The risk assessment system has been applied to the information security,energy,medical and other industries.Through the risk assessment system,it is possible to quantify the possibility of the impact or loss caused by...The risk assessment system has been applied to the information security,energy,medical and other industries.Through the risk assessment system,it is possible to quantify the possibility of the impact or loss caused by an event before or after an event,thereby avoiding the risk or reducing the loss.However,the existing risk assessment system architecture is mostly a centralized architecture,which could lead to problems such as data leakage,tampering,and central cheating.Combined with the technology of block chain,which has the characteristics of decentralization,security and credibility,collective maintenance,and untamperability.This paper proposes a new block chainbased risk assessment system architecture and a consensus mechanism algorithm based on DPOS improvement.This architecture uses an improved consensus mechanism to achieve a safe and efficient risk assessment solving the problem of data tampering in the risk assessment process,avoiding data leakage caused by improper data storage.A convenient,safe and fast risk assessment is achieved in conjunction with the improved consensus mechanism.In addition,by comparing existing risk assessment architecture,the advantages and impacts of the new block chain-based risk assessment system architecture are analyzed.展开更多
Supply chain finance has played a positive role in solving the financing difficulties of small and medium-sized enterprises.However,in the actual implementation process,there are still problems such as information asy...Supply chain finance has played a positive role in solving the financing difficulties of small and medium-sized enterprises.However,in the actual implementation process,there are still problems such as information asymmetry,doubts about the authenticity of trade background,and high operational risks,which seriously restrict the development of supply chain finance.However,block chain technology has the characteristics of de-centralization,data transparency,common maintenance and non-tampering.Applying this technology to supply chain finance can effectively solve the existing problems.Based on the research on the development status of traditional supply chain finance,this paper puts forward a new development mode of supply chain finance based on block chain technology,and through the analysis of typical cases,finally gives some policy suggestions for the development of block chain supply chain finance.展开更多
Objective To analyze the current problems in drug traceability and supply chain management,and build the drug traceability system based on the block chain technology so as to provide authenticity assurance for the rea...Objective To analyze the current problems in drug traceability and supply chain management,and build the drug traceability system based on the block chain technology so as to provide authenticity assurance for the real data in the whole life cycle of drugs.Methods A new drug regulatory traceability protocol was designed based on block chain technology.The database of drug production,circulation and use was linked closely.A traceability system was set up according to the traceability protocol,and the consensus complexity and safety performance of the system were analyzed.Results and Conclusion The distributed account book and tamper-proof functions of the block chain platform were used to establish a double-chain system based on the combination of public chain and private chain,which could make the data of drugs more reliable,transparent and traceable with good application value.The establishment of a double-chain traceability system is studied so that drug market license holders,manufacturers,operating enterprises and users can verify the data to form an interconnected drug traceability data chain.展开更多
In recent years, the rapid innovation and development of financial industry has made financial enterprises have a lot of information. However, the large amount of information is tampered with and fragmented, which can...In recent years, the rapid innovation and development of financial industry has made financial enterprises have a lot of information. However, the large amount of information is tampered with and fragmented, which cannot be shared. With the constant innovation of science and technology, it is the most effective way to solve the information lag and asymmetry of financial products. This article aims to start from the problem of asymmetric information of financial products, the analysis of the emerging block chain technology applied in the financial sector, and with the development of asset securitization information known as the typical scenario for the first time, a concrete analysis information game process, and discuss about the application of chain blocks in securitization feasibility.展开更多
Block chain is widely used in the financial field for its characteristics of decentralization, anonymity and trust. Electronic money payment is an important application hotspot. Ring signature is widely used in strong...Block chain is widely used in the financial field for its characteristics of decentralization, anonymity and trust. Electronic money payment is an important application hotspot. Ring signature is widely used in strong anonymous authentication such as electronic cash and electronic voting because of its unconditional anonymity, spontaneity and flexible group structure. Among them, the correlation ring signature can prove whether two signatures are issued by the same person without revealing the identity of the real signer. Therefore, the signature right breach can be avoided based on the premise of guaranteeing anonymity, such as repeated voting, electronic money repetition cost and so on. Most of the existing correlation ring signature security is based on the discrete logarithm problem, and most of the schemes result in the degradation of anonymity because of strong association. These methods do not apply to the block chain electronic currency transaction scene with strong anonymity. Therefore, this paper first proposes a blockchain-based electronic currency transaction security model. The model ensures not only the anonymity of both parties but also a certain degree of traceability. In order to support these two characteristics, this paper proposes an association ring signature method based on large integer decomposition problem. This method has strong anonymity and can be applied to blockchain scenes. On the other hand, it can be converted into group signatures in specific scenarios. It is therefore traceable. Finally, the adaptive selection message of the scheme and the unforgeability under the selection of public key attack are proved under the random oracle model.展开更多
Internet of Medical Things (IoMT) is a breakthrough technologyin the transfer of medical data via a communication system. Wearable sensordevices collect patient data and transfer them through mobile internet, thatis, ...Internet of Medical Things (IoMT) is a breakthrough technologyin the transfer of medical data via a communication system. Wearable sensordevices collect patient data and transfer them through mobile internet, thatis, the IoMT. Recently, the shift in paradigm from manual data storage toelectronic health recording on fog, edge, and cloud computing has been noted.These advanced computing technologies have facilitated medical services withminimum cost and available conditions. However, the IoMT raises a highconcern on network security and patient data privacy in the health caresystem. The main issue is the transmission of health data with high security inthe fog computing model. In today’s market, the best solution is blockchaintechnology. This technology provides high-end security and authenticationin storing and transferring data. In this research, a blockchain-based fogcomputing model is proposed for the IoMT. The proposed technique embedsa block chain with the yet another consensus (YAC) protocol building securityinfrastructure into fog computing for storing and transferring IoMT data inthe network. YAC is a consensus protocol that authenticates the input datain the block chain. In this scenario, the patients and their family membersare allowed to access the data. The empirical outcome of the proposedtechnique indicates high reliability and security against dangerous threats.The major advantages of using the blockchain model are high transparency,good traceability, and high processing speed. The technique also exhibitshigh reliability and efficiency in accessing data with secure transmission. Theproposed technique achieves 95% reliability in transferring a large number offiles up to 10,000.展开更多
In the context of the China-Pakistan Economic Corridor,this article evaluates how block chain technology might improve organizational performance(CPEC)through the sequential mediating role of artificial intelligence a...In the context of the China-Pakistan Economic Corridor,this article evaluates how block chain technology might improve organizational performance(CPEC)through the sequential mediating role of artificial intelligence and environmental performance.Cross-sectional data were collected from one hundred respondents through a close-ended questionnaire-based survey of manufacturing companies,which was then analyzed using structural equation modeling,which structural equation modelling was used to analyze.The block chain technology benefits businesses in terms of the environment and economics.There is a focus on technology in every industry as the Industry 4.0 era gets underway.Block chain technology,a relatively new phenomenon,offers several opportunities for company operations improvement.Our findings showed that block chain technology favors the organizational performance through the sequential mediation of artificial intelligence and environmental performance,especially thanks to features like visibility,transparency,relationship management,and smart contracts.Also,it was discovered that block chain practices had a good relationship with both the environmental and economic paths to the firms’performance.At the same time,environmental performance is also positively correlated with the firm’s economic well-being.The study found that improved economic and environmental performance were key drivers of increased organizational performance.展开更多
Blockchain technology has attracted worldwide atten-tion,and has strong application potential in complex product system supply chain and other fields.This paper focuses on the supply chain management issues of complex...Blockchain technology has attracted worldwide atten-tion,and has strong application potential in complex product system supply chain and other fields.This paper focuses on the supply chain management issues of complex product systems,and combines the technical characteristics of blockchain,such as tamper resistance and strong resistance to destruction,to conduct research on the application of blockchain based supply chain management for complex product systems.The block-chain technology is integrated into functional modules such as business interaction,privacy protection,data storage,and sys-tem services.The application technology architecture of com-plex product system supply chain integrated with blockchain is constructed.The application practice in complex product sys-tem supply chain is carried out.The results show that the sup-ply chain of complex product systems has the functions of traceability,cost reduction,and anti-counterfeiting protection.Finally,the future development direction and research focus of the complex product system supply chain based on blockchain are prospected,which provides a reference for the equipment manufacturing supply chain management in the mili-tary industry.展开更多
In the shipping industry, significant part of the documents exchange still have the traditional paper form, mainly due to security concerns, despite the size and modernization efforts of this market. We explore the ad...In the shipping industry, significant part of the documents exchange still have the traditional paper form, mainly due to security concerns, despite the size and modernization efforts of this market. We explore the adoption of the blockchain and Distributed Ledger Technologies to address document exchange in a fast and secure way.展开更多
The confidentiality of pseudonymous authentication and secure data transmission is essential for the protection of information and mitigating risks posed by compromised vehicles.The Internet of Vehicles has meaningful...The confidentiality of pseudonymous authentication and secure data transmission is essential for the protection of information and mitigating risks posed by compromised vehicles.The Internet of Vehicles has meaningful applications,enabling connected and autonomous vehicles to interact with infrastructure,sensors,computing nodes,humans,and fellow vehicles.Vehicular hoc networks play an essential role in enhancing driving efficiency and safety by reducing traffic congestion while adhering to cryptographic security standards.This paper introduces a privacy-preserving Vehicle-to-Infrastructure authentication,utilizing encryption and the Moore curve.The proposed approach enables a vehicle to deduce the planned itinerary of Roadside Units(RSUs)before embarking on a journey.Crucially,the Certification Authority remains unaware of the specific route design,ensuring privacy.The method involves transforming all Roadside Units(RSUs)in a region into a vector,allowing for instant authentication of a vehicle’s route using RSU information.Real-world performance evaluations affirm the effectiveness of the proposed model.展开更多
To solve the challenges of connecting and coordinating multiple platforms in the automotive industry and to enhance collaboration among different participants,this research focuses on addressing the complex supply rel...To solve the challenges of connecting and coordinating multiple platforms in the automotive industry and to enhance collaboration among different participants,this research focuses on addressing the complex supply relationships in the automotive market,improving data sharing and interactions across various platforms,and achieving more detailed integration of data and operations.We propose a trust evaluation permission delegation method based on the automotive industry chain.The proposed method combines smart contracts with trust evaluation mechanisms,dynamically calculating the trust value of users based on the historical behavior of the delegated entity,network environment,and other factors to avoid malicious node attacks during the permission delegation process.We also introduce strict control over the cross-domain permission granting and revocation mechanisms to manage the delegation path,prevent information leakage caused by malicious node interception,and effectively protect data integrity and privacy.Experimental analysis shows that this method meets the realtime requirements of collaborative interaction in the automotive industry chain and provides a feasible solution to permission delegation issues in the automotive industry chain,offering dynamic flexibility in authorization and scalability compared to most existing solutions.展开更多
The chain dynamics of a pair of diblock poly(styrene-b-butadiene) (PS210-b-PB960) and triblock poly(styrene-b-butadiene-b-styrene) (PS200-b-PB1815-b-PS200) copolymers in both dilute and semidilute toluene solutions ha...The chain dynamics of a pair of diblock poly(styrene-b-butadiene) (PS210-b-PB960) and triblock poly(styrene-b-butadiene-b-styrene) (PS200-b-PB1815-b-PS200) copolymers in both dilute and semidilute toluene solutions has been comparatively studied by dynamic laser light scattering. As expected, the mutual diffusion of individual chain changes into a fast cooperative diffusion of the chain segments ('blobs') between two neighboring entanglement points for both the copolymers as the solution changes from dilute to semidilute. Further increases of the concentration lead to a second slow relaxation mode. For the triblock chains, there exists an additional middle relaxation between the fast and the slow modes. The concentration (c) dependent study of the average characteristic decay time of the fast mode ((tau(f))) reveals that 1/(tau(f)) - c(-a) with 0.33 < alpha < 0.44, much smaller than 0.75 predicted or 0.72 observed for linear homopolymer chains in good solvent. It implies that the solvent quality of toluene for PB might not be as good as that for PS. Due to such a difference in solubility, it is reasonable to speculate that the PB and PS blocks are transiently segregated in semidilute solution. The relaxation of these transient PB and PS richer domains leads to the observed slow relaxation. Such a speculation is supported by the appearance of an additional slow relaxation mode in the study of polyisoprene-b-polystyrene-b-polyisoprene in semidilute solution in cyclohexane, a non-selective solvent, in which we alternated the solubility difference by a variation of the solution temperature.展开更多
The effect of the architecture of poly(ethylene glycol)/poly(L-lactide)(PEG/PLLA) block copolymers on the non-isothermal crystallization behaviors of PLLA blocks was investigated by differential scanning calorimetry(D...The effect of the architecture of poly(ethylene glycol)/poly(L-lactide)(PEG/PLLA) block copolymers on the non-isothermal crystallization behaviors of PLLA blocks was investigated by differential scanning calorimetry(DSC) and wide angle X-ray diffraction(WAXD). 1-Arm MPEG-b-PLLA and 4-arm PEG-b-PLLA(4PEG-b-PLLA) were synthesized by the ring-opening polymerization of Llactide in the presence of poly(ethylene glycol) methyl ether(MPEG) and 4-arm poly(ethylene glycol)(4PEG). 4-Arm PLLA-b-MPEG(4PLLA-b-PEG) was synthesized by coupling 4-arm PLLA and MPEG. The WAXD results indicated that the crystalline structure of PLLA blocks did not alter due to the different chain architectures. The average values of Avrami index(ˉn) were all above 4, which indicated that the nucleation mechanism of PLLA blocks was heterogeneous nucleation, regardless of the architectures. The overall crystallization rates were decreased markedly as following: MPEG-b-PLLA > 4PEG-b-PLLA > 4PLLA-b-PEG, ascribed to the different confinement by PEG blocks and to the steric hindrance of chain architectures. Therefore, the crystallization of PLLA blocks became more difficult and the crystallization activation energy of the PLLA blocks increased due to the confinement of chain architectures.展开更多
基金supported by the National Key Research and Development Project of China(No.2017YFB0802302)the National Natural Science Foundation of China(No.61572086,No.61402058)+4 种基金the Innovation Team of Quantum Security Communication of Sichuan Province(No.17TD0009)the Academic and Technical Leaders Training Funding Support Projects of Sichuan Province(No.2016120080102643)the Application Foundation Project of Sichuan Province(No.2017JY0168)the Key Research and Development Project of Sichuan Province(No.2018TJPT0012)the Science and Technology Support Project of Sichuan Province(No.2016FZ0112,No.2018GZ0204).
文摘The risk assessment system has been applied to the information security,energy,medical and other industries.Through the risk assessment system,it is possible to quantify the possibility of the impact or loss caused by an event before or after an event,thereby avoiding the risk or reducing the loss.However,the existing risk assessment system architecture is mostly a centralized architecture,which could lead to problems such as data leakage,tampering,and central cheating.Combined with the technology of block chain,which has the characteristics of decentralization,security and credibility,collective maintenance,and untamperability.This paper proposes a new block chainbased risk assessment system architecture and a consensus mechanism algorithm based on DPOS improvement.This architecture uses an improved consensus mechanism to achieve a safe and efficient risk assessment solving the problem of data tampering in the risk assessment process,avoiding data leakage caused by improper data storage.A convenient,safe and fast risk assessment is achieved in conjunction with the improved consensus mechanism.In addition,by comparing existing risk assessment architecture,the advantages and impacts of the new block chain-based risk assessment system architecture are analyzed.
基金Shandong Key Research and Development Project(Soft Science):2019RKC20001。
文摘Supply chain finance has played a positive role in solving the financing difficulties of small and medium-sized enterprises.However,in the actual implementation process,there are still problems such as information asymmetry,doubts about the authenticity of trade background,and high operational risks,which seriously restrict the development of supply chain finance.However,block chain technology has the characteristics of de-centralization,data transparency,common maintenance and non-tampering.Applying this technology to supply chain finance can effectively solve the existing problems.Based on the research on the development status of traditional supply chain finance,this paper puts forward a new development mode of supply chain finance based on block chain technology,and through the analysis of typical cases,finally gives some policy suggestions for the development of block chain supply chain finance.
文摘Objective To analyze the current problems in drug traceability and supply chain management,and build the drug traceability system based on the block chain technology so as to provide authenticity assurance for the real data in the whole life cycle of drugs.Methods A new drug regulatory traceability protocol was designed based on block chain technology.The database of drug production,circulation and use was linked closely.A traceability system was set up according to the traceability protocol,and the consensus complexity and safety performance of the system were analyzed.Results and Conclusion The distributed account book and tamper-proof functions of the block chain platform were used to establish a double-chain system based on the combination of public chain and private chain,which could make the data of drugs more reliable,transparent and traceable with good application value.The establishment of a double-chain traceability system is studied so that drug market license holders,manufacturers,operating enterprises and users can verify the data to form an interconnected drug traceability data chain.
文摘In recent years, the rapid innovation and development of financial industry has made financial enterprises have a lot of information. However, the large amount of information is tampered with and fragmented, which cannot be shared. With the constant innovation of science and technology, it is the most effective way to solve the information lag and asymmetry of financial products. This article aims to start from the problem of asymmetric information of financial products, the analysis of the emerging block chain technology applied in the financial sector, and with the development of asset securitization information known as the typical scenario for the first time, a concrete analysis information game process, and discuss about the application of chain blocks in securitization feasibility.
基金Supported by the National Natural Science Foundation of China(U1304614,U1204703)the Construct Program of the Key Discipline in Zhengzhou Normal UniversityAid Program for Science and Technology Innovative Research Team of Zhengzhou Normal University,Henan Province Education Science Plan General Topic((2018)-JKGHYB-0279)
文摘Block chain is widely used in the financial field for its characteristics of decentralization, anonymity and trust. Electronic money payment is an important application hotspot. Ring signature is widely used in strong anonymous authentication such as electronic cash and electronic voting because of its unconditional anonymity, spontaneity and flexible group structure. Among them, the correlation ring signature can prove whether two signatures are issued by the same person without revealing the identity of the real signer. Therefore, the signature right breach can be avoided based on the premise of guaranteeing anonymity, such as repeated voting, electronic money repetition cost and so on. Most of the existing correlation ring signature security is based on the discrete logarithm problem, and most of the schemes result in the degradation of anonymity because of strong association. These methods do not apply to the block chain electronic currency transaction scene with strong anonymity. Therefore, this paper first proposes a blockchain-based electronic currency transaction security model. The model ensures not only the anonymity of both parties but also a certain degree of traceability. In order to support these two characteristics, this paper proposes an association ring signature method based on large integer decomposition problem. This method has strong anonymity and can be applied to blockchain scenes. On the other hand, it can be converted into group signatures in specific scenarios. It is therefore traceable. Finally, the adaptive selection message of the scheme and the unforgeability under the selection of public key attack are proved under the random oracle model.
文摘Internet of Medical Things (IoMT) is a breakthrough technologyin the transfer of medical data via a communication system. Wearable sensordevices collect patient data and transfer them through mobile internet, thatis, the IoMT. Recently, the shift in paradigm from manual data storage toelectronic health recording on fog, edge, and cloud computing has been noted.These advanced computing technologies have facilitated medical services withminimum cost and available conditions. However, the IoMT raises a highconcern on network security and patient data privacy in the health caresystem. The main issue is the transmission of health data with high security inthe fog computing model. In today’s market, the best solution is blockchaintechnology. This technology provides high-end security and authenticationin storing and transferring data. In this research, a blockchain-based fogcomputing model is proposed for the IoMT. The proposed technique embedsa block chain with the yet another consensus (YAC) protocol building securityinfrastructure into fog computing for storing and transferring IoMT data inthe network. YAC is a consensus protocol that authenticates the input datain the block chain. In this scenario, the patients and their family membersare allowed to access the data. The empirical outcome of the proposedtechnique indicates high reliability and security against dangerous threats.The major advantages of using the blockchain model are high transparency,good traceability, and high processing speed. The technique also exhibitshigh reliability and efficiency in accessing data with secure transmission. Theproposed technique achieves 95% reliability in transferring a large number offiles up to 10,000.
文摘In the context of the China-Pakistan Economic Corridor,this article evaluates how block chain technology might improve organizational performance(CPEC)through the sequential mediating role of artificial intelligence and environmental performance.Cross-sectional data were collected from one hundred respondents through a close-ended questionnaire-based survey of manufacturing companies,which was then analyzed using structural equation modeling,which structural equation modelling was used to analyze.The block chain technology benefits businesses in terms of the environment and economics.There is a focus on technology in every industry as the Industry 4.0 era gets underway.Block chain technology,a relatively new phenomenon,offers several opportunities for company operations improvement.Our findings showed that block chain technology favors the organizational performance through the sequential mediation of artificial intelligence and environmental performance,especially thanks to features like visibility,transparency,relationship management,and smart contracts.Also,it was discovered that block chain practices had a good relationship with both the environmental and economic paths to the firms’performance.At the same time,environmental performance is also positively correlated with the firm’s economic well-being.The study found that improved economic and environmental performance were key drivers of increased organizational performance.
基金supported by the National Natural Science Foundation of China(71871007)Project of Chinese Academy of Engineering.
文摘Blockchain technology has attracted worldwide atten-tion,and has strong application potential in complex product system supply chain and other fields.This paper focuses on the supply chain management issues of complex product systems,and combines the technical characteristics of blockchain,such as tamper resistance and strong resistance to destruction,to conduct research on the application of blockchain based supply chain management for complex product systems.The block-chain technology is integrated into functional modules such as business interaction,privacy protection,data storage,and sys-tem services.The application technology architecture of com-plex product system supply chain integrated with blockchain is constructed.The application practice in complex product sys-tem supply chain is carried out.The results show that the sup-ply chain of complex product systems has the functions of traceability,cost reduction,and anti-counterfeiting protection.Finally,the future development direction and research focus of the complex product system supply chain based on blockchain are prospected,which provides a reference for the equipment manufacturing supply chain management in the mili-tary industry.
文摘In the shipping industry, significant part of the documents exchange still have the traditional paper form, mainly due to security concerns, despite the size and modernization efforts of this market. We explore the adoption of the blockchain and Distributed Ledger Technologies to address document exchange in a fast and secure way.
文摘The confidentiality of pseudonymous authentication and secure data transmission is essential for the protection of information and mitigating risks posed by compromised vehicles.The Internet of Vehicles has meaningful applications,enabling connected and autonomous vehicles to interact with infrastructure,sensors,computing nodes,humans,and fellow vehicles.Vehicular hoc networks play an essential role in enhancing driving efficiency and safety by reducing traffic congestion while adhering to cryptographic security standards.This paper introduces a privacy-preserving Vehicle-to-Infrastructure authentication,utilizing encryption and the Moore curve.The proposed approach enables a vehicle to deduce the planned itinerary of Roadside Units(RSUs)before embarking on a journey.Crucially,the Certification Authority remains unaware of the specific route design,ensuring privacy.The method involves transforming all Roadside Units(RSUs)in a region into a vector,allowing for instant authentication of a vehicle’s route using RSU information.Real-world performance evaluations affirm the effectiveness of the proposed model.
基金funded by the Sichuan Science and Technology Program,Grant Nos.2024NSFSC0515,2024ZHCG0182 and MZGC20230013.
文摘To solve the challenges of connecting and coordinating multiple platforms in the automotive industry and to enhance collaboration among different participants,this research focuses on addressing the complex supply relationships in the automotive market,improving data sharing and interactions across various platforms,and achieving more detailed integration of data and operations.We propose a trust evaluation permission delegation method based on the automotive industry chain.The proposed method combines smart contracts with trust evaluation mechanisms,dynamically calculating the trust value of users based on the historical behavior of the delegated entity,network environment,and other factors to avoid malicious node attacks during the permission delegation process.We also introduce strict control over the cross-domain permission granting and revocation mechanisms to manage the delegation path,prevent information leakage caused by malicious node interception,and effectively protect data integrity and privacy.Experimental analysis shows that this method meets the realtime requirements of collaborative interaction in the automotive industry chain and provides a feasible solution to permission delegation issues in the automotive industry chain,offering dynamic flexibility in authorization and scalability compared to most existing solutions.
基金The financial support of the Hong Kong Special Administration Region Earmarked Grants (CUHK4257/01P, 2160174), theSpecial Funds for Major State Basic Research Projects (G1999064800), the CAS Bai Ren Project and the National ScienceFoundation of China (NSFC) are gratefully acknowledged.
文摘The chain dynamics of a pair of diblock poly(styrene-b-butadiene) (PS210-b-PB960) and triblock poly(styrene-b-butadiene-b-styrene) (PS200-b-PB1815-b-PS200) copolymers in both dilute and semidilute toluene solutions has been comparatively studied by dynamic laser light scattering. As expected, the mutual diffusion of individual chain changes into a fast cooperative diffusion of the chain segments ('blobs') between two neighboring entanglement points for both the copolymers as the solution changes from dilute to semidilute. Further increases of the concentration lead to a second slow relaxation mode. For the triblock chains, there exists an additional middle relaxation between the fast and the slow modes. The concentration (c) dependent study of the average characteristic decay time of the fast mode ((tau(f))) reveals that 1/(tau(f)) - c(-a) with 0.33 < alpha < 0.44, much smaller than 0.75 predicted or 0.72 observed for linear homopolymer chains in good solvent. It implies that the solvent quality of toluene for PB might not be as good as that for PS. Due to such a difference in solubility, it is reasonable to speculate that the PB and PS blocks are transiently segregated in semidilute solution. The relaxation of these transient PB and PS richer domains leads to the observed slow relaxation. Such a speculation is supported by the appearance of an additional slow relaxation mode in the study of polyisoprene-b-polystyrene-b-polyisoprene in semidilute solution in cyclohexane, a non-selective solvent, in which we alternated the solubility difference by a variation of the solution temperature.
基金financially supported by the National Natural Science Foundation of China(Nos.51303176,51873209,51573178,and 51773194)the National Key Research and Development Program of China(No.2016YFB0302500)
文摘The effect of the architecture of poly(ethylene glycol)/poly(L-lactide)(PEG/PLLA) block copolymers on the non-isothermal crystallization behaviors of PLLA blocks was investigated by differential scanning calorimetry(DSC) and wide angle X-ray diffraction(WAXD). 1-Arm MPEG-b-PLLA and 4-arm PEG-b-PLLA(4PEG-b-PLLA) were synthesized by the ring-opening polymerization of Llactide in the presence of poly(ethylene glycol) methyl ether(MPEG) and 4-arm poly(ethylene glycol)(4PEG). 4-Arm PLLA-b-MPEG(4PLLA-b-PEG) was synthesized by coupling 4-arm PLLA and MPEG. The WAXD results indicated that the crystalline structure of PLLA blocks did not alter due to the different chain architectures. The average values of Avrami index(ˉn) were all above 4, which indicated that the nucleation mechanism of PLLA blocks was heterogeneous nucleation, regardless of the architectures. The overall crystallization rates were decreased markedly as following: MPEG-b-PLLA > 4PEG-b-PLLA > 4PLLA-b-PEG, ascribed to the different confinement by PEG blocks and to the steric hindrance of chain architectures. Therefore, the crystallization of PLLA blocks became more difficult and the crystallization activation energy of the PLLA blocks increased due to the confinement of chain architectures.
