最新刊期
卷 ， 期 11 ， 2016
- 摘要：The development of site-specific and topologically-defined protein-polymer conjugates has been challenging, which is mainly due to the tedious and low-efficient synthesis. Typically, multi-step modifications on the polymer part are necessary in order to install functionalities required for subsequent bioconjugation. A recent work has addressed this challenge by producing well-defined heterotelechelic poly(amino acid)s via a one-pot, two-step polymerization process that allows in situ installation of two different bioorthogonal functionalities. Various site-specific and topologically-defined protein-poly(amino acid) conjugates exhibiting remarkably improved protease resistance and thermostability were generated with substantially reduced synthetic efforts. The method may provide a general platform and a concise strategy to prepare protein-polymer conjugates with bright therapeutic potentials.关键词：Concise synthesis;Protein-polymer conjugates;Poly(amino acid);In situ-functionalization
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发布时间：2021-03-19
Research Highlights
- 摘要：Polymer solar cell (PSC) with bulk heterojunction structure has attracted considerable attention due to its potential for harnessing low-cost solar energy and making flexible devices.The design and application of highly efficient conjugated polymers has enabled the rapid progress in the development of organic photovoltaic technology, and the power conversion efficiency (PCE) has been boosted to over 11%.A highly efficient polymer donor should possess several intrinsic features, such as a broad absorption spectrum with high extinction coefficient, suitable molecular energy level alignment of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) levels to afford a sufficient driving force for efficient charge separation with minimum energy loss, high charge mobilities to facilitate charge transport and favorable blend morphology to facilitate exciton diffusion and charge separation.From early homopolymer polythiophene system to typical donor-acceptor (D-A) structure polymers, many conjugated polymer donors have been developed and applied in fabricating PSC device.In this review, we first summarize some of our works from the polythiophene with the two conjugated side chains to benzodithiophene (BDT)-based D-A polymers.Since the blend morphology plays a vital role in determining the performance of the PSC device, we also did some works about the morphology optimization from the aspect of molecular design.Recently, fullerene-free PSC has emerged as a new horizon in the field of PSC, and we have demonstrated fullerene-free PSC device with PCE over 11% by using BDT-based polymer.In addition, we also summarize some other works about the fullerene-free PSC in our group.In the end, after a brief summary, we present some inevitable questions about the development of commercial PSC, such as the efficiency, stability, manufacturability and reproducibility.From the materials and processing methods, we think these problems can be solved and except that PSC has real applications in the near future.关键词：Polymer solar cell;Molecular design;Polythiophene;Benzodithiophene
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发布时间：2021-03-19 - 摘要：Polymer synthesis is the starting point of polymer science, screening and using suitable organic reactions to prepare novel polymers is the core of polymer synthesis.Recently, polymer synthesis via multicomponent reactions (MCRs) has attracted widespread attention and is becoming a new vibrant branch of polymer chemistry.During the study of MCRs, the overlap between click chemistry and multicomponent reactions has been discovered, leading to the concept of multicomponent click (MCC) chemistry, i.e.some highly efficient, atom economy multicomponent reactions, which only form harmless byproducts, can also be looked at as click reactions.The MCC reactions can work as efficient coupling tools like traditional two-component click reactions, meanwhile, new functional groups can be easily introduced due to the multicomponent nature of those reactions.As a result, multifunctional polymers, which are normally prepared via laborious multi-step methods, can be facilely achieved through one-step MCC reactions, providing a new strategy to synthesize functional polymers for multipurpose applications.In this article, the similar characteristics of click chemistry and MCRs will be discussed to illuminate the concept of MCC chemistry.As concrete examples, the large-scaled prepared functional polymers via the Biginelli reaction (a typical MCC reaction) will be introduced, suggesting the Biginelli reaction an excellent elementary reaction for polymer synthesis.The chain-end or chain-middle modified polymers via the Ugi reaction (another typical MCC reaction) will also be presented, indicating the Ugi reaction a powerful tool for the preparation of high value-added polymers.In particular, the advantage and disadvantage of the Biginelli reaction and the Ugi reaction will be pointed out, respectively, and some perspectives for the future development of multicomponent click chemistry in polymer chemistry will be summarized.关键词：Polymer synthesis;Multicomponent reactions;Click chemistry;Multicomponent click chemistry
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发布时间：2021-03-19 - 摘要：The development of mechanoluminescent polymers is one of the emerging and frontier subjects in the field of polymer mechanochemistry.This important research effort has been driven by the need for advanced stress probes to report rare molecular scission events that precede failure in polymers.What is already known is that the stress-induced scission of chemical bonds often plays a critical role in failure initiation state, thus, precise location and timing of chain-scission events during fracture are although difficult in practice, yet key to understanding failure mechanisms.If these rare failure initiation events could be well characterized and cast in the language of organic and physical organic chemistry, opportunities for preventing and ameliorating early failure events will be obtained, and rational molecular strategies for advanced polymeric materials will result.Stimuli-responsive polymers, that can convert mechanical force into sensitive light signal, represent a unique platform that opens the way to the detailed study of the specific molecular failure events and the macroscopic properties of polymers, and therefore, are considered as a versatile spectroscopic probe capable of sensing and mapping deformations, stresses and damage in different polymer architectures with high spatial and temporal resolutions.In this review, the strategies for the design and synthesis of mechanoluminescent polymers, and the great efforts towards the understanding of the mechanisms of such mechanically induced light from polymers, the approaches to fine-tune the optophysical properties of the light (including light intensity, colour of light emission, and the force thresholds of light), as well as the applications of mechanoluminescence to probe the failure of different polymers are comprehensively introduced.The unique features of mechanoluminescence from polymers and the advantages of these polymers as sensitive stress probes over other responsive polymers with measureable output are revealed.The progress achieved up to now is summarized, and a short outlook concerning the development of mechanoluminescent polymers is provided.关键词：Stimuli-responsive polymer;Polymer mechanochemistry;Mechanoluminescence;1,2-Dioxetane;Stress probe
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发布时间：2021-03-19
Feature Articles
- 摘要：Wrinkles are ubiquitous in nature across multiple length scales, from corrugated blood cells to bulking mountains. Inspired by these wrinkling patterns in nature, researchers have made much progress on the fabrication of surface wrinkles, with a series of practical applications from microfluidics to metrology. Here we provide a systematic review on the fundamental mechanisms, fabrication methods and applications of surface wrinkles. Firstly, a theoretical model used to describe the mechanical behaviour of a soft material covered with a hard skin is introduced. The instability of the polymer matrix and the external stimulation are the main reasons for the instability of the surface. The external stimulations can be either physical ones such as mechanical force and thermal gradient, or chemical ones such as surface reactions induced by thermal or photo irradiation, or the both. The wavelength of the buckles is influenced by the thickness of the skin layer, the elastic moduli and the Poisson's ratio of the skin and the soft substrate. The fabrication methods are discussed in the second part of the review based on the classification of the surface wrinkles, namely, layered system, gradient film and homogeneous film. Layered films are composed of two or more layers with dissimilar mechanical properties, which, in general, are the easiest to be constructed. The elastic substrate is usually deformed before covering the skin layer. Gradient films are formed due to the gradual crosslinking of the film leading to gradual mechanical properties. In homogeneous films, however, wrinkling patterns are usually generated by swelling or heating a polymeric thin film to initiate the volume expansion. The approaches to tailor wrinkle orientation and geometry through controlling mechanical properties and thickness of the film or substrate are emphasized. In addition to the fabrication of typical wrinkles, a few new studies on the generation and application of reversible wrinkles, hierarchical wrinkles and three dimensional wrinkles are highlighted. Finally, an overview about the main applications in different fields is provided. The applications include microfluidics, microprinting, flexible electronics, superhydrophobicity, measuring elastic modulus of polymer films, surface enhanced Raman spectroscopy, surface enhanced emission of fluorophores, enhanced adhesion, and so on. In the near future, surface wrinkles with highly ordered, multi-dimensional, controllable, reversible and hierarchical patterns are highly expected. It is interesting to find more and more applications with emerging of the new patterns.关键词：Surface wrinkle;Surface instability;Superhydrophobic surface;Flexible electronic
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发布时间：2021-03-19
Reviews
- 摘要：An inorganic-organic hybrid named boehmite@ aluminum phenylphosphinate (BM@Al-PPi) with high temperature resistance was used to flame retard semi-aromatic polyamide (HTN) in combination with a modified red phosphorus (MRP) flame retardant.The flame-retardant property and mechanism of the resulting flame-retardant HTN systems were investigated.When the total content of the flame retardants was 15 wt%, the HTN could achieve UL-94 V-0 rating at the mass ratio of BM@Al-PPi to MRP ranging from 1:4 to 2:1, and the limiting oxygen index was raised to 30.0% from 23.5%.Cone calorimetry was used to investigate the combustion behaviour of flame-retardant HTN samples.For HTN/15% MRP system, MRP reduced the heat release of HTN, meanwhile a great mass loss rate during combustion led to a 30% lower effective heat of combustion (Av-EHC) and much higher smoke release than those of neat HTN, which supported that the MRP mainly work in the gas phase.With addition of 15 wt% (HTN/15% BM@Al-PPi), more compact burning char was obtained, reducing the heat release and suppressed the smoke production, and BM@Al-PPi played a role in condensed phase.The HTN flame-retarded by the binary flame retardants was endowed lower heat release values (such as PHRR, THR and MAERH) and lower smoke production than by MRP.In particular the total heat release of HTN/10% BM@Al-PPi/5% MRP decreased by 60%.These results indicated that there was a synergistic effect between BM@Al-PPi and MRP for flame-retarding HTN.The function of char forming and the synergistic flame-retardant mechanism in condensed phase were investigated by SEM-EDX, in which a uniform distribution of phosphorus element both in the outer and inner surfaces of the char layers was observed, suggesting that a continuous and compact char was formed, and the heat flow and fuel could be blocked effectively.Furthermore, the corresponding gaseous phase flame-retardant mechanism was put forwardvia pyrolysis gas chromatography coupled with mass spectrometry (Py-GC-MS).关键词：Semi-aromatic polyamide;Flame retardance;Hybrid flame retardant;Red phosphorus
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发布时间：2021-03-19 - 摘要：Hydroxyl-terminated poly(butyl acrylate)-b-poly(methyl methacrylate) block copolymer was synthesized via atom transfer radical polymerization with activators regenerated by electron transfer (ARGET ATRP) using 4-hydroxybutyl 2-bromo-2-methylpropanoate as an initiator, copper (Ⅱ) bromide (CuBr2) as a catalyst, pentamethyldiethylene triamine (PMDETA) as a ligand, and stannous octoate (Sn(EH)2) as a reducing agent.Then multi-arm poly(butyl acrylate)-b-poly(methyl methacrylate) block copolymers were prepared via the reaction between hydroxyl-terminated poly(butyl acrylate)-b-poly(methyl methacrylate) block copolymer and hexamethylene diisocyanate trimer (N3390) using dibutyltin dilaurate as a catalytic agent.The structures of the copolymers obtained were characterized by gel permeation chromatography (GPC), 1H nuclear magnetic resonance (1H-NMR), and Fourier transform infrared spectrometer (FTIR).The morphologies of the linear and multi-arm polymers were observed by atomic force microscopy (AFM).Mechanical and thermodynamic properties of the hydroxyl-terminated poly(butyl acrylate)-b-poly(methyl methacrylate) block copolymer and the multi-arm block copolymers were investigated by universal tensile machine and dynamic mechanical analyser (DMA), respectively.The results showed that the hydroxyl-terminated block copolymer and the multi-arm block copolymers were successfully synthesized.When the molar ratio of NCO/OH reached 1.2/1, maximal amount of three-arm block copolymers was obtained.The tensile strength and the elongation at break of the multi-arm copolymers were higher than those of the linear copolymers, and these values achieved maximum with NCO/OH of 1.2/1.In this case, multi-arm block copolymer showed tensile strength of 7.6 MPa and elongation at break of 73%, respectively.Compared with the linear block copolymer, the glass transition temperature (Tg) of the multi-arm block copolymer was higher.Atomic force microscopy (AFM) indicated that the multi-arm block copolymer possessed distinct core-shell structure with PBA as the core and PMMA as the shell.And the multi-arm block copolymer with core-shell structure could be used as a toughening agent for poly(methyl methacrylate).关键词：Multi-arm;Block copolymer;Acrylate;Toughening
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发布时间：2021-03-19 - 摘要：Monodisperse poly-(4-vinylpyridine-co-divinyl benzene/trimethylolpropane trimethacrylate) (poly-(4-VP-co-DVB/TRIM)) microspheres with smooth surface were successfully prepared by precipitation polymerization in acetonitrile with 4-vinylpyridine (4-VP), divinyl benzene (DVB) and trimethylolpropane trimethacrylate (TRIM) as comonomers, 2, 2-azobisisobutyronitrile (AIBN) as initiator.Effects of the polymerization conditions, such as comonomer ratio, solvents and initiator amount, on the morphology and yield of polymer microspheres were also investigated.The prepared polymers were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR), thermal gravimetric analysis (TGA) and particle size analysis.Results showed that polymerization parameters (including solvent type and amount, molar ratio of cross-linker to comonomer, ratio of the cross-linkers DVB to TRIM and initiator concentrations) had significant influence on the morphologies and yield of the resulting polymer microspheres.Particle size and uniformity of polymer increased with decreasing acetonitrile amount while increases in cross-linker and initiator loading caused larger particle sizes.The polymer yield increased gradually with the increases in the concentration of initiator and molar ratio of cross-linker, and decreased with the increase in the amount of the acetonitrile and molar ratio of cross-linker.When molar ratio of 4-VP:(DVB+TRIM) was 1:5 and DVB:TRIM was 4:1, with 2 wt%-6 wt% of AIBN as initiator (based on all monomer weight), 5.6 mL of acetonitrile as solvent, reaction temperature at 65℃, reaction time for 24 h, monodisperse poly-(4-VP-co-DVB/TRIM) microspheres with better spherical shape and high yields were obtained, and the average diameters and polydispersity index of the polymer microspheres were 4.02 μm and 1.024, respectively.Moreover, thermal gravimetric analysis showed that the weight loss for polymer microspheres in the temperature range of 320-500℃, and 84.9% of its initial mass was lost at 600℃, which gave the polymer microspheres great potential to be used as functional materials.关键词：Precipitation polymerization;Polymer microspheres;4-Vinylpyridine;Divinyl benzene;Trimethylolpropane trimethacrylate
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发布时间：2021-03-19 - 摘要：A recurring challenge in the field of polymer nanocomposites (PNCs) is to control the spatial distribution of nanoparticles (NPs) throughout a polymer matrix and thereby optimize the desired macroscopic performance of PNCs.In this study, polystyrene-grafted silica (SiO2-PS) NPs with different grafted chain length and grafting density were prepared via miniemulsion polymerization.The grafted structure of SiO2-PS NPs was characterized via combination of Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), differential scanning calorimeter (DSC), thermogravimetric analysis (TGA) and gel permeation chromatography (GPC).The core-shell structure of SiO2-PS NPs that consisted of different polymerization degrees of grafted chains (N) and grafting density (σ) can be synthesized by tuning various reaction conditions.The effect of N and σ on spatial distribution of SiO2-PS NP filled PS matrix was investigated by TEM observation.The results reveal that tunable specific spatial distribution of grafted NPs can be obtained through the control of N and σ.In the case of that N is basically the same, grafted particles with higher σ are miscible with PS matrix chains, leading to more homogeneous dispersion of NPs.While when N is very high for grafted NPs with roughly the same σ, the grafted chains and the matrix chains are dewetting between each other, which is not effective for uniform dispersion.The thermodynamics stable state of NP distribution is merely related to N and σ and independent of the particle size.Furthermore, by comparing the results of SiO2-PS NP filled PS and polymethyl methacrylate (PMMA) matrices, the contribution of the chemical structure differences and compatibility between grafted chains and matrix chains on spatial distribution of NPs are also discussed.The phase separation behavior between the PMMA matrix and grafted PS chains makes a great difference to the spatial distribution of the grafted NPs.关键词：Grafted nanoparticle;Spatial distribution;Polymerization degree of grafted chains;Grafting density;Compatibility
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发布时间：2021-03-19 - 摘要：To develop novel polysaccharide-based chiral stationary phases with high chiral recognition, five novel chitosan derivatives, bearing N-phthaloyl at 2-position of a glucose ring and four different phenylcarbamate substituents including 2-chloro, 3-chloro, 4-chloro and 3, 5-dichloro, and one chitosan derivative bearing unsubstituted phenylcarbamate at 3- and 6-positions were synthesized by combination of a procedure on the regioselective acylation of 2-position.The structures of the obtained chitosan derivatives were characterized by FTIR and 1H-NMR.They were then coated on the macroporous silica gel to be used as chiral stationary phases for high-performance liquid chromatography (HPLC).Their chiral recognition abilities were evaluated using ten racemates by HPLC.The results indicated that these coated-type chitosan CSPs exhibited characteristic chiral recognition ability, mainly depending on the position, number and steric hindrance of the substituents introduced on the aromatic moieties of the chitosan derivatives.Meanwhile, the eluent content in chromatographic tests had a great influence on the chiral recognition abilities of the chitosan-based CSPs.The racemates 1, 3, 6, 7, 8, 10 were better resolved using a hexane/2-propanol (99/1) mixture as the eluent in comparison with the results obtained using hexane/2-propanol (90/10) mixture as the eluent on chitosan 2-phthaloyl-3, 6-di(3, 5-dichlorophenylcarbamate derivative (CSP-3e).The correlations between the chiral recognition abilities and the chemical shifts of the N-H protons in the1H-NMR spectra and the N-H frequencies in the IR spectra of the carbamate moieties of these derivatives were also discussed further.Among the CSPs based on the chitosan derivatives bearing different substituents at 2 and 3, 6-postions of the glucose unit, those based on the chitosan derivatives (CSP-3e) bearing 3, 5-dichlorophenylcarbamates at 3, 6-positions showed higher chiral recognition abilities while those based on the derivatives bearing 2-chlorophenylcarbamates at 3, 6-positions showed relatively lower recognition ability.Compared to chitosan 2-(3, 5-dichlophenylurea)-3, 6-di(3, 5-dichlorophenylcarbamate) (CSP-ref) and chitosan 2-phthaloyl-3, 6-(3, 5-dichlorophenylcarbamate) (CSP-3e-ref), the chitosan derivative (CSP-3e) showed complementary and similar chiral recognition abilities for some racemates.关键词：Chitosan;Regioselective substituents;Phenylcarbamate;Chiral stationary phases;Chiral recognition
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发布时间：2021-03-19 - 摘要：Composite hydrogels of polyacrylamide-graft-polyaniline possessing both good mechanical strength and excellent electrical conductivity were prepared through a two-step polymerization route.Firstly, acrylamide (Am) andN-(4-aminophenyl)acrylamide (APAm) were radically copolymerized through Co60 γ-irradiated initiation in aqueous solution to form P(Am-co-APAm) hydrogels, of which the aminophenyl side groups facilitated the following graft polymerization of aniline.Secondly, after the lyophilized P(Am-co-APAm) hydrogels were re-swelled in aniline aqueous solution, aniline absorbed in the macroporous hydrogels underwent the oxidation coupling graft polymerization with aminophenyl side groups of P(Am-co-APAm) to result in P(Am-co-APAm)-g-PANI composite hydrogels.As expected, the produced polyaniline was naturally deposited onto the pore wall of P(Am-co-APAm) hydrogels, leading to the formation of inter-connected conductive pathway.Fourier transfer infrared spectroscopy, combined with the repeated removal of possible homopolyaniline with N-methylpyrilidone, confirmed the successful grafting.To modulating the mechanical properties, the influences of radical polymerization parameters were investigated.By changing radiation duration and dose rate, it was found that the gel fraction (GF) of P(Am-co-APAm) hydrogels increased with the increment of irradiation dose, while swelling degree (SD) had the maximum value under medium irradiation dose, reflecting that both monomer conversion and crosslinking degree affected the GF and SD of P(Am-co-APAm) hydrogels.With the increase in monomer concentration, GF was kept going up and levelled off at 1.5 c0 while SD kept going down and levelled off at the same monomer concentration.The tensile strength and elongation at break of P(Am-co-APAm) hydrogels decreased, but elastic modulus increased, reflecting the cooperative impact of crosslinking degree and polymer produced.Interestingly, as observed by scanning electron microscopy, the hydrogels prepared in neutral water had the open and macro-porous morphology while those obtained in HCl solution had no distinct pores.For both hydrogels, TEM images showed no separated polyaniline particles located in the hydrogel pores and the thickness of pore wall obviously increased, indicating the formation of continuous polyaniline layer on the previous pore wall.Therefore, after being doped with HCl, P(Am-co-APAm)-g-PANI composite hydrogels exhibited excellent conductivity as high as 7~10 S/cm, which exceeded most of the reported values for polyaniline-containing hydrogels.关键词：Hydrogel;Conductivity;Polyacrylamide;Polyaniline;Graft ploymerization;γ-Irradiation
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发布时间：2021-03-19 - 摘要：A series of waterborne latexes with hybrid particles composed of poly(methyl methacrylate) and silicone-containing polyurethane acrylate (PMMA/SiPUA) were successfully prepared via a two-step procedure.Waterborne SiPUA latexes were firstly synthesized to serve as seeds, and methyl methacrylate (MMA) was then introduced into SiPUA latexes to form polymeric cores by in situ radical polymerization.The results of Fourier transform infrared spectrometry (FTIR) and differential scanning calorimeter (DSC) confirm the polymerization of MMA occurred inside SiPUA latex particles.Transmission electron microscopy (TEM) observation showed "Salami" morphology in the hybrid latex particles, where PMMA and SiPUA acted as the dispersed core and the outer continuous shell, respectively.With increased HPMS content in the latex of SiPUA, the average size of latex particles of PMMA/SiPUA increased at first and then decreased.Meanwhile, the particle size distribution changed from a narrow unimodal to a wide bimodal distribution.The surface water contact angle of PMMA/SiPUA coating films was found to increase first and then to decrease with increasing HPMS in SiPUA, however, the water absorption of PMMA/SiPUA films showed monotonic decrease with increasing HPMS in SiPUA.Atom force microscopy (AFM) reveals that the surface roughness changes little with the presence of HPMS.With introduction of PMMA in the modified PU, phase separation occurred, which led to the reduction of transparency in PMMA/SiPUA latex films.Rheological measurement of PMMA/SiPUA latexes demonstrated the reinforcement effect of PMMA to their films, showing increased modulus and viscosity.When the mass ratio of PMMA/SiPUA and HPMS content in SiPUA were 0.5 wt% and 10 wt%, respectively, the average particle size of PMMA/SiPUA latex reached a minimum, and the size distribution exhibited a narrow unimodal distribution.Therefore, introduction of PMMA into SiPUA, leading to the formation of "Salami" structure in the latex particles, not only retained good physical and chemical properties of SiPUA, but also improved their thermal resistance.关键词：Silicon-containing polyurethane;Terminal hydroxyl acrylate;PMMA;"Salami" structure;Film properties
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发布时间：2021-03-19 - 摘要：A new kind of self-healing polyurethane (PU) based on Diels-Alder (DA) reaction (PU-DA) was synthesized via the reaction between furan-terminated prepolymer and bismaleimide.The structure, thermal property, and thermal reversibility of the resultant PU-DA were characterized by FTIR, DSC, and gel-solution-gel method.Results showed that the thermally reversible DA bonds were introduced into the polyurethane successfully.Consequently, the polyurethane got the excellent reprocessability and self-healing performance.The self-healing behavior of the PU-DA was investigated by polarized optical microscope, and results revealed that cracks with 0.5 mm in depth in the self-healing polyurethane films could be remended at 120℃ for 300 s or 130℃ for 150 s grounded on the thermal reversibility of DA bonds.Then the slight damage situation of polymer materials in the real life was simulated, and the thermal treatment temperature and time for the effective self-healing of cracks with 0.5 mm in depth were determined by the tensile test.Meanwhile, the healing efficiency of the same damage site in PU-DA film that was cut-healed for 1-3 times was investigated.Results showed that the optimal thermal treatment temperature and time for effective self-healing of cracks were 120℃ and 15 min, respectively.More importantly, the healing efficiency for once cut-healed was as much as 71%, while the healing efficiency could still reach 35% when the self-healing polyurethane was cut-healed at the same site for three times.关键词：Diels-Alder reaction;Polyurethane;Thermal reversibility;Self-healing;Reprocessability
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发布时间：2021-03-19 - 摘要：Polyols based epoxidized soybean oil was synthesized by ring-opening addition reaction of epoxidized soybean oil with 2-ethyl hexanol (isooctanol).Then sulfonated waterborne polyurethane was synthesized using isophorone diisocyanate (IPDI), polycaprolactone diol (PCL), ethylenediamine sodium acetate (AAS) and the ESO-based polyols, and the film had been fabricated successfully by using the obtained waterborne polyurethane as the binder.Polyols was characterized by FTIR and1H-NMR, which indicated polyols was successfully synthesized in the experiment.Influence of the content of polyols on the properties of sulfonated waterborne polyurethane emulsions and their films was evaluated by a series of measurements, including particle size test, water absorption test, static contact angle test, mechanical performance test and TGA.The results showed that the sulfonated waterborne polyurethane modified by ESO-based polyols had been successfully synthesized confirmed by FTIR, and with the increase of the content of polyols, the particle size of the sulfonated waterborne polyurethane emulsion increased gradually, the water absorption of the film decreased and then flatten out when the content of polyols continued to increase during the fabrication of the modified sulfonated waterborne polyurethane.Furthermore, the tensile strength of the film of sulfonated waterborne polyurethane increased, and elongation at break decreased with the increase of the content of polyols.However, too large amount of polyols in the synthesis process of sulfonated waterborne polyurethane would result in destabilization of the emulsion dispersion and lead to failure of the emulsion at last.The film of sulfonated waterborne polyurethane presented the superior performance when the mass ratio of polyols and PCL was 0.2.Water absorption rate of the film decreased from 50.14% to 12.27%, the water contact angle came to 103.3°, and the tensile strength increased greatly from 8.16 MPa to 21.77 MPa as the mass ratio of polyols and PCL increasing from 0 to 0.2.At last, the TG analysis showed the improvement of heat resistance of the film, which would be attributed to the incorporation of polyols.关键词：Sulfonated waterborne polyurethane;Epoxy soybean oil;Mechanical properties;Contact angle;TG
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发布时间：2021-03-19 - 摘要：Hollow phenolic microspheres (HPMs) with closed hollow structure were introduced into polypropylene/intumescent flame retardant (PP/IFR) composites.On the one hand, induced by IFR in PP, intumescent char was formed; on the other hand, hollow carbon microsphere was formed from HPMs during combustion, and it would be embedded in the backbone of the intumescent char layer.Thus a hierarchically porous char was constructed to regulate the intumescent char layer and to improve the flame retardancy of PP/IFR composites.The flame retardant properties of PP/IFR composites were measured by using the limiting oxygen index (LOI) and vertical burning (UL-94).The thermal degradation behaviors were tested by thermal gravimetric analysis (TGA).The surface temperature was detected by Infrared Thermal Imager during the test of UL-94.The dispersion behaviors of IFR and HPMs and char morphology were observed by scanning electron microscopy (SEM).The results showed that no more than 1 wt% HPMs was dispersed uniformly into PP.The PP composites passed UL-94 V0 test at total addition of 18 wt% IFR and 1 wt% HPMs, while the samples containing 20 wt% IFR or HPMs could not be classified in UL-94 test.This indicated good synergistic effect between IFR and HPMs in PP composites.Observing from the photos after burning, a few char residues were formed for PP/IFR and PP/HPMs but the char volume for PP/IFR/HPMs was increased evidently.TGA results showed that char residues for PP/IFR/HPMs were more than that for other samples.Moreover, HPMs modified the intumescent char morphology well.It caused a dense surface of the char and induced the inside char to form hierarchical porous structure.The intumescent char layer with high quality decreased the superficial temperature quickly, prevented fuel and heat transfer from outside to inside, causing the flame extinguished.It was because of the improved char quantity, modified char quality and hierarchically porous char, which resulted in the increased flame retardant efficiency of PP/IFR/HPMs composites.关键词：Hollow carbon microspheres;Hierarchical porous structure;Intumescent flame retardants;Efficient;Polypropylene
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发布时间：2021-03-19 - 摘要：Monolithic oil-absorbing polymers with magnetic responsiveness were prepared through solution radical polymerization combining with freeze-drying technology.A series of the polymer resins were first synthesized using different amount of 4-tert-butyl-styrene (tBS) and methyl methacrylate (MMA) in the presence of Fe3O4 nanoparticles, which were modified by methacryloxy propyl trimethoxyl silane prior to the synthesis.Divinylbenzene (DVB) was used as cross linking agent and azodiisobutyronitrile as initiator in the polymerization carried out at 80℃ for 6 h.The obtained polymers were washed by ethanol/water several times and then freeze dried to obtain monolithic polymeric resins.The as-prepared monolithic polymers were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electronic microscopy, optical microscope and contact angles of water droplet on the surface of polymers.Effects of molar ratio of MMA/tBS, DVB amount on the oil absorption capacities and absorption rate were investigated in detail.Oil-absorbing polymeric resins with optimized property were prepared by selecting MMA as 2 mL, tBS as 2 mL and DVB as 0.5 mL.The polymeric resins are hydrophobic and oleophilic.They can absorb more than 10 times of their own weight for different organic solvents and oils, such as dimethylbenzene, dichloroethane, ethyl acetate, n-hexane, cyclohexane, trichloromethane, engineering and crude oil.And the oil-saturated absorption can be achieved within 20 min.The polymeric resins can also effectively absorb organic solvents from the oil/water mixture and the polymers still float on the surface of water.The oil-saturated polymer resins can be easily separated and collected from the surface of water by applying an external magnet.Furthermore, after the treatment of the absorbed oil, the polymer resins can be reused for oil absorption.The monolithic polymers can be recycled more than 10 times without obvious damaged.These magnetic oil-absorbing polymeric resins are potential candidates for dealing with oil spills.关键词：4-Tert-butyl-styrene;Methyl methacrylate;Fe3O4 nanoparticles;Oil-absorption polymers
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发布时间：2021-03-19 - 摘要：Polylactide (PLA) underwent molecular degradation when it was exposed to gamma ray radiation, the degradation was inhibited somehow in the presence of 1-allyl 3-methylimidazolium chloride (AMIMCl).The grafting reaction of AMIMCl on PLA chains occurred during the irradiation to obtain imidazolium cations grafted PLA (PLA-IM).The molecular masses and the contents of end groups of the resultant PLA samples were measured by gel permeation chromatography (GPC) and nuclear magnetic resonance (1H-NMR), respectively.Compared with the PLA sample irradiated without AMIMCl (PLA-S), PLA-IM possessed less hydroxyl end groups and higher molecular mass (3 times as high as that of PLA-S).The nucleation and growth of crystalline during isothermal crystallization process were observed using polarized optical microscopy (POM).The results revealed that PLA-IM possessed spherulitic morphology which was same as other PLA samples, and the growth rate of the spherulites was mainly dependent on the molecular mass of PLA samples, demonstrating highest growth rate for PLA-S, followed by PLA-IM and lowest for PLA-L at the same crystallization temperature.However, different from PLA-L and PLA-S, PLA-IM showed increased nucleation density in the whole experimental temperature range due to the presence of grafted imidazolium cations on PLA chains.Isothermal crystallization kinetics for the PLA samples was then investigated by differential scanning calorimetry (DSC) and analyzed using Avrami equation.The results showed that the crystallization rate of PLA-IM had improved obviously because of its higher nucleation density.When the isothermal crystallization temperature was higher than 125℃, the half crystallization time of PLA-IM was shorter than that of PLA-S with lower molecular mass.Different from the retardant effect of ionic liquids (ILs) on PLA nucleation in PLA/ILs blends, the ionic interaction between the imidazolium cations grafted on PLA chains facilitates the orderly arrangement of PLA chains and formation of nuclei in the crystallization process, which contributes to the acceleration of crystallization kinetics.关键词：Polylactide;Imidazolium cation;Graft;Crystallization;Nucleation
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发布时间：2021-03-19 - 摘要：In order to extend the application of environmentally-friendly hemicelluloses as potential packing material, this article focuses on the preparation of high-performance polymeric films which is strong enough to protect contained product and to withstand mechanical stress during its application, transportation, and storage. Composite films based on polyvinyl alcohol (PVA) and hemicelluloses, extracted from corncob by alkaline hydrolysis and alcohol precipitation, were prepared using convenient and feasible solution casting. Furthermore, various amounts of nanocrystalline cellulose (NCC) prepared from cotton by using sulphuric acid hydrolysis were added to form enhanced composite films. Tensile test, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), infrared spectroscopy (IR) and scanning electron microscopy (SEM) were used to characterize the composite films. IR results showed that hydrogen bonding formed in blending components, which indicated good compatibility between them. DSC analysis showed that addition of hemicellulose within a certain range created a boost to the crystallinity of PVA, and addition of the rigid NCC showed an inhabiting effect to the crystallinity of the PVA component in the blend films. TGA results revealed that additions of hemicellulose and NCC also resulted in a 50℃ increase for the peak of the second-stage thermal decomposition, indicating a significant improvement for thermal resistance. Mechanical measurements showed that elongation at break of the PVA/hemicellulose composite films was increased to 380% at PVA/hemicellulose mass ratio of 3:1, while the tensile strength was maintained at a reasonably high level (50-60 MPa). It is thus obvious that there exists an increasement of toughness to the composite films. Moreover, low mass fraction of NCC (0.5%) has been found to improve the tensile strength of the PVA/hemicellulose blend film (PH1), while high mass fraction of NCC (1%, 3%, 5%) contributed to improve elongation at break.关键词：Nanocrystalline cellulose;Hemicellulose composite film;Thermal stability;Crystallinity;elongation at break
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发布时间：2021-03-19
Research Article
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