核磁共振谱研究PAA-F108-PAA嵌段共聚物的胶束化行为

摘要

采用原子转移自由基聚合伴随水解的方法合成了聚丙烯酸-聚醚嵌段共聚物(PAA-F108 -PAA),并通过氢核磁共振波谱和二维核Overhauser效应谱(2D NOE)研究了温度、羧酸基团中和度(α)及盐浓度对PAA-F108-PAA嵌段共聚物在水溶液中胶束化行为的影响.结果表明,PAA-F108-PAA分子的临界胶束化温度受α影响较小,受盐的种类和浓度影响较大.当α=0.14(0.01 mol/L KCl)时,在6℃条件下,PAA-F108-PAA分子处于塌缩状态,而在60℃条件下,聚氧化丙烯(PPO)链段发生疏水聚集形成胶束的核,PAA链段与PEO链段相互作用形成胶束的壳;当α=0.80(0.01 mol/L KCl)时,在6℃条件下,PAA-F108-PAA分子处于相对伸展状态,而在60℃条件下,PPO链段仍发生疏水聚集形成胶束的核,PEO与PAA彼此分离形成胶束的壳.增加KCl的浓度至1 mol/L,PAA-F108-PAA分子的临界胶束化温度显著降低,KCl对PPO和PEO链段都表现出脱水作用.但KI的浓度增加至1 mol/L时,PAA-F108-PAA分子的临界胶束化温度仅略微增加,KI对PPO链段表现出脱水作用,而对PEO链段表现出增溶作用.%Poly(acrylic acid)-Fl08-Poly(acrylic acid) copolymer(PAA-F108-PAA) was synthesized by atom transfer radical polymerization(ATRP) , followed by the hydrolysis of tert-butyl groups from the tert-butyl acry-late. The effects of temperature, acrylic acid neutralization degree and salt concentration on the micellization behavior of PAA-F108-PAA block copolymer were investigated by 'H NMR spectroscopy combined with nuclear Overhauser effect spectroscopy(2D NOE). The neutralization degree of carboxyl acid groups(α) had little influence on the critical micellization temperature( CMT) of PAA-F108-PAA. When α = 0. 14, the PAA-F108-PAA copolymer was in a collapsed state at low temperature, at high temperature the poly(propylene oxide) block(PPO) was dehydrated and associated into a hydrophobic micellar core, while PEO entangled with PAA and formed the micellar shell; when α = 0.80, PAA-F108-PAA copolymer was in a stretched state at low temperature, while at high temperature the micellar core was still composed of the hydrophobic PPO, with PEO and PAA separating from each other and forming the micellar shell. Salt species and concentration had great influence on the CMT of PAA-F108-PAA copolymer, which The CMT of PAA-F108-PAA copolymer decreased significantly by increasing KC1 concentration to 1 mol/L. KG showed a dehydration effect for both PPO and PEO block. In contrast, 1 mol/L KI increased the CMT of PAA-F108-PAA to a slightly higher value, suggesting that KI weakened the interaction between PPO and water but enhanced the interaction between PEO and water.