辐射接枝NVP对聚L-乳酸分子量的影响

以甲醇为溶剂,采用辐射接枝法制备了聚L-乳酸(Poly-L-lactic acid,PLLA)/N-乙烯基吡咯烷酮(N-vinyl pyrrolidone,NVP)接枝共聚物。研究了醋酸(Acetic acid,HAc)浓度、单体浓度和剂量率对接枝共聚物分子量的影响,并采用傅立叶变换红外光谱(Fourier transform infrared spectrometer,FT-IR)、核磁共振氢谱(Nuclear magnetic resonance,1H-NMR)、热重分析法(Thermogravimetry analysis,TGA)对接枝共聚物进行了表征。结果表明,在相同吸收剂量下,接枝共聚物的分子量与反应介质中HAc浓度、单体浓度以及剂量率相关。当HAc浓度为0.05 mol/L,单体浓度为30%,剂量率为500 Gy/h时,接枝共聚物的分子量分别出现极大值。随着接枝率的增大,接枝共聚物的两个热失重阶段变得更为明显。

Effect on molecular weight of poly (L-lactic acid) by irradiation graft with NVP

Copolymer of poly（L-lactic acid）（PLLA） grafted with N-vinylpyrrolidone（PLLA-g-PVP） was prepared by γ-irradiation in the presence of methanol as a solvent.The effects of acetic acid（HAc） concentration,monomer concentration and dose rate on molecular weight of PLLA-g-PVP were investigated and the structure of PLLA-g-PVP was characterized by 1H-NMR,FT-IR and TGA,respectively.It shows that,the HAc concentration,monomer concentration and dose rate have an effect on the molecular weight of PLLA-g-PVP at the same absorbed dose.The maximum molecular weight of the copolymers can be obtained in optimum condition of HAc concentration 0.05mol/L,monomer concentration 30% and dose rate 500 Gy/h,respectively.The two weight loss stages of graft copolymers have been observed more distinctly with the increment of graft ratio.