Abstract

Helical polycarbodiimides with either naphthalene or anthracene side chains display chiroptical switching properties in solution and the solid state. This interesting chiroptical switching occurs due to the expansion and contraction of the helical backbone and the simultaneous reorientation of the aromatic side chains. Herein, we modified the aliphatic side-chain structure to induce the switching behavior in simple phenyl substituted polycarbodiimides. The polymerization of 1-hexynyl-5-phenylcarbodiimide introduced a terminal alkyne appended to the polymer backbone. By using the CLICK reaction, we were able to attach steric bulky branched alkyl groups to poly(N-phenyl)-N′-(n-branched alkyl) carbodiimide (P-1B). To increase the solubility and modulate the aliphatic sidechain packing of the polymer, 1-hexynyl-5-phenylcarbodiimide was copolymerized with phenyl octadecyl carbodiimide in different mole ratios. IR spectra and Specific Optical Rotation (SOR) studies showed these simple phenyl polymers show temperature driven solution state switching between two and sometimes three conformational states akin to what was only previously observed in polymers with polyaromatic side chains. In addition, one of the copolymers, P-2B, synthesized from the 50/50 mole feed ratio of the branched monomer and phenyl octadecyl carbodiimide showed solid-state sensing of various volatile organic compounds (VOCs) and solvent vapor.

摘要

具有萘或蒽侧链的螺旋聚碳二亚胺在溶液和固态中显示出手性转换特性。这种有趣的手性切换是由于螺旋骨架的膨胀和收缩以及芳族侧链的同时重新定向而发生的。在此，我们修改了脂肪族侧链结构以诱导简单苯基取代的聚碳二亚胺的转换行为。1-己炔基-5-苯基碳二亚胺的聚合引入了附加到聚合物主链上的末端炔烃。通过使用 CLICK 反应，我们能够将空间庞大的支链烷基连接到聚（N-苯基）-N' -（n-支链烷基）碳二亚胺（P-1B）。为了增加溶解度和调节聚合物的脂肪族侧链堆积，1-己炔基-5-苯基碳二亚胺与苯基十八烷基碳二亚胺以不同的摩尔比共聚。IR 光谱和比旋光度 (SOR) 研究表明，这些简单的苯基聚合物显示出温度驱动的溶液状态在两种和有时三种构象状态之间的转换，类似于之前仅在具有多芳族侧链的聚合物中观察到的情况。此外，由 50/50 摩尔进料比的支化单体和苯基十八烷基碳二亚胺合成的共聚物之一P-2B显示出对各种挥发性有机化合物 (VOC) 和溶剂蒸气的固态传感。