Synthesis and Characterization of Isoindigo‐Based Polymers with Thermocleavable Side Chains

Abstract

Stability of bulk heterojunction films for organic solar cells is a critical factor for commercial viability. One method to stabilize these films is to include cleavable side chains, which reduce the solubility of the polymers when removed. In order to study the stabilizing effect of cleavable side chains, a series of random copolymers using isoindigo with 0, 10, 20, 50, and 100% thermally cleavable side chains based on the tert‐butyloxycarbonyl (t‐BOC) group are synthesized. The polymers show a distinct one‐step thermal cleavage of the side chains, with no separable dealkylation and decarboxylation steps. The thermal stability in film is studied with transmission electron microscopy and atomic force microscopy. The polymer with all t‐BOC side chains on isoindigo significantly improves thermal stability with regard to crystal growth and phase separation in film. These results suggest BOC‐substitution can be used for large scale processing to produce insoluble polymer films with a high degree of thermal stability.

Recent advances in the application of isoindigo derivatives in materials chemistry

“…Bini et al described the synthesis of polymer series 28a – e with different ratios of isoindigo fragments, one of which is capable of thermal cleavage of Boc groups [ 42 ]. Without studying the main characteristics of the OSCs, they showed that after annealing the mixtures of these polymers with PC 61 BM at 200 °C, the surface morphology becomes highly inhomogeneous, with the presence of a large number of crystalline domains.…”

Hydrogen‐Bonding Induced Crosslinked Polymer Network for Highly Stable Electrochromic Device and a Construction Strategy for Black‐Bilayer Electrochromic Film

“…[ 13 ] However, the residual chemical species or groups remaining after cleavage will still impact the performance of the polymer films. [ 14 ] A post‐crosslinking strategy is also an effective method of forming solvent‐resistant crosslinked network polymers via the reaction of functional groups under external stimuli. [ 15 ] Kim et al prepared solvent‐resistant P3HT‐azide copolymer films via a UV light‐induced post‐crosslinking reaction, leading to high power conversion efficiency of the organic photovoltaic device.…”

Dual Polymer Complementarity Induced Truly Black Electrochromic Film and the Construction of Intelligent Eye-Protection Filters

“…An effective strategy is multilayer composite method by combining three primary colors (including additive RGB of red-, green-, and blue- and subtractive CMY of cyan-, magenta-, and yellow-)-to-transparent displays. , According to the color mixing theory, the resulting multilayer film shows full absorption in the visible region (380–780 nm) equal to black in the neutral state, and exhibits transparency in the oxidized state. , Mei et al described a solution-processable electrochromic polymer (ECP) stacking scheme in which a cross-linker is coprocessed with three primary (CMY) ECPs, imparting solvent-resistant properties to the single layer, allowing them to be sequentially deposited, resulting in a black-to-transparent film by varying the film thickness of each layer . Thus, it can be seen that the main obstacle to solution-processed organic electrochromic materials by color superposition is the high mutual solubility of conjugated organic electrochromic materials, which leads to the erosion of the interface between different materials. − In addition, they employed an ingenious strategy by pairing a green cathodic electrochromic material with magenta/red anodic electrochromic materials to obtain a black-to-transparent dual polymer complementary electrochromic device, which has the highest reported coloration efficiency . The complementary material is rare and uncommon, and this work provides inspiration and guidance for the subsequent preparation of high-performance complementary electrochromic devices.…”