Although bioinspired sacrificial bonds have been demonstrated to be efficient in improving the mechanical properties of polymer materials, the effect of binding energy of a specific dynamic bond on the ultimate mechan...Although bioinspired sacrificial bonds have been demonstrated to be efficient in improving the mechanical properties of polymer materials, the effect of binding energy of a specific dynamic bond on the ultimate mechanical performance of a polymer network with dual-crosslink remains unclear. In this contribution, diamine and sulfur curing package are introduced simultaneously into a sulfonated cis-1,4-polyisoprene to create dually-crosslinked cis-1,4-polyisoprene network with sulfonate-aminium ionic bonds as the sacrificial bonds. Three diamines (primary, secondary and tertiary) with the same spacer between the two nitrogen atoms are used to create the ionic bonds with different binding energies. Although the binding energy of ionic bond does not affect the glass transition temperature of cis-1,4-polyisoprene (IR), it exerts definite influences on strain-induced crystallization and mechanical performance. The capabilities of diamine in dissipating energy, promoting strain-induced crystallization and enhancing the mechanical performance are in the same order of secondary diamine 〉 primary diamine 〉 tertiary diamine. The variations in mechanical performances are correlated to the binding energy of the ionic bond, which is determined by pKa values.展开更多
Neodymium chloride isopropanol complex (NdCl3.3'prOH) activated by modified methylaluminoxane (MMAO) was examined in isoprene polymerization in hexane, with regards to Nd compounds, aluminum (Al) compounds, [Al...Neodymium chloride isopropanol complex (NdCl3.3'prOH) activated by modified methylaluminoxane (MMAO) was examined in isoprene polymerization in hexane, with regards to Nd compounds, aluminum (Al) compounds, [Al]/[Nd] ratio, polymerization temperature and time. NdCl3'3iprOH exhibited high activity producing polymers feasting high cis-l,4 stereospecificity (〉 96%), very high molecular weight (Mn 〉 1.0 × 10^6) and fairly narrow molecular weight distribution (MWD, Mw/Mn 〈 2.0) simultaneously. In comparison, neodymium isopropoxide also showed high activity providing polymers with narrow MWD (Mw/Mn = 2.07), but somewhat low cis-1,4 content (ca. 92%), while neodymium chloride had no activity under present polymerization conditions. The Al compounds affected the polymer yield in the order of Al(i-Bu)3 〉 MMAO 〉 Al(i-Bu)2H. MMAO as cocatalyst afforded polyisoprene with high Mn over 1.0 × 10^6, whereas as stronger chain transfer agent than MMAO, AI(i-Bu)3 and AI(i-Bu)EH yielded polymers with low Mn (1.0 × 10^5-8.0 × 10^5). NdCl3·3'PrOH/MMAO catalyst showed a fairly good catalytic activity even at relatively low [Al]/[Nd] ratio of 30, and the produced polymer remained high cis-1,4 content of 95.8% along with high Mn over 1.0× 10^6 even at elevated temperatures up to 70℃. The polymerization rate is of the first order with respect to the concentration of isoprene. The mechanism of active species formation was discussed preliminarily.展开更多
Phase structure and crystallization behavior of polyethylene (PE) in its blends with cis-1,4-butadiene rubber (BR) at different blend ratios and sample preparation conditions were studied. The PE is finely dispers...Phase structure and crystallization behavior of polyethylene (PE) in its blends with cis-1,4-butadiene rubber (BR) at different blend ratios and sample preparation conditions were studied. The PE is finely dispersed in the BR matrix. For samples hot pressed at 145 ℃, circular PE microdomains with randomly oriented PE lamellar aggregates were produced. The domain size and number increase with increasing PE content. When the PE content is over 10 wt%, most of the PE domains impinged each other. The separated PE domains are connected by PE stripes with parallel arranged lamellar aggregates. For samples hot pressed at 140 ℃, elongated PE microdomains with oriented PE lamellar aggregates were obtained due to the shear flow. The crystallization of PE in the blends depends on the phase structure. Confined crystallization of PE occurs in small microdomains at relatively low temperature. With the increase of domain size, the crystallization ability of PE increases while the confined crystallization decreases.展开更多
Polymerization of 2-(4-halophenyl)-1,3-butadiene(2-XPB) and their copolymerization with isoprene using a yttrium catalyst have been examined. The β-diketiminato yttrium bis(alkyl) complex(1) activated by [Ph_3 C][B(C...Polymerization of 2-(4-halophenyl)-1,3-butadiene(2-XPB) and their copolymerization with isoprene using a yttrium catalyst have been examined. The β-diketiminato yttrium bis(alkyl) complex(1) activated by [Ph_3 C][B(C_(6) F_(5))_(4)] and Ali Bu3 shows high cis-1,4-selectivity(>98%) for the polymerization of 2-XPB(2-XPB = 2-FPB, 2-Cl PB and 2-Br PB) to afford halogenated plastic poly(dienes) with glass transition temperatures of30–55 ℃. Moreover, the copolymerization of 2-XPB with isoprene(IP) has also been achieved by this catalyst, and the insertion ratios of 2-XPB can be facilely tuned in a full range of 0%–100% simply by changing the 2-XPB-to-IP ratio. Quantitative hydrogenation of cis-1,4-poly(2-XPB) results in perfect alternating ethylene-halostyrene copolymers, and an alternating copolymer of 4-vinylbenzoic acid with ethylene is obtained by a consecutive reaction of ethylene-4-bromostyrene copolymer with ^(n)Bu Li, CO_(2) and HCl.展开更多
Rare earth catalysts possessing characteristics of cation-anion ion pair show advantages of adjusting electronegativity and steric hindrance of metal active sites, which can control the catalytic performance and stere...Rare earth catalysts possessing characteristics of cation-anion ion pair show advantages of adjusting electronegativity and steric hindrance of metal active sites, which can control the catalytic performance and stereoselectivity better than those of traditional metallocene and Ziegler-Natta catalysts in diene polymerization. In this work, a series of neodymium organic sulfonate complexes,Nd(CF_3SO_3)_3·x H_2O·y L(x, y: the coordination number; L refers to an organic electron donating ligand, such as acetylacetone(acac), isooctyl alcohol(IAOH), tributyl phosphate(TBP), etc.), have been synthesized to form the cationic active species in the presence of alkylaluminum such as Al(i-Bu)_3, AlEt_3, and Al(i-Bu)_2H, which display high activities and distinguishing cis-1,4 selectivities(up to99.9%) for the polymerization of butadiene. The microstructures, yield, molecular weight, and molecular weight distribution of the resulting polymer are well controlled by adjusting electronegativity/steric hindrance of the complexes. In addition, the kinetics, active species, and the possible process of polymerization are also discussed in this article.展开更多
In this work, the optimal electrospinning conditions of trans-polyisoprene (TPI) solutions were evaluated nevertheless its lower glass transition temperature than the room temperature. Subsequently, chemical crossli...In this work, the optimal electrospinning conditions of trans-polyisoprene (TPI) solutions were evaluated nevertheless its lower glass transition temperature than the room temperature. Subsequently, chemical crosslinking of TPI nonwovens was firstly investigated by vulcanizing at high temperatures in the case of the persistence of nanofiber structure. For this purpose, curing agents of TPI were embedded in TPI nanofibers by co-electrospinning, and then a protect layer was coated on TPI nanofibers by filtering gelatin solution going through TPI nonwoven before the vulcanization at 140-160 ℃. The results showed that the vulcanization of TPI fibrous nonwoven at high temperatures did not destroy the fiber morphology. Interestingly, TPI fibrous nonwovens after vulcanization showed excellent mechanical properties (N17 MPa of tensile strength) that could be comparable to or even higher than that of some bulk rubber materials.展开更多
Conformational elasticity theory recently developed has been used to explore the internal energy contribution to the elastic force f(e)/f as a function of strain for poly(cis-1,4-isoprene) and poly(trans-1,4-isoprene)...Conformational elasticity theory recently developed has been used to explore the internal energy contribution to the elastic force f(e)/f as a function of strain for poly(cis-1,4-isoprene) and poly(trans-1,4-isoprene). Calculated f(e)/f values are in good agreement with those obtained experimentally. Results show that behavior of f(e)/f is mainly contributed by chemical structure, or intramolecular interaction, supporting the experimental observations, and that the internal energy contribution is strain dependent.展开更多
Cobalt and nickel complexes (la-ld and 2a-2d, respectively) supported by 2-imidate-pyridine ligands were synthesized and used for 1,3-butadiene polymerization. The complexes were characterized by IR and element anal...Cobalt and nickel complexes (la-ld and 2a-2d, respectively) supported by 2-imidate-pyridine ligands were synthesized and used for 1,3-butadiene polymerization. The complexes were characterized by IR and element analysis, and complex la was further characterized by single-crystal X-ray diffraction. The solid state structure of complex la displayed a distorted tetrahedral geometry. Upon activation with ethylaluminum sesquichloride (EASC), all the complexes showed high activities toward 1,3-butadiene polymerization. The cobalt complexes produced polymers with high cis-1,4 contents and high molecular weights, while the nickel complexes displayed low cis-l,4 selectivity and the resulting polymers had low molecular weights. The catalytic activities of the complexes highly depended on the ligand structure. With the increment of polymerization temperature, the cis-1,4 content and the molecular weight of the resulting polymer decreased.展开更多
The efficient hydrolytic kinetic separation of trans/cis-(R)-(+)-limonene oxides was realized in a 1 : 1 mixed solvent of water and 1,4-dioxane without additional catalyst. Optically pure trans-(R)-(+)-limo...The efficient hydrolytic kinetic separation of trans/cis-(R)-(+)-limonene oxides was realized in a 1 : 1 mixed solvent of water and 1,4-dioxane without additional catalyst. Optically pure trans-(R)-(+)-limonene oxide was recovered in high yield (77%).展开更多
基金financially supported by the National Basic Research Program of China(No.2015CB654700(2015CB654703))the National Natural Science Foundation of China(Nos.51673065,51703064,51473050 and 51333003)Fundamental Research Funds for the Central Universities(No.2017PY006)
文摘Although bioinspired sacrificial bonds have been demonstrated to be efficient in improving the mechanical properties of polymer materials, the effect of binding energy of a specific dynamic bond on the ultimate mechanical performance of a polymer network with dual-crosslink remains unclear. In this contribution, diamine and sulfur curing package are introduced simultaneously into a sulfonated cis-1,4-polyisoprene to create dually-crosslinked cis-1,4-polyisoprene network with sulfonate-aminium ionic bonds as the sacrificial bonds. Three diamines (primary, secondary and tertiary) with the same spacer between the two nitrogen atoms are used to create the ionic bonds with different binding energies. Although the binding energy of ionic bond does not affect the glass transition temperature of cis-1,4-polyisoprene (IR), it exerts definite influences on strain-induced crystallization and mechanical performance. The capabilities of diamine in dissipating energy, promoting strain-induced crystallization and enhancing the mechanical performance are in the same order of secondary diamine 〉 primary diamine 〉 tertiary diamine. The variations in mechanical performances are correlated to the binding energy of the ionic bond, which is determined by pKa values.
基金supported by the Administration of Science and Technology of Jilin Province,China (No.200505254)
文摘Neodymium chloride isopropanol complex (NdCl3.3'prOH) activated by modified methylaluminoxane (MMAO) was examined in isoprene polymerization in hexane, with regards to Nd compounds, aluminum (Al) compounds, [Al]/[Nd] ratio, polymerization temperature and time. NdCl3'3iprOH exhibited high activity producing polymers feasting high cis-l,4 stereospecificity (〉 96%), very high molecular weight (Mn 〉 1.0 × 10^6) and fairly narrow molecular weight distribution (MWD, Mw/Mn 〈 2.0) simultaneously. In comparison, neodymium isopropoxide also showed high activity providing polymers with narrow MWD (Mw/Mn = 2.07), but somewhat low cis-1,4 content (ca. 92%), while neodymium chloride had no activity under present polymerization conditions. The Al compounds affected the polymer yield in the order of Al(i-Bu)3 〉 MMAO 〉 Al(i-Bu)2H. MMAO as cocatalyst afforded polyisoprene with high Mn over 1.0 × 10^6, whereas as stronger chain transfer agent than MMAO, AI(i-Bu)3 and AI(i-Bu)EH yielded polymers with low Mn (1.0 × 10^5-8.0 × 10^5). NdCl3·3'PrOH/MMAO catalyst showed a fairly good catalytic activity even at relatively low [Al]/[Nd] ratio of 30, and the produced polymer remained high cis-1,4 content of 95.8% along with high Mn over 1.0× 10^6 even at elevated temperatures up to 70℃. The polymerization rate is of the first order with respect to the concentration of isoprene. The mechanism of active species formation was discussed preliminarily.
基金financially supported by the National Natural Science Foundation of China(Nos.21274009 and 51221002)
文摘Phase structure and crystallization behavior of polyethylene (PE) in its blends with cis-1,4-butadiene rubber (BR) at different blend ratios and sample preparation conditions were studied. The PE is finely dispersed in the BR matrix. For samples hot pressed at 145 ℃, circular PE microdomains with randomly oriented PE lamellar aggregates were produced. The domain size and number increase with increasing PE content. When the PE content is over 10 wt%, most of the PE domains impinged each other. The separated PE domains are connected by PE stripes with parallel arranged lamellar aggregates. For samples hot pressed at 140 ℃, elongated PE microdomains with oriented PE lamellar aggregates were obtained due to the shear flow. The crystallization of PE in the blends depends on the phase structure. Confined crystallization of PE occurs in small microdomains at relatively low temperature. With the increase of domain size, the crystallization ability of PE increases while the confined crystallization decreases.
基金financially supported by the National Natural Science Foundation of China (Nos. 21634007 and 51773193)the Department of Science and Technology of Jilin Province(No. 20180101171JC)。
文摘Polymerization of 2-(4-halophenyl)-1,3-butadiene(2-XPB) and their copolymerization with isoprene using a yttrium catalyst have been examined. The β-diketiminato yttrium bis(alkyl) complex(1) activated by [Ph_3 C][B(C_(6) F_(5))_(4)] and Ali Bu3 shows high cis-1,4-selectivity(>98%) for the polymerization of 2-XPB(2-XPB = 2-FPB, 2-Cl PB and 2-Br PB) to afford halogenated plastic poly(dienes) with glass transition temperatures of30–55 ℃. Moreover, the copolymerization of 2-XPB with isoprene(IP) has also been achieved by this catalyst, and the insertion ratios of 2-XPB can be facilely tuned in a full range of 0%–100% simply by changing the 2-XPB-to-IP ratio. Quantitative hydrogenation of cis-1,4-poly(2-XPB) results in perfect alternating ethylene-halostyrene copolymers, and an alternating copolymer of 4-vinylbenzoic acid with ethylene is obtained by a consecutive reaction of ethylene-4-bromostyrene copolymer with ^(n)Bu Li, CO_(2) and HCl.
基金the National Natural Science Foundation of China(Nos.51473156 and 51873203)Key Projects of Jilin Province Science and Technology Development Plan(Nos.2018020108GX and 20160204028GX)
文摘Rare earth catalysts possessing characteristics of cation-anion ion pair show advantages of adjusting electronegativity and steric hindrance of metal active sites, which can control the catalytic performance and stereoselectivity better than those of traditional metallocene and Ziegler-Natta catalysts in diene polymerization. In this work, a series of neodymium organic sulfonate complexes,Nd(CF_3SO_3)_3·x H_2O·y L(x, y: the coordination number; L refers to an organic electron donating ligand, such as acetylacetone(acac), isooctyl alcohol(IAOH), tributyl phosphate(TBP), etc.), have been synthesized to form the cationic active species in the presence of alkylaluminum such as Al(i-Bu)_3, AlEt_3, and Al(i-Bu)_2H, which display high activities and distinguishing cis-1,4 selectivities(up to99.9%) for the polymerization of butadiene. The microstructures, yield, molecular weight, and molecular weight distribution of the resulting polymer are well controlled by adjusting electronegativity/steric hindrance of the complexes. In addition, the kinetics, active species, and the possible process of polymerization are also discussed in this article.
基金financially supported by the National Basic Research Program of China(No.2015CB654700(2015CB654706))the National Natural Science Foundation of China(Nos.51473083 and 21174074)+3 种基金Special Foundation of Taishan Mountain Scholar Constructive ProgramShandong Provincial Key R&D program(No.2015GGX102019)Shandong Provincial Natural Science Fund for Distinguished Young Scholars(No.JQ201213)the Yellow River Delta Scholar program(Office of National University Science&Technology Park Administrative Committee(China University of Petroleum))
文摘In this work, the optimal electrospinning conditions of trans-polyisoprene (TPI) solutions were evaluated nevertheless its lower glass transition temperature than the room temperature. Subsequently, chemical crosslinking of TPI nonwovens was firstly investigated by vulcanizing at high temperatures in the case of the persistence of nanofiber structure. For this purpose, curing agents of TPI were embedded in TPI nanofibers by co-electrospinning, and then a protect layer was coated on TPI nanofibers by filtering gelatin solution going through TPI nonwoven before the vulcanization at 140-160 ℃. The results showed that the vulcanization of TPI fibrous nonwoven at high temperatures did not destroy the fiber morphology. Interestingly, TPI fibrous nonwovens after vulcanization showed excellent mechanical properties (N17 MPa of tensile strength) that could be comparable to or even higher than that of some bulk rubber materials.
基金This project has been supported by the National Natural Science Foundation of China, 863 High Technology Project, Special Funds for Major State Basic Research Project (G1999064800).
文摘Conformational elasticity theory recently developed has been used to explore the internal energy contribution to the elastic force f(e)/f as a function of strain for poly(cis-1,4-isoprene) and poly(trans-1,4-isoprene). Calculated f(e)/f values are in good agreement with those obtained experimentally. Results show that behavior of f(e)/f is mainly contributed by chemical structure, or intramolecular interaction, supporting the experimental observations, and that the internal energy contribution is strain dependent.
基金financially supported by the 973 Program(No.2015CB654700 or 2015654702)the National Natural Science Foundation of China(Nos.51473156 and 51203147)
文摘Cobalt and nickel complexes (la-ld and 2a-2d, respectively) supported by 2-imidate-pyridine ligands were synthesized and used for 1,3-butadiene polymerization. The complexes were characterized by IR and element analysis, and complex la was further characterized by single-crystal X-ray diffraction. The solid state structure of complex la displayed a distorted tetrahedral geometry. Upon activation with ethylaluminum sesquichloride (EASC), all the complexes showed high activities toward 1,3-butadiene polymerization. The cobalt complexes produced polymers with high cis-1,4 contents and high molecular weights, while the nickel complexes displayed low cis-l,4 selectivity and the resulting polymers had low molecular weights. The catalytic activities of the complexes highly depended on the ligand structure. With the increment of polymerization temperature, the cis-1,4 content and the molecular weight of the resulting polymer decreased.
文摘The efficient hydrolytic kinetic separation of trans/cis-(R)-(+)-limonene oxides was realized in a 1 : 1 mixed solvent of water and 1,4-dioxane without additional catalyst. Optically pure trans-(R)-(+)-limonene oxide was recovered in high yield (77%).