红外光谱原位跟踪活性自由基聚合反应过程研究

使用新型可插入式红外光谱仪原位检测在4－羟基2，2，6，6－四甲基氧化哌啶醇（HTEMPO）存在下苯乙烯稳定自由基活性均聚合反应和苯乙烯／甲基丙烯酸羟丙酯的共聚合反应以及苯乙烯原子转移活性自由基聚合（ATRP）反应三个过程，分别考虑了它们的反应动力学，并给出了可能的聚合反应机理。研究结果表明，对于均相的苯乙烯（St)均聚合反应和苯乙烯（St)/甲基丙烯酸羟丙酯（HPMA）的自由基共聚合反应体系，聚合反应显示一定的诱导期，与反应体系中存在的HTEMPO捕捉自由基有关，而对于St／HPMA共聚合体系，诱导期更长，这是因为HPMA易和HTEMPO自由基发生氢转移反应，导致游离的HTEMPO浓度升高。最后用红外光谱实时跟踪苯乙烯非均相ATRP过程，发现苯乙烯聚合反应动力学接近于表现零级。因为单体分子在由增长自由基、卤化铜和联二吡啶形成的络合物的界面增长，与单体相内St浓度无关。

Study of ″Living″ Radical Polymerization by FTIR in Situ

Three types of living radical polymerization processes were monitored by means of FTIR spectrometer with handful diamond detector called as Dicomp in situ.It was found that both styrene and styrene/hydroxylpropyl methyacrylate (HPMA) could polymerize according to stable free radical polymerization (SFRP) mechanism in presence of 4-hydroxyl tetramethypiperidiyl-1-oxy(HTEMPO).For styrene/HPMA system,the styrene and HPMA conversion monitored by FTIR were linear with increase of molecular weight,but it gave longer induction period compared with that for St bulk polymerization.It was related to the hydrogen-transfer reaction between the propagating radicals with the end HPMA unit and HTEMPO.Furthermore,This following method in situ could be introduced into monitoring heterogeneous polymerization of styrene during atom transfer radical polymerization (ATRP).The apparent kinetics was found to be about zero order and not 10 order,due to propagating on the complex including radicals,CuX and bpy in heterogeneous interface.The polymerization rate will be not related to the St in bulk St phase.