Theory of polymer crystallization is listed as one of the top ten current challenges in polymer community.Clarifying the uniqueness of polymer crystallization should be the first step to search for the roadmap for tar...Theory of polymer crystallization is listed as one of the top ten current challenges in polymer community.Clarifying the uniqueness of polymer crystallization should be the first step to search for the roadmap for targeting this challenge.Chain flexibility and connectivity are two peculiar characteristics of polymers,which differentiate their dynamics and structures from that of small molecules.The uniqueness of polymer crystallization must also stem from these two peculiar characteristics,which,however,has not been attracted significant attention.A local structure order may be essential in assisting the transformation of flexible chain to rigid segment with conformational ordering.The entanglement pressure and entanglement free energy may help to understand how entanglement affect nucleation in polymer network and why the interlamellar amorphous layer always accompany the formation of crystal layer.Some recommendations will be given for future study.展开更多
In supply chain management,an important research direction is to coordinate the supply chain through introducing flexible contracts.A supply chain contract is flexible if it can satisfy two conditions at the same time...In supply chain management,an important research direction is to coordinate the supply chain through introducing flexible contracts.A supply chain contract is flexible if it can satisfy two conditions at the same time:the supply chain is coordinated,and the total profit of the supply chain can be arbitrarily divided between the supply chain members.This paper puts out two contracts,a flexible return contract and a flexible wholesale price discount contract.In contrast to many of literature,the supply chain contracts with an endogenous wholesale price is specifically considered,and a detailed sensitivity analysis of the contract parameters is given.The paper also discusses the application of the contract in vendor-managed inventory(VMI) mode.The results show that the supply chain's performance is improved after introducing above contracts.All the findings are illustrated by numerical examples.展开更多
The syntheses of porphyrin-phthalocyanine heterodimers with flexible polyatomic chains especially designed for the studies of intramolecular photoinduced processes are presented along with the effect of mutual orienta...The syntheses of porphyrin-phthalocyanine heterodimers with flexible polyatomic chains especially designed for the studies of intramolecular photoinduced processes are presented along with the effect of mutual orientation of the chromophore subunits on intramolecular energy transfer efficiency.展开更多
Mono 3 -deoxy-(N' -benzoyl-ethylenediamino)-β -CD, mono 3 -deoxy-(N' -benzimidoyl -ethylamino)-β-CD, and mono 3 -deoxy-(N' - salicylidene-ethylenediamino)- β -CD, each of which has a flexible chain that...Mono 3 -deoxy-(N' -benzoyl-ethylenediamino)-β -CD, mono 3 -deoxy-(N' -benzimidoyl -ethylamino)-β-CD, and mono 3 -deoxy-(N' - salicylidene-ethylenediamino)- β -CD, each of which has a flexible chain that bonds the aryl moiety on the secondary side of β-CD, were prepared inthis research. The reaction processes might involve the formation of mono(2, 3 -manno-epoxide )- β -CD as an intermediate in our reaction conditions.展开更多
A density functional theory (DFT) is used to investigate molecular orientation of hard rod fluids in a hard slit. The DFT approach combines a modified fundamental measure theory (MFMT) for excluded-volume effect w...A density functional theory (DFT) is used to investigate molecular orientation of hard rod fluids in a hard slit. The DFT approach combines a modified fundamental measure theory (MFMT) for excluded-volume effect with the first order thermodynamics perturbation theory for chain connectivity. In the DFT approach, the intra-molecular bonding orientation function is introduced. We consider the effects of molecular length (i.e. aspect ratio of rod) and packing fraction on the orientations of hard rod fluids and flexible chains. For the flexible chains, the chain length has no significant effect while the packing fraction shows slight effect on the molecular orientation distribution. In contrast, for the hard rod fluids, the chain length determines the molecular orientation distribution, while the packing fraction has no significant effect on the molecular orientation distribution. By making a comparison between molecular orientations of the flexible chain and the hard rod fluid, we find that the molecular stiffness distinctly affects the molecular orientation. In addition, partitioning coefficient indicates that the longer rodlike molecule is more difficult to enter the confined phase, especially at low bulk packing fractions.展开更多
This work focuses on the relationship between flexibility of molecular chains and thermal properties of polyurethane elastomer(PUE), which laid the foundation of further research about how to improve thermal propert...This work focuses on the relationship between flexibility of molecular chains and thermal properties of polyurethane elastomer(PUE), which laid the foundation of further research about how to improve thermal properties of PUE. A series of PUE samples with different flexibility of molecular chains was prepared by using 1,4-butanediol(1,4-BDO)/bisphenol-a(BPA) blends with different mole ratios including9/1, 8/2, 7/3, 6/4 and 5/5. As comparison, PUE extended with pure 1,4-BDO and BPA was also synthesized.These samples were characterized by differential scanning calorimetry(DSC), thermogravimetric analysis(TGA), dynamic mechanical analysis(DMA), etc. The results showed that with the decrease in flexibility of molecular chains the glass transition temperature(Tg) increased and low-temperature properties became worse. Besides, all samples had a certain degree of microphase separation, and soft segments in some samples were crystallized, i.e. the decreasing flexibility of molecular chains led to the impossibility of chains tightly packing and crystalline domains forming so that the degree of microphase separation decreased and the thermal properties became worse.展开更多
基金the National Key R&D Program of China(2020YFA0405800)the National Natural Science Foundation of China(Nos.51890872 and 51633009)Anhui Provincial Key R&D Program(Nos.202004a05020075 and 202104a05020008).
文摘Theory of polymer crystallization is listed as one of the top ten current challenges in polymer community.Clarifying the uniqueness of polymer crystallization should be the first step to search for the roadmap for targeting this challenge.Chain flexibility and connectivity are two peculiar characteristics of polymers,which differentiate their dynamics and structures from that of small molecules.The uniqueness of polymer crystallization must also stem from these two peculiar characteristics,which,however,has not been attracted significant attention.A local structure order may be essential in assisting the transformation of flexible chain to rigid segment with conformational ordering.The entanglement pressure and entanglement free energy may help to understand how entanglement affect nucleation in polymer network and why the interlamellar amorphous layer always accompany the formation of crystal layer.Some recommendations will be given for future study.
基金supported by the Science and Technology Project of Zhejiang Province (2009C110262009C35007)
文摘In supply chain management,an important research direction is to coordinate the supply chain through introducing flexible contracts.A supply chain contract is flexible if it can satisfy two conditions at the same time:the supply chain is coordinated,and the total profit of the supply chain can be arbitrarily divided between the supply chain members.This paper puts out two contracts,a flexible return contract and a flexible wholesale price discount contract.In contrast to many of literature,the supply chain contracts with an endogenous wholesale price is specifically considered,and a detailed sensitivity analysis of the contract parameters is given.The paper also discusses the application of the contract in vendor-managed inventory(VMI) mode.The results show that the supply chain's performance is improved after introducing above contracts.All the findings are illustrated by numerical examples.
文摘The syntheses of porphyrin-phthalocyanine heterodimers with flexible polyatomic chains especially designed for the studies of intramolecular photoinduced processes are presented along with the effect of mutual orientation of the chromophore subunits on intramolecular energy transfer efficiency.
文摘Mono 3 -deoxy-(N' -benzoyl-ethylenediamino)-β -CD, mono 3 -deoxy-(N' -benzimidoyl -ethylamino)-β-CD, and mono 3 -deoxy-(N' - salicylidene-ethylenediamino)- β -CD, each of which has a flexible chain that bonds the aryl moiety on the secondary side of β-CD, were prepared inthis research. The reaction processes might involve the formation of mono(2, 3 -manno-epoxide )- β -CD as an intermediate in our reaction conditions.
基金Project supported by the National Natural Science Foundation of China (Grant No 20646001), the Beijing Novel Program (Grant No 2006B17), the Program for New Century Excellent Talents in University (NCET), the "Chemical Grid Program" and the Excellent Talent Fund of Beijing University of Chemical Technology.
文摘A density functional theory (DFT) is used to investigate molecular orientation of hard rod fluids in a hard slit. The DFT approach combines a modified fundamental measure theory (MFMT) for excluded-volume effect with the first order thermodynamics perturbation theory for chain connectivity. In the DFT approach, the intra-molecular bonding orientation function is introduced. We consider the effects of molecular length (i.e. aspect ratio of rod) and packing fraction on the orientations of hard rod fluids and flexible chains. For the flexible chains, the chain length has no significant effect while the packing fraction shows slight effect on the molecular orientation distribution. In contrast, for the hard rod fluids, the chain length determines the molecular orientation distribution, while the packing fraction has no significant effect on the molecular orientation distribution. By making a comparison between molecular orientations of the flexible chain and the hard rod fluid, we find that the molecular stiffness distinctly affects the molecular orientation. In addition, partitioning coefficient indicates that the longer rodlike molecule is more difficult to enter the confined phase, especially at low bulk packing fractions.
基金supported financially by the National Natural Science Foundation of China (Grant No. 51372200)Program for New Century Excellent Talents in University of Ministry of Education of China (Grant No. NCET-12-1045)+2 种基金Special Program for local serving from Education Department of Shaanxi Provincial Government (Grant No. 2013JC19)Program for Innovation Team in Xi’an University of Technology (Grant No. 108-25605T401)Ph.D. Innovation Fund Projects of Xi’an University of Technology (Fund No. 310-252071501)
文摘This work focuses on the relationship between flexibility of molecular chains and thermal properties of polyurethane elastomer(PUE), which laid the foundation of further research about how to improve thermal properties of PUE. A series of PUE samples with different flexibility of molecular chains was prepared by using 1,4-butanediol(1,4-BDO)/bisphenol-a(BPA) blends with different mole ratios including9/1, 8/2, 7/3, 6/4 and 5/5. As comparison, PUE extended with pure 1,4-BDO and BPA was also synthesized.These samples were characterized by differential scanning calorimetry(DSC), thermogravimetric analysis(TGA), dynamic mechanical analysis(DMA), etc. The results showed that with the decrease in flexibility of molecular chains the glass transition temperature(Tg) increased and low-temperature properties became worse. Besides, all samples had a certain degree of microphase separation, and soft segments in some samples were crystallized, i.e. the decreasing flexibility of molecular chains led to the impossibility of chains tightly packing and crystalline domains forming so that the degree of microphase separation decreased and the thermal properties became worse.