A low-molecular-weight polylactide-poly(butylene succinate)(PLA-PBS)copolymer was synthesized and incorporated into polylactide(PLA)as a novel toughening agent by solvent casting.The copolymer had the same chemical ...A low-molecular-weight polylactide-poly(butylene succinate)(PLA-PBS)copolymer was synthesized and incorporated into polylactide(PLA)as a novel toughening agent by solvent casting.The copolymer had the same chemical structure and function as PLA and it was used as a plasticizer to PLA.The copolymer was blended with PLA at a weight ratio from 2 to 10 wt%.Phase separation between PLA and PLA-PBS was not observed from their scanning electron microscopy(SEM)images and the crystal structure of PLA almost remained unchanged based on the X-ray diffraction(XRD)measurement.The melt flow index(MFI)of the blends was higher as the amount of PLA-PBS increased,indicating that the block copolymer did improve the mobility of the PLA chains.Moreover,tensile tests revealed that PLA with greater PLA-PBS copolymer exhibited higher elongation at break and it reached the maximum at 8 wt%of PLA-PBS in PLA,which was around 6 times higher than that of pure PLA.Furthermore,the glass transition temperature,measured by differential scanning calorimetry(DSC),markedly decreased with an increasing amount of the copolymer as it decreased from 61.2℃ for pure PLA to 41.3℃when it was blended with 10 wt%PLA-PBS copolymer.Therefore,the PLA-PBS copolymer was shown to be a promising plasticizer for fully biobased and toughened PLA.展开更多
Poly（L-lactide-co-caprolactone）（85-15）[P（LLA-CL）（85-15）] was synthesized from high purity L-lactide and e-caprolactone using tin octoate as initiator by ring-opening polymerization, and characterized by infrar...Poly（L-lactide-co-caprolactone）（85-15）[P（LLA-CL）（85-15）] was synthesized from high purity L-lactide and e-caprolactone using tin octoate as initiator by ring-opening polymerization, and characterized by infrared spectrum and IH-NMR spectrum. The synthesized P（LLA-CL）（85-15） is a random copolymer. The influences of polymerization temperature, polymerization time, dosage of initiator and polymerization pressure on the weight average molecular weight and the polydispersity index of P（LLA-CL）（85-15） were investigated. The optimum preparation conditions of P（LLA-CL）（85-15） are： the polymerization pressure is less than 0.5 Pa, the polymerization temperature is 130 ~C, the n（M）/n（I） ratio is 8 000/1, and the polymerization time is 36 h. Under the condition, the weight-average molecular weight of prepared P（LLA-CL）（85-15） is 65.6x 104, and molecular weight distribution coefficient is 1.15.展开更多
The relationship between sequence distributions and molecular weight distributions of S-SBR, obtained from styrene and butadiene anionic copolymerization at various conversions with THF/Li^+ as an initiator has been s...The relationship between sequence distributions and molecular weight distributions of S-SBR, obtained from styrene and butadiene anionic copolymerization at various conversions with THF/Li^+ as an initiator has been studied by ^(13)C-NMR,GPC. The results showed that the molecular weight distributions of the copolymer couldbe correlated sophisticatedly to the binary sequcne distributions or the monomer unit distributions of the copolymer in a corrected Poisson's distribution from.展开更多
Three basic conditions for preparation of alternating copolymer with narrow molecular weight distribution were derived from the element kinetic equations of binary radical copolymerization. Using maleimide (MI) and at...Three basic conditions for preparation of alternating copolymer with narrow molecular weight distribution were derived from the element kinetic equations of binary radical copolymerization. Using maleimide (MI) and atropic acid (ATA) as model monomer pairs and dioxane as the solvent the alternating copolymer with molecular weight distribution in the range of 1.09-1.20 was prepared successfully by charger transfer complex (CTC) mechanism in the presence of benzoyl peroxide at 85 °C. The monomer reactivity ratioesr 1(MI) = 0.05±0.01 andr 2(ATA) = 0.03 ± 0.02 were measured. The alternating copolymerization was carried out through formation of a contact-type CTC and then alternating addition of MI and ATA monomers. The molecular weight of the copolymers is nearly independent of the feed ratio in a Iarge range and the polymerization rate dropped with an increase in ATA in feed ratio.展开更多
The molecular weight of acrylonitrile/itaconic acid copolymer can be calculated from the intrinsic viscosities of the dilute reaction solutions directly, when the conversion was higher than 90% during the solution pol...The molecular weight of acrylonitrile/itaconic acid copolymer can be calculated from the intrinsic viscosities of the dilute reaction solutions directly, when the conversion was higher than 90% during the solution polymerization. Because of the sample treatment processes such as film preparing, washing, drying and redissolving were simplified, the analysis time was reduced substantially. The proposed method is more suitable for rapid analysis. The measurement error compared with common method of determination for the copolymer in DMSO by single point method was about 1%.展开更多
文摘A low-molecular-weight polylactide-poly(butylene succinate)(PLA-PBS)copolymer was synthesized and incorporated into polylactide(PLA)as a novel toughening agent by solvent casting.The copolymer had the same chemical structure and function as PLA and it was used as a plasticizer to PLA.The copolymer was blended with PLA at a weight ratio from 2 to 10 wt%.Phase separation between PLA and PLA-PBS was not observed from their scanning electron microscopy(SEM)images and the crystal structure of PLA almost remained unchanged based on the X-ray diffraction(XRD)measurement.The melt flow index(MFI)of the blends was higher as the amount of PLA-PBS increased,indicating that the block copolymer did improve the mobility of the PLA chains.Moreover,tensile tests revealed that PLA with greater PLA-PBS copolymer exhibited higher elongation at break and it reached the maximum at 8 wt%of PLA-PBS in PLA,which was around 6 times higher than that of pure PLA.Furthermore,the glass transition temperature,measured by differential scanning calorimetry(DSC),markedly decreased with an increasing amount of the copolymer as it decreased from 61.2℃ for pure PLA to 41.3℃when it was blended with 10 wt%PLA-PBS copolymer.Therefore,the PLA-PBS copolymer was shown to be a promising plasticizer for fully biobased and toughened PLA.
基金Supported by the National Natural Science Foundation of China (No.20976017)the Technological Project of Hunnan Province(Nos.2010FJ3098 and 2010NK3001)the project funded by Hunnan Province Education Office(No.11C0018)
文摘Poly（L-lactide-co-caprolactone）（85-15）[P（LLA-CL）（85-15）] was synthesized from high purity L-lactide and e-caprolactone using tin octoate as initiator by ring-opening polymerization, and characterized by infrared spectrum and IH-NMR spectrum. The synthesized P（LLA-CL）（85-15） is a random copolymer. The influences of polymerization temperature, polymerization time, dosage of initiator and polymerization pressure on the weight average molecular weight and the polydispersity index of P（LLA-CL）（85-15） were investigated. The optimum preparation conditions of P（LLA-CL）（85-15） are： the polymerization pressure is less than 0.5 Pa, the polymerization temperature is 130 ~C, the n（M）/n（I） ratio is 8 000/1, and the polymerization time is 36 h. Under the condition, the weight-average molecular weight of prepared P（LLA-CL）（85-15） is 65.6x 104, and molecular weight distribution coefficient is 1.15.
文摘The relationship between sequence distributions and molecular weight distributions of S-SBR, obtained from styrene and butadiene anionic copolymerization at various conversions with THF/Li^+ as an initiator has been studied by ^(13)C-NMR,GPC. The results showed that the molecular weight distributions of the copolymer couldbe correlated sophisticatedly to the binary sequcne distributions or the monomer unit distributions of the copolymer in a corrected Poisson's distribution from.
基金Project supported by the National Natural Science Foundation of China (Grant No. 29634010-3)Doctor Training Foundation of State Education Ministry of China.
文摘Three basic conditions for preparation of alternating copolymer with narrow molecular weight distribution were derived from the element kinetic equations of binary radical copolymerization. Using maleimide (MI) and atropic acid (ATA) as model monomer pairs and dioxane as the solvent the alternating copolymer with molecular weight distribution in the range of 1.09-1.20 was prepared successfully by charger transfer complex (CTC) mechanism in the presence of benzoyl peroxide at 85 °C. The monomer reactivity ratioesr 1(MI) = 0.05±0.01 andr 2(ATA) = 0.03 ± 0.02 were measured. The alternating copolymerization was carried out through formation of a contact-type CTC and then alternating addition of MI and ATA monomers. The molecular weight of the copolymers is nearly independent of the feed ratio in a Iarge range and the polymerization rate dropped with an increase in ATA in feed ratio.
文摘The molecular weight of acrylonitrile/itaconic acid copolymer can be calculated from the intrinsic viscosities of the dilute reaction solutions directly, when the conversion was higher than 90% during the solution polymerization. Because of the sample treatment processes such as film preparing, washing, drying and redissolving were simplified, the analysis time was reduced substantially. The proposed method is more suitable for rapid analysis. The measurement error compared with common method of determination for the copolymer in DMSO by single point method was about 1%.
