Toughening Poly(lactic acid) with Imidazolium-based Elastomeric Ionomers

Imidazolium-based elastomeric ionomers （i-BIIR） were facilely synthesized by ionically modified brominated poly（isobutylene-co-isoprene） （BIIR） with different alkyl chain imidazole and thoroughly explored as novel toughening agents for poly（lactic acid） （PLA）. The miscibility, thermal behavior, phase morphology and mechanical property of ionomers and blends were investigated through dynamic mechanical analyses （DMA）, differential scanning calorimetry （DSC）, scanning electron microscopy （SEM）, tensile and impact testing. DMA and SEM results showed that better compatibility between the PLA and i-BIIR was achieved compared to the PLA/unmodified BIIR elastomer. A remarkable improvement in ductility with an optimum elongation at break up to 235% was achieved for the PLA/i-BIIR blends with 1-dodecylimidazole alkyl chain （i-BIIR-12）, more than 10 times higher than that of pure PLA. The impact strengths of PLA were enhanced from 1.9 kJ/m2 to 4.1 k J/m2 for the PLA/10 wt% i-BIIR-12 blend. Toughening mechanism had been established by systematical analysis of the compatibility, intermolecular interaction and phase structures of the blends. Interracial cavitations initiated massive shear yielding of the PLA matrix owing to a suitable interfacial adhesion which played a key role in the enormous toughening effect in these blends. We believed that introducing imidazolium group into the BIIR elastomer was vital for the formation of a suitable interfacial adhesion.

Effect of Linear and Ring-like Co-units on the Temperature Dependence of Nucleation and Growth in Ⅱ-Ⅰ Phase Transition of Butene-1 Copolymers

The phase transition from tetragonal form II to hexagonal form I was studied for the butene-1/ethylene and butene-1/1,5- hexadiene random copolymers, which have comparable molecular weight but distinct linear ethylene and ringlike methylene-1,3- cyclopentane （MCP） structural co-units, respectively. It is known that this solid phase transition follows the nucleation-growth mechanism, so the stepwise annealing protocol was utilized to investigate the influences of co-units on the optimal nucleation and growth temperatures. Compared with optimal nucleation and growth temperatures of-10 and 3 5 ℃, respectively, in polybutene-1 homopolymer, two butene-1/ethylene copolymers with 1.5 mol% and 4.3 mol% co-units have the slightly lower optimal nucleation temperature of-15 ℃ but much higher optimal growth temperature of 50 ℃. Clearly, the effect of ethylene co-unit is more significant on varying optimal temperature for growth than for nucleation. Furthermore, when the incorporated co-unit is ringlike MCP, the optimal nucleation temperature is -15 ℃ for 2.15 mol% co-units, the same with above BE copolymers, but -13 ℃ for a very low concentration of 0.65 mol%. Interestingly, the optimal growth temperature of butene-1/1,5-hexadiene copolymers with 0.65 mo1%-2.15 mol% MCP co- units increases to 55 ℃, which is also independent on co-unit concentration. These obtained values of optimal temperatures provide crucial parameters for rapid II-I phase transition.

Stereoblock Polypropylenes Prepared by Efficient Chain Shuttling Polymerization of Propylene with Binary Zirconium Catalysts and iBu3Al

Stereoblock polypropyienes bearing isotactic,atactic,and syndictactic polypropylene segments were successfully prepared by dry methylaluminoxane activated binary catalysts system,Ph2CFluCpZrCl2 and {Me2Si(2,5-Me2-3-(2-MePh)-cyclopento[2,3-b]thiophen-6-yl)2}ZCl2,in the presence of iBu3Al as a chain shutting agent.by studying the catalyst activity,chain transfer efficiency,and reversility of chain transfer reaction of each catalyst system,as well as the molecular weight and polydispersity of the resulting polymers,the allyl exchange reactions between the zirconium catalyst and different main-group metal alky were estimated,respectvely.Based on the optimized react condition,the chain shuttling polymerization was conducted by binary catalyst system in the presence of iBu3Al under both atmospheric and high pressure.Resultant polymers were identified as stereoblock polypropylenes according to microstructure and physical properties analyses by 13C{1H}-NMR,DsC,and GPC.

Effect of Olefin-based Compatibilizers on the Formation of Cocontinuous Structure in Immiscible HDPE/iPP Blends

In this work,the formation of cocontinuous structure in immiscible high density polyethylene/isotactic polypropylene(HDPE/iPP)blends was investigated for various olefin-based compatibilizers of distinct molecular architectures,including ternary random copolymer EPDM,olefin block copolymer(OBC),polypropylene-based OBC(PP-OBC),ethylene/a-olefin copolymer(POE),bottlebrush polymer poly(1-dodecene),and comb-like poly(propylene-co-high a-olefin)(PPO).The scanning electron microscopy results show that after adding OBC,PP-OBC,and POE copolymers,the finer droplet-in-matrix morphologies were obtained in 70/30 HDPE/iPP blend.Interestingly,for 70/30 HDPE/iPP blend with just 5 wt%of PPO copolymers,the phase inversion from droplet-in-matrix to cocontinuous morphology can be observed.It was proposed that the development of cocontinuous morphology contained the following steps:(1)in terfacial saturati on of compatibilizers and droplet deformation,(2)droplet-droplet coalesce nee,(3)continuity development,and(4)the formation of dual-phase con tinuity.Among the diverse copolymers studied in this work,PPO copolymer can be easily removed out of the interface during droplet coalescence and stabilize the curvature of minor fiber phase,facilitating the formation of cocontinuous morphology.In contrast,other olefin-based compatibilizers(EPDM,OBC,PP-OBC,and POE)exhibit the distinct steric repulsion effect to prohibit droplet coalescence.Moreover,the cocontinous interval varies with the compatibilizer architectures.Surprisingly,after adding 10 wt%of PPO copolymers,the cocontinuous interval was greatly broadened from HDPE/iPP range of 45/55-60/40 to that of 40/60-70/30.

Ring-opening Metathesis Polymerization of Cis-5-norbornene-endo-2,3-dicarboxylic Anhydride Derivatives Using the Grubbs Third Generation Catalyst

A series of cis-5-norbornene-endo-2,3-dicarboxylic anhydride （NDCA, M1） derivatives （M2-M4） with different types of nonpolar substituted groups were synthesized and characterized by 1H/13C-NMR and mass spectrometry （MS）. Ring- opening metathesis polymerization （ROMP） of these monomers using the Grubbs third generation catalyst （G3） generated high molecular weight polymers with much improved solubility compared with the NDCA＇s homopolymer. It was found that the solubility of these polymers increased with increased substituent＇s steric hindrance. The living polymerization of NDCA derivative containing the bulkiest substituent （M4） catalyzed by G3 in tetrahydrofuran was confirmed by the kinetic studies with low polydispersity indices （PDI） （〈 1.30）. By using sequential ROMP, well-defined diblock copolymers containing anhydride groups were synthesized.

Potassium Acetate/18-Crown-6 Pair:Robust and Versatile Catalyst for Synthesis of Polyols from Ring-Opening Copolymerization of Epoxides and Cyclic Anhydrides

Efficient synthesis of polyester polyols with tunable molecular weight and microstructures from cyclic anhydride/epoxide mixtures by taking advantage of chain transfer reaction remains a great challenge,because most of the catalysts exhibit poor tolerance to chain transfer agent(CTA).In this contribution,we demonstrated that potassium acetate(KOAc)and 18-crown-6(18-C-6)combination has great potential in the synthesis of diverse polyester polyols with controllable molecular weight and high-end group fidelity.Com-pared with KOAc,KOAc/18-C-6 pair could induce a much faster chain transfer between the active and dormant chains,and thus produce polyester polyols with narrow and monomodal distribution.In addition,polyester polyols could be efficiently prepared in laboratory by using commercially available cyclic anhydride without further purification(containing about 2%diacid residual as CTA)with an extremely low catalyst loading([catalyst pair]:[anhydride]:[epoxide]=1:50000:250000,[catalyst pair]=0.0004 mol%).KOAc/18-C-6 could also promote the self-switchable copolymerization of cyclic anhydride/epoxide/cyclic ester mixtures.Ring-opening copolymerization of cyclic ester was initiated automatically after the full conversion of cyclic anhydride,finally producing polyester polyols with ABA-type block structure.

Synthesis of High Performance Cyclic Olefin Polymers Using Highly Efficient WCl6-based Catalyst System

Cyclic olefin polymers（COPs） with high glass transition temperature, high transparency（higher than 80%） in the visible light range, excellent thermal stability and outstanding mechanical properties have been synthesized by effective ring opening metathesis polymerization（ROMP） of exo-1,4,4 a,9,9 a,10-hexahydro-9,10（1′,2′）-benzeno-l,4-methanoanthracene（HBM） and dicyclopentadiene（DCPD） or norbornene（NBE） using WCl6/i-Bu3Al/ethanol/1-hexene catalyst system, followed by hydrogenation of double bonds. 1-Hexene acted as a molecular weight controller in the polymerization reaction, tuning the number-average molecular weight（Mn） of P-HBM from 5.8 × 10^4 to 41.1 × 10^4. The monomer composition and thermal properties of the copolymers were characterized by nuclear magnetic resonance（NMR）, differential scanning calorimetry（DSC） and thermogravimetric analysis（TGA）. The saturated polymers exhibited high decomposition temperatures（Td） around 340 ℃ and glass transition temperatures（Tg） in the range from 117.5 ℃ to 219.7 ℃. What is more, tensile tests indicated that the mechanical properties of the COPs could be effectively tuned in a wide range by introducing varying amount of small cyclic olefin such as DCPD or NBE.

Phosphine/Benzocyclone-based Neutral Nickel Catalysts for Ethylene Polymerization and Copolymerization with Polar Monomers

The efficient copolymerization of olefin with polar monomers using nickel-based catalysts presents a longstanding challenge. In this contribution, three phosphine-benzocyclone ligands and corresponding neutral nickel catalysts(Ni1: Ar = Ph;Ni2: Ar = 2-(C_(6)H_(5))C_(6)H_(4);Ni3: Ar = 2-[2',6'-(Me O)_(2)-C_(6)H3]C_(6)H_(4)) were prepared and applied for the ethylene polymerization and copolymerization with polar monomers without any cocatalyst. The bulky substituent groups in complexes Ni2 and Ni3 contributed to high catalytic activities(up to 7.24×10^(6) and 9.04×10^(6)g·mol Ni^(-1)·h^(-1), respectively), and produced high-molecular-weight polyethylene(Mw up to 545.7 k Da). Complex Ni3 exhibited high activities for ethylene polymerization at the level of 10^(6) g·mol Ni^(-1)·h^(-1) across a wide range from 30 ℃ to 120 ℃, exhibiting excellent high temperature tolerance. These nickel complexes were also effectively employed in the copolymerization of ethylene with methyl acrylate, ethyl acrylate, butyl acrylate and lauryl acrylate, producing copolymers with high molecular weights(Mw up to 80.5 k Da) and high polar monomer incorporation(up to 8.2 mol%). Microstructure analyses revealed that the introduction of large sterically hindered substituents facilitated the incorporation of polar functional units into the polymer backbone. This study demonstrates the potential of these nickel-based catalysts for efficient copolymerization of olefin with polar monomers.

Radiation construction and excellent performances of Ag NPs/TiO_(2)/PEG/PVP multifunctional aerogel:Adsorption-photocatalytic degradation,photosensitive antibacterial and cytotoxicity

A cutting-edge method known as photocatalytic antibacterial technology can effectively eliminate drug-resistant bacterial strains and boast a wide-ranging antimicrobial capability.In the study,a novel Ag NPs/TiO_(2)/PEG/PVP(ATPP)aerogel photocatalyst was synthesized by an electron beam in-situ radiation method using polyethylene glycol(PEG),polyvinylpyrrolidone(PVP),AgNO_(3),and TiO_(2)as raw materials.ATPP was characterized by X-ray diffraction spectroscopy(XRD),X-ray photoelectron spectroscopy(XPS)and solid ultraviolet diffuse reflectance spectroscopy(UV-Vis DRS).The results demonstrated that silver ions were reduced to silver nanoparticles by electron beam radiation method.At the same time,the doping of silver nanoparticles(Ag NPs)enhanced visible-light adsorption.The degradation rate of methylene blue(MB)on 5%(in mass)ATPP could reach 81%under visible light for 180 min.Escherichia coli(E.coli)and Staphylococcus aureus(S.aureus)were used as model bacteria to explore the antimi-crobial properties of ATPP by zone of the inhibition method,plate counting method and live/dead bacterial staining.Cyclic antibacterial experiments showed that the antibacterial effect of ATPP was sustainable.Meanwhile,MTT assay and Hoechst33342/PI double staining were used to prove that the composite had good biocompatibility.The aerogel photocatalytic material has the potential to decrease microbial presence in both medical and environmental settings,making it a valuable tool for such applications.

Synthesis,Characterization of Polyethylene Ionomers and Their Antibacterial Properties

Owing to its high production volume and wide range of application s,polyethylene has gained a great deal of attention,but its low surface energy and non-polar nature have limited its application in some important fields.In this study,ethylene/11-iodo-1-undecene copolymers were prepared and used as the intermediates to afford a series of imidazolium-based ionomers bearing methanesulfonate(CH_(3)SO_(3)^(-)),trifluoromethanesulfonate(CF_(3)SO_(3)^(-)),or bis(trifluoromethane)sulfonimide(Tf_(2)N^(-))counteranions.The tensile test results showed that the stress-at-break(7.8-25.6 MPa)and the elongation-at-break(445%-847%)of the ionomers could be adjusted by changing the counterion species and the ionic group contents.Most importantly,the ionomers exhibited marvelous antibacterial activities against Staphylococcus aureus(S.aureus)and Escherichia coli(E.coli).The ionomers bearing Tf_(2)N^(-)exhibited antibacterial activities>99%against both S.aureus and E.coli when ionic content reached 9.1%.The imidazolium-based ionomers prepared in this work demonstrated excellent comprehensive properties,especially highefficient and broad-spectrum antibacterial ability,exhibiting the potential fo r the application as the antibacterial materials in packaging,medical,and other fields.

Distribution pattern of the snail intermediate host of schistosomiasis japonica in the Poyang Lake region of China

Background:With the closure of the Three Gorges Dam in 2003 the hydrology of Poyang Lake was altered dramatically leading to significant changes in the environment.In order to assess the impact on schistosomiasis this study assessed the spatial and temporal patterns of the snail intermediate host,Oncomelania hupensis in the Poyang Lake tributaries.The results of the study have important implications for future snail control strategies leading to disease elimination.Methods:The marshland area surrounding Poyang Lake was divided randomly into 200×200 m vector grids using ArcGIS software,and the surveyed grids were randomly selected by the software.The snail survey was conducted in each selected grid using a survey frame of 50×50 m with one sideline of each grid serving as the starting line.No less than ten frames were used in each surveyed grid with Global Positioning System(GPS)recordings for each.All snails in each frame were collected to determine infection status by microscopy.Altitude data for all frames were extracted from a lake bottom topographic map in order to analyze the average altitude.All snail survey data were collected and statistically analyzed with SPSS 20.0 software in order to determine the difference of the percentage of frames with living snails and mean density of living snails in different regions of Poyang Lake.The altitude of the snail-infested marshlands and snail dens were subsequently identified.Results:A total of 1159 potential snail sampling grids were surveyed,of which 15231 frames(0.1 m2/frame)were investigated.1241 frames had live Oncomelania snails corresponding to 8.15%of the total number of frames.The mean density of living snails was 0.463/0.1 m2 with a maximum of 57 snails per frame.The percent of frames with snails in the southern sector(8.13%)of Poyang Lake did not differ statistically from the north(8.21%).However,the mean density of live snails in the northern sector(0.164/0.1 m2)of the lake was statistically higher(F=6.727;P=0.010)than the south(0.141/0.1 m2).In the south of the lake,the elevation of snail-inhabited marshland ranged between 11-16 m,and could be further subdivided into two snail-concentrated belts at 12-13 m of elevation and 15-16 m of elevation respectively.In the north of the lake,the elevation of snail-inhabited marshland ranged between 9-16 m with the elevation of 12-14 m being the snail-concentrated zone.Conclusions:The elevation of snail-infested marshlands in the Poyang Lake region ranged from 9 to 16 m.The snail distribution and habitat has moved north of the lake and to a lower altitude due to changes in the water level post dam closure.Based on the current geological features of the snail habitant focused mollusciciding should occur in snail dense northern regions with frequent bovine and human traffic.Targeting these identified'hotspots'of transmission will assist in elimination efforts.

Refractive Index Engineering as a Novel Strategy toward Highly Transparent and Tough Sustainable Polymer Blends

High transparency and toughness are prerequisites for sustainable polymers if they are to find wide application as alternatives to petroleum-based polymers.However,the utility of sustainable polymers such as commercially available polylactide(PLA)is limited by their inherent brittleness and high cost.Unfortunately,toughening PLA-based materials via cost-effective blending strategies without sacrificing transparency remains a challenge.Herein,we report a novel strategy involving active refractive index matching for creation of highly transparent and tough PLA blends.Specifically,we engineered the refractive index of a promising renewable poly(epichlorohydrin-co-ethylene oxide)elastomer by introducing polar ionic moieties via a simple chemical method,and we blended the resulting ionomers with PLA.The best blend showed an impact strength of>80 kJ/m2,an elongation at break of 400%,and high transparency(90%).These characteristics are of great importance for potential applications such as packaging.Our strategy offers a versatile new way to prepare high-performance sustainable polymer materials with excellent transparency.

Development of an educational cartoon to prevent worm infections in Chinese schoolchildren

Background:With more than two billion people infected worldwide,soil-transmitted helminths(STH)are the most widespread infections.To date,STH control efforts rely predominantly on recurrent mass drug administration(MDA),which does not prevent reinfection.Additional public health measures including novel health educational tools are required for more sustained integrated control of STH.We describe the development of an educational cartoon video(The Magic Glasses)targeting STH infections in Chinese schoolchildren and its pilot testing in China.We applied an extensive community-based mixed methods approach involving input from the target group of 9–10 year old schoolchildren and key informants,such as teachers,doctors and parents,in order to identify potential STH infection risks in the study area and to formulate key messages for the cartoon.The development of the educational cartoon included three major steps:formative research,production,and pilot testing and revision.Results:We found that most adults and approximately 50%of the schoolchildren were aware of roundworm(Ascaris)infection,but knowledge of transmission,prevention and treatment of STH was poor.Observations in the study area showed that unhygienic food practices,such as eating raw and unwashed fruit or playing in vegetable gardens previously fertilised with human faeces,posed major STH infection risks.Conclusions:It was crucial to assess the intellectual,emotional,social and cultural background of the target population prior to video production in order to integrate the key messages of the cartoon into everyday situations.Overall,our strategy for the development of the cartoon and its incorporation into a health education package proved successful,and we provide a summary of recommendations for the development of future educational videos based on our experiences in China.

Efficient Addition Polymerization of Norbornene with Polar Norbornene Derivatives by Neutral Nickel(Ⅱ) Catalysts

A series of nickel complexes{4 a:[(2,6-iPr2C6H3)N=CHC16H12O]Ni(Me)(Py),4b:[(2,6-iPr2C6H2OCH3)N=CHC16H12O]-Ni(Me)(Py),4 c:[(2,6-iPr2C6H2Cl)N=CHC16H12O]Ni(Me)(Py),and 4d:[(2,6-iPr2C6H2CF3)N=CHC16H12O]Ni(Me)(Py)}based onβ-ketiminato ligands bearing various electron-donating or electron-withdrawing substituents on the para-position of the aniline group were synthesized and unambiguously characterized.The X-ray crystallographic analysis showed that complexes 4 b and 4 d adopted a nearsquare-planar geometry,and the anilines bearing a para-OMe or―CF3 group were found to situate on the axial position of the metal center.All complexes exhibited high activities up to 1.25×10^7–1.35×10^7 g PNB·molNi^–1·h^–1 toward norbornene(NBE)addition polymerization(conversion>91.2%in 2 min)under low loading of B(C6F5)3(B/Ni=3)at 30°C,affording polymers with high molecular weight up to 2.54×10^6–3.18×10^6.Different levels of decrease in catalytic activities could be observed for all catalysts as the reaction temperature increased;4 d bearing a strong electron-withdrawing―CF3 group showed the highest activity at 70°C,while others exhibited notable decrease in catalytic activity with the raise in reaction temperature.Complexes 4 a–4 d showed remarkable tolerance to polar groups and could efficiently promote the copolymerization of NBE with its polar derivatives,including NBE bearing small acetate and hydroxyl group,as well as bulky oligomers,yielding copolymers with high functional NBE incorporations.Novel NBE copolymers with high functional comonomer incorporations and improved solubility were obtained in high yields.

Efficient Copolymerization of Ethylene with Polar Divinyl Monomer by Phosphino-Phenolate Nickel Catalyst

Direct copolymerization of olefin with polar monomers via a coordination-insertion mechanism appears as the most efficient and at-tractive method to prepare functionalized polyolefins.Herein,we carried out direct copolymerization of ethylene and allyl acrylate by a bulky phosphino-phenolate nickel catalyst,in which high-molecular-weight copolymers bearing polar five-membered and six-membered ring structures were afforded.Comprehensive NMR and FT-I R analyses revealed multiplex structure of the obtained copolymers,in which both the noncyclic structural units bearing pendant allyl moiety(A)as well as acrylate moiety(B)and the cyclic structural units,y-butyrolactones(C)andδ-valerolactone(D)were found.Exhilaratingly,the content of different structural units of the produced copolymer could be tuned by adjusting the concentration of the comonomer.Moreover,we also proved that the nick-el-based catalyst could produce related copolymers with significantly enhanced copolymer molecular weights in the copolymeriza-tion of allyl acrylate and ethylene compared with the palladium-based catalyst under the same conditions.

The Influence of Various Cationic Group on Polynorbornene Based Anion Exchange Membranes with Hydrophobic Large Steric Hindrance Arylene Substituent

A series of brominated polynorbornene derivatives,including bulky steric hydrophobic groups and highly physical and chemical stable backbones,were synthesized via ring-opening metathesis polymerization and post-functionalized with trimethylammonium(QA),N-methylimidazole(Im),N-methylpyrrolidinium(Pyr)or N-methylpiperidinium(Pip)to construct the entire anion exchange membranes(AEMs).Benefited from prominent phase-separated morphology,PBO-x%-y(x=66,68,70;y=QA,Im,Pyr,Pip)AEMs with ion exchange capacity(IEC)approaching 2.0 meq·g^(−1)exhibited super high hydroxide conductivities.Thereinto,PBO-70%-Pip possessed the highest hydroxide conductivity of 137.3 mS·cm^(−1)at 80℃Moreover,all membranes exhibit low swelling ratio(SR)(the SR of PBO-66%-QA was just 8.6%at 80℃).That is,bulky steric hydrophobic groups play a crucial role in balancing the high hydroxide conductivity and low SR in AEMs.Furthermore,three AEMs(PBO-66%-QA,PBO-68%-Pyr,PBO-70%-Pip)showed good alkaline stability after immersion into 1.0 mol/L NaOH aqueous solution at 80℃for 480 h without any degradation.

PREFACE

Due to the great contribution in high polymer production, Karl Ziegler and Giulio Natta were awarded the Nobel Prize in Chemistry in 1963. The discovery of their catalysts initiated an era of producing polymers via coordination polymerization mechanism. Coordination polymerization of olefins allows precise control over the microstructures of the polymer products, and has experienced great developments during the past half century. Polyolefins produced by conventional Ziegler-Natta catalysts, metallocene and non-metallocene catalysts have become one of the most important commercial synthetic polymers used in our daily life

PREFACE

Metal-catalyzed polymerization is being widely used in the controlled synthesis of various polymers. As a matter of fact, metal catalysts （both transition metal complexes and main group metal complexes） are ubiquitous and indispensable in numerous polymerization reactions, including metal-catalyzed olefin polymerization and olefin/polar monomer insertion copolymerization, ring-opening metathesis polymerization,