Synthesis, characterization and behavior in aqueous solution of star-shaped poly(acrylic acid)
Synthesis, characterization and behavior in aqueous solution of star-shaped poly(acrylic acid)
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DOI：
10.1002/macp.200500238
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发表时间：
2005-09-23
影响因子：
2.5
通讯作者：
Müller, AHE
中科院分区：
文献类型：
--
作者：
Plamper, FA;Becker, H;Müller, AHE
我们报道了通过丙烯酸叔丁酯的原子转移自由基聚合合成了具有 5、8 和 21 个臂的星形聚丙烯酸 (PAA)。我们采用核心优先方法，使用基于葡萄糖、蔗糖和环糊精的引发剂。随后对聚丙烯酸叔丁酯（PtBA）进行酸处理，得到星形聚丙烯酸（PAA）。臂的碱性裂解使我们能够确定起始位点效率。 PAA 星形和臂被酯化为聚丙烯酸甲酯 (PMA)。通过 GPC/粘度、MALDI-TOF MS 和 NMR 端基测定进行的分子量测定表明，引发位点效率接近一致。 PAA 臂和星形的电位滴定结果表明，表观 pK(a) 值随着臂数的增加而增加，这是片段密度增加的直接结果。 PAA 星水溶液的渗透压测量结果显示渗透系数在 0.05 到 0.38 之间，表明大多数反离子被限制在星内。限制随着臂数的增加而增加。
We report the synthesis of star-shaped poly(acrylic acid) (PAA), with 5, 8, and 21 arms, by atom transfer radical polymerization of tert-butyl acrylate. We employ the core-first approach using glucose-, saccharose- and cyclodextrin-based initiators. Subsequent acidic treatment of poly(tert-butyl acrylate) (PtBA) leads to star-shaped poly(acrylic acid) (PAA). Alkaline cleavage of the arms enabled us to determine the initiation site efficiency. The PAA stars and arms were esterified to poly(methyl acrylate) (PMA). Molecular weight determination by means of GPC/viscosity, MALDI-TOF MS and NMR end-group determination showed that the initiation site efficiency is close to unity. Results from potentiometric titration of PAA arms and stars show that the apparent pK(a) values increase with increasing arm number, which is a direct result of increasing segment density. Osmometry measurements of aqueous solutions of the PAA stars result in osmotic coefficients between 0.05 and 0.38, indicating that most of the counterions are confined within the star. The confinement increases with arm number.