ABSTRACT Design of stimuli‐responsive chiral polydiacetylenes (PDAs) with an innate photoswitch offers exciting opportunities toward tunable chromogenesis and chiroptical behavior as a result of E ‐ Z photoisomerization. We designed a series of asymmetric photopolymerizable diacetylene bisamides bearing variable alkyl chains, DA n ( n = 2, 5, 10), to connect the DA with a chiral azobenzene motif. Topochemical polymerization in thin films of DA forms orange colored PDAs to furnish long‐ranged fibrillar nanostructures with increasing alkyl chain lengths. The polymer nanostructures exhibit axial or lateral growth after thermal annealing due to improved ordering in the polymeric domains. The PDA self‐assembly exhibits crystalline or soft‐crystalline packing based on alkyl chain stacking, aromatic interactions, and hydrogen bonding. Differential molecular packing in the PDAs dictates the E to Z photoisomerization percentages, eventually resulting in diminishing chiroptical signatures and anisotropic textures. Photoisomerization‐mediated dynamic disassembly in 1D nanofibers are observed in the PDAs bearing decyl chain spacers, which show prominent room temperature soft‐crystalline switching behavior. Reverse photoisomerization of Z to E mediated structural reordering result recovery of the chiral packing, morphology, and birefringent patterns. Such tunable soft‐crystalline PDAs provide a convenient access to soft adaptable chiroptical materials toward solid‐state actuation applications.
Maulik et al. (Mon,) studied this question.