Controlling polymer properties through the shape of the molecular-weight distribution

Abstract

The manipulation of a polymer’s properties without altering its chemical composition is a major challenge in polymer chemistry, materials science and engineering. Although variables such as chemical structure, branching, molecular weight and dispersity are routinely used to control the architecture and physical properties of polymers, little attention is given to the often profound effect of the breadth and shape of the molecular-weight distribution (MWD) on the properties of polymers. Synthetic strategies now make it possible to explore the importance of parameters such as skew and the higher moments of the MWD function beyond the average and standard deviation. In this Review, we describe early accounts of the effect of MWD shape on polymer properties; discuss synthetic strategies for controlling MWD shape; describe current endeavours to understand the influence of MWD shape on rheological and mechanical properties and phase behaviour; and provide insight into the future of using MWDs in the design of polymeric materials.

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Fig. 1: Reagent and polymer feed strategies for temporal control of polymer MWD shape.
Fig. 2: Alternative methods for control of polymer MWD shape with photochemical or centrifugal stimuli.
Fig. 3: Early work demonstrating the influence of MWD shape on the phase behaviour of block copolymers.
Fig. 4: Studies demonstrating the influence of MWD shape on the phase behaviour of block copolymers.
Fig. 5: Early theoretical and experimental work showing the influence of Ð and MWD shape on the rheological properties of polymers.
Fig. 6: Recent work showing the influence of MWD shape on the mechanical and rheological properties of homopolymers and block copolymers.

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Acknowledgements

The authors acknowledge the Cornell Center for Materials Research (CCMR) through the National Science Foundation (NSF) Materials Research Science and Engineering Centers (MRSEC) program (DMR-1719875). B.P.F. thanks 3M and the Sloan Foundation for partially supporting this work.

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Correspondence to Brett P. Fors.

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Gentekos, D.T., Sifri, R.J. & Fors, B.P. Controlling polymer properties through the shape of the molecular-weight distribution. Nat Rev Mater 4, 761–774 (2019). https://doi.org/10.1038/s41578-019-0138-8

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