Dilute-solution structure of charged arborescent graft polymer
Dilute-solution structure of charged arborescent graft polymer
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带电树状接枝聚合物的稀溶液结构
DOI：
10.1016/j.polymer.2006.02.018
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发表时间：
2006
期刊：
影响因子：
--
通讯作者：
M. Gauthier
中科院分区：
文献类型：
--
作者：
S. Yun;R. Briber;R. A. Kee;M. Gauthier
用小角中子散射(SANS)研究了带电的G1树枝状聚苯乙烯-接枝-聚(2-乙烯基吡啶)共聚物在ϕ=0.005.0 5~0.0 5(ϕ：质量分数)范围内在甲醇-d4和d2O中的溶液。加入酸(HCl)后，树枝状接枝聚合物带电，并在SANS数据中出现一个峰。从峰值位置计算的颗粒间距离(DXP)对应于均匀颗粒分布的期望值(DUNI)。这表明，由于长程库仑排斥作用，形成了类液体有序结构。甲醇-D4的介电常数较小，导致长程静电斥力持续到比D2O低的聚合物浓度。通过对相同聚合物溶液的动态光散射测量，观察到了慢模散射，表明溶液中存在结构不均匀。在溶液中加入NaC l或过量的HCl，由于静电相互作用的屏蔽，峰模式和慢模式都消失了。接枝了较长的P2VP链的G1聚合物(相对分子质量∼为30,000和5,000gmol)在加入盐酸后形成了凝胶。这一结果表明，对于具有较长(MW∼30,000)线性聚电解质支链的树枝状聚合物，分子膨胀更为显著，导致ϕ>；0.01凝胶化。当加入氯化钠或过量的盐酸时，由于静电相互作用的筛选，凝胶转变回液体。
The solutions of charged G1 arborescent polystyrene-graft-poly(2-vinylpyridine) copolymers in methanol-d4 and D2O were investigated over a dilute concentration range ϕ=0.005–0.05 (ϕ: mass fraction) using small-angle neutron scattering (SANS). Upon addition of acid (HCl) arborescent graft polymers became charged and a peak appeared in SANS data. The interparticle distance (dexp) calculated from a peak position corresponded to the expected value (duni) for a uniform particle distribution. This indicates the formation of liquid-like ordering due to long-range Coulombic repulsions. The smaller dielectric constant of methanol-d4 resulted in long-range electrostatic repulsions persisting to lower polymer concentration than in D2O. The slow mode scattering was observed by dynamic light scattering measurements for the same polymer solutions, indicating the presence of structural inhomogeneity in the solutions. Both the peak and slow mode disappeared by addition of NaCl or excess HCl into the solutions due to the screening of electrostatic interactions. The G1 polymer grafted with longer P2VP chains (Mw∼30,000 versus 5000gmol) formed a gel on addition of HCl. This result reveals that molecular expansion is more significant for arborescent polymers with longer (Mw∼30,000) linear polyelectrolyte branches, resulting in gelation for ϕ>0.01. Upon addition of NaCl or excess HCl a gel transformed back to a liquid resulted from the screening of electrostatic interactions.