because that the hydrophilic segments and hydrophobic segments were incompatible, and microphase separationoccurred after the introduction of fluorine precursor, therefore promoting the migration of PEG segments to the surface.The anti-biofouling performances of the cross-linked network coatings were evaluated by biofouling assays using FITC-BSA, bacteria Escherichia coli and the fouling diatom Navicula. The results indicated that these fluorine-containing amphiphilic coatings exhibited significant protein resistance, antibacterial property and diatom resistance for diatom Navicula, compared with the coating without fluorine segments. And the anti-fouling performances of the coating increased with increasing amount of FMS-9922.However, when the FMS-9922 content was too high, the coating compatibility decreased, causing worse antifouling performance. An appropriate content of FMS-9922 was found to be 7%.关键词：Hydrosilylation;Surface reconstruction;Amphiphilic coatings;Antifouling
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发布时间：2021-03-19 - 摘要：The residual stress in cross section of injection-molded polycarbonate (PC) was quantitatively measured by photo-elastic method. The effects of mold temperature on residual stress distribution in cross section and warpage of the whole sample were analyzed in detail. The results show that, in the cross section of the injection-molded PC, the high flow-induced residual stress exists in the skin near the wall of the mold, and the large thermal-introduced residual stress is mainly detected in the core. At the same time, there is a region with low residual stress between the core and the skin in cross section, formed by a mutual coupling of the flow-induced and the thermal-introduced residual stress. The distributions of those residual stresses are influenced by mold temperature. When mold temperature is lower than the heat distortion temperature of PC(126℃), the residual stresses both in the core and the skin are hardly changedwithchanging mold temperatures. Whilethe mold temperature is higher than the heat distortion temperature of PC, the residual stress decreases significantly with increasing mold temperature. When the mold temperature is at 140 ℃, there are uniformresidual stresses in the cross section, and the average retardation measured byphoto-elastic method is 230nm, indicating a low residual stress. Furthermore, the warpage gets worse with increased mold temperature. When the temperatures in the movable and fixed mold are dissymmetry, the shape of the residual stress in the core is trapezoidal. This distribution is caused by uneven cooling. In the movable mold side with high temperature, the region of the thermal residual stress is narrow, and in the fixed mold side with low temperature, the stress is wide. The difference of the thermal residual distribution between the movable and the fixed mold side is more obviousas the mold temperature difference is increased. Finally, the residual stress distribution in a trapezoidal shape leads to a large warpage.关键词：Injection molding;Polycarbonate;Cross section;Residual stress;Mold temperature
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发布时间：2021-03-19 - 摘要：A simple "equivalent freely-jointed chain" model, parameterized with literature data on the persistence length of linear poly(methacrylic acid) (PMA) and poly(ethylene oxide) (PEO), and the molecular weight dependence of the radius of gyration of linear PEO in aqueous solution, is developed for the so-called MPEG-type comb-shaped polycarboxylate ester-or ether-based superplasticizers (PCEs). The model yields analytical expressions of the radius of gyration, the hydrodynamic radius, as well as their respective branching parameters and the characteristic size ratio of the radius of gyration to the hydrodynamic radius as a function of backbone molecular weight, side chain molecular weight, and the number of side chains, assumed to be evenly distributed along the polymer backbone, in the continuum limit. Our calculations andexperimental results in the literature showed a fairly good agreement, especially when a correction factor of magnitude 1.1 for the radius of gyration and of 1.4 for the hydrodynamic radius weretaken into account. After model validation, more predictions were made based on this simple model. Results of the radius of gyration and the hydrodynamic radius were presented as a function of the molecular weight of the PMA backbone, the molecular weight of the PEO side chains, and the molar ratio of methacrylic acid to polyalkyleneglycol methacrylate (known as the C/E ratio). It was found that the ratio of the radius of gyration to the hydrodynamic radius of PCEs fell mostly in the range of 0.85 to 1.0, notably less than those commonly found for linear polymers. To further facilitate applications of our theoretical model in practice, predictions were made to the ratio of the apparent molecular weight measured in aqueous size exclusion chromatography by conventional column calibration using linear poly(ethylene oxide) polymer standards to the true molecular weight measured bye.g., light scattering, by assuming that polymers having the same retention volume had approximately the same hydrodynamic radius. While it was common for branched polymers that the apparent GPC molecular weight using a linear polymer standard was less than their true molecular weight, the reverse could also be found for PCEs due to its copolymer feature. The mathematical model developed in this work, besides its simplicity, does not contain undetermined numerical prefactors, which avoids ambiguity in its practice.关键词：Comb-shaped polycarboxylate-type superplasticizers;Freely jointed chain;Radius of gyration;Hydrodynamic radius;Size exclusion chromatography
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发布时间：2021-03-19
Research Article
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