Hydrogen Bonded Polymers
Description:... Control of polymeric structure is among the most important endeavours of modern macromolecular science. In particular, tailoring the positioning and strength of intermolecular forces within macromolecules by synthetic me- odsandthusgaining structuralcontrolover the'nalpolymeric materials has become feasible, resulting in the ?eld of supramolecular polymer science. - sides other intermolecular forces, hydrogen bonds are unique intermolecular forces enabling the tuning of material properties via self-assembly processes -1 overawiderangeofinteractionstrengthrangingfromseveralkJmol tosev- -1 eraltensofkJmol . Centralfortheformationofthesestructuresareprecursor molecules of small molecular weight (usually lower than 10 000), which can assembleinsolidorsolutiontoaggregatesofde'nedgeometry. Intermolecular hydrogenbondsatde'nedpositionsofthesebuildingblocksaswellastheir- spectivestartinggeometryandtheinitialsizedeterminethemodeofassembly into supramolecular polymers forming network-, rodlike-, ?brous-, disclike- , helical-, lamellar- and chainlike architectures. In all cases, weak to strong hydrogen-bondinginteractionscanactasthecentralstructure-directingforce fortheorganizationofpolymerchainsandthusthe'nalmaterials'properties. Theimportantcontributionofhydrogenbondstotheareaofsupramole- lar polymer chemistry is de'nitely outstanding, most of all since the potency of hydrogen-bonding systems has been found to be unique in relation to other supramolecular interactions. Thus the high level of structural diversity of many hydrogen-bonding systems as well as their high level of direction- ity and speci'city in recognition-phenomena is unbeaten in supramolecular chemistry. The realization, that their stability can be tuned over a wide range of binding strength is important for tuning the resulting material prop- ties, ranging from elastomeric to thermoplastic and even highly crosslinked duroplastic structures and networks. On the basis of the thermal reversib- ity, new materials with highly tunable properties can now be prepared, - ing able to change their mechanical and optoelectronic properties with very smallchangesofexternalstimuli. Thusthe'eldofhydrogen-bondedpolymers forms the basis for stimuli responsive and adaptable materials of the future.
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