Synthesis of Ladder Polymers: Developments, Challenges, and Opportunities

Abstract

Ladder polymers are unique in that their backbones consist of fused rings with adjacent rings having two or more atoms in common. The restriction of bond rotations in rigid ladder polymers greatly limits their conformational freedom, leading to many intriguing and unique properties. As a non-traditional type of polymers, rigid ladder polymers are of great fundamental interest and technical importance as advanced materials for applications such as membrane gas separation and organic electronics. Ladder polymers can be divided into non-conjugated (with kinked conformations) and conjugated (with planar conformations) structures. Their synthesis can be broadly classified into two general strategies: direct ladder polymerization, and zipping of a linear precursor polymer. This Concept article outlines the historical development of ladder polymers and the chemical strategies used for their synthesis; highlights the challenges associated with their synthesis and characterization, and presents opportunities and outlooks for this unique and intriguing type of polymers.

Flexible Thermoelectric Materials and Generators: Challenges and Innovations

“…One of the design parameters ultimately determines the energy‐transformation properties of these materials in the rigidity of the molecular chains . For example, ladder‐shaped polymers exhibit highly rigid chains due to the absence of a rotatable single‐bond connections . Such highly rigid chains can facilitate overlap of adjacent π‐conjugated orbitals and a narrow energy bandgap for more efficient carrier transport.…”

Ladder‐Type Heteroarene‐Based Organic Semiconductors

“…Although the most representative fully ladder‐type conjugated polymer (LCP) poly(benzobisimidazo‐benzophenanthroline (BBL, P1 ); Figure ) was prepared as early as the 1960s, no LCPs that were soluble in organic solvents were reported until the 1990s, when Scherf and Müllen synthesized ladder‐type poly( p ‐phenylene)s (LPPPs, P2 ; Figure ) in which peripheral substituents were incorporated and thus sufficient solubility of the material was achieved. Since then, many efforts have been devoted to the investigation of LCPs, including development of their synthetic methodology, structural and physiochemical characterization, and applications that range from optoelectronics to optics . Due to their unique fully fused and rigid coplanar structures, LCPs possess many intriguing properties, such as increased conjugation lengths, higher carrier mobility, stronger luminescence intensity, longer triplet exciton lifetime, and excellent chemical, thermal, and photostability.…”

Simple Route to Synthesize Fully Conjugated Ladder Isomer Copolymers with Carbazole Units

“…Fully conjugated ladder polymers (cLPs) have drawn extensive attention because of their rigid structure with π-conjugated systems [1,2,3,4,5,6]. The unique structure of cLPs confers favorable physical, optical, and chemical properties [7,8,9,10].…”