UNUSUAL MACROMOLECULAR ARCHITECTURES - THE CONVERGENT GROWTH APPROACH TO DENDRITIC POLYESTERS AND NOVEL BLOCK COPOLYMERS
UNUSUAL MACROMOLECULAR ARCHITECTURES - THE CONVERGENT GROWTH APPROACH TO DENDRITIC POLYESTERS AND NOVEL BLOCK COPOLYMERS
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DOI：
10.1021/ja00048a009
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发表时间：
1992-10-21
影响因子：
15
通讯作者：
FRECHET, JMJ
中科院分区：
文献类型：
--
作者：
HAWKER, CJ;FRECHET, JMJ
树突聚酯的通用方法及其在制备两种不同类型的新型大分子结构的树突嵌段共聚物中的应用被描述。树突状聚酯的化学合成包括使用二环己基碳二亚胺（DCC）和4-（二甲氨基）吡啶对甲苯磺酸（DPTS）进行酯化反应，然后在乙酸中用锌去除其三氯乙酯基团来激活焦点。不同的醚和酯化学物质以径向或同心的方式围绕中心多功能化核心进行控制，从而获得不同寻常的球状块结构。因此，通过将含有聚酯和聚醚化学成分的径向交替枝状节段连接到多官能团核上，获得了枝状节段-嵌段共聚物。同样，在制备最终与核心部分耦合的树枝状碎片时，通过将醚和酯连接的层同心交替得到树枝状层块。用于制备醚连接片段的单体单元为3,5-二羟基苯甲酸醇，而用于制备酯连接片段的单体单元为2,2,2-三氯乙基3,5-二羟基苯甲酸酯。用核磁共振光谱法和排粒径色谱法对新嵌段共聚物进行了分析，表明它们是纯的单分散的。在链端性质没有很大差异的情况下，不同嵌段共聚物的玻璃化转变温度似乎只受醚和酯构建块的相对比例控制，而不受精确几何形状的控制。
A versatile approach to dendritic polyesters and their use in the preparation of two different types of novel macromolecular architectures represent dendritic block copolymers is described. The chemistry developed for the synthesis of dendritic polyesters involves generation growth through an esterification step using dicyclohexylcarbodiimide (DCC) and 4-(dimethylamino)pyridinium p-toluenesulfonate (DPTS) followed by activation of the focal point through removal of its trichloroethyl ester group with zinc in acetic acid. Unusual globular block architectures are then obtained by the controlled placement of different ether and ester chemistries in radial or concentric fashion around a central polyfunctional core. Therefore, a dendritic segment-block copolymer is obtained through the attachment of radially alternating dendritic segments incorporating polyester and polyether chemistry to the polyfunctional core. Similarly, a dendritic layer-block is obtained by the concentric alternation of ether- and ester-linked layers in the preparation of the dendritic fragments that are finally coupled to the core moiety. The monomer unit used for the preparation of ether-linked fragments was 3,5-dihydroxybenzyl alcohol, while 2,2,2-trichloroethyl 3,5-dihydroxybenzoate was used for the ester-linked fragments. Analysis of the new block copolymers by NMR spectrometry and size-exclusion chromatography suggests that they are pure and monodispersed. In the absence of large differences in the nature of their chain ends, the glass transition temperatures for the various block copolymers appear to be controlled only by the relative proportion of the ether and ester building blocks rather than by the exact geometry.