Hydrogen Bonded Polymers

Control of polymeric structure is among the most important endeavors of modern macromolecularscience. In particular, tailoring the positioning and strength of intermolecular forces within macromoleculesby synthetic methods and thus gaining structural control over the final polymeric materials has becomefeasible, resulting in the field of supramolecular polymer science. Besides other intermolecularforces, hydrogen bonds are unique intermolecular forces enabling the tuning of material propertiesvia self-assembly processes over a wide range of interaction strength ranging from several kJ mol⁻¹to several tens of kJ mol⁻¹. The present review provides anoverview of hydrogen-bonded polymers, with a focus directed towards the type of hydrogen bondas well as their effect on the final, ordered materials. Thus, the ordering effects of single-, double-,triple-, quadruple and multiple hydrogen bonds are discussed separately. Furthermore, various architecturesas well as the use of hydrogen bonds on planar surfaces to assemble quasipolymeric structures arediscussed.

Supramolecular polymers are linear chains of low molar mass monomers held together by reversible andhighly directional non-covalent interactions. In suitable experimental conditions, they can display polymer-likerheological or mechanical properties, because of their macromolecular architecture. However, the fact thatnon-covalent interactions are involved means that the assembly can be reversibly broken and can be underthermodynamic equilibrium. This reversibility brings additional features compared to usual polymers, whichpotentially lead to new properties, such as improved processing, self-healing behavior or stimuli responsiveness.The present chapter focuses first on particular examples where macroscopic properties of HBSPs are clearlydemonstrated, and then on the numerous engineering options explored so far to obtain functional materials.Finally, because the obtained properties depend strongly on the molar mass of the supramolecular polymerin the conditions of use, the last part describes the techniques available to characterize the molar massof supramolecular polymers.

Combining supramolecular principles with block copolymer self-assembly offers unique possibilitiesto create materials with responsive and/or tunable properties. The present chapter focuses on supramolecularmaterials based on hydrogen bonding and (block co-) polymers. Several cases will be discussed where theself-assembled nanostructured morphology can be easily tuned using composition as the natural variable.A large body of the material reviewed concerns hydrogen-bonded side-chain (block co-) polymers. Sidechains both with and without mesogenic units are discussed. Frequently the thermoreversibility of the hydrogenbonds allows for responsiveness of material properties to external stimuli such as temperature, pH, andelectromagnetic fields. Temperature-dependent photonic bandgap, temperature-dependent proton conductivity,pH-erasable multilayers, temperature-induced volume transitions, and fast AC electric field-induced orientationalswitching of microdomains are the main examples.

Materials with nanoscale dimensions display electronic, photonic, and magnetic properties differentfrom those observed by their respective bulk materials. This article describes the utilization of hydrogenbonds for modular self-assembly of nano-sized building blocks into two or three-dimensional aggregates andthe precise control over their structural parameters and morphologies. We will depict recent investigationson the synthesis and assembly of polymer and nanoparticle-based composite materials both in solution phaseand on solid substrates. The advantages, potential applications, and current challenges associated withthis “bottom up” assembly approach will also be discussed.