采用一锅法,以木质素为原料,经二硫化碳、2-溴丁酸甲酯进行黄原酸酯功能化改性合成木质素基大分子链转移剂(lignin-CTA),通过FT-IR、1^H NMR、13^C NMR对其结构进行表征,并将其用于丙烯酰胺的RAFT聚合反应制备木质素-丙烯酰胺共聚物(lignin-g-PAM),考察该反应的聚合特征。木质素功能化改性前后的红外谱图显示:改性后羟基吸收峰明显减弱,并且在1148和1732cm^-1处分别出现了—C S键振动吸收峰和酯键的羰基吸收峰,说明2-溴丁酸甲酯已成功接枝到木质素大分子上;同时lignin-CTA的1^H NMR谱图中于δ0.90处出现了2-溴丁酸甲酯末端甲基的活泼氢质子峰,13^C NMR谱图中于δ162处出现了—C S的碳原子峰,进一步印证了接枝反应的进行。丙烯酰胺的RAFT聚合反应结果显示:聚合物的相对分子质量与转化率基本呈现线性关系,同时其多分散系数较低且分布相对较窄(1.26~1.53),证明该聚合反应具有高效可控特性。
Lignin based chain transfer agent(lignin-CTA)was synthesized by one-pot reaction with using lignin,carbon disulfide and methyl 2-bromobutyrate as raw materials and was characterized by FT-IR,1^H NMR and 13^C NMR spectroscopy,respectively.Then this lignin-CTA was used for performing reversible addition-fragmentation chain transfer polymerization(RAFT)of acrylamide to prepare lignin-acrylamide copolymer(lignin-g-PAM).And the polymerization characteristics of the reaction was studied.In FT-IR spectra of lignin before and after functional modification,the intensity of peak corresponding to hydroxyl group decreased obviously after modification.In addition,the peak at 1148 cm^-1 corresponding to C S bond and the peak at 1732 cm^-1 corresponding to ester carbanyl groupappeared in the spectrum of lignin-CTA,which indicated that the methyl 2-bromobutyrate was successfully grafted on the lignin.The peak atδ0.90 in the 1^H NMR spectrum of lignin-CTA was corresponded to the protons of end methyl of methyl 2-bromobutyrate and the peak atδ162 in 13^C NMR spectrum of lignin-CTA was attrubuted to the carbon atom of-C S bond.These all proved that methyl 2-bromobutyrate was grafted on lignin successfully.In the RAFT polymerization of acrylamide,number-average molecular weight(M n)and PDI values vs conversions presented linear relationship and the polydispersity index was low and distributed in a narrow range,indicating that this polymerization process was highly efficient and well controlled.
Chemistry & Industry of Forest Products
reversible addition-fragmentation chain transfer polymerization(RAFT)
chain transfer agent