The novel hyperbranced polymers containing reductive groups were successfully prepared and characterized using redox/reversible addition fragmentation chain transfer （RAFT）/self-condensing vinyl polymerization （SCV...The novel hyperbranced polymers containing reductive groups were successfully prepared and characterized using redox/reversible addition fragmentation chain transfer （RAFT）/self-condensing vinyl polymerization （SCVP） method. Several redox initiating chemicals such as Cu（III）/--CONH2, Ce（IV）/--CONH2 and Ce（IV）/--OH were chosen to increase the free radical generating rate, and the chain transfer agent （CTA） was used to reduce the molecular chain propagating rate, in order to obtain polymers with high degree of branching. Detailed analyses based on the molecular weight, α value and the degree of branching of polymers （DB） obtained from 1H-NMR spectra and multi detector size exclusion chromatography （MDSEC） suggested the acquiring of hyperbranced polyacrylamides with Cu（III）/--CONH2 and Ce（IV）/--CONH2 as initiator in the presence of the CTA. Meanwhile, the as-prepared poly（N-hydroxymethyl acrylamide） （PNHAM） with higher DB value （0.48） proved that using Ce（IV）/--OH as the initiator could increase the free radical generating rate and diminish the gap between the propagating rate and the initiation rate during the reaction procedure. In addition, the effect of oxidant concentration on the Mark-Houwink index （α） value and the DB was also studied.展开更多
A novel branched block copolymer was synthesized with self-condensing vinyl polymerization(SCVP)of macroinimer,PEGMA-b-PCL-Br,via atom transfer radical polymerization(ATRP).The macro-inimer was prepared with enzyme-ca...A novel branched block copolymer was synthesized with self-condensing vinyl polymerization(SCVP)of macroinimer,PEGMA-b-PCL-Br,via atom transfer radical polymerization(ATRP).The macro-inimer was prepared with enzyme-catalyzed ring-opening polymerization(ROP)of ε-caprolactone(ε-CL)with poly(ethylene glycol)methacrylate(PEGMA)as the initiator and esterification of the ω-hydroxyl group of the obtained PEGMA-PCL with α-bromoisobutyryl bromide.展开更多
The Server-Based Certificate Validation Protocol allows PKI clients to delegate to a server the construction or validation of certification paths. The protocol’s specification focuses on the communication between the...The Server-Based Certificate Validation Protocol allows PKI clients to delegate to a server the construction or validation of certification paths. The protocol’s specification focuses on the communication between the server and the client and its security. It does not discuss how the servers can efficiently locate the necessary PKI resources like certificate or certificate revocation lists. In this paper we concentrate on this topic. We present a simple and effective method to facilitate locating and using various PKI resources by the servers, without modifying the protocol. We use the extension mechanism of the protocol for notifying the servers about PKI repositories, certificates, and revocations. We specify the tasks of the servers and certificate issu-ers and define the messages that are exchanged between them. A proof of concept is given by implementing an SCVP server, a client, and the proposed method in Java.展开更多
The distribution function of the hyperbranched polymers formed from the self-condensing vinyl polymerization with unequal reactivities was derived and the differential equations for the second moments are established,...The distribution function of the hyperbranched polymers formed from the self-condensing vinyl polymerization with unequal reactivities was derived and the differential equations for the second moments are established, based on the variable of the conversion of B* groups. The various average degrees of branching can be designed by suitable values of reactivities ratio (r) and the conversion of A group (x). In order to reach the maximum degree of branching at a specified x, r needed is dependant on the value of x. The higher the x, the less the r needed is for the maximum value of degree of branching. At the end of the reaction, the maximum degree of branching reaches 0.5 with r=2.59.展开更多
This review introduces the kinetic theory of self-condensing vinyl polymerization (SCVP),including the SCVP of AB inimers,the SCVP with non-equal reactivity between A and B groups,the SCVP in the presence of a small a...This review introduces the kinetic theory of self-condensing vinyl polymerization (SCVP),including the SCVP of AB inimers,the SCVP with non-equal reactivity between A and B groups,the SCVP in the presence of a small amount of multifunctional initiators,also the SCVP of both inimers and comonomers.The analytical expressions of various molecular parameters for the resulting hyperbranched polymers,such as the molecular size distribution function,the average molecular weight,the polydispersity index and the degree of branching,are reviewed systematically.展开更多
Dendritic polymers,including dendrimers and hyperbranched polymers (HBPs),are the fourth major polymer architecture after linear,branched and crosslinked polymers.HBPs were theoretically predicted by Flory in the 1940...Dendritic polymers,including dendrimers and hyperbranched polymers (HBPs),are the fourth major polymer architecture after linear,branched and crosslinked polymers.HBPs were theoretically predicted by Flory in the 1940s and 1952.However,the term "hyperbranched polymer" was first coined by Kim and Webster in 1988 when they intentionally synthesized soluble hyperbranched polyphenylene.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.20904008 and 21274037)College of Science and Technology Foundation of Hebei Education Department(2010015,B2010000214)
文摘The novel hyperbranced polymers containing reductive groups were successfully prepared and characterized using redox/reversible addition fragmentation chain transfer （RAFT）/self-condensing vinyl polymerization （SCVP） method. Several redox initiating chemicals such as Cu（III）/--CONH2, Ce（IV）/--CONH2 and Ce（IV）/--OH were chosen to increase the free radical generating rate, and the chain transfer agent （CTA） was used to reduce the molecular chain propagating rate, in order to obtain polymers with high degree of branching. Detailed analyses based on the molecular weight, α value and the degree of branching of polymers （DB） obtained from 1H-NMR spectra and multi detector size exclusion chromatography （MDSEC） suggested the acquiring of hyperbranced polyacrylamides with Cu（III）/--CONH2 and Ce（IV）/--CONH2 as initiator in the presence of the CTA. Meanwhile, the as-prepared poly（N-hydroxymethyl acrylamide） （PNHAM） with higher DB value （0.48） proved that using Ce（IV）/--OH as the initiator could increase the free radical generating rate and diminish the gap between the propagating rate and the initiation rate during the reaction procedure. In addition, the effect of oxidant concentration on the Mark-Houwink index （α） value and the DB was also studied.
文摘A novel branched block copolymer was synthesized with self-condensing vinyl polymerization(SCVP)of macroinimer,PEGMA-b-PCL-Br,via atom transfer radical polymerization(ATRP).The macro-inimer was prepared with enzyme-catalyzed ring-opening polymerization(ROP)of ε-caprolactone(ε-CL)with poly(ethylene glycol)methacrylate(PEGMA)as the initiator and esterification of the ω-hydroxyl group of the obtained PEGMA-PCL with α-bromoisobutyryl bromide.
文摘The Server-Based Certificate Validation Protocol allows PKI clients to delegate to a server the construction or validation of certification paths. The protocol’s specification focuses on the communication between the server and the client and its security. It does not discuss how the servers can efficiently locate the necessary PKI resources like certificate or certificate revocation lists. In this paper we concentrate on this topic. We present a simple and effective method to facilitate locating and using various PKI resources by the servers, without modifying the protocol. We use the extension mechanism of the protocol for notifying the servers about PKI repositories, certificates, and revocations. We specify the tasks of the servers and certificate issu-ers and define the messages that are exchanged between them. A proof of concept is given by implementing an SCVP server, a client, and the proposed method in Java.
基金the National Natural Science Foundation of China (Grant No. 20774038, 50633010)the Foundation of State Key Laboratory of Metal Matrix Composites
文摘The distribution function of the hyperbranched polymers formed from the self-condensing vinyl polymerization with unequal reactivities was derived and the differential equations for the second moments are established, based on the variable of the conversion of B* groups. The various average degrees of branching can be designed by suitable values of reactivities ratio (r) and the conversion of A group (x). In order to reach the maximum degree of branching at a specified x, r needed is dependant on the value of x. The higher the x, the less the r needed is for the maximum value of degree of branching. At the end of the reaction, the maximum degree of branching reaches 0.5 with r=2.59.
基金supported by the National Natural Science Foundation of China(20774038,50633010 & 20874060)
文摘This review introduces the kinetic theory of self-condensing vinyl polymerization (SCVP),including the SCVP of AB inimers,the SCVP with non-equal reactivity between A and B groups,the SCVP in the presence of a small amount of multifunctional initiators,also the SCVP of both inimers and comonomers.The analytical expressions of various molecular parameters for the resulting hyperbranched polymers,such as the molecular size distribution function,the average molecular weight,the polydispersity index and the degree of branching,are reviewed systematically.
文摘Dendritic polymers,including dendrimers and hyperbranched polymers (HBPs),are the fourth major polymer architecture after linear,branched and crosslinked polymers.HBPs were theoretically predicted by Flory in the 1940s and 1952.However,the term "hyperbranched polymer" was first coined by Kim and Webster in 1988 when they intentionally synthesized soluble hyperbranched polyphenylene.
