通过低温31 P和15 N NMR光谱结合计算化学研究了三烷基膦催化的脂肪族异氰酸酯低聚机理。提出了一种修订的机制,其中包含几种(螺)环五配位磷中间体。通过使用15种N标记的异氰酸酯进行实验,已经重新评估了先前报道的瞬态中间体的光谱数据,并将其分配给包含PN键的环状中间体。已经使用量子化学方法计算了支持该分配的13 C,15 N和31 P NMR位移。
通过低温31 P和15 N NMR光谱结合计算化学研究了三烷基膦催化的脂肪族异氰酸酯低聚机理。提出了一种修订的机制,其中包含几种(螺)环五配位磷中间体。通过使用15种N标记的异氰酸酯进行实验,已经重新评估了先前报道的瞬态中间体的光谱数据,并将其分配给包含PN键的环状中间体。已经使用量子化学方法计算了支持该分配的13 C,15 N和31 P NMR位移。
Determining the Regioregularity in Alkyne Polycarbodiimides and Their Orthogonal Modification of Side Chains To Yield Perfectly Alternating Functional Polymers
作者:Januka Budhathoki-Uprety、James F. Reuther、Bruce M. Novak
DOI:10.1021/ma301639m
日期:2012.10.23
To understand the structure-property relationship in functional macromolecules through side chain modulation, both the accurate determination of the position of modifiable groups along the polymer chain and their subsequent modifications using high fidelity methods are crucial. In this report, the polymer microstructure of a helical alkyne polycarbodiimide has directly been probed through N-15 NMR spectroscopy on isotopic labeled poly(N-(3-ethynylphenyl)-N-15'-hexyl)carbodiimide and found to be a highly regioregular polymer structure. This polymer undergoes facile and quantitative CuAAC "click" chemistry, yielding perfectly alternating functional polymers. Advances have been made through the synthesis of new optically active alkyne polycarbodiimides with two independently modifiable pendant groups per repeat unit of polymers. Orthogonal postmodifications of the pendant groups were then performed to incorporate two different sets of small molecules in the repeat unit of polymers in a controlled manner and under mild reaction conditions using either sequential CuAAC "click" reactions when two dissimilar alkyne groups are present or a combination of CuAAC and thiol-ene click chemistries when pendant groups bear alkyne and vinyl moieties.