Hydroxypropyl methylcellulose acetate succinate(HPMCAS)was successfully synthesized from the reaction of hydroxypropyl methylcellulose with succinic anhydride and acetic anhydride in an acetone/pyridine system.Product...Hydroxypropyl methylcellulose acetate succinate(HPMCAS)was successfully synthesized from the reaction of hydroxypropyl methylcellulose with succinic anhydride and acetic anhydride in an acetone/pyridine system.Products with different contents of succinyl groups and acetyl groups were prepared by varying the reaction conditions.In the acetone/pyridine system,equipment corrosion does not occur,the product is easy to wash,and the solvent can be recycled.By varying the concentration of the esterifying agents,products with different ratios of acidic groups can be obtained.Under the optimum conditions,the obtained products had an average molecular weight between 5.39×104 and 5.41×104,a number average molecular weight from 4.97×104 to 5.13×104,and a polydispersity index from 1.05 to 1.08.The products dissolved well in acetone and methanol,and formed films on a mold.The films had good pH-sensitivity,tensile strength,and thermal stability.The formed films could dissolve in solutions with a pH value ranging from 5.4 to 6.4,and are therefore suitable for use as an enteric coating for pharmaceutical dosage forms.展开更多
Controlled and homogeneous flee-radical polymerization of acrylamide （AM） in aqueous phase was realized by using S,S＇-bis（α, α＇-dimethyl-α＂-acetic acid）-trithiocarbonate as a reversible addition-fragmentatio...Controlled and homogeneous flee-radical polymerization of acrylamide （AM） in aqueous phase was realized by using S,S＇-bis（α, α＇-dimethyl-α＂-acetic acid）-trithiocarbonate as a reversible addition-fragmentation transfer （RAFT） agent. Linear increases in molecular weight with conversion and narrow molecular weight distribution were observed for polyacrylamide （PAM） throughout the polymerization. By this method, PAMs with controlled molecular weight （up to 1.0 ~ 106） and narrow molecular weight distribution （Mw/Mn 〈 1.2） were prepared. This study provides an effective method for synthesis of PAMs with narrow molecular weight distribution under environmentally friendly conditions.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
基金The authors are grateful for the financial supports of this research from the Science and Technology Program of Guangdong(2019A1515011890)National Key R&D Program of China(2017YFD0601003).
文摘Hydroxypropyl methylcellulose acetate succinate(HPMCAS)was successfully synthesized from the reaction of hydroxypropyl methylcellulose with succinic anhydride and acetic anhydride in an acetone/pyridine system.Products with different contents of succinyl groups and acetyl groups were prepared by varying the reaction conditions.In the acetone/pyridine system,equipment corrosion does not occur,the product is easy to wash,and the solvent can be recycled.By varying the concentration of the esterifying agents,products with different ratios of acidic groups can be obtained.Under the optimum conditions,the obtained products had an average molecular weight between 5.39×104 and 5.41×104,a number average molecular weight from 4.97×104 to 5.13×104,and a polydispersity index from 1.05 to 1.08.The products dissolved well in acetone and methanol,and formed films on a mold.The films had good pH-sensitivity,tensile strength,and thermal stability.The formed films could dissolve in solutions with a pH value ranging from 5.4 to 6.4,and are therefore suitable for use as an enteric coating for pharmaceutical dosage forms.
文摘Controlled and homogeneous flee-radical polymerization of acrylamide （AM） in aqueous phase was realized by using S,S＇-bis（α, α＇-dimethyl-α＂-acetic acid）-trithiocarbonate as a reversible addition-fragmentation transfer （RAFT） agent. Linear increases in molecular weight with conversion and narrow molecular weight distribution were observed for polyacrylamide （PAM） throughout the polymerization. By this method, PAMs with controlled molecular weight （up to 1.0 ~ 106） and narrow molecular weight distribution （Mw/Mn 〈 1.2） were prepared. This study provides an effective method for synthesis of PAMs with narrow molecular weight distribution under environmentally friendly conditions.
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.
